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Comparison of small polaron migration and phase separation in olivine LiMnPO4 and LiFePO4 using hybrid density functional theory
Ong, Shyue Ping
Using hybrid density functional theory based on the Heyd-Scuseria-Ernzerhof (HSE06) functional, we compared polaron migration and phase separation in olivine LiMnPO[subscript 4] to LiFePO[subscript 4]. The barriers for ...
Thermal instability of Olivine-type LiMnPO 4 cathodes
Guoying Chen; Thomas J. Richardson
The remarkable thermal stability of LiFePO4 and its charged counterpart, FePO4, have been instrumental in its commercialization as a lithium-ion battery cathode material. Despite the similarity in composition and structure, and despite the high thermal stability of the parent compound, LiMnPO4, we find that the delithiated phase LiyMnPO4 (which contains a small amount of residual lithium), is relatively unstable and
Kinetics of synthesis olivine LiFePO 4 by using a precipitated-sintering method
Peixin Zhang; Xinyang Li; Zhongkuan Luo; Xiaoqian Huang; Jianhong Liu; Qiming Xu; Xiangzhong Ren; Xun Liang
The LiFePO4 precursor was synthesized using a precipitation with raw materials LiOHĘH2O, (NH4)2HPO4 and FeSO4Ę7H2O. The kinetics of synthesis olivine LiFePO4 was studied by using a differential thermal analysis (DTA) at different heating rates. The average activation energy of the reaction where the precursor form olivine LiFePO4 was 239.39kJmol?1, calculated by Doyle¢Ozawa and Kissinger methods. The reaction order, frequency factor,
Open-circuit voltage study on LiFePO 4 olivine cathode
Hiroki Matsui; Tatsuya Nakamura; Yo Kobayashi; Mitsuharu Tabuchi; Yoshihiro Yamada
Olivine LiFePO4 particles were prepared by solid-state reaction using Li2CO3, (NH4)2HPO4 and FeC2O42H2O as raw materials, and they were coated with an appropriate amount of carbon through thermal decomposition of C16H10 pyrene. Cathodes using the olivine particles were subjected to an open-circuit voltage measurement under the relaxation condition of 24h at each SOC and DOD states. The electrochemical reaction in
Synthesis and electrochemical properties of olivine LiFePO 4 prepared by a carbothermal reduction method
Hui-ping Liu; Zhi-xing Wang; Xin-hai Li; Hua-jun Guo; Wen-jie Peng; Yun-he Zhang; Qi-yang Hu
LiFePO4\\/C composite cathode material was prepared by carbothermal reduction method, which uses NH4H2PO4, Li2CO3 and cheap Fe2O3 as starting materials, acetylene black and glucose as carbon sources. The precursor of LiFePO4\\/C was characterized by differential thermal analysis and thermogravimetry. X-ray diffraction (XRD), scanning electron microscopy (SEM) micrographs showed that the LiFePO4\\/C is olivine-type phase, and the addition of the carbon
Synthesis and electrochemical properties of olivine LiFePO 4 as a cathode material prepared by mechanical alloying
NASA Astrophysics Data System (ADS)
Kwon, Sang Jun; Kim, Cheol Woo; Jeong, Woon Tae; Lee, Kyung Sub
Pure olivine LiFePO 4 and LiFePO 4/C composite powders are synthesized by using mechanical alloying (MA) and subsequent firing. The powder properties and the electrochemical characteristics of the prepared samples are investigated in comparison with those of a sample obtained by the conventional solid-state reaction. The olivine LiFePO 4 prepared by MA shows a maximum discharge capacity of 135 mA h g -1 at the C/20 rate (8.5 mA g -1) when fired at a relatively low temperature of 600 ░C. A LiFePO 4/C composite compound prepared by the MA process under optimum firing conditions has a high capacity of 156 mA h g -1 at the C/20 rate, i.e. 92% of the theoretical capacity. The composite also displays a better rate capability, a higher charge-discharge capacity and a more stable cycle-life than when produced by the conventional solid-state method. The improved electrode performance of MA samples originates mainly from very fine particles of sub-micron size and with a rough surface morphology. These powder characteristics increases the surface area of LiFePO 4 particles and maximizes the contact area with the conductor additive, which results in enhanced electronic conductivity. Consequently, the MA technique offers a promising synthetic process to overcome the disadvantages of olivine-type LiFePO 4 and LiFePO 4/C composite cathode materials for rechargeable lithium batteries.
High-performance, nanostructure LiMnPO4/C composites synthesized via one-step solid state reaction
NASA Astrophysics Data System (ADS)
Zheng, Jugong; Ni, Liang; Lu, Yanwen; Qin, Cancan; Liu, Panxing; Wu, Tongfu; Tang, Yuefeng; Chen, Yanfeng
LiMnPO4 is proposed as more promising cathode material as LiFePO4, while poor electronic conductivity and Jahn-Teller effects during charge/discharge processes hinder the electrochemical performance. To overcome these problems, one-step solid state reaction method is developed to synthesize LiMnPO4/C composites, which is with nanostructure, high crystallinity and good carbon coating. Manganese oxide sources and calcination temperature are investigated as factors for preparing high-performance LiMnPO4/C for Li-ion batteries. The results show that the LiMnPO4/C composites prepared with mixed manganese oxide deliver a superior initial capacity of 153 mAh g-1 at 0.05 C and high rate performance with discharge capacities of 123 mAh g-1 at 1 C and 103 mAh g-1 at 2 C. And the LiMnPO4/C composites synthesized at 600 ░C can retain 94% of the initial capacity after 200 cycles at 1 C, revealing a stable cycling stability. Therefore, one-step solid state reaction brings to light the synthesis of high performance LiMnPO4/C cathode materials and is suitable for large scale production.
Enhanced thermal safety and high power performance of carbon-coated LiFePO4 olivine cathode for Li-ion batteries
NASA Astrophysics Data System (ADS)
Zaghib, K.; Dubķ, J.; Dallaire, A.; Galoustov, K.; Guerfi, A.; Ramanathan, M.; Benmayza, A.; Prakash, J.; Mauger, A.; Julien, C. M.
The carbon-coated LiFePO4 Li-ion oxide cathode was studied for its electrochemical, thermal, and safety performance. This electrode exhibited a reversible capacity corresponding to more than 89% of the theoretical capacity when cycled between 2.5 and 4.0ĀV. Cylindrical 18,650 cells with carbon-coated LiFePO4 also showed good capacity retention at higher discharge rates up to 5C rate with 99.3% coulombic efficiency, implying that the carbon coating improves the electronic conductivity. Hybrid Pulse Power Characterization (HPPC) test performed on LiFePO4 18,650 cell indicated the suitability of this carbon-coated LiFePO4 for high power HEV applications. The heat generation during charge and discharge at 0.5C rate, studied using an Isothermal Microcalorimeter (IMC), indicated cell temperature is maintained in near ambient conditions in the absence of external cooling. Thermal studies were also investigated by Differential Scanning Calorimeter (DSC) and Accelerating Rate Calorimeter (ARC), which showed that LiFePO4 is safer, upon thermal and electrochemical abuse, than the commonly used lithium metal oxide cathodes with layered and spinel structures. Safety tests, such as nail penetration and crush test, were performed on LiFePO4 and LiCoO2 cathode based cells, to investigate on the safety hazards of the cells upon severe physical abuse and damage.
M÷ssbauer analysis of Fe ion state in lithium iron phosphate glasses and their glass-ceramics with olivine-type LiFePO 4 crystals
K. Hirose; T. Honma; Y. Doi; Y. Hinatsu; T. Komatsu
The valence and local coordination state of Fe ions in 26Li2O¢43FeO¢5Nb2O5¢26P2O5 (mol%) glasses and glass-ceramics consisting of LiFePO4 crystals (a potential candidate as cathode materials for rechargeable lithium ion batteries) are studied from Fe57 M÷ssbauer effect spectrum measurements. The main valence of Fe ions in the precursor and crystallized glasses is found to be Fe2+ (more than 80%). Fe2+ ions
Thin film rechargeable electrodes based on conductive blends of nanostructured olivine LiFePO4 and sucrose derived nanocarbons for lithium ion batteries.
Praveen, P; Jyothsna, U; Nair, Priya; Ravi, Soumya; Balakrishnan, A; Subramanian, K R V; Nair, A Sreekumaran; Nair, V Shantikumar; Sivakumar, N
The present study provides the first reports of a novel approach of electrophoretic co-deposition technique by which titanium foils are coated with LiFePO4-carbon nanocomposites synthesized by sol gel route and processed into high-surface area cathodes for lithium ion batteries. The study elucidates how sucrose additions as carbon source can affect the surface morphology and the redox reaction behaviors underlying these cathodes and thereby enhance the battery performance. The phase and morphological analysis were done using XRD and XPS where the LiFePO4 formed was confirmed to be a high purity orthorhombic system. From the analysis of the relevant electrochemical parameters using cyclic voltammetry and electrochemical impedance spectroscopy, a 20% increment and 90% decrement in capacity and impedance values were observed respectively. The composite electrodes also exhibited a specific capacity of 130 mA h/g. It has been shown that cathodes based on such composite systems can allow significant room for improvement in the cycling performance at the electrode/electrolyte interface. PMID:23882803
Synthesis of LiFePO 4 by co-precipitation and microwave heating
K. S. Park; J. T. Son; H. T. Chung; S. J. Kim; C. H. Lee; H. G. Kim
LiFePO4 is a potential candidate for the cathode material of the lithium secondary batteries. Co-precipitation method and microwave heating were adopted to study about LiFePO4. The samples were characterized by X-ray diffraction, scanning electron microscope, particle-size analysis, ICP composition analysis and electrochemical methods. Olivine phase LiFePO4 was successfully synthesized in a few minutes. The specific capacity, cycle property and rate
Preparation of LiFePO 4 powders by co-precipitation
Mu-Rong Yang; Wei-Hsin Ke; She-Huang Wu
Pure olivine LiFePO4 can be successfully prepared with co-precipitation from aqueous solution containing trivalent iron ion. The introduction of hydrolyzed sugar before heating give the best result, because the poor conductivity of the powders can be improved by synthesizing small and homogeneous powders with coatings of electronically conductive materials. The resultant LiFePO4\\/C composite with carbon scaffold and LiFePO4 embedded can
Thermal stabilities of delithiated olivine MPO 4 (M = Fe, Mn) cathodes investigated using first principles calculations
Shyue Ping Ong; Anubhav Jain; Geoffroy Hautier; Byoungwoo Kang; Gerbrand Ceder
We present an analysis of the thermal reduction of delithiated LiMnPO4 and LiFePO4 based on the quarternary phase diagrams as calculated from first principles. Our results confirm the recent experimental findings that MnPO4 decomposes at a much lower temperature than FePO4, thereby potentially posing larger safety issues for LiMnPO4 cathodes. We find that while substantial oxygen is released as MnPO4
Analysis of the size effect of LiMnPO4 particles on the battery properties by using STEM-EELS
NASA Astrophysics Data System (ADS)
Yoshida, J.; Stark, M.; Holzbock, J.; H³sing, N.; Nakanishi, S.; Iba, H.; Abe, H.; Naito, M.
The LiMnPO4 cathode material is a good candidate for rechargeable lithium ion batteries because of high voltage (4.1 V), high thermal stability and no toxicity. However, the rate performance of this material is extremely low when compared to the conventional LiMO2 (M = Ni or Co) or LiFePO4. In this study, the primary particle size was reduced by a hydrothermal synthesis, and we obtained LiMnPO4 particles with sizes less than 40 nm. The sample exhibited an excellent rate capacity, which was 136 mAh g-1 at 5 C and 120 mAh g-1 at 10 C. We also revealed the effect of the LiMnPO4 particle size on the battery by introducing STEM-EELS, which was expected to allow for the direct microscopic observation of the lithium state in the particles during the charge-discharge process. With the EELS analysis, it was clarified that the lithium diffusion distance from the inside to the surface of the primary particles had to be reduced down to about 20 nm to achieve the high rate performance.
Synthesis and electrochemical analysis of vapor-deposited carbon-coated LiFePO 4
I. Belharouak; C. Johnson; K. Amine
Carbon-coated LiFePO4 electrodes (C-LiFePO4) were prepared by a vapor deposition process. An improvement in the rate performance of C-LiFePO4 in lithium cells over uncoated LiFePO4 was observed. The coating process uses a solid\\/gas-phase reaction which consists of decomposing propylene gas, as carbon source, inside a reactor containing olivine LiFePO4 material. This process leads not only to the formation of few
Magnetic phase diagram of magnetoelectric LiMnPO4
Toft-Petersen, Rasmus; Andersen, Niels H.; Li, Haifeng; Li, Jiying; Tian, Wei; Budko, Serguei L.; Jensen, Thomas B.S.; Niedermayer, Christof; Laver, Mark; Zaharko, Oksana; Lynn, Jeffrey W.; Vaknin, David
The nature of the spin-flop (SF) transition in the magnetoelectric quasi-2D Heisenberg system LiMnPO4 is studied in fields applied along the a axis. A refinement of the magnetic structure using neutron diffraction data in the SF phase reveals that the spins reorient from being parallel to the a axis to be nearly along the c axis at magnetic fields between 4 and 4.7 T, depending on temperature. The low-field antiferromagnetic phase boundary is shown to join the spin-flop line tangentially at the so-called bicritical point, where there is a suppression of the ordering temperature. At the bicritical field, we observe an increased intensity of the Lorentz broadened elastic scattering at magnetic Bragg peaks above TN as compared to zero field and 10 T, without an increase in peak width. This suggests an increased density of fluctuations at the bicritical field as compared to zero field.
Restricted growth of LiMnPO4 nanoparticles evolved from a precursor seed
NASA Astrophysics Data System (ADS)
Kim, Tae-Hee; Park, Han-Saem; Lee, Myeong-Hee; Lee, Sang-Young; Song, Hyun-Kon
Herein, we report on a novel precipitation method to enable LiMnPO4 olivine (LMP) as a cathode material for lithium ion batteries (LIBs) to reach high capacity at high discharge rates. By confining Mn3(PO4)2 precipitation on surface of a precursor seed of Li3PO4, the size of LMP particles is limited to less than 100 nm for a smaller dimension. The cathode material delivers discharge capacities of 145 mAh g-1 at 0.1 C, 112 mAh g-1 at 1 C to 62 mAh g-1 at 5 C (comparable with top three performances [1-3]). Even if precipitation is one of the versatile strategies to prepare the cathode material, it has not been reported that such a first-tier high performance is obtained from LMP prepared by precipitation methods. When compared with LMP particles synthesized by a conventional co-precipitation method, the performances are recognized to be considerably enhanced. Also, the surface-confined precipitation process described in this work does not involve a ball milling step with a conductive agent such as carbon black [1,2,4-10] so that a low cost synthesis is feasible.
Electrochemical properties of LiFePO 4 \\/C synthesized by mechanical activation using sucrose as carbon source
Jae-Kwang Kim; Gouri Cheruvally; Jou-Hyeon Ahn
Olivine lithium iron phosphate (LiFePO4) is attracting much attention as a safe, low cost and high capacity cathode material for lithium batteries, especially for\\u000a applications in electric and hybrid-electric vehicles. In the present work, carbon-coated LiFePO4 (LiFePO4\\/C) materials are synthesized from lithium carbonate, ferrous oxalate, ammonium dihydrogen phosphate, and sucrose (varying\\u000a content) as starting materials, by the process of mechanical
Electrical conductivity studies of graphene wrapped nanocrystalline LiMnPO4 composite
NASA Astrophysics Data System (ADS)
Cheruku, Rajesh; D, Surya Bhaskaram; Govindaraj, G.; Vijayan, Lakshmi
Nanocrystalline LiMnPO4 material was synthesized by template free sucrose assisted hydrothermal method. The material possesses the orthorhombic crystal structure with Pnma, space group having four formula units. The GO was prepared by the hummer's method and it was reduced graphene oxide (rGO) with hydrazine hydrate in the presence of nitrogen atmosphere. LiMnPO4 material was wrapped by the rGO to increase its conductivity. The structural characterization was accomplished through X-ray diffraction, FT-IR and Raman spectroscopy. Morphology was identified by the SEM, Electrical characterization was done through impedance spectroscopy and the results were reported.
Thermally-induced cation disorder in LiFePO 4
Jordi Jacas Biendicho; Anthony R. West
LiFePO4 has a fully ordered olivine structure in samples prepared by solid state reaction below ~800░C but, with increasing temperature, a small amount of Li and Fe site exchange occurs reaching a value of about 4% just below melting at 975░C. The disorder is reversible on annealing at lower temperatures and is detected by changes in lattice parameters and in
Synthesis and characterization of LiFePO 4\\/(Ag + C) composite cathodes with nano-carbon webs
C. H. Mi; Y. X. Cao; X. G. Zhang; X. B. Zhao; H. L. Li
LiFePO4\\/(Ag+C) composite cathodes with a new type of nano-sized carbon webs were synthesized by two methods of an aqueous co-precipitation and a sol¢gel process, respectively. Simultaneous thermogravimetric-differential thermal analysis indicates that the crystallization temperature of LiFePO4 is about 455¢466Ā░C, which is close to the pyrolysis temperature of polypropylene, 460Ā░C. The silver and carbon co-modifying does not affect the olivine structure
Electronic Properties of LiFePO4 and Li doped LiFePO4
G. V. Zhuang; J. L. Allen; P. N. Ross; J.-H. Guo; T. R. Jow
The potential use of different iron phosphates as cathodematerials in lithium-ion batteries has recently been investigated.1 Oneof the promising candidates is LiFePO4. This compound has severaladvantages in comparison to the state-of-the-art cathode material incommercial rechargeable lithium batteries. Firstly, it has a hightheoretical capacity (170 mAh\\/g). Secondly, it occurs as mineraltriphylite in nature and is inexpensive, thermally stable, non-toxic andnon-hygroscopic. However,
A polyethylene glycol-assisted carbothermal reduction method to synthesize LiFePO4 using industrial raw materials
NASA Astrophysics Data System (ADS)
Fey, George Ting-Kuo; Huang, Kai-Pin; Kao, Hsien-Ming; Li, Wen-Hsien
Olivine LiFePO4 is synthesized by a carbothermal reduction method (CTR) using industrial raw materials with polyethylene glycol (PEG) as a reductive agent and carbon source. A required amount of acetone is added to the starting materials for the ball milling process and the precursor is sintered at 973 K for 8 h to form crystalline phase LiFePO4. The structure and morphology of the LiFePO4/C composite samples have been characterized by X-ray diffraction, field-emission scanning electron microscopy, transmission electron microscopy, energy-dispersive spectroscopy, differential scanning calorimetry and magnetic susceptibility. Electrochemical measurements show that the LiFePO4/C composite cathode delivers an initial discharge capacity of 150 mAh g-1 at a 0.2C-rate between 4.0 and 2.8 V, and almost no capacity loss is observed for up to 50 cycles. Remarkably, the cell can sustain a 30C-rate between 4.6 and 2.0 V, and this rate capability is equivalent to charge or discharge in 2 min. The simple technique, low-cost starting materials, and excellent electrochemical performance make this process easier to commercialize than other synthesized methods.
Physical and electrochemical properties of La-doped LiFePO 4 \\/C composites as cathode materials for lithium-ion batteries
Yung-Da Cho; George Ting-Kuo Fey; Hsien-Ming Kao
Olivine-type LiFePO4 is one of the most promising cathode materials for lithium-ion batteries, but its poor conductivity and low lithium-ion diffusion\\u000a limit its practical application. The electronic conductivity of LiFePO4 can be improved by carbon coating and metal doping. A small amount of La-ion was added via ball milling by a solid-state\\u000a reaction method. The samples were characterized by X-ray
Kinetics of lithium deintercalation from LiFePO 4
D. V. Safronov; I. Yu. Pinus; I. A. Profatilova; V. A. TarnopolÆskii; A. M. Skundin; A. B. Yaroslavtsev
We have studied the kinetics of lithium deintercalation from lithium iron phosphate in a cathode material for batteries. The\\u000a main contribution to the resistance of the cell is made by interfaces and the resistance of LiFePO4 grains. The FePO4 solubility in LiFePO4 is 4.0%. The lithium deintercalation process can be described in terms of a heterogeneous grain model and its
Two-magnon Raman scattering in LiMnPO4
NASA Astrophysics Data System (ADS)
Calderon Filho, C. J.; Gomes, P. F.; GarcĒa-Flores, A. F.; Barberis, G. E.; Granado, E.
Two-magnon Raman scattering is observed in the orthophosphate LiMnPO4, carrying quantitative information on the magnetic interactions between local Mn2+ moments. A simulated annealing fitting procedure of the Raman signal to theoretical curves derived from a magnetic Hamiltonian was carried out, taking exchange and anisotropy constants as free fitting parameters. Previously reported inelastic neutron scattering (INS) data [J. Li et al., Phys. Rev. B 79, 144410 (2009)] were also used in the fit. It is shown that the combined application of INS and Raman scattering data in the fit reduces the ambiguity of the determined set of exchange parameters with respect to fitting procedures using INS or Raman data independently. The temperature dependence of the Raman signal does not show a collapse of the two-magnon excitations at the long-range magnetic ordering temperature, TN = 34 K, supporting significant short-range spin correlations above TN.
Preparation and characterization of nano-particle LiFePO 4 and LiFePO 4\\/C by spray-drying and post-annealing method
Fei Gao; Zhiyuan Tang; Jianjun Xue
Pure, nano-sized LiFePO4 and LiFePO4\\/C cathode materials are synthesized by spray-drying and post-annealing method. The influence of the sintering temperature and carbon coating on the structure, particle size, morphology and electrochemical performance of LiFePO4 cathode material is investigated. The optimum processing conditions are found to be thermal treatment for 10h at 600░C. Compared with LiFePO4, LiFePO4\\/C particles are smaller in
Synthesis and characterization of LiFePO 4 \\/3-dimensional carbon nanostructure composites as possible cathode materials for Li-ion batteries
Lucangelo Dimesso; Christina Spanheimer; Susanne Jacke; Wolfram Jaegermann
Composites of three-dimensional (3D) carbon nanostructures coated with olivine-structured lithium iron phosphates (LiFePO4) as cathode materials for lithium ion batteries have been prepared through a Pechini-assisted reversed polyol process for\\u000a the first time. The coating has been successfully performed on nonfunctionalized commercially available 3D carbon used as\\u000a catalysts. Thermal analysis revealed no phase transitions till crystallization occurred at 579Ā░C. Morphological
Effect of synthesizing method on the properties of LiFePO4/C composite for rechargeable lithium-ion batteries
NASA Astrophysics Data System (ADS)
Yoon, Man-Soon; Islam, Mobinul; Park, Young Min; Ur, Soon-Chul
Olivine-type LiFePO4/C cathode materials are fabricated with FePO4 powders that are pre-synthesized by two different processes from iron chloride solution. Process I is a modified precipitation method which is implemented by the pH control of a solution using NH4OH to form FePO4 precipitates at room temperature. Process II is a conventional precipitation method, of which H3PO4 (85%) solution is gradually added to a FeCl3 solution during the process to maintain a designated mole ratio. The solution is subsequently aged at 90░C in a water bath until FePO4 precipitates appear. In order to synthesize LiFePO4/C composites, each batch of FePO4 powders is then mixed with pre-milled lithium carbonate and glucose (8 wt. %) as a carbon source in a ball-mill. The structural characteristics of both LiFePO4/C composites fabricated using iron phospates from two different routes have been examined employing XRD and SEM. The modified precipitation process is considered to be a relatively simple and effective process for the preparation of LiFePO4/C composites owing to their excellent electrochemical properties and rate capabilities.
The influence of improved carbon coating layer with nanometer-sized CeO2 interconnector on the enhanced electrochemical performance of LiMnPO4
NASA Astrophysics Data System (ADS)
Chen, Fang-Jie; Tao, Fen; Wang, Chun-Mei; Zhang, Wen-Long; Chen, Li
The CeO2/C hybrid coated LiMnPO4 composites are prepared via a simple and effective wet chemical process followed by heat treatment at 550 ░C. The nanometer-sized CeO2 acts as an interconnector in carbon network, and its influence on the electrochemical performance is investigated in detail. The 0.25 wt.% CeO2-modified LiMnPO4/C (sample-0.25) exhibits the highest discharge capacity and the best cycle life, which can deliver an initial capacity of 139.9 mAh g-1 at 0.1C and still retain a reversible capacity of 120.4 mAh g-1 after 50 cycles (capacity retention of 86.1%). While for pristine LiMnPO4/C (sample-0), only 94.4 mAh g-1 can be obtained at the 50th cycle, corresponding to 72.9% of its initial discharge capacity (129.5 mAh g-1). Scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD) results confirm that an integrated and hybrid CeO2/C coating layer is formed on LiMnPO4 surface and its existence has no influence on the structure of LiMnPO4. The reason for the improved electrochemical properties of the CeO2-modified LiMnPO4/C composites has also been studied by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) measurements.
Biocarbon-coated LiFePO4 nucleus nanoparticles enhancing electrochemical performances.
Zhang, Xueguang; Zhang, Xudong; He, Wen; Yue, Yuanzheng; Liu, Hong; Ma, Jingyun
We report a simple, inexpensive green biomimetic way for developing the high performance LiFePO(4) for high-power lithium-ion batteries. Biocarbon-coated LiFePO(4) nucleus nanoparticles are synthesized by using yeast cells as both a structural template and a biocarbon source. PMID:22936297
Columnar order in jammed LiFePO(4) cathodes: ion transport catastrophe and its mitigation.
Smith, Kyle C; Mukherjee, Partha P; Fisher, Timothy S
The high-rate, high-capacity potential of LiFePO(4)-based lithium-ion battery cathodes has motivated numerous experimental and theoretical studies aiming to realize such performance through nano-sizing, tailoring of particle shape through synthesis conditions, and doping. Here, a granular mechanics study of microstructures formed by dense jammed packings of experimentally and theoretically inspired LiFePO(4) particle shapes is presented. A strong dependence of the resultant packing structures on particle shapes is observed, in which columnar structures aligned with the [010] direction inhibit diffusion along [010] in anisotropic LiFePO(4). Transport limitations are induced by [010] columnar order and lead to catastrophic performance degradation in anisotropic LiFePO(4) electrodes. Further, judicious mixing of nanoplatelets with additive nanoparticles can frustrate columnar ordering and thereby enhance the rate capability of LiFePO(4) electrodes by nearly an order of magnitude. PMID:22476114
Shape controlled hydrothermal synthesis and characterization of LiFePO4 for lithium ion batteries.
Yu, Yang; Li, Qianwen; Ma, Yanmei; Zhang, Xing; Zhu, Yongchun; Qian, Yitai
Various LiFePO4 microstructures were synthesized via hydrothermal or solvothermal routes using different additives. In an aqueous solution, LiFePO4 spindles whose length was about 2 microm were obtained with the assistance of polyvinyl pyrrolidone (PVP). As PVP and P2O7(4-) added in water, ellipsoidal LiFePO4 particles which composed of nanoparticles around 100 nm in diameter were obtained. If the additive was cetyltrimethyl ammonium bromide (CTAB), sheet-like LiFePO4 crystals with the width of 100 nm were prepared. In the mixed solvents of water together with ethanol or acetylacetone, when adding CTAB or polyethylene glycol (20000), LiFePO4 plates or nanoparticles were obtained. The ellipsoidal LiFePO4 had the best electrochemical properties among all these products. It is found that the annealed samples were significantly better than the corresponding unannealed ones. Take the ellipsoidal LiFePO4 for example, the initial discharge capacity of annealed (161 mAh/g) was much higher than the unannealed ones (85 mAh/g) at 0.1 C and the former cell still could deliver a capacity of 143 mAh/g after 30 cycles. PMID:23646673
Electrochemical performance of CLa 3+ codoped LiFePO 4 synthesized by microwave heating
Yan Cui; Miao Wang; Ruisong Guo; Zhaohe Xu
La3+ was selected to elevate the lattice electronic conductivity of LiFePO4, and LiFePO4\\/(C+La3+) cathode powders were synthesized by microwave heating using a domestic microwave oven for 35 min. The microstructures and\\u000a morphologies of the synthesized materials were investigated by XRD and SEM. The electrochemical performances were evaluated\\u000a by galvanostatic charge-discharge. The electrochemical performance of LiFePO4 with different La3+ contents was
Probing the failure mechanism of nanoscale LiFePO4 for Li-ion batteries
NASA Astrophysics Data System (ADS)
Gu, Meng; Shi, Wei; Zheng, Jianming; Yan, Pengfei; Zhang, Ji-guang; Wang, Chongmin
LiFePO4 is a high power rate cathode material for lithium ion battery and shows remarkable capacity retention, featuring a 91% capacity retention after 3300 cycles. In this work, we use high-resolution transmission electron microscopy and electron energy loss spectroscopy to study the gradual capacity fading mechanism of LiFePO4 materials. We found that upon prolonged electrochemical cycling of the battery, the LiFePO4 cathode shows surface amorphization and loss of oxygen species, which directly contribute to the gradual capacity fading of the battery. The finding can guide the design and improvement of LiFePO4 cathode for high-energy and high-power rechargeable battery for electric transportation.
Study of LiFePO 4 cathode materials coated with high surface area carbon
Cheng-Zhang Lu; George Ting-Kuo Fey; Hsien-Ming Kao
LiFePO4 is a potential cathode material for 4V lithium-ion batteries. Carbon-coated lithium iron phosphates were prepared using a high surface area carbon to react precursors through a solid-state process, during which LiFePO4 particles were embedded in amorphous carbon. The carbonaceous materials were synthesized by the pyrolysis of peanut shells under argon, where they were carbonized in a two-step process that
New freeze-drying method for LiFePO 4 synthesis
Ver¾nica Palomares; Aintzane Go±i; Izaskun Gil de Muro; Iratxe de Meatza; Miguel Bengoechea; Oscar Miguel; Te¾filo Rojo
The freeze-drying method is proposed as an effective synthesis process for the obtaining of LiFePO4\\/C composites. The citric acid is used as a complexing agent and carbon source. After the low temperature annealing, the freeze-dried solution leads to a homogeneous carbon covered LiFePO4 sample. The chemical characterization of the material included ICP and elemental analysis, infrared spectroscopy, X-ray diffraction, magnetic
Electrochemical properties of LiFePO 4 prepared via ball-milling
George Ting-Kuo Fey; Yun Geng Chen; Hsien-Ming Kao
LiFePO4 cathode materials with distinct particle sizes were prepared by a planetary ball-milling method. The effects of particle size on the morphology, thermal stability and electrochemical performance of LiFePO4 cathode materials were investigated. The ball-milling method decreased particle size, thereby reducing the length of diffusion and improving the reversibility of the lithium ion intercalation\\/deintercalation. It is worth noting that the
Reaction behavior of LiFePO 4 as a cathode material for rechargeable lithium batteries
Masaya Takahashi; Shin-ichi Tobishima; Koji Takei; Yoji Sakurai
We investigated the effect of cell temperature on the electrochemical reaction behavior of LiFePO4. We evaluated its electrochemical characteristics by using cyclic voltammetry and electrochemical impedance spectroscopy (EIS). Both the electron transfer activity and the lithium ion diffusion rate in the LiFePO4 electrode increased as we increased the operating temperature. The apparent activation energy for the lithium diffusion was more
Synthesis and characterization of LiFePO 4 prepared by sol¢gel technique
M. A. E. Sanchez; G. E. S. Brito; M. C. A. Fantini; G. F. Goya; J. R. Matos
LiFePO4 powder was synthesized by means of a new route, using a two step process. In the first step, an intermediate compound was synthesized by the sol¢gel method. This precursor compound to LiFePO4 was characterized by thermal analysis (TG\\/DTG and DSC), M÷ssbauer spectroscopy, Transmission Electronic Microscopy (TEM) and Small Angle Scattering (SAXS). In the second step, the precursor was sintered
Preparation of LiFePO 4\\/C in a reductive atmosphere generated by windward aerobic decomposition of glucose
Shengping Wang; Chenggang Zhou; Quan Zhou; Gang Ni; Jinping Wu
We report the preparation of LiFePO4\\/C electrode materials by thermal treating the hydrothermal LiFePO4\\/C precursors in a reductive atmosphere from windward aerobic decomposition of glucose. XRD and ESEM characterization indicate that the procedure produces well carbon coated single-phase orthorhombic LiFePO4 with small and evenly distributed particle-sizes. Comparing with the typical Ar\\/H2 reductive atmosphere, samples from this procedure host larger initial
Hydrothermal synthesis of monodispersed LiFePO 4 cathode materials in alcohol¢water mixed solutions
Chunhua Zhang; Xiang Huang; Yansheng Yin; Jinhui Dai; Zhibin Zhu
Monodispersed LiFePO4 powders were prepared by thermal decomposition of Fe(II)¢citric acid complex precursor and application of isopropanol as a dielectric constant tuner. The powders morphology was greatly influenced by the volume ratio of isopropanol to water (RH ratio). Monodispersed short rod-like LiFePO4 crystals were obtained when RH ratio was 1.0, while column-like LiFePO4 particles composed of much smaller crystals were
Reaction mechanism and electrochemical performance of LiFePO 4\\/C cathode materials synthesized by carbothermal method
Feng Yu; Jingjie Zhang; Yanfeng Yang; Guangzhi Song
Spray drying and carbothermal method was employed to investigate reaction mechanism and electrochemical performance of LiFePO4\\/C cathode by using different carbon sources. Micro-structural variations of LiFePO4\\/C precursors using different carbon sources were studied by Thermo-gravimetric (TG)\\/Differential Thermal Analysis (DTA). The LiFePO4\\/C samples were characterized by X-ray diffraction (XRD) and Fourier transform infrared (FTIR) absorption spectroscopy. The results indicated that the
Physical and electrochemical properties of LiFePO 4\\/C composite cathode prepared from various polymer-containing precursors
Yao-Hong Nien; James R. Carey; Jenn-Shing Chen
The goal of this research was to study the effect of various polymer-containing precursors on the performance of LiFePO4\\/C composite. A coprecipitation method was applied to prepare a series of LiFePO4\\/C materials by calcinating amorphous LiFePO4 with various polymer compounds at 600░C. The materials were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, particle size analysis, thermal analysis,
Synthesis of Nanowire and Hollow LiFePO4 Cathodes for High-Performance Lithium Batteries
Cho, Jaephil
Articles Synthesis of Nanowire and Hollow LiFePO4 Cathodes for High-Performance Lithium Batteries of the electrode materials for lithium batteries, such as TiO2,1Ł4 Li4Ti5O12,5 and LiFePO4,6Ł11 have been reported LiFePO4 cathodes using the hard templates KIT-6 and SBA-15 is reported for high-performance lithium
Thermal Stability and Phase Transformation of Electrochemically Charged/Discharged LiMnPO4 Cathode for Li-Ion Battery
Choi, Daiwon; Xiao, Jie; Choi, Young Joon; Hardy, John S.; Vijayakumar, M.; Bhuvaneswari, M. S.; Liu, Jun; Xu, Wu; Wang, Wei; Yang, Zhenguo; Graff, Gordon L.; Zhang, Jiguang
Electrochemically active LiMnPO4 nanoplate at lithiated/delithiated state were subjected to thermal stability and phase transformation evaluate for safety as a cathode material for Li-ion battery. The phase transformation and oxygen evolution temperature on the delithiated MnPO4 were characterized using in-situ hot-stage X-ray diffraction (XRD), X-ray Photoelectron Spectroscopy (XPS), thermogravimetric - differential scanning calorimetry - mass spectroscopy (TGA-DSC-MS), transmission electron microscopy and scanning electron microscopy (SEM) - energy dispersive X-ray analysis (EDAX).
Mixed-solvent thermal synthesis of porous LiFePO4.
Pei, Zhenzhao; Zhang, Xia; Gao, Xiang
Porous structure LiFePO4 with pore size from 2 to 15 nm was successfully synthesized in mixed solvents system of glycol and water. By changing stirring time from 5 to 60 min, LiFePO4 morphologies were adjusted and percentage of porous LiFePO4 was higher and higher in sequence. Stirring time is the key cause of controlling morphologies of final products for its influence on diffusion rate of the initial formed particles of final products. Through adjusting this factor, products with specific morphologies and functions can be obtained. The morphologies and microstructures were observed by transmission electron microscopy (TEM), and the phase composition was verified by X-ray diffraction (XRD). This synthetic method provides a new route to obtain porous structure materials. PMID:23763214
Cycling performance of LiFePO 4 cathode material for lithium secondary batteries
Hyung-Sun Kim; Byung-Won Cho; Won-Il Cho
Lithium iron phosphate (LiFePO4) cathode material has been synthesized by a solid-state reaction which uses Li3PO4 and Fe3(PO4)2Ę8H2O as starting materials. These materials were mixed with alumina balls and treated thermally at various temperatures in an argon and hydrogen atmosphere. The crystalline intensity of LiFePO4 powder prepared at 700░C is higher than that of powders prepared at 600 and 800░C.
Particle-size and morphology dependence of the preferred interface orientation in LiFePO4 nano-
Ceder, Gerbrand
Particle-size and morphology dependence of the preferred interface orientation in LiFePO4 nano insights into the equilibrium properties and potential two-phase lithiation mechanisms in LiFePO4 nano, if experimentally-relevant nano-particles were to (de)lithiate under a thermodynamic two-phase mechanism
Hierarchical LiFePO4 with a controllable growth of the (010) facet for lithium-ion batteries
Guo, Binbin; Ruan, Hongcheng; Zheng, Cheng; Fei, Hailong; Wei, Mingdeng
Hierarchically structured LiFePO4 was successfully synthesized by ionic liquid solvothermal method. These hierarchically structured LiFePO4 samples were constructed from nanostructured platelets with their (010) facets mainly exposed. To the best of our knowledge, facet control of a hierarchical LiFePO4 crystal has not been reported yet. Based on a series of experimental results, a tentative mechanism for the formation of these hierarchical structures was proposed. After these hierarchically structured LiFePO4 samples were coated with a thin carbon layer and used as cathode materials for lithium-ion batteries, they exhibited excellent high-rate discharge capability and cycling stability. For instance, a capacity of 95% can be maintained for the LiFePO4 sample at a rate as high as 20 C, even after 1000 cycles. PMID:24071818
Enhanced electrochemical performance of graphene modified LiFePO4 as a cathode material for lithium ion batteries
NASA Astrophysics Data System (ADS)
Dhindsa, K. S.; Mandal, B. P.; Lin, M. W.; Nazri, M.; Nazri, G. A.; Naik, V. M.; Vaishnava, P.; Naik, R.; Zhou, Z. X.
We have synthesized LiFePO4/graphene nano-composites using a sol-gel method by adding water dispersed graphene oxide to the LiFePO4 precursors during the synthesis. The graphene oxide was reduced by annealing the composite at 600^oC for 5h in flowing forming gas (90% Ar and 10% H2). The phase purity of the product was characterized by X-Ray diffraction and Raman spectroscopy. The reduction of graphene oxide was verified by Raman spectroscopy and X-ray Photoelectron spectroscopy. The electronic conductivity of LiFePO4/graphene composite was found to be six orders of magnitude higher than that of pure LiFePO4 synthesized following otherwise the same procedure except that no graphene oxide was added. SEM and TEM images show that LiFePO4 particles are wrapped in uniformly distributed graphene sheets throughout the material forming a three dimensional conducting network. At low currents, the capacity of the composite cathode reaches 160 mAh/g, which is very close to the theoretical limit. More significantly, the graphene wrapped LiFePO4 shows a dramatically improved rate capability and excellent charge-discharge cycle stability in comparison with the LiFePO4 without graphene.
Electrochemical characteristics of LiFePO 4 \\/LiCoO 2 mixed electrode for Li secondary battery
Hyun-Soo Kim; Mingzhe Kong; Ketack Kim; Ick-Jun Kim; Hal-Bon Gu
LiFePO4 cathode active material was synthesized using a solid state method and a mixed cathode was prepared by adding LiCoO2. A coin cell was prepared using the mixed cathode and its electrochemical performances were evaluated. The LiFePO4 material improved both in thermal stability and rate capability. The discharge capacity of the 5Āwt.% LiCoO2-added LiFePO4 material was 139.4ĀmAh\\/g at 0.2ĀC rate,
Synthesis of LiFePO 4\\/C cathode material from ferric oxide and organic lithium salts
Zhongqi Shi; Ming Huang; Yongjian Huai; Ziji Lin; Kerun Yang; Xuebu Hu; Zhenghua Deng
LiFePO4\\/C cathode material has been simply synthesized via a modified in situ solid-state reaction route using the raw materials of Fe2O3, NH4H2PO4, Li2C2O4 and lithium polyacrylate (PAALi). The sintering temperature of LiFePO4\\/C precursor is studied by thermo-gravimetric (TG)\\/differential thermal analysis (DTA). The physical properties of LiFePO4\\/C are then investigated through analysis using by X-ray diffraction (XRD), scanning electron microscopy (SEM),
Nanocomposite of LiFePO4 and mesoporous carbon prepared by microwave heating for rechargeable lithium batteries
NASA Astrophysics Data System (ADS)
Roh, Kwang Chul; Lee, Ho Jun; Lee, Jae-Won
A nanocomposite of LiFePO4 and mesoporous carbon was synthesized from MgO-templated mesoporous carbon by microwave heating for use as a cathode material in rechargeable Li batteries. Our research group reported a composition method using a porous template in the a previous paper.[1] Despite its low carbon content, the present composite shows better electrochemical performance than our previously reported version. The LiFePO4 nanoparticles were homogeneously dispersed in the template because of the suppressed growth of LiFePO4 crystals in the template pores and small thermal gradient resulting from microwave heating. The three-dimensional conducting carbon network between the LiFePO4 nanoparticles led to excellent cycling stability and rate capability. No decrease in discharge capacity was observed up to 100 cycles, and 85% of the reversible capacity at a Crate of 0.1 was retained at a C-rate of 30.
Analysis of the thermal behavior of a LiFePO4 battery cell
NASA Astrophysics Data System (ADS)
Niculu??, Marian-Ciprian; Veje, Christian
This paper presents theory, experiments and numerical modeling results for the electrothermal analysis of Lithium Iron Phosphate (LiFePO4) battery cells. Thermal management of batteries is important for several reasons including thermal runaway and maintaining battery operating time. A battery pack is comprised of battery cells which are stacked together without cooling surfaces except for the pack outer surface. The central cells in the pack are therefore exposed to the risk of overheating. A model for a single specific commercial LiFePO4 battery cell is presented together with preliminary experiments and results for determination of heating sources during charging and discharging. Based on the experimental results we extract model parameters for use in the model. The experiments lead to relations for the cell surface temperature and the lump temperature of the cell. A reasonable agreement between experiments and the model is found and suggestions for further work is indicated.
Effect of synthesis temperature on the properties of LiFePO 4\\/C composites prepared by carbothermal reduction
L. Wang; G. C. Liang; X. Q. Ou; X. K. Zhi; J. P. Zhang; J. Y. Cui
LiFePO4\\/C composite cathode materials were synthesized by carbothermal reduction method using inexpensive FePO4 as raw materials and glucose as conductive additive and reducing agent. The precursor of LiFePO4\\/C was characterized by differential thermal analysis and thermogravimetry. The microstructure and morphology of the samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscope (TEM) and particle size
A new charging mode of Li-ion batteries with LiFePO 4 \\/C composites under low temperature
Xiao Wei Zhao; Guo Yu Zhang; Lin Yang; Jia Xi Qiang; Zi Qiang Chen
Li-ion batteries with LiFePO4\\/C composites are difficult to be charged at low temperatures. In order to improve the low temperature performance of LiFePO4\\/C power batteries, the charge¢discharge characteristics were studied at different temperatures, and a new charging mode under\\u000a low temperature was proposed. In the new charging mode, the batteries were excited by current pulses with the charge rates\\u000a between
Improvement of electrochemical and thermal stability of LiFePO 4@C batteries by depositing amorphous silicon film
Yingbin Lin; Yanmin Yang; Ying Lin; Baozhi Zeng; Guiying Zhao; Zhigao Huang
Amorphous silicon (?-Si) films are deposited on LiFePO4@C electrode by using vacuum thermal evaporation deposition technique and the effect of ?-Si film on electrochemical performance of LiFePO4@C cells is investigated systematically by the charge¢discharge testing, cyclic voltammograms and AC impedance spectroscopy, respectively. The results reveal that the present of ?-Si film on electrode surface could remarkably improve the electrochemical performance
Particle size distribution and electrochemical properties of LiFePO 4 prepared by a freeze-drying method
E. Zhecheva; Ml. Mladenov; P. Zlatilova; V. Koleva; R. Stoyanova
The electrochemical performance of carbon-coated nanocrystalline LiFePO4 prepared by a freeze-drying method is examined. This method is based on the thermal decomposition of homogeneous phosphate-formate precursors. Structural and morphological characterization of LiFePO4 is carried out by powder XRD, BET measurements, SEM and XPS analyses. The electrochemical behaviour is tested in model lithium cells using galvanostatic mode. By changing the solution
Synthesis, characterization and properties of LiFePO 4 \\/C cathode material
Zhou Xin-wen; Zhan Dan; Wang Li-na; Liu Qiao-yun; Zong Hong-xing; Zhang Ke-li
Lithium iron phosphate coated with carbon (LiFePO4\\/C) was synthesized by improved solid-state reaction using comparatively lower temperature and fewer sintering time. The carbon\\u000a came from citric acid, which acted as a new carbon source. It was characterized by thermogravimetry and differential thermal\\u000a analysis (TG\\/DTA), X ray diffractometer (XRD), Element Analysis (EA) and Scanning electron microscope (SEM). We also studied\\u000a the
Factor affecting rate performance of undoped LiFePO 4
Daniela Zane; Maria Carewska; Silvera Scaccia; Francesco Cardellini; Pier Paolo Prosini
Undoped lithium iron phosphate (LiFePO4) was prepared and characterized by scanning electron microscope (SEM) and X-ray diffraction (XRD) analysis. The material has a single crystal globular structure with grain-sizes ca. 100¢150nm. It was used to prepare composite electrodes containing different amounts of carbon (10, 15 and 20wt.%, respectively) used as cathodes in non-aqueous lithium cells. By increasing the carbon content,
Thermal modeling of a cylindrical LiFePO 4\\/graphite lithium-ion battery
Christophe Forgez; Dinh Vinh Do; Guy Friedrich; Mathieu Morcrette; Charles Delacourt
A lumped-parameter thermal model of a cylindrical LiFePO4\\/graphite lithium-ion battery is developed. Heat transfer coefficients and heat capacity are determined from simultaneous measurements of the surface temperature and the internal temperature of the battery while applying 2Hz current pulses of different magnitudes. For internal temperature measurements, a thermocouple is introduced into the battery under inert atmosphere. Heat transfer coefficients (thermal
Moisture driven aging mechanism of LiFePO 4 subjected to air exposure
Marine Cuisinier; Jean-Frķdķric Martin; Nicolas Duprķ; Atsuo Yamada; Ryoji Kanno; Dominique Guyomard
The impact of air exposure on LiFePO4¢C nanocomposites has been investigated at moderate temperature. We show here that the storage in 120░C hot air for 30days leads not only to the material delithiation but also to the formation of an amorphous ferric phosphate side-phase, accounting for 38% of the total iron. The formed phase is found to be partially hydrated,
High temperature electrochemical performance of nanosized LiFePO 4
F. Mestre-Aizpurua; S. Hamelet; C. Masquelier; M. R. PalacĒn
The electrochemical performance of LiFePO4 was tested at temperatures up to 150░C for micrometric and nanometric size samples. Among the latter, both highly defective samples obtained by direct precipitation and annealed samples were tested. The comparison of voltage composition profiles for these samples coupled to GITT experiments allowed to conclude that defects seem to be the major factor in inducing
Temperature characterization analysis of LiFePO 4 \\/C power battery during charging and discharging
Kai Yang; Jin Jing An; Shi Chen
In order to study the surface temperature change and distribution during charging and discharging and in the simulation working\\u000a condition of LiFePO4\\/C power battery at normal temperature, the surface temperature is tested by placing the battery in the incubator and fixing\\u000a 10 temperature probes on the battery surface. Results show that the temperature of the upper part is higher, and
Enhanced electrochemical performance of graphene modified LiFePO4 as a cathode material for lithium ion batteries
NASA Astrophysics Data System (ADS)
Dhindsa, Kulwinder; Mandal, Balaji; Lin, Ming-Wei; Nazri, Maryam; Nazri, Gholam; Naik, Vaman; Vaishnava, Prem; Naik, Ratna; Zhou, Zhixian
We synthesized LiFePO4/graphene nano-composites using a sol-gel method by adding water dispersed graphene oxide to the LiFePO4 precursors during the synthesis. The graphene oxide was subsequently reduced to graphene by annealing the composite which was confirmed by Raman spectroscopy and X-ray Photoelectron spectroscopy. The electronic conductivity of the composite was found to be six orders of magnitude higher than that of pure LiFePO4 Scanning Electron microscopy and Transmission electron microscopy images show LiFePO4 particles are wrapped in uniformly distributed graphene sheets throughout the material forming a three dimensional conducting network. At low currents, (C/3), the capacity of the composite cathode reaches 160 mAh/g, which is very close to the theoretical limit. More significantly, the graphene wrapped LiFePO4 shows a dramatically improved rate capability up to 27C, and excellent charge-discharge cycle stability over 500 stable cycles as compared to the pure LiFePO4.
Charge-discharge rate of spinel lithium manganese oxide and olivine lithium iron phosphate in ionic liquid-based electrolytes
NASA Astrophysics Data System (ADS)
Egashira, Minato; Kanetomo, Akinori; Yoshimoto, Nobuko; Morita, Masayuki
Rate capability of Li/spinel LiMn2O4 or olivine LiFePO4 positive electrode cells containing mixed imidazolium ionic liquids electrolytes has been investigated under comparison with conventional organic solvent electrolyte and piperidinium ionic liquid. The LiMn2O4 electrode provides variation of rate capabilities among the ionic liquid electrolytes, while ionic liquid electrolytes provide similar extent of capacity degradation under high rate compared with organic solvent electrolyte for LiFePO4 electrode. Such differences in electrolyte dependences of the rate capabilities can be explained in relation to parameters in the high frequency resistances on AC impedance, assumed as interfacial resistances. The rate capability of LiMn2O4 is somewhat related to the activation energy of the high frequency resistance, while for LiFePO4 the resistance value appears to contribute to the rate capability.
Effect of carbon coating on low temperature electrochemical performance of LiFePO 4\\/C by using polystyrene sphere as carbon source
Y. Zhou; C. D. Gu; J. P. Zhou; L. J. Cheng; W. L. Liu; Y. Q. Qiao; X. L. Wang; J. P. Tu
Carbon perfectly coated LiFePO4 cathode materials are synthesized by carbon-thermal reduction method using polystyrene (PS) spheres as carbon source. The PS spheres with diameters of 150¢300nm used for the pyrolysis reaction not only inhibit the particle growth but also lead to uniform distribution of carbon coating on the surface of LiFePO4 particles. Rate capability and cycling stability of LiFePO4\\/C with
Electrochemical and kinetic studies of ultrafast laser structured LiFePO4 electrodes
NASA Astrophysics Data System (ADS)
Mangang, M.; Gotcu-Freis, P.; Seifert, H. J.; Pfleging, W.
Due to a growing demand of cost-efficient lithium-ion batteries with an increased energy and power density as well as an increased life-time, the focus is set on intercalation cathode materials like LiFePO4. It has a high practical capacity, is environmentally friendly and has low material costs. However, its low electrical conductivity and low ionic diffusivity are major drawbacks for its use in electrochemical storage devices or electric vehicles. By adding conductive agents, the electrical conductivity can be enhanced. By increasing the surface of the cathode material which is in direct contact with the liquid electrolyte the lithium-ion diffusion kinetics can be improved. A new approach to increase the surface of the active material without changing the active particle packing density or the weight proportion of carbon black is the laser-assisted generation of 3D surface structures in electrode materials. In this work, ultrafast laser radiation was used to create a defined surface structure in LiFePO4 electrodes. It was shown that by using ultrashort laser pulses instead of nanosecond laser pulses, the ablation efficiency could be significantly increased. Furthermore, melting and debris formation were reduced. To investigate the diffusion kinetics, electrochemical methods such as cyclic voltammetry and galvanostatic intermittent titration technique were applied. It could be shown that due to a laser generated 3D structure, the lithium-ion diffusion kinetic, the capacity retention and cell life-time can be significantly improved.
Redirected charge transport arising from diazonium grafting of carbon coated LiFePO4.
Madec, L; Seid, K A; Badot, J-C; Humbert, B; Moreau, P; Dubrunfaut, O; Lestriez, B; Guyomard, D; Gaubicher, J
The morphological and the electrical properties of carbon coated LiFePO4 (LFPC) active material functionalized by 4-ethynylbenzene tetrafluoroboratediazonium salt were investigated. For this purpose, FTIR, Raman, XPS, High Resolution Transmission Electron Microscopy (HRTEM) and Broadband Dielectric Spectroscopy (BDS) were considered. Electronic conductivities of LFPC samples at room temperature were found to decrease in a large frequency range upon simple immersion in polar solvents and to decrease further upon functionalization. Due to their high dipole moment, strongly physisorbed molecules detected by XPS likely add barriers to electron hopping. Significant alteration of the carbon coating conductivity was only observed, however, upon functionalization. This effect is most presumably associated with an increase in the sp(3) content determined by Raman spectroscopy, which is a strong indication of the formation of a covalent bond between the organic layer and the carbon coating. In this case, the electron flux appears to be redirected and relayed by short-range (intra chain) and long-range (inter chain) electron transport through molecular oligomers anchored at the LFPC surface. The latter are controlled by tunnelling and slightly activated hopping, which enable higher conductivity at low temperature (T < 250 K). Alteration of the electron transport within the carbon coating also allows detection of a relaxation phenomenon that corresponds to small polaron hopping in bulk LiFePO4. XPS and HRTEM images allow a clear correlation of these findings with the island type oligomeric structure of grafted molecules. PMID:25234701
Ab-initio Calculation of the XANES of Lithium Phosphates and LiFePO4
NASA Astrophysics Data System (ADS)
Yiu, Y. M.; Yang, Songlan; Wang, Dongniu; Sun, Xueliang; Sham, T. K.
Lithium iron phosphate has been regarded as a promising cathode material for the next generation lithium ion batteries due to its high specific capacity, superior thermal and cyclic stability [1]. In this study, the XANES (X-ray Absorption Near Edge Structure) spectra of lithium iron phosphate and lithium phosphates of various compositions at the Li K, P L3,2, Fe M3,2 and O K-edges have been simulated self-consistently using ab-initio calculations based on multiple scattering theory (the FEFF9 code) and DFT (Density Functional Theory, the Wien2k code). The lithium phosphates under investigation include LiFePO4, ?-Li3PO4, Li4P2O7 and LiPO3. The calculated spectra are compared to the experimental XANES recorded in total electron yield (TEY) and fluorescence yield (FLY). This work was carried out to assess the XANES of possible phases presented in LiFePO4 based Li ion battery applications [2].
LiFePO 4 safe Li-ion polymer batteries for clean environment
NASA Astrophysics Data System (ADS)
Zaghib, K.; Charest, P.; Guerfi, A.; Shim, J.; Perrier, M.; Striebel, K.
The performance of natural graphite-fibers/PEO-based gel electrolyte/LiFePO 4 cells (7 mAh, 4 cm 2) is reported. The gel polymer electrolytes were produced by electron-beam irradiation and then soaked in a liquid electrolyte. The natural graphite-fiber composite anode in gel electrolyte containing 1.5 M LiFSI-EC/GBL (1:3) exhibited high reversible capacity (361 mAh g -1) and high Coulombic efficiency (92%). The LiFePO 4 cathode in the same gel polymer exhibited a reversible capacity of 161 mAh g -1 and 93% Coulombic efficiency. A 1.5 M solution of LiFSI in ethylene carbonate (EC)/?-butyrolactone (GBL) (1:3, v/v) mixed solvent is advantageous for use as the electrolyte in the laminated film bag because of its high flame point (135 ░C), high boiling point (219 ░C), low vapor pressure and high conductivity (10.2 mS cm -1 at 20 ░C). The Li-ion gel polymer battery shows a very low capacity fade of 5% after 500 cycles and also has high-rate capability. The Li-ion gel polymer cell using LiFePO 4 cathodes is suitable for HEV applications.
Effect of Fe(III) impurity on the electrochemical performance of LiFePO 4 prepared by hydrothermal process
XiuQin Ou; ShengZhao Xu; GuangChuan Liang; Li Wang; Xia Zhao
Lithium iron phosphate (LiFePO4) was synthesized from LiOH, FeSO4 and H3PO4 by a hydrothermal process at 180░C. The samples were characterized by X-ray diffraction, scanning electron microscopy and\\u000a chemical analysis. Electrochemical performance of the samples was tested in terms of charge-discharge capacity and cycling\\u000a behavior. The results indicated that Fe(III) impurity had obviously effect on the electrochemical properties of LiFePO4,
Improvement of electrochemical and thermal stability of LiFePO 4 cathode modified by CeO 2
Yan Liu; Changhuan Mi; Changzhou Yuan; Xiaogang Zhang
CeO2-modified LiFePO4 cathode was synthesized by using the triblock copolymer poly(ethylene oxide)¢block¢poly(propylene oxide)¢block¢poly(ethane oxide) (P123) as a template. CeO2-modified (2wt.%), 5wt.% CeO2-modified and pristine LiFePO4 powders were characterized by XRD and SEM measurements. The electrochemical behaviors were investigated by cyclic voltammetry measurements in Li2SO4 aqueous electrolyte. It was shown that all compounds undergone lithium-ion deintercalation and intercalation upon oxidation and
Experimental and numerical study of phase transition of LiFePO 4 material in lithium ion batteries
NASA Astrophysics Data System (ADS)
Siddique, Md Noor E. Alam
Phase transition behavior of LiFePO4 material has been studied in this work. During electrochemical charge/discharge processes, LiFePO 4 transforms into FePO4 and this electrochemically driven phase transition of the two-phase system results in a potential plateau in a battery discharge curve. Besides, battery performance, especially under high rates, depends critically on this two-phase transition. However, this phase transition mechanism in the LiFePO4 crystal structure has yet not been understood in details. Developing better understanding is essential for designing high performing, safe and stable batteries. Currently available phase transition models for LiFePO4, such as the classical `core-shrinking model' and recently the `domino cascade model', have shed lights on the phase transition mechanism, however, with somewhat contradicting conclusions. The former predicted a continuous phase transition between LiFePO4 and FePO4 within an individual particle. In contrast, the latter, based on the fact of anisotropic diffusion of Li, provided a microscopically heterogeneous picture of phase transition: phase transition is abrupt, and de-lithiated and lithiated particles co-exist in a battery electrode. To achieve a better understanding of the two-phase transition phenomena, two specially designed sophisticated methods, i.e., in-situ Raman spectroscopy and in-situ X-ray Diffraction (XRD), have been developed in this work. The particle level phase transition of LiFePO4 was probed in the in-situ Raman study. Under slow-rate discharge/charge, it was found that the particles were either fully transformed or untransformed indicating that the phase transition in LiFePO4 material was not uniform at the particle level. Electronic conductivity and local electrode microstructure determined the preferred sequence of phase transition of the particles. This study also revealed that non-equilibrium phase transition occurred as a result of delayed phase transition. The in-situ XRD study attempted to investigate the bulk level phase transition behavior of LiFePO4 and was conducted at four different discharge rates. Analysis of the high-resolution diffraction patterns showed a gradual and continuous change in phase transition. Again, a delayed phase transition was observed at high-rate discharge due to the non-equilibrium pathway. From both in-situ Raman and in-situ XRD experiments, only two stoichiometric compounds (LiFePO4 and FePO4) was detected, indicating that during electrochemical charge/discharge processes once Li ion de-intercalates/intercalates, it immediately forms the end-members and no intermediate compounds exist. Particle size and morphology of LiFePO4 were also studied using numerical models in the phase transition behavior. At a slow discharge rate, plate shaped particles showed higher capacity than spherical particles and the opposite trend was observed at high discharge rates above some critical discharge rates. Big particles and high discharge rates induced non-equilibrium phase transition in the LiFePO4 particles which expands the miscibility gap between the end-members and gave sharp narrow two-phase interfaces.
Li ion diffusion mechanisms in LiFePO4: an ab initio molecular dynamics study.
Yang, Jianjun; Tse, John S
The mechanisms for thermal (self) diffusion of Li ions in fully lithiated LiFePO(4) have been investigated with spin polarized ab initio molecular dynamics calculations. The effect of electron correlation is taken into account with the GGA+U formalism. It was found that Li ion diffusion is not a continuous process but through a series of jumps from one site to another. A dominant process is the hopping between neighboring Li sites around the PO(4) groups, which results in a zigzag pathway along the crystallographic b-axis. This observation is in agreement with a recent neutron diffraction experiment. A second process involves the collaborative movements of the Fe ions leading to the formation of antisite defects and promotes Li diffusion across the Li ion channels. The finding of the second mechanism demonstrates the benefit of ab initio molecular dynamics simulation in sampling diffusion pathways that may not be anticipated. PMID:21932862
Improvement of overcharge performance using Li 4 Ti 5 O 12 as negative electrode for LiFePO 4 power battery
Wei Cui; Yan-Bing He; Zhi-Yuan Tang; Quan-Hong Yang; Qiang Xu; Fang-Yuan Su; Li Ma
Liquid state soft packed LiFePO4 cathode lithium ion cells with capacity of 2ĀAh were fabricated using graphite or Li4Ti5O12 as negative electrodes to investigate the 3ĀC\\/10ĀV overcharge characteristics at room temperature. The LiFePO4\\/Li4Ti5O12 cell remained safe after the 3ĀC\\/10ĀV overcharge test while the LiFePO4\\/graphite cell went to thermal runaway. Temperature and voltage variations during overcharge were recorded and analyzed. The
Small capacity decay of lithium iron phosphate (LiFePO 4) synthesized continuously in supercritical water: Comparison with solid-state method
Seung-Ah Hong; Su Jin Kim; Jaehoon Kim; Kyung Yoon Chung; Byung-Won Cho; Jeong Won Kang
Nanosize lithium iron phosphate (LiFePO4) particles are synthesized using a continuous supercritical hydrothermal synthesis method at 25MPa and 400░C under various flow rates. The properties of LiFePO4 synthesized in supercritical water including purity, crystallinity, atomic composition, particle size, surface area and thermal stability are compared with those of particles synthesized using a conventional solid-state method. Smaller size particles ranging 200¢800nm,
Current density and state of charge inhomogeneities in Li-ion battery cells with LiFePO 4 as cathode material due to temperature gradients
Matthias Fleckenstein; Oliver Bohlen; Michael A. Roscher; Bernard Bõker
Current density distributions and local state of charge (SoC) differences that are caused by temperature gradients inside actively cooled Li-ion battery cells are discussed and quantified. As an example, a cylindrical Li-ion cell with LiFePO4 as cathode material (LiFePO4-cell) is analyzed in detail both experimentally and by means of spatial electro-thermal co-simulations. The reason for current density inhomogeneities is found
Preparation and electrochemical characterization of LiFePO 4 nanoparticles with high rate capability by a sol¢gel method
S. B. Lee; I. C. Jang; H. H. Lim; V. Aravindan; H. S. Kim; Y. S. Lee
The synthesis of LiFePO4 nanoparticles by an adipic acid-assisted sol¢gel route has been optimized based on cycling and structural analysis. Formation of the crystalline phase was investigated through thermogravimetric-differential thermal analysis (TG-DTA). Among the optimized conditions, a 0.5 molar ratio of the adipic acid to total metal ions at a 670░C calcination temperature under an Ar atmosphere yielded LiFePO4 particles
Quantifying the effects of strains on the conductivity and porosity of LiFePO 4 based Li-ion composite cathodes using a multi-scale approach
Ali Awarke; Sven Lauer; Michael Wittler; Stefan Pischinger
The effects of the lithium concentration-induced and external load-induced strains on the porosity and electrical conductivity of a LiFePO4 based Li-ion composite cathode are within the focus of this paper. A micro finite element analysis is first performed considering the arrangement and interaction of the particles in a representative volume element (RVE) of a LiFePO4¢PVDF mixture. The aim is to
Domain structure in Delithiated LiFePO 4 , a cathode material for Li ion Battery Applications
M. Kinyanjui; A. Chuvilin; U. Kaiser; P. Axmann; M. Wohlfahrt-Mehrens
Delithiation is a basic step in the operation of the Li ion battery and it involves the extraction of Li ions from the lattice\\u000a of the cathode material and insertion into the lattice of the anode. LiFePO4 is a cathode material whose wide application in high energy Li ion batteries, is limited by low ion and electron diffusion\\u000a [1]. Partially
Porous, carbon-decorated LiFePO 4 prepared by sol¢gel method based on citric acid
Miran Gaberscek; Robert Dominko; Marjan Bele; Maja Remskar; Darko Hanzel; Janko Jamnik
A new type of LiFePO4¢carbon composite cathode material was prepared. The active component consists of micrometer-sized particles containing pores with wide distribution of sizes. When filled with electrolyte, the pores are responsible for supply of ions while the distance between the pores (30¢150 nm) determines the solid-state diffusion kinetics. The walls of pores are covered with a carbon layer which
LiFePO 4-based electrode using micro-porous current collector for high power lithium ion battery
Masaru Yao; Kazuki Okuno; Tsutomu Iwaki; Masahiro Kato; Shigeo Tanase; Katsuji Emura; Tetsuo Sakai
In order to improve the power performance of the lithium ion battery based on lithium iron phosphate (LiFePO4), a new methodology using a three-dimensional micro-porous current collector was described. The three-dimensional current collector was manufactured based on foamed polyurethane and nickel¢chromium alloy. The cell using the three-dimensional current collector exhibited a superior high-rate discharge capability as compared to a conventional-type
Simulation and experiment of thermal energy management with phase change material for ageing LiFePO 4 power battery
Zhonghao Rao; Shuangfeng Wang; Guoqing Zhang
Thermal energy management performance of ageing commercial rectangular LiFePO4 power batteries using phase change material (PCM) and thermal behavior related to thermal conductivity between the PCM and the cell are discussed in this paper. The heat sources are simplified according to the experimental results of the cells discharged at 35A (?5C). 3-D modules of a single cell and battery pack
Performance of LiFePO 4 as lithium battery cathode and comparison with manganese and vanadium oxides
Shoufeng Yang; Yanning Song; Katana Ngala; Peter Y. Zavalij; M. Stanley Whittingham
LiFePO4 was synthesized by a high temperature method and high purity was confirmed by both powder X-ray diffraction and thermal analysis. It can deliver 136Ah\\/kg, 80% of theoretical capacity at 1mA\\/cm2 at high cathode load levels at room temperature; 100% capacity can be obtained by raising the temperature to 60░C or reducing the discharge rate to 0.1mA\\/cm2. The method of
Optimization of reaction condition for solid-state synthesis of LiFePO 4-C composite cathodes
NASA Astrophysics Data System (ADS)
Zhang, S. S.; Allen, J. L.; Xu, K.; Jow, T. R.
We optimized synthesis condition of LiFePO 4-C composites by solid-state reaction of LiH 2PO 4 and FeC 2O 4Ę2H 2O in the presence of carbon powder. The preparation was conducted under a N 2 flow through two heating steps. First, the starting materials were thoroughly mixed in a stoichiometric ratio and decomposed at 350-380 ░C to form the precursor. Second, the resulting precursor was heated at a high temperature to form the crystalline phase LiFePO 4. For formation of the precursor, the optimized temperature was 350 ░C for LiFePO 4 and 380 ░C for LiFePO 4-C composites, respectively. For formation of crystalline phase composites, the optimized condition was to heat the precursor in a pelletized form at 800 ░C for 5 h, and the optimized content of carbon was 3-10 wt.%. In composites, the carbon not only increases the rate capability, but also enhances capacity stability. We found that capacity of the composites increases with specific surface area of carbon. The best result was observed from a composite made of 8.7 wt.% of black pearls BP 2000 having a specific surface area of 1500 m 2 g -1. At room temperature and low current rate (0.02 C), such a composite shows a specific capacity of 159 mAh g -1. Electrochemical properties and cycling performance of the optimized composite also were evaluated.
X-ray Diffraction and Polarized X-ray Absorption Study of Single Crystal LiFePO4
NASA Astrophysics Data System (ADS)
Liang, Gan; Benson, Ron; Li, Jiying; Vaknin, David; Croft, Mark
Large size LiFePO4 single crystals have been grown by standard flux growth technique with the LiCl as the flux. Single crystal x-ray diffraction (XRD) and synchrotron polarized x-ray absorption spectroscopy (XAS) measurements have been performed on the crystals. The XRD measurements were performed at T = 293 K using Mo K? radiation (? = 0.7107Õ) to a resolution corresponding to sin?/? = 0.6486 Õ-1, with 2?max = 54.9 . A total number of 1330 reflections were processed with 350 unique data. The obtained crystal structure data were the following: lithium iron (II) phosphate, LiFePO4, orthorhombic, space group Pnma, lattice constants: a = 10.3172 (11) Õ, b = 6.0096(8) Õ, c = 4.6775 (4) Õ, Z = 4, formula weight: 157.76, density: 3.613, ? = 55.562 cm-1. The bond lengths between Fe and O and between P and O were obtained. The polarized XAS was performed at the Fe K-edge with the x-ray E-vector along the a-, b-, and c-axis. The XAS results show that the Fe ions in the LiFePO4 single crystals are divalent. We also observed a big shift in both the energies of the pre-edge 1s -> 3d transition feature and the main edge when the polarization direction of the E-vector changes from along a-axis to along c-axis.
Role of PO4 tetrahedron in LiFePO4 and FePO4 system.
Zeng, Yuewu
Using high resolution transmission electron microscopy with image simulation and Fourier analysis, the Li1- x FePO4 (x?0.01), Li1- x FePO4 (x ? 0.5), and FePO4 particles, prepared by charging or discharging the 053048 electrochemical cells (thickness: 5 mm, width: 30 mm, height: 48 mm) and dismantled inside an Ar-filled dry box, were investigated. The high resolution images reveal: (1) the solid solution of Li1- x FePO4 (x?0.01) contains some missing Li ions leading PO4 group distorted around M1 tunnel of the unit cell; (2) the texture of the particles of Li1- x FePO4 (x ?0.5) has homogeneously distributed compositional domains of LiFePO4 and FePO4 resulting from spinodal decomposition which promote Li ion easily getting into the particle due to uphill diffusion, (3) the particles of FePO4 formed in charging have heavily distorted lattice and contain some isolated LiFePO4 , (4) interface between LiFePO4 and FePO4 and between amorphous and crystal region provides the lattice distortion of small polarons. Microsc. Res. Tech. 78:462-471, 2015. ® 2015 Wiley Periodicals, Inc. PMID:25846750
Excellent Temperature Performance of Spherical LiFePO4/C Composites Modified with Composite Carbon and Metal Oxides
Zhang, Bao; Zeng, Tao; Zhang, Jiafeng; Peng, Chunli; Zheng, Junchao; Chen, Guomin
Nanosized spherical LiFePO4/C composite was synthesized from nanosized spherical FePO4Ę2H2O, Li2C2O4, aluminum oxide, titanium oxide, oxalic acid, and sucrose by binary sintering process. The phases and morphologies of LiFePO4/C were characterized using SEM, TEM, CV, EIS, EDS, and EDX as well as charging and discharging measurements. The results showed that the as-prepared LiFePO4/C composite with good conductive webs from nanosized spherical FePO4Ę2H2O exhibits excellent electrochemical performances, delivering an initial discharge capacity of 161.7?mAhĘg?1 at a 0.1?C rate, 152.4?mAhĘg?1 at a 1?C rate and 131.7?mAhĘg?1 at a 5?C rate, and the capacity retention of 99.1%, 98.7%, and 95.8%, respectively, after 50 cycles. Meanwhile, the high and low temperature performance is excellent for 18650 battery, maintaining capacity retention of 101.7%, 95.0%, 88.3%, and 79.3% at 55░C, 0░C, ?10░C, and ?20░C by comparison withthat of room temperature (25░C) at the 0.5 C rate over a voltage range of 2.2?V to 3.6?V, respectively. PMID:24526888
Thermal analyses of LiFePO4/graphite battery discharge processes
NASA Astrophysics Data System (ADS)
Jiang, Fangming; Peng, Peng; Sun, Yiqiong
An electrochemical-thermal coupling model is developed to describe the LiFePO4/graphite battery discharge and charge processes. Various heat generations/consumptions including Joule heat, reversible entropy heat, contact resistance heat, irreversible electrochemical reaction heat, ionic migration heat, and convective heat release to the ambient during charge or discharge processes are calculated in detail. The developed model is first validated by experimental data. Then systematic and comprehensive thermal analyses with respect to various discharge processes are performed based on the simulated results. For the specific cell considered, the irreversible electrochemical reaction heat and contact resistance heat are found to be the two main heat generation sources; for discharge processes of higher C-rate, the contact resistance heat take more proportion of the total heat generation as it is directly proportional to the squared discharge current density; the ionic migration heat is a sink with magnitude being about 1/3 of the Joule heat. The reversible entropy heat changes its sign from a negative heat sink to a positive heat source during a discharge process and its changing magnitude may be comparable to the irreversible electrochemical reaction heat for all the discharge processes of different C-rates.
Ab initio study of the migration of small polarons in olivine LixFePO4 and their association with lithium ions and vacancies
Thomas Maxisch; Fei Zhou; Gerbrand Ceder
Using first-principles pseudopotential calculations, we investigate the formation and transport of small polarons in olivine LixFePO4 . It is demonstrated that excess charge carriers form small polarons in LiFePO4 and FePO4 . Lower limits to the activation barrier for small polaron migration are calculated within the GGA+U framework. Additionally, the interaction between lithium ions and polarons is investigated and estimates
Synthesis and electrochemical characterizations of nano-crystalline LiFePO 4 and Mg-doped LiFePO 4 cathode materials for rechargeable lithium-ion batteries
D. Arumugam; G. Paruthimal Kalaignan; P. Manisankar
Nano-crystalline LiFePO4 and LiMg0.05Fe0.95PO4 cathode materials were synthesized by sol¢gel method in argon atmosphere using succinic acid as a chelating agent. Physico-chemical\\u000a characterizations were done by thermogravimetric and differential thermal analysis, X-ray diffraction, scanning electron microscopy,\\u000a transmittance electron microscopy, and Raman spectroscopy. Electrochemical behavior of the cathode materials were analyzed\\u000a using cyclic voltammetry, and galvanostatic charge\\/discharge cycling studies were employed
Effect of complexing agents on the electrochemical performance of LiFePO4/C prepared by sol-gel method
LiFePO4/C is synthesized via sol-gel method using Fe3+ as iron sources and different complexing agents, followed by sintering at high temperature for crystallization. The amount of carbon in these composites is less than 6.8 wt.%, and the X-ray diffraction experiment confirms that all samples are pure single phase indexed with the orthorhombic Pnma space group. The particle size of the LiFePO4/C synthesized by acetic acid as a complexing agent is very fine with a size of 200 nm. The electrochemical performance of this material, including reversible capacity, cycle number, and charge-discharge characteristics, is better than those of LiFePO4/C synthesized by other complexing agents. The cell of this sample can deliver a discharge capacity of 161.1 mAh g-1 at the first cycle. After 30 cycles, the capacity decreases to 157.5 mAh g-1, and the capacity fading rate is 2.2%. The mechanism is studied to explain the effect of a complexing agent on the synthesis of LiFePO4/C by sol-gel method. The results show that the complexing agent with a low stability constant may be proper for the synthetic process of LiFePO4/C via sol-gel method. PMID:22221711
Synthesis of the LiFePO4/C core-shell nanocomposite using a nano-FePO4/polythiophene as an iron source
NASA Astrophysics Data System (ADS)
Liu, Jing; Yang, Guiling; Zhang, Xianfa; Wang, Jiawei; Wang, Rongshun
For the first time, a LiFePO4/C core-shell nanocomposite has been synthesized using a nano-FePO4/polythiophene (PTh) as an iron source. With this method, the PTh is in situ polymerized to restrain the growth of FePO4 particles, and the typical size of FePO4/PTh particles is in the range of 20-50 nm. The optimized LiFePO4/C nanocomposite is synthesized at 750 ░C using 40% citric acid. The prepared LiFePO4 particles show a typical size of 50-100 nm and they are fully coated by carbon of 2-4 nm thickness. The LiFePO4/C core-shell nanocomposite gives an improved high electronic conductivity and a good electrochemical behavior at high rates. Thus, this novel method is an effective and facile strategy to improve the rate performance of the LiFePO4 cathode.
Long-term cycle stability at a high current for nanocrystalline LiFePO4 coated with a conductive polymer
NASA Astrophysics Data System (ADS)
Dinh, Hung-Cuong; Lim, Hanjo; Park, Ki Dong; Yeo, In-Hyeong; Kang, Yongku; Mho, Sun-il
Highly uniform hierarchical-microstructured LiFePO4 particles with dumbbell- and donut-shape and individual LiFePO4 nanocrystals were prepared by a hydrothermal method utilizing citric acid or a triblock copolymer (Pluronic P123) as a surfactant. The cathode composed of the individual nanocrystalline LiFePO4 particles exhibited higher specific capacity than the cathodes composed of the hierarchically assembled microparticles. Coating a conductive polymer, poly-3,4-ethylenedioxythiophene (PEDOT), on the surface of LiFePO4 particles improved the battery performances such as large specific capacities, high rate capability and an improved cycle stability. The nanocrystalline LiFePO4 particles coated with PEDOT (20 wt%) exhibited the highest discharge capacities of 175 and 136 mAh g?1 for the first battery cycle and 163 and 128 mAh g?1 after 500 battery cycles, with a degradation rate of 6¢7%, at the rates of 1 and 10 C, respectively.
Etched colloidal LiFePO4 nanoplatelets toward high-rate capable Li-ion battery electrodes.
Paolella, Andrea; Bertoni, Giovanni; Marras, Sergio; Dilena, Enrico; Colombo, Massimo; Prato, Mirko; Riedinger, Andreas; Povia, Mauro; Ansaldo, Alberto; Zaghib, Karim; Manna, Liberato; George, Chandramohan
LiFePO4 has been intensively investigated as a cathode material in Li-ion batteries, as it can in principle enable the development of high power electrodes. LiFePO4, on the other hand, is inherently "plagued" by poor electronic and ionic conductivity. While the problems with low electron conductivity are partially solved by carbon coating and further by doping or by downsizing the active particles to nanoscale dimensions, poor ionic conductivity is still an issue. To develop colloidally synthesized LiFePO4 nanocrystals (NCs) optimized for high rate applications, we propose here a surface treatment of the NCs. The particles as delivered from the synthesis have a surface passivated with long chain organic surfactants, and therefore can be dispersed only in aprotic solvents such as chloroform or toluene. Glucose that is commonly used as carbon source for carbon-coating procedure is not soluble in these solvents, but it can be dissolved in water. In order to make the NCs hydrophilic, we treated them with lithium hexafluorophosphate (LiPF6), which removes the surfactant ligand shell while preserving the structural and morphological properties of the NCs. Only a roughening of the edges of NCs was observed due to a partial etching of their surface. Electrodes prepared from these platelet NCs (after carbon coating) delivered a capacity of ? 155 mAh/g, ? 135 mAh/g, and ? 125 mAh/g, at 1 C, 5 C, and 10 C, respectively, with significant capacity retention and remarkable rate capability. For example, at 61 C (10.3 A/g), a capacity of ? 70 mAh/g was obtained, and at 122 C (20.7 A/g), the capacity was ? 30 mAh/g. The rate capability and the ease of scalability in the preparation of these surface-treated nanoplatelets make them highly suitable as electrodes in Li-ion batteries. PMID:25372361
Etched Colloidal LiFePO4 Nanoplatelets toward High-Rate Capable Li-Ion Battery Electrodes
LiFePO4 has been intensively investigated as a cathode material in Li-ion batteries, as it can in principle enable the development of high power electrodes. LiFePO4, on the other hand, is inherently ōplaguedö by poor electronic and ionic conductivity. While the problems with low electron conductivity are partially solved by carbon coating and further by doping or by downsizing the active particles to nanoscale dimensions, poor ionic conductivity is still an issue. To develop colloidally synthesized LiFePO4 nanocrystals (NCs) optimized for high rate applications, we propose here a surface treatment of the NCs. The particles as delivered from the synthesis have a surface passivated with long chain organic surfactants, and therefore can be dispersed only in aprotic solvents such as chloroform or toluene. Glucose that is commonly used as carbon source for carbon-coating procedure is not soluble in these solvents, but it can be dissolved in water. In order to make the NCs hydrophilic, we treated them with lithium hexafluorophosphate (LiPF6), which removes the surfactant ligand shell while preserving the structural and morphological properties of the NCs. Only a roughening of the edges of NCs was observed due to a partial etching of their surface. Electrodes prepared from these platelet NCs (after carbon coating) delivered a capacity of ?155 mAh/g, ?135 mAh/g, and ?125 mAh/g, at 1 C, 5 C, and 10 C, respectively, with significant capacity retention and remarkable rate capability. For example, at 61 C (10.3 A/g), a capacity of ?70 mAh/g was obtained, and at 122 C (20.7 A/g), the capacity was ?30 mAh/g. The rate capability and the ease of scalability in the preparation of these surface-treated nanoplatelets make them highly suitable as electrodes in Li-ion batteries. PMID:25372361
Effects of neodymium aliovalent substitution on the structure and electrochemical performance of LiFePO 4
Xian Zhao; Xiaozhen Tang; Li Zhang; Minshou Zhao; Jing Zhai
LiFe1?xNdxPO4\\/C (x=0¢0.08) cathode material was synthesized using a solid-state reaction. The synthesis conditions were optimized by thermal analysis of the precursor and magnetic properties of LiFePO4\\/C. The structure and electrochemical performances of the material were studied using XRD, FE-SEM, EDS, electrochemical impedance spectroscopy and galvanostatic charge¢discharge. The results show that a small amount of aliovalent Nd3+ ion-dopant substitution on Fe2+
Li-Ion Battery with LiFePO4 Cathode and Li4Ti5O12 Anode for Stationary Energy Storage
Wang, Wei; Choi, Daiwon; Yang, Zhenguo
i-ion batteries based on commercially available LiFePO4 cathode and Li4Ti5O12 anode were investigated for potential stationary energy storage applications. The full cell that operated at flat 1.85V demonstrated stable cycling for 200 cycles followed by a rapid fade. A significant improvement in cycling stability was achieved via Ketjen black coating of the cathode. A Li-ion full cell with Ketjen black modified LiFePO4 cathode and an unmodified Li4Ti5O12 anode exhibited negligible fade after more than 1200 cycles with a capacity of ~130mAh/g. The improved stability, along with its cost-effectiveness, environmentally benignity and safety, make the LiFePO4/ Li4Ti5O12 Li-ion battery a promising option of storing renewable energy.
Impedance Spectroscopy Studies of Nano-Crystalline LiFePO4 Cathode Synthesized by Hydrothermal Method
NASA Astrophysics Data System (ADS)
Rosaiah, P.; Hussain, O. M.
LiFePO4 has become of great interest as storage cathodes for rechargeable lithium batteries because of their high energy density, low raw materials cost, environmental friendliness, high thermal stability. In the present investigation, lithium iron phosphate (LiFePO4) cathode material has been prepared by using hydrothermal synthesis. The structure of the sample has been studies by using X-ray diffraction. The XRD spectrum exhibited different characteristic peaks along with (311) predominant orientation corresponding to an orthorhombic crystal structure with Pnma space group. Electrical and dielectric properties were studied over a frequency range of 1 Hz - 1 MHz at different temperatures. The electrical conductivity was found to be increased with increasing temperature following Arrhenius relation with an estimated activation energy of 0.44 eV. The dielectric properties were analyzed in the framework of complex dielectric permittivity and complex electric modulus formalisms. The evolution of the complex permittivity as a function of frequency and temperature was investigated. Several important parameters such as activation energy, ionic hopping frequency, carrier concentration, ionic mobility and diffusion coefficient etc, were determined.
Sequential Monte Carlo filter for state estimation of LiFePO4 batteries based on an online updated model
NASA Astrophysics Data System (ADS)
Li, Jiahao; Klee Barillas, Joaquin; Guenther, Clemens; Danzer, Michael A.
Battery state monitoring is one of the key techniques in battery management systems e.g. in electric vehicles. An accurate estimation can help to improve the system performance and to prolong the battery remaining useful life. Main challenges for the state estimation for LiFePO4 batteries are the flat characteristic of open-circuit-voltage over battery state of charge (SOC) and the existence of hysteresis phenomena. Classical estimation approaches like Kalman filtering show limitations to handle nonlinear and non-Gaussian error distribution problems. In addition, uncertainties in the battery model parameters must be taken into account to describe the battery degradation. In this paper, a novel model-based method combining a Sequential Monte Carlo filter with adaptive control to determine the cell SOC and its electric impedance is presented. The applicability of this dual estimator is verified using measurement data acquired from a commercial LiFePO4 cell. Due to a better handling of the hysteresis problem, results show the benefits of the proposed method against the estimation with an Extended Kalman filter.
Safety properties of liquid state soft pack high power batteries with carbon-coated LiFePO 4 \\/graphite electrodes
Yan-Bing He; Guo-Wei Ling; Zhi-Yuan Tang; Quan-Sheng Song; Quan-Hong Yang; Wu Chen; Wei Lv; Yan-Jun Su; Qiang Xu
The carbon-coated LiFePO4 materials were synthesized, and their structure and morphology were characterized by X-ray diffraction and transmission electron\\u000a microscopy. The safety and heating mechanism of the 066094-type liquid state soft pack high power batteries with carbon-coated\\u000a LiFePO4\\/graphite electrodes under abusive conditions, such as overcharge, overdischarge, and short current were extensively investigated.\\u000a It was found that the increase in the
Effect of synthesis temperature and molar ratio of organic lithium salts on the properties and electrochemical performance of LiFePO 4 \\/C composites
Zhongqi Shi; Ming Huang; Kerun Yang; Xuebu Hu; Bin Tan; Xinglan Huang; Zhenghua Deng
LiFePO4\\/C cathode materials were synthesized through in situ solid-state reaction route using Fe2O3, NH4H2PO4, Li2C2O4, and lithium polyacrylate as raw materials. The precursor of LiFePO4\\/C was investigated by thermogravimetric\\/differential thermal analysis. The effects of synthesis temperature and molar ratio\\u000a of organic lithium salts on the performance of samples were characterized by X-ray diffraction, scanning electron microscopy,\\u000a electrochemical impedance spectra, cyclic
Improved electrochemical performances of 9LiFePO 4ĘLi 3V 2(PO 4)\\/C composite prepared by a simple solid-state method
J. Y. Xiang; J. P. Tu; L. Zhang; X. L. Wang; Y. Zhou; Y. Q. Qiao; Y. Lu
9LiFePO4ĘLi3V2(PO4)3\\/C is synthesized via a carbon thermal reaction using petroleum coke as both reduction agent and carbon source. The as-prepared material is not a simple mixture of LiFePO4 (LFP) and Li3V2(PO4)3 (LVP), but a composite possessing two phases: one is V-doped LFP and the other is Fe-doped LVP. The typical structure enhances the electrical conductivity of the composite and improves
C-containing LiFePO 4 materials Ś Part II: Electrochemical characterization
M. Maccario; L. Croguennec; F. Weill; F. Le Cras; C. Delmas
A series of carbon-coated olivine phase (C¢LiFePO4) was synthesized under argon by mechano-chemical activation, with two thermal-treatments (ōslowö or ōfastö) and two temperatures (575Ā░C or 800Ā░C). In spite of similar chemical and structural properties, they showed rather good, but very different, electrochemical behaviors in long range cycling or high rate conditions. All the studied C¢LiFePO4 materials were characterized by an
Effect of C and Au additives produced by simple coaters on the surface and the electrochemical properties of nanosized LiFePO 4
Julißn Morales; Rafael Tr¾coli; Enrique RodrĒguez-Castell¾n; Sylvain Franger; Jes·s Santos-Pe±a
We examined the use of two conductive additives (C and Au) to boost the performance of lithium iron phosphate as a positive electrode material for lithium ion batteries. The phosphate was prepared by using a new, fast synthetic method that provides nanosized particles. Carbon and gold were sputtered on LiFePO4. Additional sample was an intimate mixture of carbon and phosphate
Current density and state of charge inhomogeneities in Li-ion battery cells with LiFePO4 as cathode material due to temperature gradients
NASA Astrophysics Data System (ADS)
Fleckenstein, Matthias; Bohlen, Oliver; Roscher, Michael A.; Bõker, Bernard
Current density distributions and local state of charge (SoC) differences that are caused by temperature gradients inside actively cooled Li-ion battery cells are discussed and quantified. As an example, a cylindrical Li-ion cell with LiFePO4 as cathode material (LiFePO4-cell) is analyzed in detail both experimentally and by means of spatial electro-thermal co-simulations. The reason for current density inhomogeneities is found to be the local electrochemical impedance varying with temperature in different regions of the jelly roll. For the investigated cell, high power cycling and the resulting temperature gradient additionally cause SoC-gradients inside the jelly roll. The local SoCs inside one cell diverge firstly because of asymmetric current density distributions during charge and discharge inside the cell and secondly because of the temperature dependence of the local open circuit potential. Even after long relaxation periods, the SoC distribution in cycled LiFePO4-cells remains inhomogeneous across the jelly roll as a result of hysteresis in the open circuit voltage. The occurring thermal electrical inhomogeneities are expected to influence local aging differences and thus, global cell aging. Additionally the occurrence of inhomogeneous current flow and SoC-development inside non-uniformly cooled battery packs of parallel connected LiFePO4-cells is measured and discussed.
Desired crystal oriented LiFePO4 nanoplatelets in situ anchored on a graphene cross-linked conductive network for fast lithium storage
NASA Astrophysics Data System (ADS)
Wang, Bo; Liu, Anmin; Abdulla, Wael Al; Wang, Dianlong; Zhao, X. S.
Electron transfer and lithium ion diffusion rates are the key factors limiting the lithium ion storage in anisotropic LiFePO4 electrodes. In this work, we employed a facile solvothermal method to synthesize a ``platelet-on-sheet'' LiFePO4/graphene composite (LFP@GNs), which is LiFePO4 nanoplatelets in situ grown on graphene sheets with highly oriented (010) facets of LiFePO4 crystals. Such a two-phase contact mode with graphene sheets cross-linked to form a three-dimensional porous network is favourable for both fast lithium ion and electron transports. As a result, the designed LFP@GNs displayed a high rate capability (~56 mA h g-1 at 60 C) and long life cycling stability (~87% capacity retention over 1000 cycles at 10 C). For comparison purposes, samples ex situ modified with graphene (LFP/GNs) as well as pure LiFePO4 platelets (LFP) were also prepared and investigated. More importantly, the obtained LFP@GNs can be used as a basic unit for constructing more complex structures to further improve electrochemical performance, such as coating the exposed LFP surface with a thin layer of carbon to build a C@LFP@GN composite to further enhance its cycling stability (~98% capacity retention over 1000 cycles at 10 C).Electron transfer and lithium ion diffusion rates are the key factors limiting the lithium ion storage in anisotropic LiFePO4 electrodes. In this work, we employed a facile solvothermal method to synthesize a ``platelet-on-sheet'' LiFePO4/graphene composite (LFP@GNs), which is LiFePO4 nanoplatelets in situ grown on graphene sheets with highly oriented (010) facets of LiFePO4 crystals. Such a two-phase contact mode with graphene sheets cross-linked to form a three-dimensional porous network is favourable for both fast lithium ion and electron transports. As a result, the designed LFP@GNs displayed a high rate capability (~56 mA h g-1 at 60 C) and long life cycling stability (~87% capacity retention over 1000 cycles at 10 C). For comparison purposes, samples ex situ modified with graphene (LFP/GNs) as well as pure LiFePO4 platelets (LFP) were also prepared and investigated. More importantly, the obtained LFP@GNs can be used as a basic unit for constructing more complex structures to further improve electrochemical performance, such as coating the exposed LFP surface with a thin layer of carbon to build a C@LFP@GN composite to further enhance its cycling stability (~98% capacity retention over 1000 cycles at 10 C). Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr01831e
Image based modelling of microstructural heterogeneity in LiFePO4 electrodes for Li-ion batteries
NASA Astrophysics Data System (ADS)
Cooper, S. J.; Eastwood, D. S.; Gelb, J.; Damblanc, G.; Brett, D. J. L.; Bradley, R. S.; Withers, P. J.; Lee, P. D.; Marquis, A. J.; Brandon, N. P.; Shearing, P. R.
Battery and fuel cell simulations commonly assume that electrodes are macro-homogeneous and isotropic. These simulations have been used to successfully model performance, but give little insight into predicting failure. In Li-ion battery electrodes, it is understood that local tortuosity impacts charging rates, which may cause increased degradation. This report describes a novel approach to quantifying tortuosity based on a heat transfer analogy applied to X-ray microscopy data of a commercially available LiFePO4 electrode. This combination of X-ray imaging and image-based simulation reveals the microscopic performance of the electrode; notably, the tortuosity was observed to vary significantly depending on the direction considered, which suggests that tortuosity might best be quantified using vectors rather than scalars.
Nonequilibrium Phase Transformation and Particle Shape Effect in LiFePO4 Materials for Li-Ion Batteries
Mukherjee, Partha P [ORNL
The nonequilibrium phase transformation and particle shape effects in LiFePO4 materials of Li-ion batteries are explored in this work. A continuum model employing the mushy-zone (MZ) approach, accounting for sluggish Li diffusion across the two-phase boundary, has been developed to study the kinetically-induced nonequilibrium phenomenon in Li-ion batteries. A theoretical analysis is presented to show that the nonequilibrium miscibility gap expands and shifts to higher Li composition at high discharge rates, due to insufficient compositional readjustments at the two-phase boundary. Furthermore, critical effects of particle shape on nonequilibrium phase transformation and discharge capacity have been discovered by the model.
NSDL National Science Digital Library
Keith Putirka
This assignment is ostensibly about geothermometry, but is also part of a sequence of assignments where students learn about mineral components Ō what they represent (in regards to solid solution phenomena especially), and how they calculated. I begin with olivine because its components are simple, and reasonably good thermometers do not require long equations. I also use this assignment to teach about binary solid solutions and phase diagrams, though the interpretations of such are based within other assignments. This is part of a sequence of assignments where students learn about mineral components Ō what they represent (in regards to solid solution phenomena especially), and how they calculated. Though students will not use a binary solid solution diagram per se, I use this HW assignment to re-emphasize such concepts. This assignment also allows students to begin tests of equilibrium, so they must understand the concept and use of an equilibrium constant.
Synthesis, characterization and modification of LiFePO4 by doping with platinum and palladium for lithium-ion batteries
NASA Astrophysics Data System (ADS)
Talebi-Esfandarani, Majid
Lithium iron phosphate (LiFePO4) with features of excellent thermal stability, non-toxicity, low cost and abundance in nature is one of the most promising cathode materials to be used in lithium ion batteries. However, as it suffers from the low electrical conductivity and poor ionic diffusion, it operates only at low charge/discharge current rates. In this thesis, a dual approach of metal doping and carbon coating was employed to solve the aforementioned problem. This work is mainly on the study, for the first time, of the effect of platinum and palladium doping of LiFePO 4 on its physical-chemical properties. The effect of Pt and Pd doping on the LiFePO4 performance as Li-ion cathode will be also shown. Sol-gel and hydrothermal methods were used to synthesize the LiFePO4 and doped-LiFePO4 cathode materials. The prepared materials were characterized using different methods such as XRD (X-ray Diffraction), XPS (X-ray Photoelectron Spectroscopy), SEM (Scanning Electron Microscopy) and BET (Brunauer Emmett Teller). The electrochemical characterization techniques including charge/discharge test, CV (Cyclic Voltammetry), EIS (Electrochemical Impedance Spectroscopy) and cycling were also used. The effects of metals doping on chemical-physical properties, particles sizes, morphology, structure and purity of the electrodes were investigated and their correlation to the electrochemical properties of materials were studied. In the first section, we determine the optimized amount of carbon support and morphology of the particles using SEM which help to obtain LiFePO 4/C cathode material with an excellent electrochemical performance. It was found that when the amount of coated carbon exceeds the optimized value, the discharge capacity of the LiFePO4/C material decreased. This might indicate a low diffusion of the Li+ ions through the carbon layers during the charge/discharge process. On the other hand, for LiFePO4 coated with carbon quantity lower than the optimum value, LiFePO4/C cathode exhibited poor capacity performance due to its low electrical conductivity. Therefore, both the quality and quantity of carbon coating on the surface of LiFePO4 particles are important and only optimized carbon content can lead to a more uniform carbon distribution. Optimized surface area and conductivity, which give high electrochemical performance, can be only achieved if the appropriate carbon content and method of electrode preparation are obtained. In the second part, the effect of doping the LiFePO4/C electrodes with Pt and Pd on the structure, their chemical compositions and electrochemical properties were investigated. The electrodes were prepared using sol-gel method. The chemical composition analysis by XPS of the Pd doped electrodes showed that Pd was detected in the Pd-doped nano composite materials. Also, for Pt doped electrode, Pt was detected in Pt-doped based nano composite materials. Based on the structure and morphology of the non doped and doped electrodes, the results showed that palladium doping facilitated formation of Li 3PO4 impurity in the LiFe0.98Pd0.02PO 4/C and LiFe0.96Pd0.04PO4/C electrodes. Consequently the presence of the Pd in the doped sample reduced the lattice parameters, increased the size of particles and caused their agglomeration. The electrochemical performances of the electrodes showed that their specific capacity decreased when the palladium content increases. Then, the Pd-doped electrodes fabricated using sol-gel method exhibit less discharge capacity than samples of the non-doped LiFePO4/C electrode. The reduction in the level of performance is attributed to several reasons such as the shrinking of the lattice parameters, the formation of Li3PO4 impurity phase, and large particles size. In contrast, for LiFePO4/C doped with Pt using sol-gel method, it was found that the crystallinity and the lattice parameters of LiFe 0.96Pt0.04PO4/C nanocomposite material increased when compared with LiFePO4/C electrode. No impurity was formed in the Pt-doped electrode. In addition, the Pt doped samples exhibited smalle
Synthesis of LiFePO4/C cathode materials by carbothermal reduction method using two kinds of Fe3+ precursors
NASA Astrophysics Data System (ADS)
Zhong, M. E.; Zhou, Z. T.
LiFePO4/C cathode materials were synthesized by carbothermal reduction method using FePO4 and citrate ferric (FeC6H5O7Ę5H2O) as Fe3+ precursors. The samples were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), X-ray photoelectron spectrometry (XPS) and charge-discharge test. The results showed that both the crystallization degree and particle size increased markedly with the increase of synthesis temperature. Among the synthesized cathode materials, LiFePO4/C prepared at 650░C showed the best electrochemical properties with an initial discharge specific capacity of 138 mAhĘg-1 at 0.2 C, 128 mAhĘg-1 at 0.5 C and 116 mAhĘg-1 at 1.0 C, respectively.
The effect of Cr doping on Li ion diffusion in LiFePO4 from first principles investigations and Monte Carlo simulations
C Y Ouyang; S Q Shi; Z X Wang; H Li; X J Huang; L Q Chen
Using the adiabatic trajectory method, the migration energy barriers for the migration of Li ions and Cr ions along the one-dimensional diffusion pathway in pure and Cr doped LiFePO4 are obtained from first principles calculations. The results show that while Li ions can diffuse along the diffusion pathway easily, Cr ions do not easily diffuse away from their initial positions.
Fine-particle lithium iron phosphate LiFePO 4 synthesized by a new low-cost aqueous precipitation technique
G Arnold; J Garche; R Hemmer; S Str÷bele; C Vogler; M Wohlfahrt-Mehrens
Phase pure, homogeneous, and well-crystallized lithium iron phosphate LiFePO4 was synthesized by aqueous co-precipitation of an Fe(II) precursor material and succeeding heat treatment in nitrogen. The particle morphology of the precursor is preserved during the heat treatments. Excellent electrochemical properties in terms of capacity, reversibility, cycling stability and rate capability have been achieved. The thermal stability of charged electrodes is
Origin of electrochemical reactivity enhancement of post-annealed LiFePO 4 thin films: Preparation of heterosite-type FePO 4
F. Sauvage; E. Baudrin; L. Laffont; J.-M. Tarascon
We reported the dependence of the LiFePO4 thin films growth by Pulsed Laser Deposition (PLD) on their electrochemical properties. Whether the crystallized films are directly grown within the PLD chambers or post annealed, they present different textures and levels of surface carbon contamination, with the post-annealing films being the most contaminated. The post-annealed thermal treatment induces a drastic increase in
Effect of milling method and time on the properties and electrochemical performance of LiFePO 4\\/C composites prepared by ball milling and thermal treatment
Di Zhang; Rui Cai; Yinke Zhou; Zongping Shao; Xiao-Zhen Liao; Zi-Feng Ma
Effects of ball milling way and time on the phase formation, particulate morphology, carbon content, and consequent electrode performance of LiFePO4\\/C composite, prepared by high-energy ball milling of Li2CO3, NH4H2PO4, FeC2O4 raw materials with citric acid as organic carbon source followed by thermal treatment, were investigated. Three ball milling ways and five different milling durations varied from 0 to 8h
Template-free reverse micelle process for the synthesis of a rod-like LiFePO 4\\/C composite cathode material for lithium batteries
Bing-Joe Hwang; Kuei-Feng Hsu; Shao-Kang Hu; Ming-Yao Cheng; Tse-Chuan Chou; Sun-Yuan Tsay; Raman Santhanam
The synthesis of rod-like LiFePO4\\/C cathodes using template-free reverse micelle process is reported for high performance lithium batteries. We have demonstrated that the size of the primary particles could be controlled based on sintering temperature and sintering time and size of the large aggregates is adjustable based on the carbon content of the sample. Thermogravimetry and differential thermal analysis have
Process investigation, electrochemical characterization and optimization of LiFePO 4\\/C composite from mechanical activation using sucrose as carbon source
Ke Wang; Rui Cai; Tao Yuan; Xing Yu; Ran Ran; Zongping Shao
LiFePO4\\/C composite was synthesized by mechanical activation using sucrose as carbon source. High-energy ball milling facilitated phase formation during thermal treatment. TG¢DSC and TPR experiments demonstrated sucrose was converted to CHx intermediate before completely decomposed to carbon. Ball milling time, calcination temperature and dwelling time all had significant impact on the discharge capacity and rate performance of the resulted power.
Magnetic susceptibility as a direct measure of oxidation state in LiFePO4 batteries and cyclic water gas shift reactors.
Kadyk, Thomas; Eikerling, Michael
The possibility of correlating the magnetic susceptibility to the oxidation state of the porous active mass in a chemical or electrochemical reactor was analyzed. The magnetic permeability was calculated using a hierarchical model of the reactor. This model was applied to two practical examples: LiFePO4 batteries, in which the oxidation state corresponds with the state-of-charge, and cyclic water gas shift reactors, in which the oxidation state corresponds to the depletion of the catalyst. In LiFePO4 batteries phase separation of the lithiated and delithiated phases in the LiFePO4 particles in the positive electrode gives rise to a hysteresis effect, i.e. the magnetic permeability depends on the history of the electrode. During fast charge or discharge, non-uniform lithium distributionin the electrode decreases the hysteresis effect. However, the overall sensitivity of the magnetic response to the state-of-charge lies in the range of 0.03%, which makes practical measurement challenging. In cyclic water gas shift reactors, the sensitivity is 4 orders of magnitude higher and without phase separation, no hysteresis occurs. This shows that the method is suitable for such reactors, in which large changes of the magnetic permeability of the active material occurs. PMID:26156571
Size Control of LiFePO4/C Cathode Material by Surface Treated FePO4 with Citric Acid
NASA Astrophysics Data System (ADS)
Hong, Jianhe; Lv, Lu; Wang, Yanfen; He, Mingzhong; He, Gang
Size controllable LiFePO4/C composite with good electrochemical properties was synthesized via a novel FePO4Ę2H2O-based route: citric acid was used to partly dissociate FePO4 starting material and to chelate the dissolved ferric ions, where the size and morphology of FePO4 were controlled by adjusting the amount of citric acid. The LiFePO4/C composites synthesized with citric acid present high specific capacities (149.8 mAhĘg-1 at 0.2 C) and good rate performances (141.3 mAhĘg-1 at 1 C, 131.9 mAhĘg-1 at 2 C, and 107.0 mAhĘg-1 at 5 C), which can be attributed to small particle sizes and better carbon coating. The present route is economic and efficient, and suitable for mass production of LiFePO4 cathode material.
Thermal characteristics of a FeF3 cathode via conversion reaction in comparison with LiFePO4
NASA Astrophysics Data System (ADS)
Zhou, Mingjiong; Zhao, Liwei; Okada, Shigeto; Yamaki, Jun-ichi
The thermal stability of a FeF3 cathode via a conversion reaction was quantitatively studied using differential scanning calorimetry (DSC). Mixtures of charged and discharged FeF3 electrodes and electrolyte were measured by changing the ratio of electrode to electrolyte. A mild exothermic peak was observed at temperatures ranging from 210 to 380 ░C for the mixtures of charged electrode and electrolyte even if the electrode/electrolyte ratio was changed. Moreover, the cycling depth had no effect on the thermal stability of the charged electrode in the electrolyte. For the mixtures of discharged electrode and electrolyte, exothermic reactions occurred in the range of 250-350 ░C, which varied with the electrode/electrolyte ratio. Although the exothermic reactions of the mixtures varied with the electrode/electrolyte ratio, the thermal risk for both charged and discharged electrodes coexisted with the electrolyte appeared to be mainly due to electrolyte decomposition. By comparing the heat values of mixtures of the charged and discharged electrodes and electrolyte, the FeF3 electrodes in the electrolyte demonstrated better thermal stability than LiFePO4 electrodes at elevated temperatures.
Inorganic-based sol¢gel synthesis of nano-structured LiFePO 4 \\/C composite materials for lithium ion batteries
Jun Ma; Baohua Li; Hongda Du; Chengjun Xu; Feiyu Kang
An inorganic and non-toxic compounds combination of FeCl2Ę4H2O, Li2CO3 and H3PO4 was chosen to synthesize homogeneous nano-structured LiFePO4\\/C composite material via a simplified sol¢gel route. The dependency of the physicochemical properties and the corresponding\\u000a electrochemical responses on the residual carbon content were investigated in details. Rietveld refinement of X-ray diffraction\\u000a measurement and X-ray photoelectron spectroscopy analysis confirmed the feasibility of
A new phosphate-formate precursor method for the preparation of carbon coated nano-crystalline LiFePO 4
V. Koleva; E. Zhecheva; R. Stoyanova
Mixed phosphate-formate precursors, LiFePO4Hx(HCOO)xĘyH2O (x?1, 1
Morphological investigation of sub-micron FePO 4 and LiFePO 4 particles for rechargeable lithium batteries
Silvera Scaccia; Maria Carewska; Pawel Wisniewski; Pier Paolo Prosini
Microstructural variations of amorphous FePO4 and LiFePO4 (the latter obtained by chemical lithiation of the former) as a result of the annealing temperature have been studied by Thermogravimetric Analysis (TGA)\\/Differential Thermal Analysis (DTA), chemical analysis, Brunauer¢Emmet¢Taylor (BET) and Scanning Electron Microscopy (SEM) techniques. Round-shaped amorphous FePO4 particles 40¢80nm in size are obtained after heating (at 400░C) amorphous FePO4Ę2H2O in air
Synthesis and electrochemical properties of K-doped LiFePO 4 \\/C composite as cathode material for lithium-ion batteries
Xuesong Fang; Jing Li; Kelong Huang; Suqin Liu; Chenghuan Huang; Shuxin Zhuang; Jinbao Zhang
Li1???x\\u000a K\\u000a x\\u000a FePO4\\/C (x?=?0, 0.03, 0.05, and 0.07) composites were synthesized at 700Ā░C in an argon atmosphere by carbon thermal reduction method.\\u000a Based on X-ray diffraction, scanning electron microscopy, and transmission electron microscopy analysis, the composite was\\u000a ultrafine sphere-like particles with 100¢300Ānm size, and the lattice structure of LiFePO4 was not destroyed by K doping, while the lattice volume
NASA Astrophysics Data System (ADS)
Cherniak, D. J.; Van Orman, J. A.
Diffusion of tungsten has been characterized in synthetic forsterite and natural olivine (Fo90) under dry conditions. The source of diffusant was a mixture of magnesium tungstate and olivine powders. Experiments were prepared by sealing the source material and polished olivine under vacuum in silica glass ampoules with solid buffers to buffer at NNO or IW. Prepared capsules were annealed in 1 atm furnaces for times ranging from 45 min to several weeks, at temperatures from 1050 to 1450 ░C. Tungsten distributions in the olivine were profiled by Rutherford Backscattering Spectrometry (RBS). The following Arrhenius relation is obtained for W diffusion in forsterite: D=1.0ū10-8exp(-365▒28 kJ mol/RT) m s Diffusivities for the synthetic forsterite and natural Fe-bearing olivine are similar, and tungsten diffusion in olivine shows little dependence on crystallographic orientation or oxygen fugacity. The slow diffusivities measured for W in olivine indicate that Hf-W ages in olivine-metal systems will close to diffusive exchange at higher temperatures than other chronometers commonly used in cosmochronology, and that tungsten isotopic signatures will be less likely to be reset by subsequent thermal events.
C-containing LiFePO 4 materials Ś Part I: Mechano-chemical synthesis and structural characterization
M. Maccario; L. Croguennec; A. Wattiaux; E. Suard; F. Le Cras; C. Delmas
C¢LiFePO4 composites were synthesized by mechano-chemical activation using iron and lithium phosphates, and also cellulose as carbon precursor; this mixture was treated with 2 thermal treatments (ōslowö or ōfastö treatment) and 2 temperatures (575Ā░C or 800Ā░C). The four synthesized samples were pure olivine-type materials (XRD), but chemical analyses and M÷ssbauer spectroscopy show Li\\/Fe and P\\/Fe ratios larger than 1 and
NASA Astrophysics Data System (ADS)
Cherniak, Daniele J.; Liang, Yan
Diffusion of Ti has been characterized in natural olivine and synthetic forsterite. Experiments on the natural olivines were run under buffered conditions (IW and NNO), and those on synthetic forsterite were run in air. Titanium diffusion appears relatively insensitive to crystallographic orientation and oxygen fugacity under the range of investigated conditions, and diffusivities are similar for Fe-bearing olivine and forsterite. For Ti diffusion in synthetic forsterite, we obtain the following Arrhenius relation for diffusion over the temperature range 900-1400 ░C:
Probing the aging effects on nanomechanical properties of a LiFePO4 cathode in a large format prismatic cell
NASA Astrophysics Data System (ADS)
Demirocak, Dervis Emre; Bhushan, Bharat
Li-ion batteries offer great promise for the future of energy storage due to their superior gravimetric and volumetric energy density. One of the challenges in promoting their expanded use is to improve the cycle life of Li-ion batteries. This requires detailed understanding of the aging phenomenon. The aging mechanism of Li-ion batteries can have both chemical and mechanical origins. While the chemical degradation mechanisms have been studied extensively, mechanical degradation mechanisms have received little attention so far. In this study, we probe the changes in mechanical properties of a LiFePO4 cathode in a large format prismatic cell. Results indicate that mechanical degradation increases by aging; in addition, local degradation is observed in the composite cathode. Implications of the degradation in mechanical properties on binder degradation are discussed in detail.
Synthesis and Performance of LiFe1-xMnxPO4 in Lithium-ion Battery
NASA Astrophysics Data System (ADS)
Bazzi, Khadije; Nazri, Maryam; Vaishnava, Prem; Naik, Vaman; Nazri, Gholam-Abbas; Naik, Ratna
Olivine-type lithium transition metal phosphates (i.e. LiFePO4) have been intensively investigated as promising electrode materials for rechargeable lithium-ion batteries. There have been attempts to improve energy density and voltage quality of phosphate based electrode. In this study, we have partially substituted FeII/FeIII redox center with MnII/MnIII in LiFePO4 that provides over 600 mV higher voltage. We prepared various compositions of LiFe1-xMnxPO4 (x =0, 0.2, 0.4, 0.6, 0.8 and 1) between the two end members (LiFePO4 - LiMnPO4) . Due to intrinsic low electronic conductivity of lithium transition metal phosphates, we coat these materials with a uniform conductive carbon through a unique sol-gel process developed in our laboratory. In addition, we made a composite of the carbon coated phosphate with carbon nano-tubes to develop a highly conductive matrix electrode. We report the materials structure, morphology, electrical conductivity and electrochemical performances of LiFe1-xMnxPO4 using XRD, Raman spectroscopy, SEM, TEM, XPS, electrical conductivity and galvanostatic charge/discharge measurements.
"Black-colored olivines" in peridotites: dehydrogenation from hydrous olivines
NASA Astrophysics Data System (ADS)
Arai, Shoji; Hoshikawa, Chihiro; Miura, Makoto
Fresh olivines that are black to the naked eye are found in some dunites. Peridotites are easily converted to be black in color, when serpentinized, due to production of secondary fine magnetite particles. The dunites that contain fresh but black-colored olivines are usually coarse-grained. These coarse olivine grains are sometimes very heterogeneous in color; the blackish part grades to whitish parts in single grains. The black color is due to homegeneous distribution of minute (< 10 microns) black particles in olivine. They are rod-like or plate-like in shape in thin section, sometimes being aligned under crystallographic control of the host olivine. Olivines are clear and free of these inclusions around primary chromian spinel inclusions or chromian spinel lamellae (Arai, 1978). Raman spectroscopy indicates the minute black particles are magnetite always associated with diopside. It is interesting to note that olivine in mantle peridotites accompanied by the black-colored dunites is totally free of the black inclusions, giving the ordinary colors (pale yellow to whitish) of Mg-rich olivine. It is not likely that the magnetite inclusions formed through secondary oxidation of olivine by invasion of oxygen, which is possible along cracks or grain boundaries. They most probably formed due to dehydrogenation from primary OH-bearing olivines upon cooling. Hydrogen was quickly diffused out from the olivines to leave magnetite and excess silica. The excess silica was possibly combined with a monticellite component to form diopside. The OH-bearing (hydrous) olivines can be precipitated from hydrous magmas, and the hydrous nature of the magma can promote an increase in grain size due to faster diffusion of elements. The minute inclusions of magnetite + diopside is thus an indicator of primary hydrous character of host olivine.
On the complex ageing characteristics of high-power LiFePO4/graphite battery cells cycled with high charge and discharge currents
NASA Astrophysics Data System (ADS)
Groot, Jens; Swierczynski, Maciej; Stan, Ana Irina; Kµr, S°ren Knudsen
Li-ion batteries are known to undergo complex ageing processes, where the operating conditions have a profound and non-linear effect on both calendar life and cycle life. This is especially a challenge for the automotive industry, where the requirements on product lifetime and reliability are demanding. The aim of the present work is to quantify the ageing in terms of capacity fade and impedance growth as a function of operating conditions typical to high-power automotive applications; high charge and discharge rate, elevated temperatures and wide state-of-charge windows. The cycle life of 34 power-optimised LiFePO4/graphite cells was quantified by testing with charge and discharge rates between 1 and 4C-rate, temperatures between +23 ░C and +53 ░C, and a depth-of-discharge of either 100% or 60%. Although all cells show similar ageing pattern in general, the cycle life and the impedance growth is remarkably different for the tested cases. In addition, it is concluded that high charging rates, high temperatures or intensive cycling do not always lead to a shorter cycle life. One specifically interesting finding is that the combination of 1C-rate discharge in combination with 3.75C-rate charging was found to degrade the tested cells more rapidly than a symmetric cycle with 3.75C-rate in both directions.
Entropy change effects on the thermal behavior of a LiFePO4/graphite lithium-ion cell at different states of charge
NASA Astrophysics Data System (ADS)
Jalkanen, K.; Aho, T.; Vuorilehto, K.
The enthalpy and entropy changes in a commercial lithium-ion cell were studied by using potentiometric measurements. The experiments were done on the full cell and individually on its electrode materials, LiFePO4 and artificial graphite. The graphite electrode entropy change follows the amount of intercalated lithium, whereas the LFP electrode entropy change is independent of the lithium content. The full cell entropy change behavior can be concluded to originate from the graphite electrode. For the states of charge between 30 and 75%, the full cell entropy change is positive in the discharge direction, causing the cell to absorb heat. Thus when low discharge currents are used, this entropy effect dominates over the irreversible, heat producing losses, and as a result the cell cools down. In the charge direction the entropy change has the same absolute value but is negative in sign. Because of this, the cell produces extra heat in addition to the irreversible heat production, and thus warms up. These phenomena were confirmed in a calorimetric experiment. The thermal behavior results can be utilized in designing the battery pack cooling system and in choosing favorable states of charge for the battery cycling.
Thermal modeling of large prismatic LiFePO4/graphite battery. Coupled thermal and heat generation models for characterization and simulation
NASA Astrophysics Data System (ADS)
Damay, Nicolas; Forgez, Christophe; Bichat, Marie-Pierre; Friedrich, Guy
This paper deals with the thermal modeling of a large prismatic Li-ion battery (LiFePO4/graphite). A lumped model representing the main thermal phenomena in the cell, in and outside the casing, is hereby proposed. Most of the parameters are determined analytically using physical and geometrical properties. The heat capacity, the internal and the interfacial thermal resistances between the battery and its cooling system are experimentally identified. On the other hand, the heat sources modeling is considered to be one of the most difficult task. In order to overcome this problem, a heat generation model is included. More specifically, the electrical losses are computed thanks to an electrical model which is represented by an equivalent electric circuit. A method is also proposed for parameter determination which is based on a quasi-steady state assumption. It also takes into account the battery heating during characterization which is the temperature variation due to heat generation during current pulses. This temperature variation is estimated thanks to the coupled thermal and heat generation models. The electrical parameters are determined as function of state of charge (SoC), temperature and current. Finally, the proposed coupled models are experimentally validated with a precision of 1 ░C.
Olivine in Antarctic micrometeorites - Comparison with other extraterrestrial olivine
NASA Technical Reports Server (NTRS)
Steele, Ian M.
The compositions of 5-micron or larger Mg-rich olivines from 26 Antarctic micrometeorite particles were examined and compared with those of other extraterrestrial olivine. The following differences were noted between the Antarctic meteorites and the generally recognized meteorite groups: (1) while refractory-rich (e.g., high Al2O3 or CaO) are common in C2, C3, and UOC meteorites, there are only rare, or possibly no refractory-rich olivines in Antarctic micrometeorites; (2) Mg-rich olivine compositions with FeO less than 1.9 wt pct are underrepresented in the Antarctic micrometeorites, relative to other unequilibrated meteorites; and (3) no Mn-rich, high-Mg olivines were found similar to those described in interplanetary dust, C1, C2, C3, and UOC meteorites.
Electrical conduction in olivine
Schock, R. N.; Duba, A. G.; Shankland, T. J.
This paper reports detailed measurements of electrical conductivitysigma and thermoelectric effect /ital S/ in the mineral olivine and in syntheticforsterite as functions of temperature in the range from 1000/degree/ to1500 /degree/C and oxygen partial pressure in the range from 10/sup /minus/10/ to10/sup 4/ Pa. The two most striking observations are strong conductivityanisotropy in forsterite and a sign change in /ital S/ in olivine at 1390 /degree/C.These results are interpreted to show that both materials have mixed ionic andextrinsic electronic conduction under these conditions. On the basis ofthese interpretations, we infer that forsterite conductivity is dominatedby electronic conduction in the /ital a/ and /ital b/ directions and probably bymovement involving magnesium vacancies in the /ital c/ direction, wherefar higher /ital P//sub O/sub 2//-independent conductivity is observed. Olivineappears to show mixed conduction under all the circumstances observed; at low temperature, electron holes dominate but are superseded bymagnesium vacancies at high temperatures./copyright/ American Geophysical Union 1989
Nano-network electronic conduction in iron and nickel olivine phosphates.
Herle, P Subramanya; Ellis, B; Coombs, N; Nazar, L F
The provision of efficient electron and ion transport is a critical issue in an exciting new group of materials based on lithium metal phosphates that are important as cathodes for lithium-ion batteries. Much interest centres on olivine-type LiFePO(4), the most prominent member of this family. Whereas the one-dimensional lithium-ion mobility in this framework is high, the electronically insulating phosphate groups that benefit the voltage also isolate the redox centres within the lattice. The pristine compound is a very poor conductor (sigma approximately 10(-9) S cm(-1)), thus limiting its electrochemical response. One approach to overcome this is to include conductive phases, increasing its capacity to near-theoretical values. There have also been attempts to alter the inherent conductivity of the lattice by doping it with a supervalent ion. Compositions were reported to be black p-type semiconductors with conductivities of approximately 10(-2) S cm(-1) arising from minority Fe(3+) hole carriers. Our results for doped (and undoped) LiMPO(4) (M = Fe, Ni) show that a percolating nano-network of metal-rich phosphides are responsible for the enhanced conductivity. We believe our demonstration of non-carbonaceous-network grain-boundary conduction to be the first in these materials, and that it holds promise for other insulating phosphates. PMID:14991015
Formation conditions of pyroxene-olivine and magnesian olivine chondrules
Radomsky, P.M.; Hewins, R.H. (Rutgers Univ., New Brunswick, NJ (USA))
Dynamic crystallization experiments performed on a Type I and an intermediate Type II/III composition demonstrate chondrule texture is controlled by the abundance of heterogeneous nuclei. This factor is controlled by the maximum initial temperature relative to the olivine disappearance temperature for the given heating time. Glassy and excentroradial textures form from superheated melts with no nuclei, and barred textures form with initial temperatures near the olivine disappearance temperature. Porphyritic and granular textures form with initial temperatures below the liquidus with abundant nuclei. Comparison of zoning characteristics of experimental olivines with those in natural porphyritic olivine chondrules indicates cooling rates of 100 to 1000{degree}C/h, whereas olivine morphology indicates barred olivines cooled at rates of 250 to 1,000{degree}C/h. Texture/composition relationships suggest chondrules experienced initial temperatures below 1,750{degree}C. These observations are consistent with the idea that chondrules formed by transient heating in dust-rich regions (i.e., in the midplane) of the solar nebula.
The characteristic of carbon-coated LiFePO4 as cathode material for lithium ion battery synthesized by sol-gel process in one step heating and varied pH
NASA Astrophysics Data System (ADS)
Triwibowo, J.; Yuniarti, E.; Suharyadi, E.
This research has been done on the synthesis of carbon coated LiFePO4 through sol-gel process. Carbon layer serves for improving electronic conductivity, while the variation of pH in the sol-gel process is intended to obtain the morphology of the material that may improve battery performance. LiFePO4/C precursors are Li2CO3, NH4H2PO4 and FeC2O4?H2O and citric acid. In the synthesis process, consisting of a colloidal suspension FeC2O4?H2O and distilled water mixed with a colloidal suspension consisting of NH4H2PO4, Li2CO3, and distilled water. Variations addition of citric acid is used to control the pH of the gel formed by mixing two colloidal suspensions. Sol in this study had a pH of 5, 5.4 and 5.8. The obtained wet gel is further dried in the oven and then sintered at a temperature 700░C for 10 hours. The resulting material is further characterized by XRD to determine the phases formed. The resulting powder morphology is observed through SEM. Specific surface area of the powder was tested by BET, while the electronic conductivity characterized with EIS.
Supernova olivine from cometary dust.
Messenger, Scott; Keller, Lindsay P; Lauretta, Dante S
An interplanetary dust particle contains a submicrometer crystalline silicate aggregate of probable supernova origin. The grain has a pronounced enrichment in 18O/16O (13 times the solar value) and depletions in 17O/16O (one-third solar) and 29Si/28Si (<0.8 times solar), indicative of formation from a type II supernova. The aggregate contains olivine (forsterite 83) grains <100 nanometers in size, with microstructures that are consistent with minimal thermal alteration. This unusually iron-rich olivine grain could have formed by equilibrium condensation from cooling supernova ejecta if several different nucleosynthetic zones mixed in the proper proportions. The supernova grain is also partially encased in nitrogen-15-rich organic matter that likely formed in a presolar cold molecular cloud. PMID:15994379
Multiple origins for olivine at Copernicus crater
NASA Astrophysics Data System (ADS)
Dhingra, Deepak; Pieters, Carle M.; Head, James W.
Multiple origins for olivine-bearing lithologies at Copernicus crater are recognized based on integrated analysis of data from Chandrayaan-1 Moon Mineralogy Mapper (M3), Lunar Reconnaissance Orbiter (LRO) Narrow Angle Camera (NAC) and Kaguya Terrain Camera (TC). We report the diverse morphological and spectral character of previously known olivine-bearing exposures as well as the new olivine occurrences identified in this study. Prominent albedo differences exist between olivine-bearing exposures in the central peaks and a northern wall unit (the latter being ?40% darker). The low-albedo wall unit occurs as a linear mantling deposit and is interpreted to be of impact melt origin, in contrast with the largely unmodified nature of olivine-bearing peaks. Small and localized occurrences of olivine-bearing lithology have also been identified on the impact melt-rich floor, representing a third geologic setting (apart from crater wall and peaks). Recent remote sensing missions have identified olivine-bearing exposures around lunar basins (e.g. Yamamoto et al., 2010; Pieters et al., 2011; Kramer et al., 2013) and at other craters (e.g. Sun and Li, 2014), renewing strong interest in its origin and provenance. A direct mantle exposure has commonly been suggested in this regard. Our detailed observations of the morphological and spectral diversity in the olivine-bearing exposures at Copernicus have provided critical constraints on their origin and source regions, emphasizing multiple formation mechanisms. These findings directly impact the interpretation of olivine exposures elsewhere on the Moon. Olivine can occur in diverse environments including an impact melt origin, and therefore it is unlikely for all olivine exposures to be direct mantle occurrences as has generally been suggested.
The ascent of kimberlite: Insights from olivine
NASA Astrophysics Data System (ADS)
Brett, R. C.; Russell, J. K.; Andrews, G. D. M.; Jones, T. J.
Olivine xenocrysts are ubiquitous in kimberlite deposits worldwide and derive from the disaggregation of mantle-derived peridotitic xenoliths. Here, we provide descriptions of textural features in xenocrystic olivine from kimberlite deposits at the Diavik Diamond Mine, Canada and at Igwisi Hills volcano, Tanzania. We establish a relative sequence of textural events recorded by olivine during magma ascent through the cratonic mantle lithosphere, including: xenolith disaggregation, decompression fracturing expressed as mineral- and fluid-inclusion-rich sealed and healed cracks, grain size and shape modification by chemical dissolution and abrasion, late-stage crystallization of overgrowths on olivine xenocrysts, and lastly, mechanical milling and rounding of the olivine cargo prior to emplacement. Ascent through the lithosphere operates as a "kimberlite factory" wherein progressive upward dyke propagation of the initial carbonatitic melt fractures the overlying mantle to entrain and disaggregate mantle xenoliths. Preferential assimilation of orthopyroxene (Opx) xenocrysts by the silica-undersaturated carbonatitic melt leads to deep-seated exsolution of CO2-rich fluid generating buoyancy and supporting rapid ascent. Concomitant dissolution of olivine produces irregular-shaped relict grains preserved as cores to most kimberlitic olivine. Multiple generations of decompression cracks in olivine provide evidence for a progression in ambient fluid compositions (e.g., from carbonatitic to silicic) during ascent. Numerical modelling predicts tensile failure of xenoliths (disaggregation) and olivine (cracks) over ascent distances of 2-7 km and 15-25 km, respectively, at velocities of 0.1 to >4 m s-1. Efficient assimilation of Opx during ascent results in a silica-enriched, olivine-saturated kimberlitic melt (i.e. SiO2 >20 wt.%) that crystallizes overgrowths on partially digested and abraded olivine xenocrysts. Olivine saturation is constrained to occur at pressures <1 GPa; an absence of decompression cracks within olivine overgrowths suggests depths <25 km. Late stage (<25 km) resurfacing and reshaping of olivine by particle-particle milling is indicative of turbulent flow conditions within a fully fluidized, gas-charged, crystal-rich magma.
Experimental Study of Olivine-rich Troctolites
NASA Astrophysics Data System (ADS)
Mu, S.; Faul, U.
This experimental study is designed to complement field observations of olivine-rich troctolites in ophiolites and from mid-ocean ridges. The olivine-rich troctolites are characterized by high volume proportion of olivine with interstitial plagioclase and clinopyroxene. Typically the clinopyroxene occurs in the form of few large, poikilitic grains. The primary purpose of this study is to investigate the effects of cooling process on the geometry of the interstitial phases (clinopyroxene and plagioclase). Experiments are conducted in a piston cylinder apparatus by first annealing olivine plus a basaltic melt with a composition designed to be in equilibrium with four phases at ~ 1 GPa and 1250║C. Initially, we anneal the olivine-basalt aggregates at 1350 ░C and 0.7 GPa for one week to produce a steady state microstructure. At this temperature only olivine and minor opx are present as crystalline phases. We then cool the samples over two weeks below their solidus temperature, following different protocols. The post-run samples are sectioned, polished, and imaged at high resolution and analyzed by using a field emission SEM. Initial observations show that under certain conditions clinopyroxene nucleates distributed throughout the aggregate at many sites, forming relatively small, rounded to near euhedral grains. Under certain conditions few cpx grains nucleate and grow with a poikilitic shape, partially or fully enclosing olivine grains, as is observed in natural samples. As for partially molten aggregates quenched form the annealing temperature, the microstructure will be characterized by tracing phase boundaries on screen by using ImageJ software. The geometry of the interstitial phases will be quantified by determining the grain boundary wetness, in this case the ratio of the length of polyphase to single phase (olivine-olivine) boundaries. Compositional data will also be used to study the change in major element compositions before and after the cooling process.
Olivine as tar removal catalyst for biomass gasifiers: Catalyst characterization
Lopamudra Devi; Menno Craje; Peter Th³ne; Krzysztof J. Ptasinski; Frans J. J. G. Janssen
In the present paper olivine is considered as a prospective in-bed tar removal catalyst for fluidized bed biomass gasifiers. The catalytic activity of olivine is investigated via steam reforming reaction of naphthalene as a model biomass tar compound. It is observed that the calcination of olivine improves the performance of the catalyst. Calcination of olivine is done with air at
Primary trapped melt inclusions in olivine in the olivine-augite-orthopyroxene ureilite Hughes 009
Cyrena Anne Goodrich; Anna Maria Fioretti; Mario Tribaudino; Gianmario Molin
We describe the first known occurrence of primary melt inclusions in a ureilite. The ureilite is Hughes 009, one of a small number of ureilites whose primary mineralogy is olivine-augite-orthopyroxene, rather than olivine-pigeonite. Hughes 009 has a coarse-grained, equilibrated texture typical of ureilites, and homogeneous primary mineral compositions: olivine Ś mg 87.3; augite Ś mg 89.2, Wo 37.0, Al2O3 =
Cations in olivine, Part 2: Diffusion in olivine xenocrysts, with applications to petrology and mineral physics
Amy J. G. Jurewicz; E. Bruce Watson
Diffusivities for calcium, iron, magnesium, manganese and aluminum have been measured for St. John's olivine undergoing cation exchange with synthetic basaltic melts. The variety of temperature, pressure and fO2 conditions under which the diffusivities were measured complement the equilibrium-partitioning study of calcium in olivine-bearing basalts by Jurewicz and Watson, 1988. Olivine was found to be anisotropic with respect to the
Drastically Enhanced High-Rate Performance of Carbon-Coated LiFePO4 Nanorods Using a Green Chemical Vapor Deposition (CVD) Method for Lithium Ion Battery: A Selective Carbon Coating Process.
Tian, Ruiyuan; Liu, Haiqiang; Jiang, Yi; Chen, Jiankun; Tan, Xinghua; Liu, Guangyao; Zhang, Lina; Gu, Xiaohua; Guo, Yanjun; Wang, Hanfu; Sun, Lianfeng; Chu, Weiguo
Application of LiFePO4 (LFP) to large current power supplies is greatly hindered by its poor electrical conductivity (10(-9) S cm(-1)) and sluggish Li(+) transport. Carbon coating is considered to be necessary for improving its interparticle electronic conductivity and thus electrochemical performance. Here, we proposed a novel, green, low cost and controllable CVD approach using solid glucose as carbon source which can be extended to most cathode and anode materials in need of carbon coating. Hydrothermally synthesized LFP nanorods with optimized thickness of carbon coated by this recipe are shown to have superb high-rate performance, high energy, and power densities, as well as long high-rate cycle lifetime. For 200 C (18s) charge and discharge, the discharge capacity and voltage are 89.69 mAh g(-1) and 3.030 V, respectively, and the energy and power densities are 271.80 Wh kg(-1) and 54.36 kW kg(-1), respectively. The capacity retention of 93.0%, and the energy and power density retention of 93.6% after 500 cycles at 100 C were achieved. Compared to the conventional carbon coating through direct mixing with glucose (or other organic substances) followed by annealing (DMGA), the carbon phase coated using this CVD recipe is of higher quality and better uniformity. Undoubtedly, this approach enhances significantly the electrochemical performance of high power LFP and thus broadens greatly the prospect of its applications to large current power supplies such as electric and hybrid electric vehicles. PMID:25970716
Olivine on Vesta: clues for the interior
NASA Astrophysics Data System (ADS)
De Sanctis, M. C.; Ammannito, E.; McSween, H.; Mittlefehldt, D. W.; Capaccioni, F.; Capria, M. T.; Frigeri, A.; Fonte, S.; Longobardo, A.; Magni, G.; Marchi, S.; Palomba, E.; Pieters, C. M.; Tosi, F.; Zambon, F.; Raymond, C. A.; Russell, C. T.; Sunshine, J.
Data from the Dawn VIR (Visible InfraRed mapping Spectrometer) instrument [1,2] have been used to characterize and map the distribution of minerals on Vesta. Howardite, eucrite and diogenite meteorites represent the basaltic crust and possibly ultramafic mantle samples of Vesta, the only surviving large basaltic differentiated rocky protoplanet. Olivine is a major component of the mantles of differentiated bodies, including Vesta. Here we report on the discovery of olivine and its constraints on the Vesta evolution models.
Incompatible Trace Element Abundances in Hawaiian Olivines
NASA Astrophysics Data System (ADS)
Yu, G.; Huang, S.; Mukhopadhyay, S.; Jacobsen, S. B.
Our understanding of trace elements partitioning between olivine and silicate melt is clouded by large variations in values of partition coefficients presented in the literature. In general, partition coefficients from phenocryst-matrix results are higher than those from experimental equilibration and in-situ measurements (such as LA-ICP-MS and Ion-probe) (Blard and Farley, 2008; Lee et al., 2007). This discrepancy is possibly caused by the presence of melt or micromineral inclusions in the analyzed phenocrysts, or contamination of grain boundaries by enriched glasses or accessory phases or uranium pick up from alteration of olivines. To further investigate why analysis of natural phenocrysts usually results in relative high apparent DÆs for incompatible trace elements, six aliquots of olivine grains from a single sediment sample of Waimea river watershed, on the western side of the island of Kauai, Hawaii, were analyzed by solution ICP-MS at Harvard University for trace element concentrations. Two aliquots of olivines were leached in 1% oxalic acid for 45-60 min at 90 OC before dissolution. Leached and unleached olivines mostly show positive linear correlations in plots of incompatible trace elements versus La, which possibly indicates mixing lines between olivine and one end-member with higher incompatible element concentration (possibly melt inclusion). Assuming La concentration in olivine is zero, we estimate concentration of other incompatible elements in olivines using intercepts of these mixing lines. We obtain that U and Th concentration in the olivines to be about 1 ppb and 0.1 ppb respectively, corresponding to apparent DUol/melt and DThol/melt of 0.003 and 0.0001 if host lave has U of 0.3 ppm and Th of 1ppm (Gayer et al.,2008). Recently, helium isotopic measurements were made in these olivines (Gayer et al., 2008) and the results yield a basin-wide average erosion rate of 0.056 mma-1 for Waimea river watershed. Gayer et al. (2008) argued that radiogenic 4He in these ~4.5 Ma old olivines is negligible using DUol/melt=2ū10-5 and DThol/melt=5ū10-5 (Beattie 1993; Kennedy et al., 1993) and 0.3 ppm U and 1 ppm Th for host lavas. This assumption has been challenged by Blard and Farley (2008), who argued that radiogenic 4He in these olivines are significant and could affect the calculated erosion rate by a factor of 10-100. They used apparent DUol/melt and DThol/melt ranging between 0.03 and 0.1, which were obtained from analyses of whole natural phenocrysts and host lava (Blard and Farley, 2008). In contrast, using our measured U and Th contents in the Kauai olivines suggest revisions to erosion rates on order of only 15%. Therefore, Blard and Farley (2008)Æs apparent D values may not be representative of Kauai olivines and their assertion that Gayer et al. (2008)Æs erosion rates from Hawaii require revision by more than a factore of 10 is incorrect.
FIRST Ti-XANES ANALYSES OF OLIVINE IN AMOEBOID OLIVINE AGGREGATES
Grossman, Lawrence
FIRST Ti-XANES ANALYSES OF OLIVINE IN AMOEBOID OLIVINE AGGREGATES S. B. Simon1 , S. R. Sutton1]. Their primary phases are very 16 O-rich [3], indicating formation in a solar gas. We measured the valence of Ti in oli- vine in two AOAs (a) to see if they contain Ti3+ , the presence of which would suggest formation
ARC studies of the thermal stability of three different cathode materials: LiCoO 2; Li[Ni 0.1Co 0.8Mn 0.1]O 2; and LiFePO 4, in LiPF 6 and LiBoB EC\\/DEC electrolytes
J. Jiang; J. R. Dahn
Accelerating rate calorimetry (ARC) has been used to compare the thermal stability of three different cathode materials, LiCoO2, Li[Ni0.1Co0.8Mn0.1]O2, and LiFePO4, in EC\\/DEC solvent and in 1.0 M LiPF6 EC\\/DEC or 0.8 M LiBoB EC\\/DEC electrolytes. The cathode materials were charged to 4.2 V vs. Li metal before analysis. In EC\\/DEC solvent, the onset temperatures for self-sustained exothermic reactions are
Raman spectra of shocked minerals. I - Olivine
NASA Technical Reports Server (NTRS)
Heymann, D.; Celucci, T. A.
The Raman spectra of olivine contained in a chip of the Twin Sisters Peak (Washington) dunite shocked to 22.2 GPa is shown to be identical to that of unshocked olivine in the same rock. The Raman spectra of powder of the rock shocked to 20.1 GPa and of chips shocked to 59.5 GPa and 60.7 GPa display strong and broad low-frequency features with crests at 475/cm, 556/cm, and 572/cm, and broad high-frequency features near 1100/cm. It is suggested that these features are due to the formation of olivine glass with a considerable degree of three-dimensional Si-O-Si linkage having scattered domains of greatly variable grain size, internal structure, and chemical composition.
In Situ Raman Study of Phase Stability of Li3V2(PO4)3 upon Thermal and Laser Heating
Henkelman, Graeme
features. 1. INTRODUCTION Transition-metal phosphates that include LiFePO4, LiMnPO4, and Li3V2(PO4)3 haveIn Situ Raman Study of Phase Stability of Li3V2(PO4)3 upon Thermal and Laser Heating Nellymar gravimetric capacity, its thermal and electrochemical stability make it of great interest as a cathode
Shock Effects in Olivine from Mocs Chondrite
NASA Astrophysics Data System (ADS)
Iancu, O. G.; Miura, Y.; Iancu, G.
The Mocs (syn. Moci) meteorite, classified as L6 chondrite by Van Schmus and Wood [1] and recently reclassified as L5-6 by Miura et al. [2], fell on February 3, 1882, 16.00 hrs. , over a large area (15 km by 3 km) in Transylvania (Cluj District). Olivine from six fragments of the Mocs chondrite was analyzed by optical microscopy, scanning electron microscopy with energy dispersive X-ray analysis and X-ray powder diffractometry. Olivine occurs as grains in matrix or chondrules: barred olivine chondrules, composed of parallel sets of prismatic olivine crystals and devitrified glass and porphyritic olivine chondrules, which consist mainly of fine-grained olivine crystals and glassy materials of feldspsr composition. In order to determine the mineralogical and chemical effects of shock metamorphism (induced by collisions in space of the Mocs chondrite parent body), in every thin section, ten to twenty of the largest, randomly distributed olivine single crystals were examined by optical polarizing microscope with 20X- or 40X- objectives [3] and with a JEOL JSM-5400 scanning electron microscope for higher magnifications. The mineralogical effects observed are: undulatory extinction, irregular fractures, planar fractures, mosaicism and planar deformation features. These, correlated with the presence of small amounts of maskelynite (An 12-19) indicate that the maximum shock degree this meteorite experienced was S-5 [3]. The quantitative chemical analysis of 77 olivine grains in matrix from all thin sections (6), determined by a JEOL JSM-5400 scanning electron microscope with JED 2001 energy dispersive X-ray analysis at the Yamaguchi University, shows a variation in composition from Fa23 to Fa27 mole % fayalite (Avg. Fa25; PMD 2.3%), indicative of the L-group. The Fayalite content of olivine from chondrules ranges from Fa23 to Fa27 (Avg. Fa25; PMD 1.74%). According to DEER et al. [4], olivine composition can be measured also by X-ray powder diffractometry as Fa (mol per cent) = 100-(4233.91-1494.59 x d130). By using a RIGAKU computer assisted-diffractometer (radiation Cu K alpha = 1.54059) at the Yamaguchi University, the d130 value of olivine from Mocs meteorite was calculated as 2.781 A and the fayalite content as Fa23 mole % fayalite (Forsterite-ferroan as of IMA files, 1993) consistent also with the L-group. The cell parameters and density determined from the X-ray diffraction pattern are: a=4.779; b=10.297; c=6.032; V=296.857 and Dx=3.446 g/cm3. References: [1] Van Schmus W. R. and Wood J. A. (1967) GCA, 31, 747-765. [2] Miura Y. et al. (1995) Proc. NIPR Symp. Antarct. Meteorites, 8, in press. [3] Stoffler D. et al. (1991) GCA, 55, 3845-3867. [4] Deer W. A. et al. (1992) 2nd edition, 4.
Synthetic olivine supported nickel catalysts for gasification of glycerol
Duangduen Atong; Chiravoot Pechyen; Duangdao Aht-Ong; Viboon Sricharoenchaikul
Olivine and olivine-supported nickel catalysts were synthesized and tested to study their potential to be used as active in-bed materials for steam reforming\\/gasification of glycerol waste. Olivine was synthesized by a co-precipitation method followed by wet impregnation of nickel. Ni\\/olivine calcined at 800░C and then reduced at 700░C exhibited a desirable phase with the highest surface area and nickel content.
A Chemical Model of Micrometeorite Impact into Olivine
NASA Technical Reports Server (NTRS)
Sheffer, A. A.; Melosh, H. J.
Laboratory simulations of space weathering using laser irradiation have been successful in reproducing space weathering characteristics such as the reduction of olivine to form nanophase iron particles. However, the chemistry of the reduction of Fe2+ in olivine to Fe metal has not been fully explored. We present a thermodynamic model of olivine undergoing post-impact cooling and decompression.
Primary trapped melt inclusions in olivine in the olivine-augite-orthopyroxene ureilite Hughes 009
NASA Astrophysics Data System (ADS)
Goodrich, Cyrena Anne; Fioretti, Anna Maria; Tribaudino, Mario; Molin, Gianmario
We describe the first known occurrence of primary melt inclusions in a ureilite. The ureilite is Hughes 009, one of a small number of ureilites whose primary mineralogy is olivine-augite-orthopyroxene, rather than olivine-pigeonite. Hughes 009 has a coarse-grained, equilibrated texture typical of ureilites, and homogeneous primary mineral compositions: olivine - mg 87.3; augite - mg 89.2, Wo 37.0, Al 2O 3 = 1.6 wt.%; orthopyroxene - mg 88.3, Wo 4.9. It shows only limited secondary reduction effects and no petrographically recognizable carbon phases, which indicates that its original carbon content was lower than in most ureilites. The melt inclusions occur in olivine crystals. They are concentrated in the central regions of their hosts, showing elongate (mostly 20-60 ?m in maximum dimension), negative olivine crystal shapes and parallel alignment. These and other features indicate that they were trapped during initial growth of their hosts from a liquid, and are likely to be representative samples of that liquid. They consist of glass and single, subhedral crystals of high-Ca pyroxene, with minor Cr-rich spinel and metal-phosphide-sulfide spherules. They are surrounded by halos of olivine with rounded outlines defined by tiny bits of metal and thin arcs of glass. Pyroxenes within each inclusion show zonation patterns indicating that they nucleated at the olivine/ liquid interface with compositions close to that of the primary augite, and then grew inward with dramatically increasing Al 2O 3 (to 10.8 wt.%), Wo (to ?50), TiO 2 and Cr 2O 3 contents. Glasses within each inclusion are relatively homogeneous. Glasses from all inclusions show well-defined trends of CaO, TiO 2, Cr 2O 3, Na 2O and SiO 2 vs. Al 2O 3, (16-23 wt.%) that can be modelled as resulting principally from crystallization of various amounts of the pyroxene. The halos, which represent olivine that grew from the trapped melts, are zoned in Cr and Ca with concentrations decreasing inward, reflecting cocrystallization of pyroxene; they have homogeneous Fe/Mg identical to that of the primary olivine, indicating reequilibration with the host. We develop a petrologic model for the postentrapment history (crystallization, reaction and reequilibration) of the inclusions, based on which we reconstruct the composition of the primary trapped liquid (PTL). The PTL was saturated only with olivine. This result implies that Hughes 009 is a cumulate (consistent with the high Mn/Mg ratio of its olivine and a low abundance of graphite) and that the composition of the PTL is close to that of its parent magma. The low-pressure equilibrium crystallization sequence predicted by MAGPOX calculations for the PTL (olivine ? augite ? plagioclase ? pigeonite) is not, however, consistent with the primary mineralogy of Hughes 009. If the conditions of these calculations are, indeed, appropriate, then complex processes such as magma mixing must have been involved in the petrogenesis of this ureilite. This conclusion is consistent with other evidence that the olivine-augite-orthopyroxene ureilites record a more complex magmatic evolution than is evident in the olivine-pigeonite ureilites. TEM investigations of microtextural features in all phases and XRD determination of Fe 2+-Mg site distribution in orthopyroxene have elucidated the cooling and shock history of this ureilite. Hughes 009 experienced an extremely high cooling rate (7 ▒ 5░C/h at the closure T of 630░C) late in its evolution, and two distinguishable shock events - the first at peak pressures of 5 to 10 GPa, resulting in mechanical polysynthetic twinning in augite and orthopyroxene and mild undulatory extinction in olivine; and the second at lower pressures, resulting only in brecciation and redistribution of metal. Its late history is similar to that of most ureilites, and probably reflects impact excavation.
Toward a unified hydrous olivine electrical conductivity law
NASA Astrophysics Data System (ADS)
Gardķs, Emmanuel; Gaillard, Fabrice; Tarits, Pascal
has long been proposed that water incorporation in olivine has dramatic effects on the upper mantle properties, affecting large-scale geodynamics, and triggering high electrical conductivity. But the laboratory-based laws of olivine electrical conductivity predict contrasting effects of water, precluding the interpretation of geophysical data in term of mantle hydration. We review the experimental measurements of hydrous olivine conductivity and conclude that most of data are consistent when errors in samples water contents are considered. We report a new law calibrated on the largest database of measurements on hydrous olivine oriented single crystals and polycrystals. It fits most of measurements within uncertainties, and is compatible with most of geophysical data within petrological constraints on mantle olivine hydration. The conductivity anisotropy of hydrous olivine might be higher than dry olivine, but preferential orientation should produce moderate anisotropy (ś0-0.8 log unit). In the oceanic mantle, the enhancement of olivine conductivity is limited to ś1 log unit in the maximum range of mantle olivine water concentrations (0-500 wt ppm). Strongest enhancements are expected in colder regions, like cratonic lithospheres and subduction settings. High conductivities in melt-free mantle require great depths and high water concentrations in olivine (>0.1 S/m at >250 km and >200 wt ppm). Thus, the hydration of olivine appears unlikely to produce the highest conductivities of the upper mantle.
Shock-produced olivine glass: First observation
Jeanloz, R.; Ahrens, T.J.; Lally, J.S.; Nord, G.L., Jr.; Christie, J.M.; Heuer, A.H.
Transmission electron microscope (TEM) observations of an experimentally shock-deformed single crystal of natural peridot, (Mg0.88Fe 0.12SiO4 recovered from peak pressures of about 56 ?? 109 pascals revealed the presence of amorphous zones located within crystalline regions with a high density of tangled dislocations. This is the first reported observation ofolivine glass. The shocked sample exhibits a wide variation in the degree of shock deformation on a small scale, and the glass appears to be intimately associated with the highest density of dislocations. This study suggests that olivine glass may be formed as a result of shock at pressures above about 50 to 55 ?? 109 pascals and that further TEM observations of naturally shocked olivines may demonstrate the presence of glass.
Mechanisms of electrical conductivity in olivine
Schock, R.N.; Duba, A.G.; Shankland, T.J.
Data on the electrical conductivity and the thermoelectric effect in single crystals indicate that the charge conduction mechanism in pure magnesium forsterite is electrons. The concentration of electrons can be varied by controlling the number of oxygen vacancies through manipulation of the oxygen pressure. For iron bearing olivine, the conduction mechanism is by electron holes localized on an iron ion. Since iron strongly affects the creep process as well, oxidation of iron is probably accompanied by the production of magnesium vacancies. 15 references.
Search for Olivine Spectral Signatures on the Surface of Vesta
NASA Technical Reports Server (NTRS)
Palomba, E.; De Sanctis, M. C.; Ammannito, E.; Capaccioni, F.; Capria, M. T.; Farina, M.; Frigeri, A.; Longobardo, A.; Tosi, F.; Zambon, F.; McSween, H. Y.; Mittlefehldt, D. W.; Russell, C. T.; Raymond, C. A.; Sunshine, J.; McCord, T. B.
The occurrence of olivines on Vesta were first postulated from traditional petrogenetic models which suggest the formation of olivine as lower crustal cumulates. An indirect confirmation is given by their presence as a minor component in some samples of diogenite meteorites, the harzburgitic diogenites and the dunitic diogenites, and as olivine mineral clasts in howardites. Another indication for this mineral was given by interpretations of groundbased and Hubble Space Telescope observations that suggested the presence of local olivine-bearing units on the surface of Vesta. The VIR instrument onboard the DAWN mission has been mapping Vesta since July 2011. VIR acquired hyperspectral images of Vesta s surface in the wavelength range from 0.25 to 5.1 m during Approach, Survey and High Altitude Mapping (HAMO) orbits that allowed a 2/3 of the entire asteroid surface to be mapped. The VIR operative spectral interval, resolution and coverage is suitable for the detection and mapping of any olivine rich regions that may occur on the Vesta surface. The abundance of olivine in diogenites is typically lower than 10% but some samples richer in olivine are known. However, we do not expect to have extensive exposures of olivine-rich material on Vesta. Moreover, the partial overlap of olivine and pyroxene spectral signatures will make olivine difficult to detect. Different spectral parameters have been used to map olivine on extraterrestrial bodies, and here we discuss the different approaches used, and develop new ones specifically for Vesta. Our new methods are based on combinations of the spectral parameters relative to the 1 and 2 micron bands (the most prominent spectral features of Vesta surface in the visible and the infrared), such as band center locations, band depths, band areas, band area ratios. Before the direct application to the VIR data, the efficiency of each approach is evaluated by means of analysis of laboratory spectra of HED meteorites, pyroxenes, olivines and their mixtures.
Shock effects in olivine and implications for Hugoniot data
NASA Technical Reports Server (NTRS)
Jeanloz, R.
New observations of shock deformation in single-crystal olivine are presented for the range in peak pressures from about 16 to 75 GPa. A nonequilibrium model is suggested for the behavior of olivine under shock which explains the densification associated with a mixed-phase region and which is consistent with all available observations, yet which bears little similarity to the equilibrium behavior of olivine at high pressure.
A scanning electron microscope study of olivine crystal surfaces
NASA Technical Reports Server (NTRS)
Olsen, E. J.; Grossman, L.
SEM photographs were taken of euhedral olivine grains from the Murchison C2 chondrite and several terrestrial and lunar occurrences. In general, the crystal faces of the meteorite grains are rough and uneven, with irregular growth patterns. They are very similar to crystal faces on terrestrial olivine grains that formed by sublimation from a vapor phase. They are very different from the relatively smooth and featureless surfaces of magmatic olivine crystals that precipitated from igneous melts. Qualitatively, the surface morphology of the crystal supports the contention that many euhedral crystals of olivine in C2 meteorites condensed from a gas phase.
Discovery of Olivine in the Nili Fossae Region of Mars
Hoefen, T.M.; Clark, R.N.; Bandfield, J.L.; Smith, M.D.; Pearl, J.C.; Christensen, P.R.
We have detected a 30,000-square-kilometer area rich in olivine in the Nili Fossae region of Mars. Nili Fossae has been interpreted as a complex of grabens and fractures related to the formation of the Isidis impact basin. We propose that post-impact faulting of this area has exposed subsurface layers rich in olivine. Linear mixture analysis of Thermal Emission Spectrometer spectra shows surface exposures of 30% olivine, where the composition of the olivine ranges from Fo30 to Fo70.
Fedkin and Grossman: Fayalite Content of Chondritic Olivine 279 The Fayalite Content of Chondritic Olivine
Grossman, Lawrence
enrichment factors near the maximum produced in coagulation and settling models, together with C1 chondrite dust whose O content has been enhanced by admixture of water ice, can yield olivine condensate grains during condensation of a so- lar gas. 1.2. Dust-enriched Systems While thermodynamic treatments
Olivine in an unexpected location on Vesta's surface
NASA Astrophysics Data System (ADS)
Ammannito, E.; de Sanctis, M. C.; Palomba, E.; Longobardo, A.; Mittlefehldt, D. W.; McSween, H. Y.; Marchi, S.; Capria, M. T.; Capaccioni, F.; Frigeri, A.; Pieters, C. M.; Ruesch, O.; Tosi, F.; Zambon, F.; Carraro, F.; Fonte, S.; Hiesinger, H.; Magni, G.; McFadden, L. A.; Raymond, C. A.; Russell, C. T.; Sunshine, J. M.
Olivine is a major component of the mantle of differentiated bodies, including Earth. Howardite, eucrite and diogenite (HED) meteorites represent regolith, basaltic-crust, lower-crust and possibly ultramafic-mantle samples of asteroid Vesta, which is the lone surviving, large, differentiated, basaltic rocky protoplanet in the Solar System. Only a few of these meteorites, the orthopyroxene-rich diogenites, contain olivine, typically with a concentration of less than 25 per cent by volume. Olivine was tentatively identified on Vesta, on the basis of spectral and colour data, but other observations did not confirm its presence. Here we report that olivine is indeed present locally on Vesta's surface but that, unexpectedly, it has not been found within the deep, south-pole basins, which are thought to be excavated mantle rocks. Instead, it occurs as near-surface materials in the northern hemisphere. Unlike the meteorites, the olivine-rich (more than 50 per cent by volume) material is not associated with diogenite but seems to be mixed with howardite, the most common surface material. Olivine is exposed in crater walls and in ejecta scattered diffusely over a broad area. The size of the olivine exposures and the absence of associated diogenite favour a mantle source, but the exposures are located far from the deep impact basins. The amount and distribution of observed olivine-rich material suggest a complex evolutionary history for Vesta.
Olivine in an unexpected location on Vesta's surface.
Ammannito, E; De Sanctis, M C; Palomba, E; Longobardo, A; Mittlefehldt, D W; McSween, H Y; Marchi, S; Capria, M T; Capaccioni, F; Frigeri, A; Pieters, C M; Ruesch, O; Tosi, F; Zambon, F; Carraro, F; Fonte, S; Hiesinger, H; Magni, G; McFadden, L A; Raymond, C A; Russell, C T; Sunshine, J M
Olivine is a major component of the mantle of differentiated bodies, including Earth. Howardite, eucrite and diogenite (HED) meteorites represent regolith, basaltic-crust, lower-crust and possibly ultramafic-mantle samples of asteroid Vesta, which is the lone surviving, large, differentiated, basaltic rocky protoplanet in the Solar System. Only a few of these meteorites, the orthopyroxene-rich diogenites, contain olivine, typically with a concentration of less than 25 per cent by volume. Olivine was tentatively identified on Vesta, on the basis of spectral and colour data, but other observations did not confirm its presence. Here we report that olivine is indeed present locally on Vesta's surface but that, unexpectedly, it has not been found within the deep, south-pole basins, which are thought to be excavated mantle rocks. Instead, it occurs as near-surface materials in the northern hemisphere. Unlike the meteorites, the olivine-rich (more than 50 per cent by volume) material is not associated with diogenite but seems to be mixed with howardite, the most common surface material. Olivine is exposed in crater walls and in ejecta scattered diffusely over a broad area. The size of the olivine exposures and the absence of associated diogenite favour a mantle source, but the exposures are located far from the deep impact basins. The amount and distribution of observed olivine-rich material suggest a complex evolutionary history for Vesta. PMID:24196707
Ringwoodite lamellae in olivine: Clues to olivine¢ringwoodite phase transition mechanisms in shocked meteorites and subducting slabs
Chen, Ming; Goresy, Ahmed El; Gillet, Philippe
The first natural occurrence of ringwoodite lamellae was found in the olivine grains inside and in areas adjacent to the shock veins of a chondritic meteorite, and these lamellae show distinct growth mechanism. Inside the veins where pressure and temperature were higher than elsewhere, ringwoodite lamellae formed parallel to the {101} planes of olivine, whereas outside they lie parallel to the (100) plane of olivine. The lamellae replaced the host olivine from a few percent to complete. Formation of these lamellae relates to a diffusion-controlled growth of ringwoodite along shear-induced planar defects in olivine. The planar defects and ringwoodite lamellae parallel to the {101} planes of olivine should have been produced in higher shear stress and temperature region than that parallel to the (100) plane of olivine. This study suggests that the time duration of high pressure and temperature for the growth of ringwoodite lamellae might have lasted at least for several seconds, and that an intracrystalline transformation mechanism of ringwoodite in olivine could favorably operate in the subducting lithospheric slabs in the deep Earth. PMID:15479764
Relative strengths of orthopyroxene and olivine at asthenospheric conditions
NASA Astrophysics Data System (ADS)
Holyoke, C. W., III; Raterron, P.; Girard, J.
Orthopyroxene is the second most common mineral in the Earth's upper mantle. However, very little is known about its strength relative to olivine and clinopyroxene, both of which are well studied. Analyses of microstructures in peridotites containing orthopyroxene and olivine that were deformed at lithospheric conditions (relatively low temperatures and pressures) indicate that the orthopyroxene is stronger than surrounding olivine. In contrast, analyses of microstructures in asthenospheric peridotite xenoliths indicate that olivine and orthopyroxene have similar strengths. In order to better determine the pressure, temperature and strain rate sensitivity of the strength of orthopyroxene aggregates, we have performed an experimental study on stacked cylinders of orthopyroxene aggregates and olivine aggregates in the D-DIA. Cylinders of Bamble orthopyroxene (d~5-30 microns) or San Carlos olivine (d~25 microns) were hot-pressed in-situ at 1300oC for 1 hour prior to deformation. Although the assemblies and powders were dried at >100oC for >12 hours prior to installation in the apparatus, minor concentrations of water were observed (OPx ~ 500 H/106 Si; Ol ~ 200 H/106 Si). Multiple deformation steps were performed in each experiment over a range of strain rates (5x10-6 to 2x10-4/s) at a single temperature and pressure (T = 1000 - 1400oC and P = 2 - 5 GPa). At almost all conditions tested in these experiments, the orthopyroxene aggregates deformed at the same strain rate as the olivine cylinders, indicating both materials have the same stress exponent and very similar activation enthalpy. The microstructures observed in both the orthopyroxene and olivine cylinders are consistent with dislocation creep and lattice preferred orientations consistent with those observed in naturally deformed peridotites. These results indicate that at asthenospheric mantle conditions, the strengths of orthopyroxene and olivine in the dislocation creep field are very similar.
Experimental Reproduction of Olivine rich Type-I Chondrules
NASA Technical Reports Server (NTRS)
Smith, Robert K.
Ordinary chondritic meteorites are an abundant type of stony meteorite characterized by the presence of chondrules. Chondrules are small spheres consisting of silicate, metal, and sulfide minerals that experienced melting in the nebula before incorporation into chondritic meteorite parent bodies. Therefore, chondrules record a variety of processes that occurred in the early solar nebula. Two common types of unequilibrated chondrules with porphyritic textures include FeO-poor (type I) and FeO-rich (type II) each subdivided into an A (SiO2-poor) and B (SiO2-rich) series. Type IA chondrules include those with high proportions of olivine phenocrysts (>80% olivine) and type IB chondrules include those with high proportions of pyroxene phenocrysts (<20% olivine). An intermediate composition, type IAB chondrules include those chondrules in which the proportion of olivine phenocrysts is between 20-80%. We conducted high-temperature laboratory experiments (melting at 1550 C) to produce type I chondrules from average unequilibrated ordinary chondrite (UOC) material mixed with small amounts of additional olivine. The experiments were conducted by adding forsteritic rich olivine (San Carlos olivine, Fo 91) to UOC material (GRO 95544) in a 30/70 ratio, respectively. Results of these high temperature experiments suggest that we have replicated type IA chondrule textures and compositions with dynamic crystallization experiments in which a heterogeneous mixture of UOC (GRO 95544) and olivine (San Carlos olivine) were melted at 1550 C for 1 hr. and cooled at 5-1000 C/hr using graphite crucibles in evacuated silica tubes to provide a reducing environment.
Olivine diogenites: The mantle of the eucrite parent body
Sack, R.O.; Azeredo, W.J.; Lipschutz, M.E. (Purdue Univ., IN (USA))
Two olivine-rich Antarctic diogenites (ALH A77256 and ALH 84001) of the howardite-eucritediogenite (HED) meteorite association have olivine/pyroxene ratios similar to normative ratios in devolatilized ordinary chondrites. Based on chemical data and petrological analysis, these meteorites represent the residuum of partial melting of the mantle in the eucrite parent body (EPB). Mineral assemblages in these olivine-rich diogenites record a continuum in thermal histories from initial partial melting (1150-1200{degree}C) to subsolidus re-equilibration (795 {plus minus} 55{degree}C). The small number of olivine-rich diogenites known hints that only the outer portion of the EPB has been sampled.
Systematics of Vanadium in Olivine from Planetary Basalts
NASA Technical Reports Server (NTRS)
Karner, J. M.; Papike, J. J.; Shearer, C. K.
The systematics of vanadium in olivines from the Earth, Moon and Mars allows for the comparison of planetary basalt origin and igneous setting and process. Additional information is contained in the original extended abstract.
Thermo-Reflectance Spectra of Eros: Unambiguous Detection of Olivine
NASA Technical Reports Server (NTRS)
Lucey, P. G.; Hinrichs, J. L.; Urquhart-Kelly, M.; Wellnitz, D.; Bell, J. F., III; Clark, B. E.
Olivine is readily detected on 433 Eros using the new thermo-reflectance spectral technique applied to near-IR spectra obtained at Eros by the NEAR spacecraft. Additional information is contained in the original extended abstract.
Mineralogy of Olivine-hosted Inclusions from the Omolon Pallasite
NASA Astrophysics Data System (ADS)
Sharygin, V. V.; Kovyazin, S. V.; Podgornykh, N. M.
This paper is concerning mineralogy of olivine-hosted inclusions from the Omolon pallasite. Troilite, kamacite, nickelphosphide, taenite, stanfieldite, chromite, whitlockite, eskolaite and Si-O-bearing phase were found in metal-sulfide blebs.
Detection of new olivine-rich locations on Vesta
NASA Astrophysics Data System (ADS)
Palomba, E.; Longobardo, A.; De Sanctis, M.; Tosi, F.; Capria, M.; Capaccioni, F.; Ammannito, E.; Raymond, C.; Russell, C.
The recent discovery of olivines on Vesta by the VIR imaging spectrometer onboard the Dawn space mission changed dramatically the vision about the Vestan petrogenetic models [1]. Before that, olivines were expected to be present in the Vesta interior: in the mantle of a vertically layered body as invoked by the magma ocean models [2] or at the base of (or within) the mantle-crust boundary as claimed by fractionation models [3]. Olivines were detected by VIR-Dawn in two wide areas near the Arruntia and Bellicia regions. These are located in the northern hemisphere and not in the south, where the Rheasilvia and the more ancient Veneneia huge basins should have excavated the crust down to reach the mantle. In this work, we present our attempts to retrieve other undetected olivine-rich areas on Vesta by using spectral parameters sensitive to olivine such as the Band Area Ratio (BAR) and other specific parameters created for the detection of olivines on Mars (forsterite, fayalite, and a generic olivine index [4,5]). As a preliminary step, we calibrated these parameters by means of VIS-IR spectra of different HED meteorite samples: their behaviors as a function of sample grain size and albedo were retrieved and discussed. We selected the BAR and the forsterite index as the best parameters that can be used on Vesta and applied two independent methods to detect olivine signatures on the VIR hyperspectral cubes: a cross-correlation and an anti-correlation analysis between the BAR and one of the olivine parameters. In agreement with the recent discovery, Arruntia and Bellicia were the most olivine rich areas. In addition, we detected 6 new regions, all but one located in Vesta's northern hemisphere. This result confirms again that the old petrogenetic models cannot be applied, in a straightforward way, to Vesta and should be reshaped in the view of these new detections. An alternative and very recent option can be represented by the model described in [4], in which surface ''eruption'' of material from the mantle, including olivine, can reach the surface of Vesta.
Olivine and Pyroxene Diversity in the Crust of Mars
J. F. Mustard; F. Poulet; A. Gendrin; J.-P. Bibring; Y. Langevin; B. Gondet; N. Mangold; G. Bellucci; F. Altieri
Data from the Observatoire pour la Minķralogie, l'Eau, les Glaces, et l'Activitķ (OMEGA) on the Mars Express spacecraft identify the distinct mafic, rock-forming minerals olivine, low-calcium pyroxene (LCP), and high-calcium pyroxene (HCP) on the surface of Mars. Olivine- and HCP-rich regions are found in deposits that span the age range of geologic units. However, LCP-rich regions are found only in
Diffusion and mobility of electrically conducting defects in olivine
S. Constable; A. Duba
Electrical conductivity of lherzolite (65% olivine), measured as a function of time after changes in the oxygen fugacity\\u000a (f\\u000a o2) of the surrounding CO2\\/CO atmosphere, is used to infer the diffusivity of the point defects responsible for conduction in olivine. A total of 63\\u000a equilibration runs at temperatures of 900, 1000, 1100, and 1200??C were fit using nonlinear parameter estimation
Dissolution of olivine in basaltic liquids: experimental observations and applications.
Thornber, C.R.; Huebner, J.S.
Rates of olivine dissolution in synthetic lunar basalt 77115 and a silica-enriched 77115 composition (Sil-77115) at superliquidus temperatures have been determined. Dissolution-rate data have been applied to the problem of the thermal history of fragment-laden impact-melt rocks of the lunar highlands. Textural and chemical criteria are discussed for the recognition of olivine resorption (and growth) phenomena in igneous rocks. -J.A.Z.
Petrogenesis of olivine-phyric shergottite Yamato 980459, revisited
Tomohiro Usui; Harry Y. McSween Jr.; Christine Floss
Primitive magmas provide critical information on mantle sources, but most Martian meteorites crystallized from fractionated melts. An olivine-phyric shergottite, Yamato 980459 (Y-980459), has been interpreted to represent a primary melt, because its olivine megacrysts have magnesian cores (Fo84¢86) that appear to be in equilibrium with the Y-980459 whole-rock composition based on Fe¢Mg partitioning. However, crystal size distribution (CSD) plots for
Thermal Emission Spectroscopy of 1 Ceres: Evidence for Olivine
NASA Technical Reports Server (NTRS)
Witteborn, F. C.; Roush, T. L.; Cohen, M.
Thermal emission spectra of the largest asteroid 1 Ceres obtained from the Kuiper Airborne Observatory display features that may provide information on its surface mineralogy. A plot of the Ceres spectrum (calibrated using alpha Boo as a standard) divided by a standard thermal model (STM) is shown. Also shown is the emissivity spectrum deduced from reflectivity measurements for olivine grains <5 microns in diameter. The general shape of the Ceres and the olivine curves agree in essential details, such as the maxima from 8 to 12 microns, the minimum between 12 and 14 microns, the broad peak near 17.5 micron, and the slope beyond 22 micron. (Use of the 10 to 15-micron grain reflectivities provides a better match to the 12- to 14-micron dip. We used a value of unity for beta, the beaming factor associated with small-scale surface roughness in our STM. Adjustment of beta to a lower value raises the long-wavelength side of the Ceres spectrum, providing an even better match to the olivine curve.) The emissivity behavior roughly matches the emission coefficients which were calculated for olivine particles with a particle radius of 3 microns. Their calculations show not only the negative slope from 23 to 25 pm, but a continued decrease past 30 micron. The Ceres emissivity is thus similar to that of small olivine grains from 8 to 30 micron, but olivine's emissivity is lower from 5 to 8 pm.
Olivine and pyroxene from the mantle of asteroid 4 Vesta
NASA Astrophysics Data System (ADS)
Lunning, Nicole G.; McSween, Harry Y.; Tenner, Travis J.; Kita, Noriko T.; Bodnar, Robert J.
A number of meteorites contain evidence that rocky bodies formed and differentiated early in our solar system's history, and similar bodies likely contributed material to form the planets. These differentiated rocky bodies are expected to have mantles dominated by Mg-rich olivine, but direct evidence for such mantles beyond our own planet has been elusive. Here, we identify olivine fragments (Mg# = 80-92) in howardite meteorites. These Mg-rich olivine fragments do not correspond to an established lithology in the howardite-eucrite-diogenite (HED) meteorites, which are thought to be from the asteroid 4 Vesta; their occurrence in howardite breccias, combined with diagnostic oxygen three-isotope signatures and minor element chemistry, indicates they are vestan. The major element chemistry of these Mg-rich olivines suggests that they formed as mantle residues, in crustal layered intrusions, or in Mg-rich basalts. The trace element chemistry of these Mg-rich olivines supports an origin as mantle samples, but other formation scenarios could be possible. Interpreted as mantle samples, the range of Mg-rich olivine compositions indicates that Vesta's structure differs from that predicted by conventional models: Vesta has a chemically heterogeneous mantle that feeds serial magmatism. The range of olivine major element chemistries is consistent with models of an incompletely melted mantle such as in the model proposed by Wilson and Keil (2013) rather than a whole-mantle magma ocean for Vesta. Trace element chemistries of Mg-rich pyroxenes (Mg# = 85-92) provide support that some of these pyroxenes may represent initial fractional crystallization of mantle partial melts.
Olivine Composite Cathode Materials for Improved Lithium Ion Battery Performance
Ward, R.M.; Vaughey, J.T.
Composite cathode materials in lithium ion batteries have become the subject of a great amount of research recently as cost and safety issues related to LiCoO2 and other layered structures have been discovered. Alternatives to these layered materials include materials with the spinel and olivine structures, but these present different problems, e.g. spinels have low capacities and cycle poorly at elevated temperatures, and olivines exhibit extremely low intrinsic conductivity. Previous work has shown that composite structures containing spinel and layered materials have shown improved electrochemical properties. These types of composite structures have been studied in order to evaluate their performance and safety characteristics necessary for use in lithium ion batteries in portable electronic devices, particularly hybrid-electric vehicles. In this study, we extended that work to layered-olivine and spinel-olivine composites. These materials were synthesized from precursor salts using three methods: direct reaction, ball-milling, and a coreshell synthesis method. X-ray diffraction spectra and electrochemical cycling data show that the core-shell method was the most successful in forming the desired products. The electrochemical performance of the cells containing the composite cathodes varied dramatically, but the low overpotential and reasonable capacities of the spinel-olivine composites make them a promising class for the next generation of lithium ion battery cathodes.
Effect of Mineralogy on the Rheological Properties of Olivine, Othopyroxene and Olivine/Orthopyroxene Mixtures at High Temperature and Pressure
NASA Astrophysics Data System (ADS)
Homburg, J. M.; Mei, S.; Kohlstedt, D. L.
To better understand the influence of mineralogy on the rheological properties of the upper mantle, we have carried out a series of triaxial compressive creep experiments on olivine/orthopyroxene mixtures under high pressures (~6 GPa) and high temperatures (1373 - 1473 K) under anhydrous conditions. Experiments were performed using the deformation-DIA (D-DIA) apparatus on beamline X17B2 at the National Synchrotron Light Source at Brookhaven National Laboratory. Samples of three mineralogical compositions (olivine, orthopyroxene and 50:50 volumetric ratio of olivine:orthopyroxene) were prepared from fine-grained (~10 ?m) mineral separates of San Carlos olivine and orthopyroxene. Orthopyroxene and olivine/orthopyroxene samples were cold pressed to attain a cylinder ~1 mm in length and 1.1 mm in diameter. The cold pressed sample was then stacked with a hot-pressed olivine sample of similar size and assembled with alumina pistons, a boron nitride sleeve and graphite resistance heater into a 6.2-mm edge length cubic pressure medium. Nickel disks were placed at the ends of both samples to act as strain markers. During each experiment, in-situ stress and strain measurements were obtained from X-ray diffraction and radiography, respectively. After annealing the samples at the pressure/temperature conditions of deformation for ~2 hours to insure compaction of the cold pressed sample, experiments were conducted at constant strain rates between 2.2x10^-5 and 3.3x10^-5 s^-1 up to axial strains of 5 to 20%. The orthopyroxene and olivine/orthopyroxene mixture deformed at approximately the same rate with the mixed phase system displaying some weakening relative to the single-phase system. This observation suggests that orthopyroxene may be controlling sample behavior in the mixed phase material. In contrast, the orthopyroxene and olivine/orthopyroxene samples crept ~ 2 - 3 times faster than olivine. This contrast in rheological behavior was observed at lower temperatures/higher differential stresses but not at higher temperatures/lower differential stresses, indicating that the weakening effect of orthopyroxene may be temperature dependent. Alternatively, this behavior may be due to grain size variations between the hot pressed and cold pressed samples; more work needs to be done to better constrain this possibility. Taken together, these findings suggest that variations in orthopyroxene content may significantly alter the rheological behavior of the upper mantle providing an important constraint for future geodynamic models of upper mantle behavior.
Global investigation of olivine on Mars: Insights into crust and mantle compositions
NASA Astrophysics Data System (ADS)
Ody, A.; Poulet, F.; Bibring, J.-P.; Loizeau, D.; Carter, J.; Gondet, B.; Langevin, Y.
present the distribution of olivine on Mars, derived from spectral parameters based on the 1 Ąm olivine absorption band. The olivine can be defined with respect to two spectral end-members: type 1 corresponds to olivine with low iron content and/or small grain size and/or small abundance, and type 2, which corresponds to olivine with higher iron content and/or larger grain size and/or larger abundance. The spatial and statistical analysis of the global olivine distribution points out five major geological settings where olivine is detected: (1) Early Hesperian olivine-bearing smooth crater floors and flat intercrater plains throughout the southern highlands; (2) olivine deposits around the three main basins Argyre, Hellas, and Isidis; (3) olivine in intercrater dunes, crater ejecta, or extended deposits in the northern plains; (4) olivine associated with outcrops and sand in the floor of Valles Marineris; and (5) olivine-bearing butte outcrops in the vicinity of Hellas. The geological context, the age, and the composition of the olivine detections associated with these five major geological settings are detailed. Their origin and the implication of their occurrence on the composition of the Martian mantle and crust, as well as on the evolution of Mars volcanism are discussed.
Thermal Emission Spectroscopy of 1 Ceres: Evidence for Olivine
NASA Technical Reports Server (NTRS)
Witteborn, Fred. C.; Roush, Ted L.; Cohen, Martin
Thermal emission spectra of the largest asteroid, 1 Ceres, obtained from the Kuiper Airborne Observatory display features that may provide information about its surface mineralogy. The emissivity, obtained by dividing the spectra by a standard thermal model, is compared with emissivity spectra of olivines and phyllosilicates deduced via Kirchoff's law from reflectivity measurements. The spectra provide a fairly good match to fine grained olivines (0 to 5 micrometer size range). The smoothness of the spectrum beyond 18 micrometers is an indication of particles smaller than 50 micrometers. While the abrupt rise in emissivity near 8 micrometers matches many silicates, the distinct emissivity minimum centered near 12.8 micrometers is consistant with iron-poor olivines, but not with phyllosilicates. It suggests the presence of opaques and does not exclude a mixture with organics and fine-grained phyllosilicates.
The identification of crystalline olivine in cometary silicates
NASA Astrophysics Data System (ADS)
Campins, H.; Ryan, E. V.
An intermediate-resolution spectrum of the 8-13 micron region in comet Halley is obtained which shows a prominent silicate emission feature with structure not observed before in other comets or in interstellar silicates. The presence of a strong 11.3 micron peak reported by Bregman and coworkers is confirmed, and evidence is found for additional structure in the band. By comparison with spectra of interplanetary dust particles and laboratory silicates, it is concluded that small crystalline olivine particles are a major component of the silicates in this comet; other silicates (e.g., amorphous or hydrated) must also be present. The identification of crystalline olivine in this part of the spectrum is supported by the observation of four peaks in 20-50 micron airborne spectra of this comet which have also been attributed to olivine.
Applicability of Henry's Law to helium solubility in olivine
NASA Astrophysics Data System (ADS)
Jackson, C.; Parman, S. W.; Kelley, S. P.; Cooper, R. F.
Applicability of Henry's Law to helium solubility in olivine We have experimentally determined helium solubility in San Carlos olivine across a range of helium partial pressures (PHe) with the goal of quantifying how noble gases behave during partial melting of peridotite. Helium solubility in olivine correlates linearly with PHe between 55 and 1680 bar. This linear relationship suggests Henry's Law is applicable to helium dissolution into olivine up to 1680 bar PHe, providing a basis for extrapolation of solubility relationships determined at high PHe to natural systems. This is the first demonstration of Henry's Law for helium dissolution into olivine. Averaging all the data of the PHe series yields a Henry's coefficient of 3.8(ū3.1)ū10-12 mol g-1 bar-1. However, the population of Henry's coefficients shows a positive skew (skewness = 1.17), i.e. the data are skewed to higher values. This skew is reflected in the large standard deviation of the population of Henry's coefficients. Averaging the median values from each experiment yields a lower Henry's coefficient and standard deviation: 3.2(ū 2.3)ū10-12 mol g-1 bar-1. Combining the presently determined helium Henry's coefficient for olivine with previous determinations of helium Henry's coefficients for basaltic melts (e.g. 1) yields a partition coefficient of ~10-4. This value is similar to previous determinations obtained at higher PHe (2). The applicability of Henry's Law here suggests helium is incorporated onto relatively abundant sites within olivine that are not saturated by 1680 bar PHe or ~5ū10-9 mol g-1. Large radius vacancies, i.e. oxygen vacancies, are energetically favorable sites for noble gas dissolution (3). However, oxygen vacancies are not abundant enough in San Carlos olivine to account for this solubility (e.g. 4), suggesting the 3x10-12 mol g-1 bar-1 Henry's coefficient is associated with interstitial dissolution of helium. Helium was dissolved into olivine using an externally heated pressure vessel (Brown University). The starting materials were prepared by cutting gem-quality San Carlos olivine (~Fo90) into small blocks (~4ū2ū1 mm) using a diamond wafering blade saw and polishing with alumina slurries and colloidal silica. Analysis was completed by laser ablation-mass spectrometry using a 193 nm excimer laser and a MAP 215-50 specifically tuned for He (Open University, UK). Laser ablation pit depth varied from 2 to 40 ?m, and no correlation between pit depth and [He] is observed after accounting for variations PHe across the different experiments. This lack of correlation indicates a close approach to equilibrium was achieved over the experimental durations. Two analyses yielded spuriously high [He] (>3 std. dev. from the population mean, n = 85), and these analyses were not used to calculate Henry's coefficients. The two spuriously high analyses, in combination with the right skew of Henry's coefficients calculated from individual data points, suggests gem-quality San Carlos olivine contains volumes with anomalously high helium solubility. The nature of these volumes is currently under investigation. However, despite their presence, helium is still highly incompatible in olivine during partial melting. [1] Lux GCA 1987 [2] Heber et al. GCA 2007 [3] Shcheka & Keppler Nature 2012 [4] Walker et al. PEPI 2009
Water Retention and Rheology of Ti-doped, Synthetic Olivine
NASA Astrophysics Data System (ADS)
Faul, U.; Jackson, I.; Fitz Gerald, J. D.
Upper mantle flow laws are currently based almost entirely on experiments with olivine from San Carlos in Arizona. Synthetically produced olivine enables the exploration of the effects of trace elements on the rheology. We have conducted a range of experiments in a gas medium apparatus with solution-gelation derived olivine that show that titanium is the most effective in binding water in the olivine structure. The FTIR signature of this structurally bound water is most similar to that of water-undersaturated natural olivine with absorption bands at 3575 and 3525 cm-1. Water added, titanium-free solgel contains little water after hotpressing and shows adsorption bands at wavenumbers near 3200 cm-1. Noble metal capsules such as Pt or AuPd, providing more oxidizing conditions, are more effective in retaining water. Experiments with NiFe-lined welded Pt capsules retain no more water than NiFe lined samples without Pt capsule. Water retention is, however, again dependent on trace element content, with Ti doped samples containing tens of ppm after hotpressing. By comparison undoped samples run under the same conditions contain little water, again with different FTIR spectra to Ti-doped samples. Our experiments suggest that Ti by itself, or with water contents at the FTIR detection limit enhances diffusion creep rates relative to undoped, dry solgel olivine. Water contents around 10 ppm in NiFe wrapped samples show an enhancement of strain rates of more than one order of magnitude. The addition of Ti, together with the presence of water, also enhances grain growth. For more coarse-grained samples in the dislocation creep regime the enhancement of the stain rate as a function of water content is approximately consistent with the flow laws of Hirth and Kohlstedt (2003).
Chemical zonation in olivine-hosted melt inclusions
NASA Astrophysics Data System (ADS)
Newcombe, M. E.; Fabbrizio, A.; Zhang, Youxue; Ma, C.; Le Voyer, M.; Guan, Y.; Eiler, J. M.; Saal, A. E.; Stolper, E. M.
Significant zonation in major, minor, trace, and volatile elements has been documented in naturally glassy olivine-hosted melt inclusions from the Siqueiros Fracture Zone and the Galapagos Islands. Components with a higher concentration in the host olivine than in the melt (e.g., MgO, FeO, Cr2O3, and MnO) are depleted at the edges of the zoned melt inclusions relative to their centers, whereas except for CaO, H2O, and F, components with a lower concentration in the host olivine than in the melt (e.g., Al2O3, SiO2, Na2O, K2O, TiO2, S, and Cl) are enriched near the melt inclusion edges. This zonation is due to formation of an olivine-depleted boundary layer in the adjacent melt in response to cooling and crystallization of olivine on the walls of the melt inclusions, concurrent with diffusive propagation of the boundary layer toward the inclusion center. Concentration profiles of some components in the melt inclusions exhibit multicomponent diffusion effects such as uphill diffusion (CaO, FeO) or slowing of the diffusion of typically rapidly diffusing components (Na2O, K2O) by coupling to slow diffusing components such as SiO2 and Al2O3. Concentrations of H2O and F decrease toward the edges of some of the Siqueiros melt inclusions, suggesting either that these components have been lost from the inclusions into the host olivine late in their cooling histories and/or that these components are exhibiting multicomponent diffusion effects. A model has been developed of the time-dependent evolution of MgO concentration profiles in melt inclusions due to simultaneous depletion of MgO at the inclusion walls due to olivine growth and diffusion of MgO in the melt inclusions in response to this depletion. Observed concentration profiles were fit to this model to constrain their thermal histories. Cooling rates determined by a single-stage linear cooling model are 150-13,000 ░C h-1 from the liquidus down to ~1,000 ░C, consistent with previously determined cooling rates for basaltic glasses; compositional trends with melt inclusion size observed in the Siqueiros melt inclusions are described well by this simple single-stage linear cooling model. Despite the overall success of the modeling of MgO concentration profiles using a single-stage cooling history, MgO concentration profiles in some melt inclusions are better fit by a two-stage cooling history with a slower-cooling first stage followed by a faster-cooling second stage; the inferred total duration of cooling from the liquidus down to ~1,000 ░C ranges from 40 s to just over 1 h. Based on our observations and models, compositions of zoned melt inclusions (even if measured at the centers of the inclusions) will typically have been diffusively fractionated relative to the initially trapped melt; for such inclusions, the initial composition cannot be simply reconstructed based on olivine-addition calculations, so caution should be exercised in application of such reconstructions to correct for post-entrapment crystallization of olivine on inclusion walls. Off-center analyses of a melt inclusion can also give results significantly fractionated relative to simple olivine crystallization. All melt inclusions from the Siqueiros and Galapagos sample suites exhibit zoning profiles, and this feature may be nearly universal in glassy, olivine-hosted inclusions. If so, zoning profiles in melt inclusions could be widely useful to constrain late-stage syneruptive processes and as natural diffusion experiments.
Textural evidence bearing on the origin of isolated olivine crystals in C2 carbonaceous chondrites
NASA Technical Reports Server (NTRS)
Richardson, S. M.; Mcsween, H. Y., Jr.
In some cases the mechanical competence of chondrules in carbonaceous chondrites has been reduced by alteration of their mesostasis glass to friable phyllosilicate, providing a mechanism by which euhedral olivines can be separated from chondrules. Morphological features of isolate olivine grains found in carbonaceous chondrites are similar to those of olivine phenocrysts in chondrules. These observations suggest that the isolated olivine grains formed in chondrules, by crystallization from a liquid, rather than by condensation from a vapor.
Experimental constraints on magnetic stability of chondrules and the paleomagnetic significance of dusty olivines
Minoru Uehara; Norihiro Nakamura
Dynamic crystallization experiments are conducted under a magnetic field to determine both magnetic and mineralogical properties of chondrules. The experiment reproduced synthetic dusty olivine samples that were formed by a high temperature reduction of an initially fayalitic olivine. Backscattered-electron microscopy observations confirmed that synthetic dusty olivine contains abundant fine, submicron-sized Ni-poor Fe inclusions in the cores of MgO-rich olivine grains,
Amoeboid olivine aggregates from CH carbonaceous chondrites
NASA Astrophysics Data System (ADS)
Krot, Alexander N.; Park, Changkun; Nagashima, Kazuhide
Amoeboid olivine aggregates (AOAs) in CH carbonaceous chondrites are texturally and mineralogically similar to those in other carbonaceous chondrite groups. They show no evidence for alteration and thermal metamorphism in an asteroidal setting and consist of nearly pure forsterite (Fa<3; in wt%, CaO = 0.1-0.8, Cr2O3 = 0.04-0.48; MnO < 0.5), anorthite, Al-diopside (in wt%, Al2O3 = 0.7-8.1; TiO2 < 1), Fe,Ni-metal, spinel, and, occasionally, low-Ca pyroxene (Fs1Wo2-3), and calcium-aluminum-rich inclusions (CAIs). The CAIs inside AOAs are composed of hibonite, grossite, melilite (┼k13-44), spinel, perovskite, Al,Ti-diopside (in wt%, Al2O3 up to 19.6; TiO2 up to 13.9), and anorthite. The CH AOAs, including CAIs within AOAs, have isotopically uniform 16O-rich compositions (average ?17O = -23.4 ▒ 2.3ē, 2SD) and on a three-isotope oxygen diagram plot along ?slope-1 line. The only exception is a low-Ca pyroxene-bearing AOA 1-103 that shows a range of ?17O values, from -24ē to -13ē. Melilite, grossite, and hibonite in four CAIs within AOAs show no evidence for radiogenic 26Mg excess (?26Mg). In contrast, anorthite in five out of six AOAs measured has ?26Mg corresponding to the inferred initial 26Al/27Al ratio of (4.3 ▒ 0.7) ū 10-5, (4.2 ▒ 0.6) ū 10-5, (4.0 ▒ 0.3) ū 10-5, (1.7 ▒ 0.2) ū 10-5, and (3.0 ▒ 2.6) ū 10-6. Anorthite in another AOA shows no resolvable ?26Mg excess; an upper limit on the initial 26Al/27Al ratio is 5 ū 10-6. We infer that CH AOAs formed by gas-solid condensation and aggregation of the solar nebula condensates (forsterite and Fe,Ni-metal) mixed with the previously formed CAIs. Subsequently they experienced thermal annealing and possibly melting to a small degree in a 16O-rich gaseous reservoir during a brief epoch of CAI formation. The low-Ca pyroxene-bearing AOA 1-103 may have experienced incomplete melting and isotope exchange in an 16O-poor gaseous reservoir. The lack of resolvable ?26Mg excess in melilite, grossite, and hibonite in CAIs within AOAs reflects heterogeneous distribution of 26Al in the solar nebula during this epoch. The observed variations of the inferred initial 26Al/27Al ratios in anorthite of the mineralogically pristine and uniformly 16O-rich CH AOAs could have recorded (i) admixing of 26Al in the protoplanetary disk during the earliest stages of its evolution and/or (ii) closed-system Mg-isotope exchange between anorthite and Mg-rich minerals (spinel, forsterite, and Al-diopside) during subsequent prolonged (days-to-weeks) thermal annealing at high temperature (?1100 ░C) and slow cooling rates (?0.01 K h-1) that has not affected their O-isotope systematics. The proposed thermal annealing may have occurred in an impact-generated plume invoked for the origin of non-porphyritic magnesian chondrules and Fe,Ni-metal grains in CH and CB carbonaceous chondrites about 5 Myr after formation of CV CAIs.
Local structure in the Li-ion battery cathode material Li x (Mn y Fe 1? y )PO 4 for 0 < x ? 1 and y = 0.0, 0.5 and 1.0
Christopher M. Burba; Roger Frech
Infrared and Raman spectroscopy have been used to investigate the Li-ion battery cathode materials Lix(MnyFe1?y)PO4 for 0
Evidence for equilibrium conditions during the partitioning of nickel between olivine and komatiite liquids.
Budahn, J.R.
Olivine-liquid partition coefficients for Ni(DNi), calculated from Ni vs MgO abundance variations in komatiite series basalts, compare favourably with experimentally determined values, if Ni variations in olivine-controlled basalts can be modelled with an equation that assumes equilibrium between the entire olivine crystal and its coexisting liquid.-J.A.Z.
Mineral replacement rate of olivine by chrysotile and brucite under high1 alkaline conditions2
Paris-Sud XI, Universitķ de
1 Mineral replacement rate of olivine by chrysotile and brucite under high1 alkaline conditions2 3 replaced by18 chrysotile and brucite under high alkaline conditions. In our study, olivine replacement19 between olivine and chrysotile-brucite minerals. Coupled dissolution-precipitation21 led to the alteration
Metastable olivine wedge and deep dry cold slab beneath southwest Japan Hitoshi Kawakatsu a,
Kawakatsu, Hitoshi
Metastable olivine wedge and deep dry cold slab beneath southwest Japan Hitoshi Kawakatsu a Available online 28 January 2011 Keywords: metastable olivine receiver function slab mantle transition zone plates (slabs) due to kinetic effects, and it has been suggested that metastable olivine may persist
Martian Dunite NWA 2737: Petrographic constraints on geological history, shock events, and olivine color
Treiman, Allan H.
Martian Dunite NWA 2737: Petrographic constraints on geological history, shock events, and olivine on geological history, shock events, and olivine color, J. Geophys. Res., 112, E04002, doi:10.1029/2006JE002777 two shock events. The first shock, to stage S5ŁS6, affected the olivine by producing in it planar
Challenges in detecting olivine on the surface of 4 Vesta
NASA Astrophysics Data System (ADS)
Beck, Andrew W.; McCoy, Timothy J.; Sunshine, Jessica M.; Viviano, Christina E.; Corrigan, Catherine M.; Hiroi, Takahiro; Mayne, Rhiannon G.
Identifying and mapping olivine on asteroid 4 Vesta are important components to understanding differentiation on that body, which is one of the objectives of the Dawn mission. Harzburgitic diogenites are the main olivine-bearing lithology in the howardite-eucrite-diogenite (HED) meteorites, a group of samples thought to originate from Vesta. Here, we examine all the Antarctic harzburgites and estimate that, on scales resolvable by Dawn, olivine abundances in putative harzburgite exposures on the surface of Vesta are likely at best in the 10-30% range, but probably lower due to impact mixing. We examine the visible/near-infrared spectra of two harzburgitic diogenites representative of the 10-30% olivine range and demonstrate that they are spectrally indistinguishable from orthopyroxenitic diogenites, the dominant diogenitic lithology in the HED group. This suggests that the visible/near-infrared spectrometer onboard Dawn (VIR) will be unable to resolve harzburgites from orthopyroxenites on the surface of Vesta, which may explain the current lack of identification of harzburgitic diogenite on Vesta.
Scanning electron microscope observation of dislocations in olivine
S. Karato
Dislocations in olivine decorated by oxidation in air were observed with a scanning electron microscope (SEM) using a backscattered electron image (BEI). The decorated dislocations (and grain boundaries) were found to give clear bright images in this mode, indicating an increase of mean atomic number near the dislocation cores (and grain boundaries). This method of dislocation observation has a resolution
Shock effects in olivine and implications for Hugoniot data
Raymond Jeanloz
Deformation produced in single-crystal olivine samples by shock wave stresses ranging between 16 and 75 GPa are documented by microscopy and spectroscopy. No evidence was found for phase transformation throughout the 'mixed-phase' region (about 25 to 70 GPa) contrary to expectations based on the current interpretations of Hugoniot data. Samples retrieved from peak pressures above 20 GPa exhibit extensive plastic
ORIGINAL PAPER Dislocation recovery in fine-grained polycrystalline olivine
. Kokkonen Ę J. D. Fitz Gerald Ę A. Barnhoorn Ę U. H. Faul Ę I. Jackson Received: 10 February 2009 / Accepted interest for experimental research (Mei and Kohlstedt 2000; Karato and Jung 2003; Jackson et al. 2004; Du on the use of pure polycrystalline iron-bearing olivine, (Mg,Fe)2SiO4, synthesized from lab- oratory reagents
Deformation of olivine in torsion under hydrous conditions
NASA Astrophysics Data System (ADS)
Demouchy, Sylvie; Tommasi, Andrķa; Barou, Fabrice; Mainprice, David; Cordier, Patrick
We performed torsional deformation experiments on pre-hydrated fine-grained olivine aggregates using an innovative experimental assembly to investigate water weakening in mantle rocks at high shear strains. San Carlos olivine powder was cold-pressed and then hot-pressed under hydrous conditions, producing aggregates with average grain sizes of 7 or 15 ?m. Deformation experiments were performed in a high-resolution gas-medium apparatus equipped with a torsional actuator, under a confining pressure of 300 MPa, a temperature of 1200 ░C, and constant shear strain rates ranging from 8 ū 10-5 to 1.4 ū 10-4 s-1. Maximum shear stresses range from 150 to 195 MPa. These values are 30% lower relative to those determined in previous torsion experiments on dry, fined-grained dunites under similar conditions. Textures and microstructures of the starting and deformed specimens were characterized by scanning and transmission electron microscopy. All deformed aggregates exhibit a shape-preferred orientation marking a foliation and lineation, as well as a reduction in mean grain size from 15 ?m down to 3-4 ?m due to dynamic recrystallization. Olivine crystallographic fabrics developed rapidly (? < 0.1), but their strength, characterized by the J-index, is low compared to naturally deformed peridotites or to polycrystalline olivine deformed at similar finite shear strains under dry conditions. The crystallographic fabrics are consistent with deformation by a dislocation accommodated creep mechanism with activation of multiple {0 k l}[1 0 0] systems, among which the (0 1 0)[1 0 0] slip system is dominant, and minor participation of the (0 1 0)[0 0 1] slip system. Transmission electron microscopy confirmed the occurrence of dislocations with [1 0 0] and [0 0 1] Burgers vectors in most grains. Analysis of unpolarized infrared spectra indicates that hydrogen concentration in the olivine lattice is below the saturation level of 18 ppm wt H2O, which is similar to those typically observed in spinel-bearing peridotite xenoliths, and also provide evidence for water-rich inter-granular material trapped in pores and grain boundaries. Seismic properties computed from the CPO observations correspond to those most commonly observed in naturally deformed mantle peridotites with fast P-wave propagation and S-wave polarization subparallel to the shear direction. These torsion experiments on fine-grained olivine polycrystals under hydrous conditions indicate that water weakening under lithospheric conditions is linked to various defects with hydrogen in the olivine structure, as well as with water-derived species in grain boundaries or pores.
The effect of mineral paragenesis on Al diffusion in olivine
NASA Astrophysics Data System (ADS)
Zhukova, Irina; O'Neill, Hugh; Capbell, Ian
Al is the most abundant trivalent impurity of olivine and is particularly important because its concentration in olivine is temperature dependant, and it therefore has potential as a geothermometer (Wan, et al. 2008). Furthermore recent studies show that the incorporation of water into the olivine lattice is affected by the presents of trivalent cations such as Al3+ (Berry, et al. 2007; Hauri, et al. 2006). The Al distribution in olivines from volcanic rocks is often zoned and mantle olivines may also show an inhomogeneous distribution of Al, whereas the majority of other trace elements homogenized by diffusion (Mallmann, et al. 2009; McKibbin, et al.). However, there are no quantitative experimental data for Al diffusion in olivine, probably because the combination of low concentration rate and low diffusion rate make measurement difficult. We investigated the effect of silica activity on the diffusion rate of Al in forsterite at varying temperatures using solid-state buffer assemblages. Our study aimed to quantify the effect of major cation activities on the diffusion and concentration of Al in forsterite and also provide insights into the mechanism of Al substitution into the olivine lattice. The activities of SiO2, MgO and Al2O3 were buffered in each experiment by four different mineral associations: forsterite + periclase + spinel (fo+per+sp); forsterite + spinel + sapphirine (fo+sp+spr); forsterite + sapphirine + cordierite (fo+spr+cor); forsterite + cordierite + enstatite (fo+cor+en). Iron oxide in proportion of FeO/(FeO+MgO) = 0.1 was added to mixtures for San Carlos olivine experiments. Diffusion experiments were performed at the one-atmosphere vertical tube furnaces modified to control the fO2 by CO-CO2 gas mixing or in a box furnace in air for 10 - 28 days at temperatures from 1100 to 1500oC and logfO2 -0.7 and -5.7. The experiment with the San Carlos olivine was performed at 1300oC and at logfO2 = -5.7. In order to obtain equilibrium concentrations of the point defects we performed some experiments with pre-annealing. Diffusion profiles were measured by LA-ICP-MS in a traverse mode. The Al content of forsterite decreases with temperature dependence, increasing the potential of Al in olivine as a geothermometer. We obtain the activation energy of 379 kJ/mol for the high aSiO2 experiments, which is close within error of the value of 364 kJ/mol for the low aSiO2 experiments implying a common diffusion mechanism. The pre-exponential factor, however, increases by 5 orders of magnitude from low aSiO2 (fo+per+sp buffer) to high aSiO2 (fo+cor+en buffer). The much higher diffusivity at high aSiO2 indicates that Al diffusion occurs through octahedral cation site vacancies.
Characterization by EBSD of dislocations and disclinations in olivine: implications for the rheology of olivine-rich aggregates
NASA Astrophysics Data System (ADS)
Cordier, P.; Demouchy, S. A.; Beausir, B.; Taupin, V.; Fressengeas, C.
The rheology of olivine-rich rocks remains poorly understood. Only intracrystalline deformation mechanisms involving dislocations are quite well known. In orthorhombic olivine only two slip directions, [100] and [001] can be activated. Most characterizations performed so far involve transmission electron microscopy studies at high magnifications or, at a larger scale, optical or scanning electron microscopy on decorated samples. In the latter case, no detailed characterization of the defects could be done. Orientation maps obtained from high-resolution electron backscattered diffraction allow recovering components of the lattice curvature tensor which in turn allow determination of components of the dislocation density tensor. The geometrically necessary dislocation content can thus be imaged. Recently Beausir & Fressengeas (2013) have shown that with this technique, components of the disclination density tensor could also be determined. Several examples have been provided in metallic alloys. In this study we show that olivine aggregates (both experimentally and naturally deformed) contain pervasive evidence of disclinations dipoles at grain boundaries. The implications on the plastic behavior of olivine rocks are discussed based on a numerical model of the response to an applied shear stress of a grain boundary made of disclinations. Beausir, B. & Fressengeas, C., Disclination densities from EBSD orientation mapping. International Journal of Solids and Structures 50 (1), 137-146 (2013).
Real Time Pore Structure Evolution during Olivine Mineral Carbonation
NASA Astrophysics Data System (ADS)
Zhu, W.; Fusseis, F.; Lisabeth, H. P.; Xiao, X.
Aqueous carbonation of ultramafic rocks has been proposed as a promising method for long-term, secure sequestration of carbon dioxide. While chemical kinetics data indicate that carbonation reaction in olivine is one of the fastest among the mg-bearing minerals, in practice, the factors that limit the extent and rate of carbonation in ultramafic rocks are fluid supply and flux. On the one hand, reaction products could produce passivating layer that prohibits further reactions. On the other hand, the increases in solid volume during carbonation could lead to cracking and create new fluid paths. Whether carbonation in ultramafic rocks is self-limiting or self-sustaining has been hotly debated. Experimental evidence of precipitation of reaction products during olivine carbonation was reported. To date, reaction-driven cracking has not been observed. In this paper, we present the first real-time pore structure evolution data using the x-ray synchrotron microtomography. Sodium bicarbonate (NaHCO3) solution was injected into porous olivine aggregates and in-situ pore structure change during olivine carbonation at a constant confining pressure (12 MPa) and a temperature of 200oC was captured at 30 min. interval for ~160 hours. Shortly after the experiment started, filling-in of the existing pores by precipitation of reaction products was visible. The size of the in-fills kept increasing as reactions continued. After ~48 hours, cracking around the in-fill materials became visible. After ~60 hours, these cracks started to show a clear polygonal pattern, similar to the crack patterns usually seen on the surface of drying mud. After ~72 hours, some of the cracks coalesced into large fractures that cut-through the olivine aggregates. New fractures continued to develop and at the end of the experiment, the sample was completely disintegrated by these fractures. We also conducted nanotomography experiments on a sub-volume of the reacted olivine aggregate. Orthogonal sets of incipient cracks were observed, providing clear evidence that these cracks are generated by isotropic tensile stresses. This strongly indicates that the observed cracking was caused by volume expansion during mineral carbonation. The experimental results provide a mechanism for near 100% alteration of ultramafic rocks observed in nature.
High shear strain of olivine aggregates: rheological and seismic consequences.
Bystricky, M; Kunze, K; Burlini, L; Burg, J
High-pressure and high-temperature torsion experiments on olivine aggregates in dislocation creep show about 15 to 20% strain weakening before steady-state behavior, characterized by subgrain-rotation recrystallization and a strong lattice preferred orientation. Such weakening may provide a way to focus flow in the upper mantle without a change in deformation mechanism. Flow laws derived from low strain data may not be appropriate for use in modeling high strain regions. In such areas, seismic wave propagation will be anisotropic with an axis of approximate rotational symmetry about the shear direction. In contrast to current thinking, the anisotropy will not indicate the orientation of the shear plane in highly strained, recrystallized olivine-rich rocks. PMID:11090352
Effects of hydration on the elastic properties of olivine
Steven D. Jacobsen; Fuming Jiang; Zhu Mao; Thomas S. Duffy; Joseph R. Smyth; Christopher M. Holl; Daniel J. Frost
Water, dissolved as hydroxyl (OH)? into the solid silicate minerals of the upper mantle can reduce adiabatic wave speeds through associated defects. Here we report Brillouin spectroscopy measurements of the sound velocities and single-crystal elastic constants of hydrous forsterite (hy-Fo100) and hydrous olivine (hy-Fo97) containing 0.8¢0.9 wt% H2O. The samples, synthesized at 12 GPa and 1250░C, represent nearly the maximum
Effects of hydration on the elastic properties of olivine
Steven D. Jacobsen; Fuming Jiang; Zhu Mao; Thomas S. Duffy; Joseph R. Smyth; Christopher M. Holl; Daniel J. Frost
Water, dissolved as hydroxyl (OH)- into the solid silicate minerals of the upper mantle can reduce adiabatic wave speeds through associated defects. Here we report Brillouin spectroscopy measurements of the sound velocities and single-crystal elastic constants of hydrous forsterite (hy-Fo100) and hydrous olivine (hy-Fo97) containing 0.8-0.9 wt% H2O. The samples, synthesized at 12 GPa and 1250░C, represent nearly the maximum
Olivine and pyroxene-rich deposits in Holden Crater, Mars
NASA Astrophysics Data System (ADS)
Glotch, T. D.
Holden crater is a ~150 km diameter crater centered at 326 E, 26S breached in the south by Uzboi Vallis. Holden has been proposed as a possible landing site for the Mars Science Laboratory (MSL) rover and has been the subject of intense scrutiny due to its potential as a paleolake basin. Near the region where Uzboi Vallis breaches the southern Holden Crater wall are layered rocks that have been suggested to be aqeously deposited. Additionally, fan-shaped deposits originate in the southern and western crater walls that have been interpreted as alluvial fans and fan deltas. New analyses of THEMIS and TES data indicate that both the basement and layered rocks - those interpreted to have been deposited in an aqueous environment - near the breach point of Holden crater are olivine and pyoxene- rich. Based on THEMIS IR imagery, these units have a higher thermal inertia than the surrounding terrain. The higher-TI units correspond with lighter-toned layered units seen in THEMIS Vis and MOC imagery that also have a distinct mafic signature in THEMIS daytime IR false-color decorrelation stretch images. The fan deposit in western Holden Crater, which has been proposed as a specific landing site for MSL may also have an elevated olivine abundance based on TES data. High olivine and pyroxene abundances in the sedimentary units of Holden crater do not preclude the presence of water in the history of the crater. However, based on analysis of TES and THEMIS data over the region, there is no evidence for extended chemical weathering present at the surface. Olivine-rich bedrock is likely to be a regional property as it is also present in chaos terrain to the northeast of Holden which is the source of the Landon Vallis outflow channel. These regions should be considered high priority targets for future investigations by OMEGA and CRISM.
Noble Gas Partitioning Between Olivine and Melt to 2 GPa
S. W. Parman; S. P. Kelley; C. J. Ballentine; J. A. van Orman; G. Holland
We have extended our experimental measurements of noble gas partition coefficients to 2 GPa in the piston-cylinder device. The experimental set-up involves surrounding wafers of gem quality San Carlos olivine (250-1000 microns thick, 3-4 mm diameter) with diamond powder or vitreous carbon spheres. A layer of melt is placed at the bottom of the capsule which infiltrates the porous media
Space Weathering Evolution on Airless Bodies - Laboratory Simulations with Olivine
NASA Astrophysics Data System (ADS)
Kohout, Tomas; Cuda, J.; Bradley, T.; Britt, D.; Filip, J.; Tucek, J.; Malina, O.; Kaslik, J.; Siskova, K.; Kletetschka, G.; Zboril, R.
Lunar-type space weathering of airless bodies is associated with nanophase iron (npFe0) production in Fe bearing silicate minerals that is often responsible for observable changes of its reflectance spectra. A new method of controlled npFe0 production on olivine grains was developed in order to quantitatively evaluate spectral changes related to space weathering and presence of npFe0. Through a two-step thermal treatment a series of olivine samples with increasing concentration of iron nanoparticles on the grain surfaces was prepared. The grain size of the npFe0 particles was kept in the same range 5-20 nm). Magnetic methods were used to estimate npFe0 concentration. Compared to fresh olivine, treated samples exhibit the spectral characteristics of lunar type space weathering (darkening, shallowing of 1 Ąm olivine absorption band, and reddening) related to increasing presence of npFe0. From quantitative point of view, a logarithmic trend was found between spectral changes and npFe0 concentration. One sample with additional population of larger ~50 nm npFe0 particles follows the darkening and the 1 Ąm band shallowing trend, but does not fully follow the reddening trend. This is due to fact that the larger 40 50 nm sized) npFe0 particles do not contribute to the spectral slope change. The observed logarithmic trend between the spectral changes and the npFe0 concentration give constrains on time evolution of space weathering. In the case of constant micro impact, solar wind and cosmic radiation on a regolith, the npFe0 concentration increases linearly with time while spectral changes related to space weathering evolve logarithmically with time.
The effect of water on the electrical conductivity of olivine
NASA Astrophysics Data System (ADS)
Wang, Duojun; Mookherjee, Mainak; Xu, Yousheng; Karato, Shun-Ichiro
It is well known that water (as a source of hydrogen) affects the physical and chemical properties of minerals-for example, plastic deformation and melting temperature-and accordingly plays an important role in the dynamics and geochemical evolution of the Earth. Estimating the water content of the Earth's mantle by direct sampling provides only a limited data set from shallow regions (<200km depth). Geophysical observations such as electrical conductivity are considered to be sensitive to water content, but there has been no experimental study to determine the effect of water on the electrical conductivity of olivine, the most abundant mineral in the Earth's mantle. Here we report a laboratory study of the dependence of the electrical conductivity of olivine aggregates on water content at high temperature and pressure. The electrical conductivity of synthetic polycrystalline olivine was determined from a.c. impedance measurements at a pressure of 4GPa for a temperature range of 873-1,273K for water contents of 0.01-0.08wt%. The results show that the electrical conductivity is strongly dependent on water content but depends only modestly on temperature. The water content dependence of conductivity is best explained by a model in which electrical conduction is due to the motion of free protons. A comparison of the laboratory data with geophysical observations suggests that the typical oceanic asthenosphere contains ~10-2wt% water, whereas the water content in the continental upper mantle is less than ~10-3wt%.
Olivine crystals align during diffusion creep of Earth's upper mantle.
Miyazaki, Tomonori; Sueyoshi, Kenta; Hiraga, Takehiko
The crystallographic preferred orientation (CPO) of olivine produced during dislocation creep is considered to be the primary cause of elastic anisotropy in Earth's upper mantle and is often used to determine the direction of mantle flow. A fundamental question remains, however, as to whether the alignment of olivine crystals is uniquely produced by dislocation creep. Here we report the development of CPO in iron-free olivine (that is, forsterite) during diffusion creep; the intensity and pattern of CPO depend on temperature and the presence of melt, which control the appearance of crystallographic planes on grain boundaries. Grain boundary sliding on these crystallography-controlled boundaries accommodated by diffusion contributes to grain rotation, resulting in a CPO. We show that strong radial anisotropy is anticipated at temperatures corresponding to depths where melting initiates to depths where strongly anisotropic and low seismic velocities are detected. Conversely, weak anisotropy is anticipated at temperatures corresponding to depths where almost isotropic mantle is found. We propose diffusion creep to be the primary means of mantle flow. PMID:24132289
Diffusion creep of dry, melt-free olivine
NASA Astrophysics Data System (ADS)
Faul, Ulrich H.; Jackson, Ian
Deformation experiments were conducted on fine-grained (3-6 ?m), fully synthetic Fo90 olivine aggregates in a gas-medium apparatus at 300 MPa confining pressure and temperatures of 1150-1360░C. The strain rates of the solution-gelation-derived and therefore genuinely melt-free, dry samples are about two orders of magnitude lower than the strain rates for nominally melt-free aggregates at the same pressure and temperature conditions and grain size. Benchmark deformation tests with Anita Bay dunite and mild steel reproduce published data. The creep strength of melt-added sol-gel olivine is similar to the published creep strength of dry, melt-bearing olivine derived from natural rocks. Nonlinear least-squares fits to the melt-free deformation data give an activation energy of 484 kJ/mol, a stress exponent of 1.4, and a grain-size exponent of 3 over a range of stresses from 15 to 210 MPa. These results suggest that small amounts of melt may be similarly effective in reducing the creep strength of upper mantle rocks as small amounts of water. However, a possible contribution of grain boundary composition to the observed differences in rheology in the absence of melt cannot be conclusively ruled out by the current experiments.
The morphology and surface features of olivine in kimberlite lava: implications for ascent and emplacement mechanisms
NASA Astrophysics Data System (ADS)
Jones, T. J.; Russell, J. K.; Porritt, L. A.; Brown, R. J.
Many kimberlite rocks contain large proportions of ellipsoidal-shaped xenocrystic olivine grains that are derived mainly from the disaggregation of peridotite. Xenocrystic olivine grains from a lava erupted from the Quaternary Igwisi Hills kimberlites, Tanzania, are compared to phenocrystic olivine, liberated from picritic lavas, and mantle olivine, liberated from a fresh peridotite xenolith, in order to examine the potential modification of olivine surface textures due to transport from the mantle to the surface within kimberlite magmas. Image analysis, SEM imagery and laser microscopy reveals significant differences in the surface features and morphologies of the three crystal populations. Xenocrystic olivine grains are characterised by rough surfaces, ellipsoidal shapes and impact pits. Mantle olivines are characterised by flaked surfaces and indented shapes consistent with growth as a crystal aggregates. Phenocrystic olivines are smooth-surfaced and exhibit flat crystal faces. We infer that the distinctive shapes and surfaces of xenocrystic olivine grains resulted from three distinct mechanical processes attending their rapid transport from their source in the mantle lithosphere: (1) penetrative flaking from micro-tensile failure induced by rapid decompression; (2) sustained abrasion and attrition arising from particle-particle collisions between grains in a turbulent, volatile-rich flow regime, and; (3) higher energy particle-particle collisions that produced impact cavities superimposed on decompression structures. The combination of these processes during the rapid ascent of kimberlite magmas is responsible for the distinctive ellipsoidal shape of olivine xenocrysts found in kimberlites worldwide.
From olivine to ringwoodite: a TEM study of a complex process
NASA Astrophysics Data System (ADS)
Pittarello, Lidia; Ji, Gang; Yamaguchi, Akira; Schryvers, Dominique; Debaille, Vinciane; Claeys, Philippe
The study of shock metamorphism of olivine might help to constrain impact events in the history of meteorites. Although shock features in olivine are well known, so far, there are processes that are not yet completely understood. In shock veins, olivine clasts with a complex structure, with a ringwoodite rim and a dense network of lamellae of unidentified nature in the core, have been reported in the literature. A highly shocked (S5-6), L6 meteorite, Asuka 09584, which was recently collected in Antarctica by a Belgian-Japanese joint expedition, contains this type of shocked olivine clasts and has been, therefore, selected for detailed investigations of these features by transmission electron microscopy (TEM). Petrographic, geochemical, and crystallographic studies showed that the rim of these shocked clasts consists of an aggregate of nanocrystals of ringwoodite, with lower Mg/Fe ratio than the unshocked olivine. The clast's core consists of an aggregate of iso-oriented grains of olivine and wadsleyite, with higher Mg/Fe ratio than the unshocked olivine. This aggregate is crosscut by veinlets of nanocrystals of olivine, with extremely low Mg/Fe ratio. The formation of the ringwoodite rim is likely due to solid-state, diffusion-controlled, transformation from olivine under high-temperature conditions. The aggregate of iso-oriented olivine and wadsleyite crystals is interpreted to have formed also by a solid-state process, likely by coherent intracrystalline nucleation. Following the compression, shock release is believed to have caused opening of cracks and fractures in olivine and formation of olivine melt, which has lately crystallized under postshock equilibrium pressure conditions as olivine.
A New Spinel-Olivine Oxybarometer: Near-Liquidus Partitioning of V between Olivine-Melt, Spinel-Melt, and Spinel-Olivine in Martian Basalt Composition Y980459 as a Function of Oxygen Fugacity
NASA Technical Reports Server (NTRS)
Papike, J. J.; Le, L.; Burger, P. V.; Shearer, C. K.; Bell, A. S.; Jones, J.
Our research on valence state partitioning began in 2005 with a review of Cr, Fe, Ti, and V partitioning among crystallographic sites in olivine, pyroxene, and spinel [1]. That paper was followed by several on QUE94201 melt composition and specifically on Cr, V, and Eu partitioning between pyroxene and melt [2-5]. This paper represents the continuation of our examination of the partitioning of multivalent V between olivine, spinel, and melt in martian olivine-phyric basalts of Y980459 composition [6, 7]. Here we introduce a new, potentially powerful oxybarometer, V partitioning between spinel and olivine, which can be used when no melt is preserved in the meteorite. The bulk composition of QUE94201 was ideal for our study of martian pyroxene-phyric basalts and specifically the partitioning between pyroxene-melt for Cr, V, and Eu. Likewise, bulk composition Y980459 is ideal for the study of martian olivine-phyric basalts and specifically for olivine-melt, spinel-melt, and spinel-olivine partitioning of V as a function of oxygen fugacity.
Fe/Mn in olivine of carbonaceous meteorites
NASA Technical Reports Server (NTRS)
Steele, Ian M.
Olivines in primitive meteorites show a range of Fe/Mn both within one grain and among grains suggesting that they have recorded changing conditions during or after growth. Because olivine should be an early forming phase, Fe/Mn is used here to infer these earliest conditions. Initial Fe/Mn in cores of isolated, euhedral forsterite in both C2 and C3 meteorites ranges from 25 to 35 but differs at grain edge. Murchison (C2) forsterites show Fe/Mn approaching 1.0 at the grain edge while Ornans Fe/Mn is near 60 at grain edge. These values are lower than the matrix Fe/Mn for both meteorites and the distinct difference in zoning profile indicates different processes operating during and after grain growth. The Fe/Mn of bulk samples from a particular source such as the Moon is nearly constant. Individual samples show variation suggesting that there is some fractionation of Mn from Fe. Minerals have their individual ranges of Fe/Mn which has been used to recognize different types of olivine within one meteorite. Extreme values of Fe/Mn below 1.0 occur in forsterite from some IDP's, UOC matrix, and C1 meteorites. There are apparently no detailed studies of Fe/Mn variation within single olivine grains. Forsterite grains in C2 and C3 carbonaceous chondrites show complex zoning, and the nearly pure forsterites (Fo greater than approximately 99.5) have high levels of some minor elements including Ti, Al, V, and Sc. There is disagreement on the original source of these grains and both chondrule and vapor growth have been proposed. In addition, there is clear evidence that diffusion has affected the outer margins but in some cases the whole grain. Within the cores, the FeO range is limited, and if growing under constant conditions, the Fe/Mn should be near constant as there is little fractionation of Mn from Fe by forsterite. Additionally, there are apparently no co-crystallizing phases as evidenced by a lack of common inclusions in the forsterites. These observations are now followed by analyses of isolated olivine grains in C2 and C3 meteorites.
Olivine Morphology and Trace Element Fractionation in Metal of Main Group Pallasites
NASA Astrophysics Data System (ADS)
Kissin, S. A.
Pallasites are stony-iron meteorites consisting largely of olivine macrocrysts in a matrix of iron-nickel alloy in the form of kamacite-taenite intergrowth. Pallasites have been divided into Main Group (PMG), Eagle Station Grouplet (PES) and ungrouped (IrUn) also called pyroxene pallasites. Within PMG, six have anomalous metal contents (PMGam) and five have anomalous olivine compositions (PMGas). The morphologies of olivine macrocrysts in PMG are essentially of two types, angular or rounded. Of 19 normal PMG whose compositions and olivine morphologies are known, 17 have angular olivines. In the remaining two PMG, olivines are rounded as well as those of three PMGam and three PMGas. Experimental studies have demonstrated that rounding of olivines in molten iron-nickel alloy occurs in short times on a geological scale. Metallic cooling rates for PMG have been shown to be rapid at high temperature and slow at low temperature. Detailed analyses have demonstrated that angular olivines are compositionally zoned and therefore not in equilibrium with metal. These conditions imply that molten metal was injected into angular olivines fractured by an impact event. However, the presence of rounded olivine macrocrysts in PMGam and PMGas, as well as in two normal PMG, implies that these pallasites have retained an earlier generation of olivine. A long-standing theory for the origin of pallasites is that they represent the core-mantle boundary of a parent- body, subsequently disrupted by impact and injected by impact-melted metal. A relationship between the trace element fractionation trend in group IIIAB iron meteorites and metal of PMG is evident in that normal members cluster at the end of this fractionation trend. However, the theory does not account for the presence of rounded olivine macrocrysts. Log trace element vs log Au plots of indicate that most PMGam members exhibit the same fractionation trend as that seen for group IIIAB irons, and these correlate with PMGam and PMGas members with rounded olivines. The rounded olivine marcrocrysts may represent pre-impact olivines trapped in fractionating group IIIAB metal. Some scatter in these plots may be attributed to crystallization of melt trapped among olivine macrocrysts. Thus, the core-mantle boundary theory for the original of PMG is consistent with the evidence seen in olivine macrocrysts.
Normalized Homologous Temperature of Olivine: Implications for the Effect of Iron Content on Mantle Deforamtio
NASA Astrophysics Data System (ADS)
Wang, Q.
The flow laws and fabric transition of olivine under different thermal-mechanical conditions are generally obtained from HP-HT experiments on San Carlos olivine (Fo90), which hampers our understanding of the effect of iron content on the mantle flow and deforamtion. Because the melting temperature is related with the strength of the bonds binding a crystalline material together, the normalized homologous temperature T/Tm(P), is defined by the ratio between the absolute temperature of olivine and its melting point Tm at certain pressure P. Using the forsterite-fayalite melting loop at room pressure, the generalized mean is adopted to predict the dependence of Tm on pressure and iron content of olivine up to 7.5 GPa. Using T/Tm(P), we can evaluate the integreted effect of temperature and pressure on the deformation mechanisms of olivine. A new olivine fabric diagram is set up as a function T/Tm(P) and water content. The result indicates that the A-type olivine fabric becomes dominant at T/Tm(P) > 0.72, while the B- and C-type olivine fabrics are favorable at T/Tm(P) < 0.7, no matter their water content. Partial melting will produce resudies with higher Fo number in olivine, and consequently, a more rigid mantle with higher Tm. The relatively smaller T/Tm(P) of olivine beneath cratons can explain the long-term stability of the continental roots. In addition, a 2D profile of olivine T/Tm(P) for the oceanic lithosphere shows good correlation between T/Tm(P) and the distribution of earthquakes. Therefore T/Tm(P) of olivine can be used as a parameter to model the rheology of the upper manlte, especailly when taking into account of the compostional change in different tectonic processes.
Partition of Ni between olivine and sulfide and its application to Ni-Cu sulfide deposits
M. E. Fleet; N. D. MacRae
Equilibration of natural olivine with (Fe, Ni)S in sealed silica glass tubes yields a value for the distribution constant for Ni\\/Fe exchange (KD3) of 27.7▒3.5, for 1,200░ C, product olivine and sulfide compositions in the ranges 96 to 97 mol% Fo and 15 to 70 mol% NiS, respectively, and run durations of 28 days. Electron microprobe analysis of product olivine
Phosphorus zoning in olivine of Kilauea Iki lava lake, Hawaii
NASA Astrophysics Data System (ADS)
Fabbrizio, Alessandro; Beckett, John R.; Baker, Michael B.; Stolper, Edward M.
Kilauea Iki lava lake was formed when the lavas of the 1959 summit eruption of Kilauea volcano ponded in Kilauea Iki pit crater, as described by [1]. The main chamber of this lake has been drilled repeatedly from 1960 to 1981 as the lake has cooled and crystallized and partial descriptions of core can be found in [2-7]. The bulk of the core consists of a gray, olivine-phyric basalt matrix [3]. Rapid diffusion of divalent cations through olivine at magmatic temperatures can delete information on early-formed zoning and thus information on early magmatic history, recorded in olivine during its growth, is often largely lost [8-11]. In the last years many studies [8-11] have shown that natural olivine, terrestrial and extraterrestrial, from several localities and rock types can preserve a complex zoning in P (sometimes associated with Cr and Al). Simple crystallization experiments conducted by [10] and [11] were able to replicate these features (i.e., sector and oscillatory zoning). Here, we describe P, Cr and Al zoning in olivine from the 1981 drilling of Kilauea Iki lava lake hole #1 (KI81-1) [6]. K? X-ray intensity maps and major and minor element quantitative analyses were obtained using the Caltech JEOL JXA-8200 electron microprobe. We acquired P, Cr, Al, Fe and Ti X-ray maps simultaneously at 15 kV and 400 nA, a beam diameter of 1 ?m, pixel spacing of 1-2 ?m, and count times of 420-1500 msec/step were used depending on the dimension of the crystal. 15 kV and 40 nA with a beam diameter of 1 ?m were used to collect quantitative analyses. P2O5 contents of the Iki olivines range from below detection limit to 0.30 wt%. Zoning in phosphorus, based on X-ray intensity maps, was observed in all olivines we examined. The P zoning patterns of the olivines display several styles. P shows oscillatory zoning comparable to that seen in terrestrial and extraterrestrial igneous olivines and in experimentally grown olivine [8-11]; high P regions, inside the crystals, outline low P chambers and P enriched zones were also observed; near the margins of the crystals is possible to find the presence of discontinuous sets of P-enriched bands that generally outline euhedral crystal forms; some crystals are characterized by P-enriched ghosts of relict crystals in their interior that are associated with probable undercooling and/or with an initial pulse of rapid crystal growth [8, 10]. Phenocrysts and microphenocrysts are frequently unzoned in major and minor divalent cations (Fe, Mg, Mn, Ca, Ni), but all are zoned in P. Variations in Cr and Al correlate spatially with P but are much fainter or absents, in some crystal the P-enriched bands are superimposed with small crystals of chromite (?1 ?m) aligned along the P zoning. Probably these chromites were formed by precipitation from the original Cr and Al bands. In no case was observed Ti zoning. [1] Richter D.H. et al. (1970) US Geol Surv Prof Pap 537-E, 73 p. [2] Richter D.H., Moore J.G. (1966) US Geol Surv Prof Pap 537-B, 26 p. [3] Helz R.T. (1980) Bull Volcanol 43-4, 675-701. [4] Helz R.T. et al. (1984) US Geol Surv Open File Rep 84-484, 72 p. [5] Hardee H.C. et al. (1981) Geophys Res Lett 8, 1211-1214. [6] Helz R.T., Wright T.L. (1983) US Geol Surv Open File Rep 83-326, 66 p. [7] Helz R.T. (1987) Geochem Soc Spec Pub 1, 241-258. [8] Beckett J.R. et al. (2008) LPSC abs. 1726. [9] Mccanta M.C. et al. (2008) LPSC abs. 1807. [10] Milmann-Barris M.S. et al. (2008) CMP 155, 739-765. [11] Mccanta M.C. et al. (2008) GCA 72-12, S1, A610.
Olivine-rich exposures at Bellicia and Arruntia craters on (4) Vesta from Dawn FC
NASA Astrophysics Data System (ADS)
Thangjam, Guneshwar; Nathues, Andreas; Mengel, Kurt; Hoffmann, Martin; Schõfer, Michael; Reddy, Vishnu; Cloutis, Edward A.; Christensen, Ulrich; Sierks, Holger; Corre, Lucille Le; Vincent, Jean-Baptiste; Russell, Christopher T.
We present an analysis of olivine-rich exposures at Bellicia and Arruntia craters using Dawn Framing Camera (FC) color data. Our results confirm the existence of olivine-rich materials at these localities as described by Ammannito et al. using Visual Infrared Spectrometer (VIR) data. Analyzing laboratory spectra of various howardite-eucrite-diogenite meteorites, high-Ca pyroxenes, olivines, and olivine-orthopyroxene mixtures, we derive three FC spectral band parameters that are indicators of olivine-rich materials. Combining the three band parameters allows us, for the first time, to reliably identify sites showing modal olivine contents >40%. The olivine-rich exposures at Bellicia and Arruntia are mapped using higher spatial resolution FC data. The exposures are located on the slopes of outer/inner crater walls, on the floor of Arruntia, in the ejecta, as well as in nearby fresh small impact craters. The spatial extent of the exposures ranges from a few hundred meters to few kilometers. The olivine-rich exposures are in accordance with both the magma ocean and the serial magmatism model (e.g., Righter and Drake; Yamaguchi et al.). However, it remains unsolved why the olivine-rich materials are mainly concentrated in the northern hemisphere (approximately 36-42░N, 46-74░E) and are almost absent in the Rheasilvia basin.
Origin of graphitic carbon and pentlandite in matrix olivines in the Allende meteorite.
Brearley, A J
Matrix olivines in the Allende carbonaceous chondrite are believed to have formed by condensation processes in the primitive solar nebula. However, transmission electron microscope observations of numerous matrix olivines show that they contain abundant, previously unrecognized, nanometer-sized inclusions of pentlandite and poorly graphitized carbon. Neither of these phases would have been stable at the high-temperature conditions required to condense iron-rich olivine in the solar nebula. The presence of these inclusions is consistent with formation of the olivines by parent body processes that involved overgrowth of fine-grained organic materials and sulfides in the precursor matrix materials. PMID:10464092
Relation of the spectroscopic reflectance of olivine to mineral chemistry and some remote sensing implications.
King, T.V.V.; Ridley, W.I.
Using high-resolution visible and near-infrared diffuse spectral reflectance, systematically investigates apparent wavelength shifts as a function of mineral chemistry in the Fe/Mg olivine series from Fo11 to Fo91. The study also shows that trace amounts of nickel can be spectrally detected in the olivine structure. Significant spectral variation as a function of grain size is also demonstrated, adding a further complication to the interpretation of remotely sensed data from olivine-rich surfaces. Some permutations of Fe-Mg-Ni relations in olivines are discussed as they apply to the interpretation of asteroid surfaces and other extraterrestrial bodies. -from Authors
Deformation of olivine single crystals under lithospheric conditions
NASA Astrophysics Data System (ADS)
Demouchy, S.; Tommasi, A.; Cordier, P.
The rheology of mantle rocks at lithospheric temperatures (<1000░C) remains poorly constrained, in contrast to the extensive experimental data on creep of olivine single crystals and polycrystalline aggregates at high temperature (T > 1200░C). Consequently, we have performed tri-axial compression experiments on oriented single crystals and polycrystalline aggregates of San Carlos olivine at temperatures ranging from 800░ to 1090░C. The experiments were carried out at a confining pressure of 300 MPa in a high-resolution gas-medium mechanical testing apparatus at constant strain rates ranging from 7 ū 10-6 s-1 to 1 ū 10-4 s-1 . Compression was applied along three different crystallographic directions: [101]c, [110]c and [011]c, to activate the several slip systems. Yield differential stresses range from 88 to 1076 MPa. To constrain hardening, stick-and-slip, or strain localization behaviors, all samples were deformed at constant displacement rate for finite strains between 4 to 23 %. Hardening was observed in all experiments and the maximum differential stress often overcame the confining pressure. EBSD mapping highlights macroscale bending of the crystalline network in three crystals. TEM observations on several samples show dislocations with [100] and [001] Burgers vectors in all samples, but dislocation arrangements vary. The results from the present study permit to refining the power-law expressing the strain rate dependence on stress and temperature for olivine, allowing its application to the lithospheric mantle. Our experiments confirm that previous published high-temperature power flow laws overestimate the strength of lithospheric mantle and that the transition to low-temperature creep occurs at higher temperatures than it has previously been established.
Destabilization of olivine by 10kV electron irradiation
NASA Astrophysics Data System (ADS)
Lemelle, L.; Beaunier, L.; Borensztajn, S.; Fialin, M.; Guyot, F.
Mineral phases in the interplanetary medium are subjected to the solar wind irradiation. Irradiation induces fractional volatilization of chemical elements in silicates; if large scale directional flow occurs, such as predicted by numerous models in the early solar system, then large scale chemical fractionnations occur. Electron irradiation experiments were performed using a 30 keV electron beam on single crystals of olivine in a scanning electron microscope (SEM) and in an electron microprobe (EMP) (Lemelle et al. 2003). Structural damage is caused to the irradiated surface of the iron-bearing olivines. The irradiated areas comprise spherules with sizes of hundreds of nanometers and micrometer-sized holes observed on Focused Ion Beam cuts. In the immediate vicinities of the irradiated areas, droplets with sizes of tens of nanometers and tracks are observed. With increasing total charge, the hundreds of nanometer-sized spherules become larger and more irregular in shape. The size and shape of the nanometer-sized droplets remain almost constant, but their surface density increases (in cm-2). Compared to the initial olivine, irradiated areas are slightly enriched in MgO, whereas the deposits are enriched in SiO_2. This destabilization of olivine results most probably from electrostatic discharges leading to the breakdown of the dielectric lattice. The possibility that such processes could be responsible for significant space weathering of interplanetary dust particles and regoliths of planetary surfaces should be taken into account. In the interplanetary medium, 10 keV-range electrons are carried by the solar wind, whereas at 1 AU from the Sun, the lifetime of cometary dust and the exposure time of lunar regolith are, at least, 10 to 100 times greater than the duration required to accumulate the damaging electronic doses applied in this study. Moreover, the comparison of the microstructures of samples irradiated in the present study with features of lunar regolith grains reveals several chemical and structural similarities. Interestingly, experiments carried out in transmission EM, with 100 keV-range electrons (Carrez et al. 2002) showed different mechanism of destabilization and chemical fractionation elemental loss from the silicate matrix. Lemelle et al. (2003) to be printed in Geochimica Cosmochimica Acta. Carrez P., Leroux H., Cordier P. and Guyot F. (2001) Philos. Mag. A 81, 2823-2840.
Weil, Matthias
The title compound, sodium cadmium orthoarsenate, adopts the olivine [Mg2(SiO4)] structure type in space group Pnma, with Na (site symmetry -1) and Cd (.m.) replacing the two Mg positions, and the AsO4 tetraŁhedron (.m.) the SiO4 tetraŁhedron. The crystal structure is made up of a nearly hexaŁgonal closed-packed arrangement of O atoms stacked along [001]. The Na and Cd atoms occupy one half of the octaŁhedral voids in alternate layers stacked along [100], and one eighth of the tetraŁhedral voids are occupied by As atoms. PMID:24454011
Argon Diffusion in Shocked Pyroxene, Feldspar, and Olivine
NASA Astrophysics Data System (ADS)
Weirich, J.; Isachsen, C. E.; Johnson, J. R.; Swindle, T.
Background: The diffusion rate of argon (Ar) in unshocked feldspar has been well studied, but studies on pyroxene and olivine are limited or non-existent. Likewise, the effects of shock on these mineral groups is also limited or non-existent. Understanding how shock affects these mineral groups is important for determining the thermal history of shocked meteorites and collisional impact craters. We have analyzed the Ar diffusion rate of an albitite and a pyroxenite at various experimental shock pressures up to ~60GPa, unshocked high-Ca pyroxene, and an olivine mineral separate from the Springwater meteorite. A previous study of shocked feldspar has shown that Ar diffusion in plagioclase (An67) is unaffected by experimental shock [1]. Re-reduction of data from another study [2] suggests naturally shocked K-rich feldspar is affected, though experimentally shocked oligoclase feldspar (An10-30) is not affected. However, previous shock experiments on feldspar were performed with low temperature resolution and only a single extraction at each temperature. This makes determining the diffusion parameters difficult because the presence of multiple grain sizes can compromise the data. By performing our experiments with a higher temperature resolution and with two extractions at each temperature, we can attain higher quality and more reliable data. The effects of shock on pyroxene and olivine have never been studied. Results: We have found that experimental shock undoubtedly raises the diffusivity of albite (Ab97), and lowers the activation energy required for diffusion. Comparison with previous data indicates that the Ca content may be controlling the response to shock. Pyroxene seems to be somewhat variable regardless of shock pressure, even within the same sample. Shock may have an effect on the diffusion rate of pyroxene, but given the variability it is difficult to delineate. The range of pyroxene diffusion rates is similar to previous studies. Olivine is found to have a low activation energy, somewhat similar to that of unshocked alkali feldspar, despite remaining a high temperature mineral due to a much lower frequency factor. References: [1]Jessberger E. K. and Ostertag R. (1982). GCA 46:1465-1471. [2]Stephan T. and Jessberger E. K. (1992). GCA 56:1591-1605.
Serpentinization of sintered olivine during seawater percolation experiments
NASA Astrophysics Data System (ADS)
Luquot, L.; Andreani, M.; Godard, M.; Gouze, P.; Gibert, B.
The mantle exposed at slow to ultra-slow spreading ridges is pervasively and variably serpentinized down to depth of 4-8km according to available geophysical data. The onset and durability of this hydration process require efficient penetration and renewal of fluids at the mineral-fluid interface. Moreover, serpentinization is exovolumic if a mass-conservative system is assumed, or chemical elements have to be leached out to conserve rock volume. Thus, the extent of serpentinization depends of the system capacity to create space and/or to drive mass transfers. In order to investigate these coupled hydrodynamic and chemical mechanisms, we did a laboratory experiment during which seawater was injected in a sintered San Carlos olivine sample at conditions representative of low temperature, ultramafic-hosted, hydrothermal systems. The percolation-reaction experiment was carried out at 19 MPa and 190░C; the initial water flow was set at 0.2 mL/h then decreased down to 0.06 mL/h after 8 days. During experiment, permeability decreases continuously although the high Si concentrations in outlet fluids indicate steady olivine dissolution. Fluids are also depleted in Fe and Mg, suggesting precipitation of Fe- and Mg-rich mineral phases. SEM and AEM/TEM analyses of the reacted samples allowed to characterize hematite and poorly crystallized serpentine, both formed at the expanse of olivine. Mass balance calculations indicate that, ca. 8 wt. % olivine was dissolved while the same mass of serpentine (+/- brucite) was formed finally resulting in a porosity decrease from ~ 12% to 5 %. We infer that the structure of the newly formed serpentine resulted in the clogging of fluid paths and explain the decrease of permeability during experiments. Hematite (<1 wt.%) is also observed, indicating redox reactions. We observed that the outlet fluid composition is not modified by changes in the fluid flow. These experimental results are used better understand the scale and efficiency of serpentinization at the onset of the alteration reactions (effective reaction rates in porous/fractured media).
Phosphorus as indicator of magmatic olivine residence time, morphology and growth rate
NASA Astrophysics Data System (ADS)
Sobolev, Alexander; Batanova, Valentina
Phosphorus is among of slowest elements by diffusion rate in silicate melts and crystals (e.g. Spandler et al, 2007). In the same time it is moderately incompatible to compatible with olivine (Brunet & Chazot, 2001; Grant & Kohn, 2013). This makes phosphorus valuable tracer of olivine crystallization in natural conditions. Indeed, it is shown that natural magmatic olivine crystals commonly posses strong and complicated zoning in phosphorus (Milman-Barris et al, 2008; Welsch et al, 2014). In this paper we intend to review phosphorus behavior in olivine in published experimental and natural olivine studies and present large set of new EPMA data on phosphorus zoning in olivine phenocrysts from MORBs, OIBs, komatiites and kimberlites. We will show that sharp olivine zones enriched in phosphorus by a factor of 10-20 over prediction by equilibrium partition may be due to formation of P-rich boundary layer on the interface of fast growing olivine. This is proved by finding of small-size (normally 10 mkm or less) exceptionally P-rich melt inclusions in olivine, which are otherwise similar in composition to typical melt. These observations could provide potential olivine growth speedometer. We will also demonstrate, that sharp zoning in phosphorus may provide valuable information on the residence time of olivine crystals in different environments: magma chambers and conduits as well as mantle sources. This study has been founded by Russian Science Foundation grant 14-17-00491. References: Spandler, et al, 2007, Nature, v. 447, p. 303-306; Brunet & Chazot, 2001, Chemical Geology, v. 176, p. 51-72; Grant & Kohn, 2013, American Mineralogist, v. 98, p. 1860-1869; Milman-Barris et al, 2008, Contr. Min. Petrol. v. 155, p.739-765; Welsch et al, 2014, Geology, v. 42, p.867-870.
An experimental investigation into the metastable formation of phosphoran olivine and pyroxene
NASA Astrophysics Data System (ADS)
Boesenberg, Joseph S.; Hewins, Roger H.
The formation of phosphoran olivine by crystallization from a melt was investigated experimentally using a one atmosphere furnace, using San Carlos olivine [(Mg,Fe) 2SiO 4] mixed with either iron phosphide (FeP) or magnesium pyrophosphate (Mg 2P 2O 7). Both dynamic crystallization and isothermal experiments produced phosphoran olivine as zoned single crystals and as overgrowths surrounding normal, phosphorus-free olivine grains. The crystallization pathways that form phosphoran olivine were traced and confirm that it is a metastable phase that can crystallize from a phosphorus-rich melt over timescales of hours to days. Removal of the P and equilibration of the olivine however requires weeks to months in the presence of silicate melt. Phosphoran olivine with up to 27 wt% P 2O 5 was generated and up to 69% of the Si tetrahedral sites were replaced by P. The substitution of Si by P into olivine was confirmed as 4 VIM +2 + 2 IVSi +4 ? 3 VIM +2 + 2 IVP +5 + VI[]. Phosphoran olivine compositions that vary from (Mg,Fe) 2SiO 4 to (Mg,Fe) 1.65[] 0.35Si 0.3P 0.7O 4 have been produced in these experiments. Phosphoran pyroxene was also generated in a few experiments and forms when phosphoran olivine reacts with either tridymite or melt. It has compositions compatible with protopyroxene, orthopyroxene, pigeonite and sub-calcic augite, and can contain up to 31.5 wt% P 2O 5. Like phosphoran olivine, it is also a metastable phase. Phosphorus replaces Si in pyroxene by the following substitution methods: 8 IVSi +4 ? 3 IVSi +4 + 4 IVP +5 + IV[] with Al entering the structure by the exchange 2 IVSi +4 ? IVAl +3 + IVP +5. Phosphoran pyroxene compositions vary from (Mg,Fe) 8Si 8O 24 to (Mg,Fe) 8Si 3P 4[]O 24.
Temperature-dependent Infrared Optical Constants of Olivine and Enstatite
NASA Astrophysics Data System (ADS)
Zeidler, S.; Mutschke, H.; Posch, Th.
Since the Infrared Space Observatory (ISO) mission, it has become clear that dust in circumstellar disks and outflows consists partly of crystalline silicates of pyroxene and olivine type. An exact mineralogical analysis of the dust infrared emission spectra relies on laboratory spectra, which, however, have been mostly measured at room temperature so far. Given that infrared spectral features depend on the thermal excitation of the crystal's vibrational modes, laboratory spectra measured at various (low and high) temperatures, corresponding to the thermal conditions at different distances from the star, can improve the accuracy of such analyses considerably. We have measured the complex refractive index in a temperature range of 10-973 K for one mineral of each of those types of silicate, i.e., for an olivine and an enstatite of typical (terrestrial) composition. Thus, our data extend the temperature range of previous data to higher values and the compositional range to higher iron contents. We analyze the temperature dependence of oscillator frequencies and damping parameters governing the spectral characteristics of the bands and calculate absorption cross-sectional spectra that can be compared with astronomical emission spectra. We demonstrate the usefulness of our new data by comparing spectra calculated for a 100 K dust temperature with the ISO SWS spectrum of IRAS 09425-6040.
Serpentinization of Olivine by Seawater: A Flow-Through Experiment
NASA Astrophysics Data System (ADS)
Gouze, P.; Luquot, L.; Andreani, M.; Godard, M.; Gibert, B.
The mantle exposed at slow spreading ridges is pervasively serpentinized, down to ca. 5km according to geophysical data. The onset and durability of this hydration process require efficient penetration and renewal of fluids at the mineral-fluid interface. However, the mechanisms of fluid penetration are still poorly understood. Moreover, serpentinization is exovolumic, if a mass-conservative system is assumed, or chemical elements are leached out to conserve rock volume. Thus, the extent of serpentinization depends of the system capacity to create space and/or to drive mass transfers. In order to investigate these hydrodynamic and chemical mechanisms, we did a laboratory experiment during which seawater was injected in a sintered San Carlos olivine sample at conditions representative of low temperature ultramafic hydrothermal systems. The percolation-reaction experiment was carried out at 19 MPa and 190░C; the initial water flow was set at 0.2 mL/h then decreased down to 0.06 mL/h after 8 days. During the experiment (23 days), permeability decreased continuously. The composition of the outlet fluid varied strongly during the first 24h of the experiment, then reached equilibrium values. The high Si concentrations in outlet fluids indicated steady olivine dissolution, while their low Fe and Mg concentrations suggested precipitation of Fe- and Mg-rich mineral phases. The reacted sample acquired a reddish brown color, indicating oxidation reactions occurred. Optical observation and SEM imaging revealed the presence of a soft white material filling the pores of the reacted sample. It was identified as a poorly crystallized serpentine type material by AEM/TEM analyses. This proto-serpentine is intimately associated to <100 nm Fe-oxide patches (probably hematite) growing on the olivine surface. We interpret the precipitation of this proto-serpentine together with Fe-oxides throughout the sample as marking the early stages of serpentinization. The fluid composition not being modified by changes in fluid flow, we posit that olivine serpentinization is not controlled by elemental transport and/or by chemical kinetics, but takes place at-equilibrium; the reaction velocity is very fast and independent on the changes in the reaction surface area. Indeed, mass balance calculations indicate that more than 15 wt. % olivine was dissolved while the same mass of proto-serpentine was formed; concurrently, porosity decreased from ś 12% to 5 %. We infer that the structure of the newly formed proto-serpentine resulted in the clogging of fluid paths and explain the decrease of permeability during experiments. Yet the loose structure of the proto-serpentine allows maintaining a connected pore structure ensuring the perennial renewing (diffusion and/or advection) of the reactants at the reaction surfaces. These experimental results are used to constrain numerical reactive transport models and better understand the scale and efficiency of serpentinization reactions (effective reaction rates in porous/fractured media) at the scale of spreading ridges.
Olivine-rich exposures at Bellicia and Arruntia craters on (4) Vesta from Dawn FC
Thangjam, Guneshwar; Mengel, Kurt; Hoffmann, Martin; Schõfer, Michael; Reddy, Vishnu; Cloutis, Edward A; Christensen, Ulrich; Sierks, Holger; Corre, Lucille Le; Vincent, Jean-Baptiste; Russell, Christopher T
We present an analysis of the olivine-rich exposures at Bellicia and Arruntia craters using Dawn Framing Camera (FC) color data. Our results confirm the existence of olivine-rich materials at these localities as described by Ammannito et al. (2013a) using Visual Infrared Spectrometer (VIR) data. Analyzing laboratory spectra of various Howardite-Eucrite-Diogenite meteorites, high-Ca pyroxenes, olivines and olivine-orthopyroxene mixtures, we derive three FC spectral band parameters that are indicators of olivine-rich materials. Combining the three band parameters allows us, for the first time, to reliably identify sites showing modal olivine contents >40%. The olivine-rich exposures at Bellicia and Arruntia are mapped using higher spatial resolution FC data. The exposures are located on the slopes of outer/inner crater walls, on the floor of Arruntia, in the ejecta, as well as in nearby fresh small impact craters. The spatial extent of the exposures ranges from a few hundred meters to few kilometers. The olivin...
Systematics of Ni, Co, Cr and V in Olivine from Planetary Melt Systems: Martian Basalts
NASA Technical Reports Server (NTRS)
Herd, C. D. K.; Jones, J. H.; Shearer, C. K.; Papike, J. J.
Secondary Ion Mass Spectrometry (SIMS) data for Ni, Co, Cr, and V in olivine in martian basalts is compared to data from lunar and terrestrial basalts. We use experimentally-derived and published D values to calculate as-yet unsampled, olivine-bearing, non-cumulus melt compositions. Additional information is contained in the original extended abstract.
Shear wave attenuation and dispersion in melt-bearing olivine polycrystals
Shear wave attenuation and dispersion in melt-bearing olivine polycrystals: 1. Specimen fabrication 2003; accepted 7 January 2004; published 23 June 2004. [1] Five melt-bearing polycrystalline olivine behavior of melt-free materials, a broad dissipation peak is observed for each of the melt-bearing
Shear wave attenuation and dispersion in melt-bearing olivine polycrystals
Shear wave attenuation and dispersion in melt-bearing olivine polycrystals: 2. Microstructural forced oscillation tests of melt-bearing olivine aggregates reported by Jackson et al. [2004. While the nanometer scale grain boundary structure in the melt-bearing aggregates is essentially
Possible mantle origin of olivine around lunar impact basins detected by SELENE
Satoru Yamamoto; Ryosuke Nakamura; Tsuneo Matsunaga; Yoshiko Ogawa; Yoshiaki Ishihara; Tomokatsu Morota; Naru Hirata; Makiko Ohtake; Takahiro Hiroi; Yasuhiro Yokota; Junichi Haruyama
The composition, structure and evolution of the Moon's mantle is poorly constrained. The mineral olivine, one of the main constituents of Earth's mantle, has been identified by Earth-based telescopic observations at two craters on the near side of the Moon, Aristarchus and Copernicus. Global reflectance spectra in five discrete spectral bands produced by the spacecraft Clementine suggested several possible olivine-bearing
High-temperature condensation of iron-rich olivine in the solar nebula
Herbert Palme; Bruce Fegley Jr.
The origin of oxidized iron in chondritic meteorites is a fundamental problem in meteoritics. Conventional models of meteorite formation assume FeO incorporation into olivine and pyroxene at around 500 K. There is evidence that at least some fayalitic olivine in Allende must have formed by condensation. Thermodynamic equilibrium calculations presented here define the nebular conditions that would enable condensation of
Experimental modeling of the cooling history of Apollo 12 olivine basalts
NASA Technical Reports Server (NTRS)
Donaldson, C. H.; Usselman, T. M.; Williams, R. J.; Lofgren, G. E.
An analog of the Apollo 12 olivine vitrophyres has been crystallized in a 1-atm gas-mixing furnace at cooling rates ranging between 1250 and 0.7 C/hr and isothermally at degrees of supercooling ranging from 10 C to 325 C. Mineral chemistry, crystal shapes, grain sizes and textures are systematically related to cooling rate and degree of supercooling. At linear cooling rates not exceeding 40 C/hr the texture is porphyritic - large olivine crystals are set in a groundmass of finer-grained pyroxene, plagioclase, and ilmenite; a later generation of olivine never crystallizes. There are three shapes of olivine crystals in the Apollo 12 olivine vitrophyres: glomerocrysts of subhedral crystals, large subequant skeletons, and highly elongate skeletons. These result from three generations of nucleation and a two-stage cooling history - a slow preeruption stage and a rapid continuously increasing posteruption stage. It seems likely that the Apollo 12 olivine basalt magmas were erupted with olivine crystals in suspension. The nucleation temperature of olivine in cooling-rate experiments is dependent on the experimental technique, and hence results of cooling experiments should be applied with caution.
Upper mantle tectonics: three-dimensional deformation, olivine crystallographic fabrics and seismic properties
Andrķa Tommasi; Basil Tikoff; Alain Vauchez
Forward numerical models are used to investigate the effect of deformation regime on the development of olivine lattice-preferred orientations (LPO) and associated seismic anisotropy within continental deformation zones. LPO predicted to form by pure shear, simple shear, transpression, or transtension are compared to a database comprising ca. 200 olivine LPO from naturally deformed upper mantle rocks. This comparison suggests that
Li Conductivity in LixMPO4 ,,M Mn, Fe, Co, Ni... Olivine Materials
Ceder, Gerbrand
Li Conductivity in LixMPO4 ,,M ─ Mn, Fe, Co, Ni... Olivine Materials D. Morgan,z A. Van der Ven. Materials with M Mn, Fe, Co, Ni are considered. Li diffuses through one-dimensional channels with high than those of LixCoO2 .2 The olivines represent a whole class of potential cathode materials
The Mn-Fe negative correlation in olivines in ALHA 77257 ureilite
NASA Technical Reports Server (NTRS)
Miyamoto, M.; Furuta, T.; Fujii, N.; Mckay, D. S.; Lofgren, G. E.; Duke, M. B.
An electron probe microanalyzer is used to measure the Mn, Fe, and oxygen zoning profiles of olivines in the ALHA 77257 ureilite. This is done to study the effects of reduction on the Mn-Fe value, as ureilite olivines exhibit thin reduced rims. Since the Mn content gradually increases toward the rim of ureilite olivines, while the Fa (= 100 x Fe/(Mg + Fe), mol percent) component decreases, the Mn-Fe content of olivine is likely related to redox conditions. The results of melting experiments suggest that the Mn-Fe positive correlation is related to temperature and that the negative correlation of Mn-Fe in olivine and low-Ca pyroxene is related to reduction.
The Mn-Fe negative correlation in olivines in ALHA 77257 ureilite
NASA Astrophysics Data System (ADS)
Miyamoto, M.; Furuta, T.; Fujii, N.; McKay, D. S.; Lofgren, G. E.; Duke, M. B.
An electron probe microanalyzer is used to measure the Mn, Fe, and oxygen zoning profiles of olivines in the ALHA 77257 ureilite. This is done to study the effects of reduction on the Mn-Fe value, as ureilite olivines exhibit thin reduced rims. Since the Mn content gradually increases toward the rim of ureilite olivines, while the Fa (= 100 x Fe/(Mg + Fe), mol percent) component decreases, the Mn-Fe content of olivine is likely related to redox conditions. The results of melting experiments suggest that the Mn-Fe positive correlation is related to temperature and that the negative correlation of Mn-Fe in olivine and low-Ca pyroxene is related to reduction.
The x ray microprobe determination of chromium oxidation state in olivine from lunar basalt and kimberlitic diamonds
NASA Technical Reports Server (NTRS)
Sutton, S. R.; Bajt, S.; Rivers, M. L.; Smith, J. V.
The synchrotron x-ray microprobe is being used to obtain oxidation state information on planetary materials with high spatial resolution. Initial results on chromium in olivine from various sources including laboratory experiments, lunar basalt, and kimberlitic diamonds are reported. The lunar olivine was dominated by Cr(2+) whereas the diamond inclusions had Cr(2+/Cr(3+) ratios up to about 0.3. The simpliest interpretation is that the terrestrial olivine crystallized in a more oxidizing environment than the lunar olivine.
In situ observation of crystallographic preferred orientation of deforming olivine at high pressure and high temperature
NASA Astrophysics Data System (ADS)
Ohuchi, Tomohiro; Nishihara, Yu; Seto, Yusuke; Kawazoe, Takaaki; Nishi, Masayuki; Maruyama, Genta; Hashimoto, Mika; Higo, Yuji; Funakoshi, Ken-ichi; Suzuki, Akio; Kikegawa, Takumi; Irifune, Tetsuo
Simple-shear deformation experiments on polycrystalline olivine and olivine single-crystal were conducted at pressures of 1.3-3.8 GPa and temperatures of 1223-1573 K to understand the achievement of steady-state fabric strength and the process of dynamic recrystallization. Development of crystallographic preferred orientation (CPO) of olivine was evaluated from two-dimensional X-ray diffraction patterns, and shear strain was measured from X-ray radiographs. The steady-state fabric strength of the A-type fabric was achieved within total shear strain of ? = 2. At strains higher than ? = 1, an increase in concentration of the [0 1 0] axes mainly contributes to an increase in fabric strength. At strains higher than ? = 2, the magnitude of VSH/VSV (i.e., ratio of horizontally and vertically polarized shear wave velocities) scarcely increased in most of the runs. The VSH/VSV of peridotite (70 vol.% olivine + 30 vol.% minor phases) having the steady-state A-type olivine fabric coincides with that of recent global one-dimensional models under the assumption of horizontal flow, suggesting that the seismic anisotropy observed in the shallow upper mantle is mostly explained by the development of A-type olivine fabric. Experimental results on the deformation of single-crystal olivine showed that the CPO of olivine is influenced by the initial orientation of the starting single crystal because strain is concentrated in the recrystallized areas and the relic of the starting single crystal remains. In the upper mantle, the old CPO of olivine developed in the past may affect the olivine CPO developed in the present.
Extended planar defects and the rapid incorporation of Ti4+ into olivine
NASA Astrophysics Data System (ADS)
Burgess, Katherine D.; Cooper, Reid F.
The formation of extended planar defects in minerals such as olivine is related to high point defect concentration and can be driven by large gradients in chemical potential, where the energy of the system is lowered by the ordering of defects along specific planes in the crystal. The presence of extended defects has the potential to create the (apparently) anomalous ionic diffusion in olivine as reported recently (Spandler and O'Neill in Contrib Mineral Petrol 159(6):791-818, 2010). High-resolution transmission electron microscopy and energy-filtered imaging were done using experimental samples designed to examine the impact of a TiO2 and f O2 on the potential to form such defects in ferromagnesian olivine. Doped basalt (5 wt% TiO2)-olivine reaction couple experiments were run at 1 atm and 1,310 and 1,410 ░C for 50 h at various f O2, ranging from 102 below to 102 above the quartz-fayalite-magnetite buffer. Our results show that extended planar defects in olivine, parallel to {101}ol and occurring in ordered "clusters" with a prolate spheroid geometry 5-25 nm across and extending up to 150 nm into the olivine, are present near the olivine-glass interfaces in all of our experimental high-TiO2 basalt-olivine samples. Increased Ti content in the olivine is associated with the defects; ordering of Ti4+ and octahedral site vacancies leads to a two- or three-layer superstructure in the olivine. Defect nucleation and growth is driven by the large TiO2 chemical potential gradient across the phase boundary at the start of the experiments, which provides access to microstructures not otherwise present.
Collisional Processing of Comet Surfaces: Impact Experiments into Olivine
NASA Technical Reports Server (NTRS)
Lederer, S. M.; Jensen, E. A.; Cintala, M. J.; Smith, D. C.; Nakamura-Messenger, K.; Keller, L. P.; Wooden, D. H.; Fernandez, Y. R.; Zolensky, M. E.
A new paradigm has emerged where 3.9 Ga ago, a violent reshuffling reshaped the placement of small bodies in the solar system (the Nice model). Surface properties of these objects may have been affected by collisions caused by this event, and by collisions with other small bodies since their emplacement. In addition, objects in the Kuiper Belt are believed to undergo extensive collisional processing while in the Kuiper Belt. Physical manifestations of shock effects (e.g., planar dislocations) in minerals typically found in comets will be correlated with spectral changes (e.g. reddening, loss and shift of peaks, new signatures) to allow astronomers to better understand geophysical impact processing that has occurred on small bodies. Targets will include solid and granular olivine (forsterite), impacted over a range of impact speeds with the Experimental Impact Laboratory at NASA JSC. Analyses include quantification of the dependence of the spectral changes with respect to impact speed, texture of the target, and temperature.
Serpentinization of Sintered Olivine during Seawater Percolation Experiments
NASA Astrophysics Data System (ADS)
Luquot, L.; Andreani, M.; Godard, M.; Gouze, P.; Gibert, B.; Lods, G.
Hydration of the mantle lithosphere exposed at slow spreading ridges leads to significant changes of the rock rheological, geophysical, mineralogical and geochemical properties, and to the production of large amounts of H2 and CH4, and of complex carbon molecules that support primitive ecosystems. The onset and efficiency of these hydrothermal processes requires penetration and renewal of fluids at the mineral-fluid interface. However, the mechanisms and the depth of fluid penetration are still poorly understood. Moreover, serpentinization is exovolumic, if a mass-conservative system is assumed, or chemical elements are leached out to conserve rock volume. Thus, the durability and extent of serpentinisation depends of the system capacity to create space and/or to drive mass transfers. In order to investigate these hydrodynamic and chemical mechanisms, we did a series of laboratory experiments during which seawater was injected in sintered San Carlos olivine samples at conditions representative of low temperature ultramafic hydrothermal systems. The percolation-reaction experiments were carried out using the ICARE 2 experimental bench at a confined pressure of 19 MPa and a temperature of 190░C; water flow was set at a constant specific discharge of 0.06 mL/h. During experiments (up to 23 days), permeability decreases continuously although the high Si concentrations in outlet fluids indicate steady olivine dissolution. Fluids are also depleted in Fe and Mg, suggesting precipitation of Fe- and Mg-rich mineral phases; SEM and AEM/TEM analyses of the reacted samples allowed to characterize hematite and poorly crystallized serpentine, both formed at the expense of olivine. Mass balance calculations indicate that, on average, 15 wt. % olivine was dissolved while the same mass of serpentine (+/- brucite) was formed; concurrently, porosity decreased from ~ 12% to 5 %. We infer that the structure of the newly formed serpentine resulted in the clogging of fluid paths and explain the decrease of permeability during experiments. Hematite (<1 wt.%) is also observed, indicating redox reactions. The estimated total hydrogen content of outlet fluids is 4.5 mmol/kg. Although these values are in the same range as those measured at the Lost City hydrothermal vent (e.g., Kelley et al, 2001), they are significantly lower than theoretical estimates of hydrogen composition of serpentinisation fluids (e.g., 21-170 mmol/kg, Wetzel & Shock, 2000). We infer that these differences result, in part, from poor fluid renewal at the mineral interface during experiments, and maybe also in natural systems. These experimental results are used to constrain numerical reactive transport models and better understand the scale and efficiency of serpentinization reactions (effective reaction rates in porous/fractured media) at the scale of spreading ridges. Ref.: Kelley et al., Nature, 412, 145-149, 2001; Wetzel & Shock, JGR, 105, 8319-8340, 2000.
Infrared spectra of olivine polymorphs - Alpha, beta phase and spinel
NASA Technical Reports Server (NTRS)
Jeanloz, R.
The infrared absorption spectra of several olivines (alpha phase) and their corresponding beta phase (modified spinel) and spinel (gamma) high-pressure polymorphs are determined. Spectra were measured for ground and pressed samples of alpha and gamma A2SiO4, where A = Fe, Ni, Co; alpha and gamma Mg2GeO4; alpha Mg2SiO4; and beta Co2SiO4. The spectra are interpreted in terms of internal, tetrahedral and octagonal, and lattice vibration modes, and the spinel results are used to predict the spectrum of gamma Mg2SiO4. Analysis of spectra obtained from samples of gamma Mg2GeO4 heated to 730 and 1000 C provides evidence that partial inversion could occur in silicate spinels at elevated temperatures and pressures.
Additional Sr Isotopic Heterogeneity in Zagami Olivine-Rich Lithology
NASA Technical Reports Server (NTRS)
Misawa, K.; Niihara, T.; Shih, C.-Y; Reese, Y. D.; Nyquist, L. E.; Yoneda, S.; Yamashita, H.
Prior isotopic analyses of Zagami have established differing initial Sr-87/Sr-86 (ISr) ratios of among Zagami lithologies, fine-grained (FG), coarse-grained (CG), and dark mottled lithologies (DML)]. The Zagami sample (KPM-NLH000057) newly allocated from the Kanagawa Prefectural Museum of Natural History contained DML and the Ol-rich lithology which included more ferroan olivines (Ol-rich: Fa(sub 97- 99) vs late-stage melt pockets: Fa(sub 90-97)]). We have combined mineralogy-petrology and Rb-Sr isotopic studies on the Kanagawa Zagami sample, which will provide additional clues to the genesis of enriched shergottites and to the evolution of Martian crust and mantle
Origin of plagioclase-olivine inclusions in carbonaceous chondrites
NASA Astrophysics Data System (ADS)
Sheng, Y. J.; Hutcheon, I. D.; Wasserburg, G. J.
The origin of plagioclase-olivine inclusions (POIs) from three CV chondrites and one ungrouped chondrite was investigated by examining the chemical, mineralogical, and isotopic characteristics of a group of POIs from these chondrites. Results of these analyses demonstrate that the mixing and the partial melting processes in these inclusions were superimposed on more ancient isotopically heterogeneous material. A comparison of the essential characteristics of POIs and CAIs suggests that the major processes leading to the formation of POIs (such as condensation, dust/gas fractionation, aggregation of chemically and isotopically disparate materials, and partial melting) are common to most CAIs and chondrules. A scenario for the origin of POIs is proposed, showing that the homogeneity of the final assemblage (whether a POI, a CAI, or a chondrite) is primarily a reflection of the thermal history rather than the nature of precursor materials.
Serpentinization of sintered olivine during seawater percolation experiments
NASA Astrophysics Data System (ADS)
Luquot, Linda; Andreani, Muriel; Godard, Marguerite; Gouze, Philippe; Gibert, Benoit
Hydration of the mantle lithosphere exposed along detachment faults at slow-spreading ridges leads to strong modification of rock rheological, geophysical and geochemical properties, and to the emission of large amounts of H2 and CH4, and of complex carbon molecules that support primitive ecosystems. The sustainability and efficiency of this hydration process, serpentinisation, and of associated reactions, requires penetration and renewal of fluids at the mineral-fluid interface. However, precipitation of material along flow paths will affect porosity and permeability that, in turn, will have feedbacks effects on the reactions. It is thus necessary to investigate the sustainability of flow paths, and the evolution of reaction rates for a dynamic system under representative conditions. We investigate these processes by percolation experiments carried out under P, T representative conditions, using the ICARE Microlab experimental bench. We present the preliminary results of seawater percolation within samples of sintered San Carlos olivine. The experiments were carried out under a confined pressure of 190 bars and a temperature of 190░ C and water flow was set at a constant specific discharge of 0.06 ml/h.. The experiments were performed at very slow flow rate to be more representative of natural systems. ICARE Microlab allows measuring continuously the permeability changes during the percolation experiment and sampling the brine at the outlet of the sample. After 20 days of experiments, poorly crystallized serpentine and iron oxide formed within the micro-cracks while permeability strongly decreases. Such rapid precipitation of serpentine results in clogging of fluid paths. The chemical composition of the outlet fluid is dominated by Si and is depleted in Mg relative to stoechiometric dissolution of olivine during the whole experiment suggesting that brucite possibly formed. SEM and AEM/TEM are used to characterize the reactive interfaces and the neoformed materials.
Oxygen isotopic composition of individual olivine grains from the Allende meteorite
NASA Technical Reports Server (NTRS)
Weinbruch, S.; Zinner, E. K.; El Goresy, A.; Steele, I. M.; Palme, H.
The oxygen isotopic composition of a variety of individual olivine grains (including refractory forsterite grains, cores of isolated olivine grains, FeO-rich rims, and individual matrix olivine grains) from the Allende CV3 meteorite was investigated by ion microprobe mass spectrometry, in order to obtain information on the formation mechanism of these samples. It was found that the most primitive (i.e., refractory) olivine in Allende is far less enriched in O-16 than are spinel and pyroxene in Ca,Al-rich inclusions, suggesting that Allende olivine must have formed in an environment that is less enriched in O-16 compared to the gas from which Ca,Al-inclusions are formed. FeO-rich (26-30 wt pct) rims of isolated olivine grains are significantly higher in delta-O-17 and delta-O-18 than forsteritic cores, suggesting that these rims formed by condensation from an oxidized gas with higher delta-O-17 than delta-O-18. Matrix olivine was found to be highest in FeO and to have the lowest enrichment in O-16.
The composition of mesosiderite olivine clasts and implications for the origin of pallasites
NASA Technical Reports Server (NTRS)
Mittlefehldt, D. W.
The composition of olivine clasts from the mesosiderites Emery, Mincy and Pinnaroo is investigated, and implications of the results for the origin of the pallasites, which, although chemically distinct, may be related to the diogenites, eucrites, howardites and mesosiderites, are discussed. Centimeter-sized olivines were analyzed by electron microprobe, and instrumental neutron activation analysis was performed on one olivine each from Emery and Pinnaroo and an olivine separate from the Brenham pallasite. The olivine compositions are found to range from Fa8 to Fa28, with Emery samples having values from Fa18 to Fa28, and to require essentially total melting of a source composition rich enough in FeO to produce basaltic clasts. It is argued that the mesosiderite olivines were formed in the outer few kilometers of their parent body, as were those of the pallasites, which have the same compositions as the mesosiderite olivines. A model is then developed for the origin of the pallasites as a by-product of igneous differentiation in the external heating of a chondritic parent body.
Melt Connectivity and Its Effect on Grain Growth in Natural Olivine Aggregates: An Experimental Study
NASA Astrophysics Data System (ADS)
Hashim, L.; Sifre, D.; Prķcigout, J.; Gardķs, E.; Le Trong, E.; Gaillard, F.
To better constrain the rheology of the mantle, experimental studies on olivine grain growth have been conducted (Faul and Scott, 2006; Karato, 1989; Nichols and Mackwell, 1991) since the grain size is an important parameter under dynamic regimes (e.g. diffusion creep and grain boundary sliding). In order to better define the melt effect on the rheological response of a partially molten olivine aggregate, we have experimentally investigated the effect of melt on olivine grain growth and the connectivity of this melt phase. Experiments were performed in 3/4" piston cylinders at 500 MPa confining pressure, different temperatures (i.e. 1100░C, 1250░C and 1400░C) and four durations (1h, 12h, 72h and 15 days). Starting material was composed of natural San Carlos olivine (5 ?m
Detections and geologic context of local enrichments in olivine on Vesta with VIR/Dawn data
NASA Astrophysics Data System (ADS)
Ruesch, Ottaviano; Hiesinger, Harald; De Sanctis, Maria Cristina; Ammannito, Eleonora; Palomba, Ernesto; Longobardo, Andrea; Zambon, Francesca; Tosi, Federico; Capria, Maria Teresa; Capaccioni, Fabrizio; Frigeri, Alessandro; Fonte, Sergio; Magni, Gianfranco; Raymond, Carol A.; Russell, Christopher T.
The magmatism characterizing the early history of the asteroid Vesta has long been investigated with the mafic and ultramafic meteorites howardite, eucrite, and diogenite (HED). The lack of geologic context for the meteorites, however, has limited its understanding. Here we use the visible to near-IR (VIR) orbital observations of Vesta's surface to detect relative enrichments in olivine and to study the associated geologic features. Because the near-IR signature of olivine on Vesta's surface is subtle relative to the widespread pyroxene absorption bands, a method was developed to distinguish olivine enrichments from admixture of pyroxenes with high Fe2+/M1, dark material, and potential Fe-bearing glass. Relative enrichment of olivine (~<50-60 vol %) is found in 2-5 km wide, morphologically fresh areas. Our global survey reveals a dozen of these areas clustering in the eastern hemisphere of Vesta. The hemispherical coincidence with a widespread, low enrichment in diogenite-like pyroxene suggests the presence of a distinct compositional terrain. On the central mound of the Rheasilvia impact basin, no olivine enrichment was found, suggesting the absence of an olivine-dominated mantle above the basin's excavation depth or, alternatively, a low amount of olivine homogeneously mixed with diogenite-like pyroxenes. Rare olivine-enriched areas in close proximity to diogenite-like pyroxene are found as part of material ejected by the Rheasilvia impact. Such cooccurrence is reminiscent of local, ultramafic lithologies within the crust. The possible formation of such lithologies on Vesta is supported by some HED meteorites dominated by olivine and orthopyroxene.
H Diffusion in Olivine and Pyroxene from Peridotite Xenoliths and a Hawaiian Magma Speedometer
NASA Technical Reports Server (NTRS)
Peslier, A. H.; Bizimis, M.
Hydrogen is present as a trace element in olivine and pyroxene and its content distribution in the mantle results from melting and metasomatic processes. Here we examine how these H contents can be disturbed during decompression. Hydrogen was analyzed by FTIR in olivine and pyroxene of spinel peridotite xenoliths from Salt Lake Crater (SLC) nephelinites which are part of the rejuvenated volcanism at Oahu (Hawaii) [1,2]. H mobility in pyroxene resulting from spinel exsolution during mantle upwelling Most pyroxenes in SLC peridotites exhibit exsolutions, characterized by spinel inclusions. Pyroxene edges where no exsolution are present have less H then their core near the spinel. Given that H does not enter spinel [3], subsolidus requilibration may have concentrated H in the pyroxene adjacent to the spinel exsolution during mantle upwelling. H diffusion in olivine during xenolith transport by its host magma and host magma ascent rates Olivines have lower water contents at the edge and near fractures compared to at their core, while the concentrations of all other chemical elements appear homogeneous. This suggests that some of the initial water has diffused out of the olivine. Water loss from the olivine is thought to occur during host-magma ascent and xenolith transport to the surface [4-6]. Diffusion modeling matches best the data when the initial water content used is that measured at the core of the olivines, implying that mantle water contents are preserved at the core of the olivines. The 3225 cm(sup -1) OH band at times varies independantly of other OH bands, suggesting uneven H distribution in olivine defects likely acquired during mantle metasomatism just prior to eruption and unequilibrated. Diffusion times (1-48 hrs) combined with depths of peridotite equilibration or of magma start of degassing allow to calculate ascent rates for the host nephelinite of 0.1 to 27 m/s.
New insights into the formation of fayalitic olivine from Allende dark inclusions
NASA Astrophysics Data System (ADS)
Varela, Maria E.; Zinner, Ernst; Kurat, Gero; Chu, Hao-Tsu; Hoppe, Peter
Although considerable progress has been made in unraveling the origin(s) of fayalitic olivines in dark inclusions (DIs), many questions remain still unresolved and/or controversial. We combine a chemical and petrographic study of the Allende dark inclusion 4884-2B (AMNH, New York) and ATEM studies of a fragment of the dark inclusion Allende AF (NHM, Vienna) and discuss an alternative way in which fayalitic olivines could have formed. Allende dark inclusion 4884-2B contains a few aggregates with variable proportions of transparent and feathery olivine. Two such objects (aggregates A and B) are the focus of this study as they preserve glasses that can help in deciphering the nature of the processes involved during olivine growth and subsequent olivine transformation. The petrographic and chemical characteristics of aggregates A and B indicate that the forsteritic stack olivines may be pseudomorphs of clear olivine crystals. The ATEM studies in All-AF suggest that fayalitic olivines may be the result of secondary processes (e.g., metasomatic exchange reactions) operating in the solar nebula. Transformation may have occurred through the mediation of a dry gas phase involving nonvolatile major elements, such as Mg and Fe (e.g., Dohmen et al. 1998). This mechanism could reveal olivine growth patterns (e.g., stacked platelets due to a rapid growth regime) and may have contributed to the development of their fibrous aspect while preserving the shape (i.e., volume) of the crystals. This highly selective process did completely or partially transform ferromagnesian minerals, but affected the fine-grained mesostasis only slightly.
3D Quantitative Confocal Laser Microscopy of Ilmenite Volume Distribution in Alpe Arami Olivine
NASA Astrophysics Data System (ADS)
Bozhilov, K. N.
The deep origin of the Alpe Arami garnet lherzolite massif in the Swiss Alps proposed by Dobrzhinetskaya et al. (Science, 1996) has been a focus of heated debate. One of the lines of evidence supporting an exhumation from more than 200 km depth includes the abundance, distribution, and orientation of magnesian ilmenite rods in the oldest generation of olivine. This argument has been disputed in terms of the abundance of ilmenite and consequently the maximum TiO2 content in the discussed olivine. In order to address this issue, we have directly measured the volume fraction of ilmenite of the oldest generation of olivine by applying confocal laser scanning microscopy (CLSM). CLSM is a method which allows for three-dimensional imaging and quantitative volume determination by optical sectioning of the objects. The images for 3D reconstruction and measurements were acquired from petrographic thin sections in reflected laser light with 488 nm wavelength. Measurements of more than 80 olivine grains in six thin sections of our material yielded an average volume fraction of 0.31% ilmenite in the oldest generation of olivine from Alpe Arami. This translates into 0.23 wt.% TiO2 in olivine with error in determination of ▒0.097 wt.%, a value significantly different from that of 0.02 to 0.03 wt.% TiO2 determined by Hacker et al. (Science, 1997) by a broad-beam microanalysis technique. During the complex geological history of the Alpe Arami massif, several events of metamorphism are recorded which all could have caused increased mobility of the mineral components. Evidence for loss of TiO2 from olivine is the tendency for high densities of ilmenite to be restricted to cores of old grains, the complete absence of ilmenite inclusions from the younger, recrystallized, generation of olivine, and reduction in ilmenite size and abundance in more serpentinized specimens. These observations suggest that only olivine grains with the highest concentrations of ilmenite are close to the original amount of TiO2 incorporated in the olivine. Our measurements show maximum volume fraction of ilmenite of 1.21%, corresponding to 0.9▒0.38 wt.% of TiO2. Even the most conservative scenario reveals concentration of TiO2 in olivine of more than 0.5 wt.%, a value comparable to that reported by Dobrzhinetskaya et al. (1996) and an order of magnitude greater than any previous measurement of TiO2 in olivine. Experiments by Dobrzhinetskaya et al. (Chem. Geol, 2000) found that such high solubility can occur, but only at P>10GPa at mantle temperatures.
Fe-Mg-Mn relations of ureilite olivines and pyroxenes and the genesis of ureilites
NASA Technical Reports Server (NTRS)
Mittlefehldt, D. W.
Microprobe analyses of ureilite and pigeonite cores are studied. The Fe/Mn-Fe/Mg relationship in the olivine core is examined. It is observed that magnetic processs such as fractional crystallization and partial melting, and FeO reduction contribute to the olivine core composition. The study of the Mg/Mn and Fe/Mn distributions reveals that these two distributions are not in equilibrium in the olivine and pigeonite cores. The effect of a reducing agent, carbon, on the ureilite genesis is investigated. It is concluded that fractional crystallization and FeO reduction are the major processes of ureilite genesis.
Olivine CPO in non-deformed peridotite due to topotactic replacement of antigorite
NASA Astrophysics Data System (ADS)
Nagaya, Takayoshi; Wallis, Simon; Kobayashi, Hiroaki; Michibayashi, Katsuyoshi; Mizukami, Tomoyuki; Seto, Yusuke; Miyake, Akira; Matsumoto, Megumi
Olivine crystallographic preferred orientation (CPO) is thought to be the main cause of seismic anisotropy in the mantle, and its formation is generally considered to be the result of plastic deformation of mantle by dislocation creep. Olivine CPO has been reproduced in laboratory deformation experiments and considerable success has been achieved in understanding the deformation conditions (e.g. stress, temperature and water content) under which different olivine CPO patterns develop. This opens the possibility of mapping conditions in the mantle using seismic anisotropy and has been the subject of considerable study. Here we report an alternative mechanism for olivine CPO without the need for deformation. This process may be important in understanding the seismic properties of mantle in convergent margins. Metamorphic studies show peridotite in the Happo area, central Japan, formed by the dehydration of antigorite-schist related to contact metamorphism around a granite intrusion. Both field and microstructural observations suggest the olivine has not undergone strong plastic deformation. This was confirmed by TEM work that shows the olivine has very low dislocation densities and lacks low angle tilt boundaries. Such tilt boundaries are general stable even after annealing. These features show that peridotite in the Happo area formed in the absence of solid-state deformation. The olivine of the Happo peridotite formed dominantly by the dehydration breakdown of antigorite schist. We propose that the olivine CPO formed as a result of topotactic replacement of antigorite by the newly formed olivine. EBSD measurements in samples where both antigorite and new olivine are present and in contact show a very close crystallographic relationship between the two minerals: the a-axes are parallel, and the b- and c-axes are perpendicular. We conclude the strong olivine CPO in the Happo area was inherited from the original CPO of the antigorite. Such a process is likely to also occur in subduction zones where serpentinite is dragged down by plate movement. Topotactic growth of olivine may be an important cause of mantle anisotropy in convergent margins.
Olivines in the Kaba carbonaceous chondrite and constraints on their formation
NASA Technical Reports Server (NTRS)
Hua, X.; Buseck, P. R.
Kaba is unique in containing almost pure fayalitic olivine (Fo(sub 0.1)). Its coexistence with pure forsterite up to Fo(sub 99.6) and normal (Fo(sub 92) to Fo(sub 59)) and reversely (Fo(sub 0.4) to Fo(sub 4.7)) zoned olivines suggest that the Kaba olivines are in thermodynamic disequilibrium and experienced a complicated history. The fayalite is sufficiently pure that it is unlikely that it could have been produced by fractional crystallization. A gas-solid reaction under oxidizing conditions (H2O/H2 ratio approximately 10) is probably responsible for its formation.
Cr, Mn, and Ca distributions for olivine in angritic systems: Constraints on the origins of Cr-rich and Ca-poor core olivine in angrite LEW87051
NASA Technical Reports Server (NTRS)
Mikouchi, T.; Mckay, G.; Le, L.
Angrite meteorites are a type of basaltic achondrites that are noted for their very old cyrstallization ages (4.55 b.y.) and unusual chemical and mineralogical properties. In spite of great interest, only four angrites have been found. LEW87051 is the smallest one which weighs 0.6 g. It is a porphyritic rock with coarse subhedral to euhedral olivines set in a fine-grained groundmass which clearly represents a crystallized melt. The largest uncertainty about the petrogenesis of LEW87051 is the relationship between the large olivine crystals and the groundmass. Prinz et al. suggests that olivines are xenocrysts, while McKay et al. proposed a fractional cyrstallization model based on experimental studies. However, the crystals have Cr-rich and Ca-poor cores which do not match experimental olivines. Although Jurewicz and McKay tried to explaine the zoning of the rim by diffusion, some features are not explained. There also exists a definite composition boundary of Fe(2+) and MnO between the core and the rim. To clarify the origin of these olivines, we have performed experiments using LEW87051 analogs to measure the effects of oxygen fugacity on distribution coefficients of various elements in an angritic system.
An Olivine-Rich Crater in Tyrrhena Terra
NASA Technical Reports Server (NTRS)
2008-01-01This image of the ejecta of a crater in the Tyrrhena Terra region was taken by the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) at 0328 UTC on February 23, 2007 (10:28 p.m. EST on February 22, 2007), near 13 degrees south latitude, 67 degrees east longitude. CRISM's image was taken in 544 colors covering 0.36-3.92 micrometers, and shows features as small as 18 meters (60 feet) across. The region covered is roughly 9 kilometers (5.6 miles) wide at its narrowest point. Named for a classic albedo feature, Tyrrhena Terra is an extensive, heavily-cratered part of Mars' southern highlands, some 2,300 kilometers (1,430 miles) at its broadest extent. It is located to the northeast of the Hellas basin. The region imaged by CRISM is to the north of Hellas Planitia and just east of the crater Huygens in Tyrrhena Terra's western end. The uppermost image in the montage above reveals the location of the CRISM image on a mosaic taken by the Mars Odyssey spacecraft's Thermal Emission Imaging System (THEMIS). The CRISM image is located inside a large, flat-floored crater measuring about 52 kilometers (32 miles) across. The image includes a small crater and its ejecta blanket, an apron of material thrown out during a crater's formation, both located inside the larger crater. The lower left image is an infrared false-color image that reveals the extent of the ejecta blanket. It also includes ejecta from another small crater located just east of the CRISM image. The lower right image shows the strengths of mineral absorptions, and reveals the composition of the ejecta and surrounding material. The ejecta surrounding the small impact crater is thickest at the crater's rim, and becomes thinner to discontinuous at the blanket's outer edge. This small crater's ejecta blanket shows an enhanced spectral signature of the mineral olivine, as does the ejecta from the small crater just out of view to the east. In contrast the surrounding material is rich in the volcanic mineral pyroxene. This relationship demonstrates the layered characteristic of rocks forming the southern highlands: olivine-rich rock was buried by pyroxene-rich materials on the larger crater's floor, probably volcanic lavas. Later, the small crater penetrated the pyroxene-rich rock, excavated the underlying olivine-bearing unit, and deposited it as ejecta. CRISM is one of six science instruments on NASA's Mars Reconnaissance Orbiter. Led by The Johns Hopkins University Applied Physics Laboratory, Laurel, Md., the CRISM team includes expertise from universities, government agencies and small businesses in the United States and abroad. NASA's Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the Mars Reconnaissance Orbiter and the Mars Science Laboratory for NASA's Science Mission Directorate, Washington. Lockheed Martin Space Systems, Denver, built the orbiter.
LETTER doi:10.1038/nature12665 Olivine in an unexpected location on Vesta's surface
Cai, Long
Earth. Howardite, eucrite and diogenite (HED) meteorites represent regolith, basaltic-crust, lower is not associated with diogenite but seems to be mixed with howardite, the most common7,9 surface material. Olivine
First-principles investigation of Li intercalation kinetics in phospho-olivines
Malik, Rahul
This thesis focuses broadly on characterizing and understanding the Li intercalation mechanism in phospho-olivines, namely LiFePO? and Li(Fe,Mn)PO?, using first-principles calculations. Currently Li-ion battery technology ...
Raman Spectroscopy of Olivine in Dunite Experimentally Shocked to Pressures Between 5 and 59 GPa
NASA Astrophysics Data System (ADS)
Turner, S.; Reimold, W. U.; Niewoudt, M.; Erasmus, R.
Raman spectroscopic analysis of olivine in dunite samples experimentally shock-loaded to pressures between 5 and 59 GPa showed no significant shift of the 824 and 856 cm^ 1 Raman bands with increasing shock pressure.
Optical absorption and radiative heat transport in olivine at high temperature
NASA Technical Reports Server (NTRS)
Shankland, T. J.; Nitsan, U.; Duba, A. G.
Results are presented of measurements of the optical absorption spectra (300-8000 nm) of olivine as a function of temperature (300-1700 K) under conditions of controlled and known oxygen fugacity within the stability field of the samples. The absorption spectra are used to calculate the temperature-dependent radiative transfer coefficient of olivine and to numerically study the accuracy of the method. The present absorption measurements in olivine under oxidizing conditions known to be within the olivine stability field indicate that the effective radiative conductivity K(R) is lower than that obtained in previous studies under different experimental conditions. The lower value of K(R) makes it more likely that some of the earth's internal heat is removed by convection and less likely that thermal models involving conduction and radiation alone will satisfactorily explain thermal conditions in the earth's mantle.
FULL PAPER Open Access Characterization of olivine fabrics and mylonite in
Jung, Haemyeong
of the surrounding anorthosite complex is displayed in ultramafic lenses as a modal variation in olivine, pyroxenes, and spinel, and the Caledonian eclogite-facies structure in the surrounding anorthosite gabbro is represented
Phase diagram and electrochemical properties of mixed olivines from first-principles calculations
Malik, Rahul
Using first-principles calculations, we study the effect of cation substitution on the transition-metal sublattice in phospho-olivines, with special attention given to the Li[subscript x](Fe[subscript 1?y]Mn[subscript ...
ELEMENTAL ABUNDANCE CONSTRAINTS ON CONDENSATION OF ALLENDE MATRIX OLIVINE. L. Grossman1
Grossman, Lawrence
at 1450-1250K at reasonable nebular pressures, causing the co-condensing olivine to be pure forsterite+ to condense at equilibrium, it must diffuse into the interiors of previously condensed forsterite grains
Evidence for Microimpact in an Olivine-Dominated Hayabusa Dust Particle
NASA Astrophysics Data System (ADS)
Langenhorst, F.; Harries, D.; Pollok, K.; van Aken, P. A.
We report the results of a TEM study on a dust particle returned by the Hayabusa space mission. The particle consists of olivine, tetrataenite, troilite, and diopside. Dislocations, microtwins and stacking faults in minerals point to a microimpact.
Olivine and Ca-Phosphate in the Diogenites Manegaon and Roda
NASA Astrophysics Data System (ADS)
Domanik, K. J.; Sideras, L. C.; Drake, M. J.
This abstract describes igneous contacts in Manegaon and Roda that involve olivine and orthopyroxene (plus other phases), as well as contacts involving orthopyroxene and Ca-phosphate minerals (both F-apatite and REE-bearing whitlockite).
Water in Olivine and its High-Pressure Polymorphs
NASA Astrophysics Data System (ADS)
Thomas, S. M.; Jacobsen, S. D.; Bina, C. R.; Reichart, P.; Moser, M.; Dollinger, G.; Hauri, E. H.
Theory and high-pressure experiments imply a significant water storage capacity of nominally anhydrous minerals (NAMs), such as olivine, wadsleyite and ringwoodite, composing the Earth's upper mantle and transition zone to a depth of 660 km. The presence of water, dissolved as OH into such nominally anhydrous high-pressure silicates, notably influences phase relations, melting behavior, conductivity, elasticity, viscosity and rheology. The first direct evidence for hydration of the transition zone has recently been reported by Pearson et al. (2014) and Schmandt et al. (2014). Knowledge of absolute water contents in NAMs is essential for modeling the Earth's interior water cycle. To take advantage of IR spectroscopy as highly sensitive water quantification tool, mineral-specific absorption coefficients are required. Such calibration constants can be derived from hydrogen concentrations determined by independent techniques, such as secondary ion mass spectrometry (SIMS), Raman spectroscopy or proton-proton(pp)-scattering. Broad beam pp-scattering has been performed on double-polished mm-sized mineral platelets (Thomas et al. 2008), but until recently analysis was not feasible for smaller samples synthetized in high-pressure apparati. Here we present first results from pp-scattering microscopy studies on ?m-sized single crystals of hydrous olivine, wadsleyite and ringwoodite, which were synthesized at various pressure-temperature conditions in a multi-anvil press. The method allows us to quantify 3D distributions of atomic hydrogen in ?m dimensions. These self-calibrating measurements were carried out at the nuclear microprobe SNAKE at the Munich tandem accelerator lab using a 25 MeV proton microbeam. We provide hydrogen depth-profiles, hydrogen maps and H2O concentrations. Pp-scattering data and results from independent Raman and SIMS analyses are in good agreement. Water contents for a set of high-pressure polymorphs with varying Fe-concentrations range from 0.8 wt% to 2.5 wt% H2O. From experimental data for Fo83, Fo87, Fo90 and Fo100 compositions we calculate mineral-specific absorption coefficients for the quantification of H2O using IR-spectroscopy, compare them with previously estimated values and discuss IR calibrations for major phases of the Earth's mantle.
Raman spectroscopy of olivine in dunite experimentally shocked to pressures between 5 and 59 GPa
NASA Astrophysics Data System (ADS)
Farrell-Turner, S.; Reimold, W. U.; Nieuwoudt, M.; Erasmus, R. M.
Previous Raman investigations on experimentally shocked ingle-crystal olivine indicated that the olivine Raman bands seemingly shift to a higher wave number with increasing shock pressure. If this effect could be confirmed, Raman analysis of natural shock-metamorphosed minerals could potentially provide an important shock barometric tool. We carried out a Raman spectroscopic study on olivine in a series of natural dunite samples experimentally shocked to pressures between 5 and 59 GPa. In addition, we analyzed olivine grains in a sample of the Cold Bokkeveld C1 meteorite. We studied samples of several dunites with olivine of 90.64-92.00 mole% Fo to determine Raman effects in the region from 200 to 900 cm-1. Several olivine grains per sample/shock pressure stage were analyzed. Raman analysis, however, showed little or no shift with increasing shock pressure. The shifts to higher or lower frequencies observed were not specific for a given pressure stage, with some grains within a sample showing more shift than others. This finding is unrelated to the crystallographic orientation of analyzed grains and cannot be related systematically to the different degrees of optically determined shock metamorphism of the analyzed grains. We identified an increase in full width at half maximum (FWHM) for the 824 cm-1 band with increased shock pressure in the shocked ┼heim samples above 45 GPa and, to a lesser extent, for the 856 cm-1 band. Evaluation of band broadening of olivine in the Cold Bokkeveld meteorite showed FWHM values that were much greater (9-20 cm-1) than those of olivine in the shocked dunite samples (7-12 cm-1). We concluded that these differences in FWHM are due to differences in chemical composition between the meteoritic and the experimentally shocked olivine. Therefore, using Raman spectroscopy to detect small shifts in wave numbers to higher frequencies with increased shock pressure does not yield consistent effects for polycrystalline dunite. An extra band at 650 cm-1 was identified in the Raman spectra of the unshocked Mooihoek dunite and the ┼heim dunite samples shocked to 5, 29.3, and 59 GPa, as well as another at 696 cm-1 in all the spectra of the 59 GPa ┼heim sample. The cause of these extra bands is not known. Comparison of these results with Raman spectra of olivine from the Cold Bokkeveld C1 meteorite did not allow us to determine shock pressures for the meteoritic olivine.
Effect of metamorphism on isolated olivine grains in CO3 chondrites
NASA Astrophysics Data System (ADS)
Jones, R. H.
The presence of a metamorphic sequence in the CO3 chondrite group has been shown previously to result in changes in properties of chondrule silicates. However, the role of isolated olivine grains during metamorphism of these chondrites has not been addressed. Isolated olivine grains in two metamorphosed CO3 chondrites, Lance and Isna, have been investigated in this study in order to assess the compositional properties of isolated olivine grains that may be attributable to metamorphism. Compositional changes in isolated olivines with increasing petrologic subtype are very similar to changes in chondrule olivines in the same chondrites. Olivine compositions from all occurrences (chondrules, isolated grains, and matrix) converge with increasing petrologic subtype. The degree of equilibration of minor elements is qualitatively related to the diffusion rate of each element in olivine, suggesting that diffusion-controlled processes are the most important processes responsible for compositional changes within the metamorphic sequence. The data are consistent with metamorphism taking place in a closed system on the CO3 chondrite parent body. Fe-poor olivine grains in metamorphosed chondrites are characterized by an Fe-rich rim, which is the result of diffusion of Fe into the grains from Fe-rich matrix. In some instances, 'complex', Fe-rich rims have been identified, which appear to have originated as igneous overgrowths and subsequently to have been overprinted by diffusion processes during metamorphism. Processes experienced by CO3 chondrites are more similar to those experienced by the ordinary chondrites than to those encountered by other carbonaceous chondrites, such as the CV3 group.
A Tale of Two Olivines: Magma Ascent in the Auckland Volcanic Field, New Zealand
NASA Astrophysics Data System (ADS)
Smid, E. R.; McGee, L. E.; Smith, I. E.; Lindsay, J. M.
The Auckland Volcanic Field (AVF) is a nephelinitic to subalkali basaltic monogenetic field centered on the city of Auckland, New Zealand. Lavas are olivine-phyric, and the deposits of several volcanoes in the field contain olivine crystals with chrome spinel (Cr-spinel) inclusions. Microprobe analyses show at least two populations of olivine, categorised by their Mg# and their spinel inclusion compositions: the first has olivines that are euhedral, have compositions slightly less forsteritic than expected for whole rock Mg#, and have Cr-spinel inclusions with relatively low Cr2O3 contents of ~20%. These are interpreted as antecrysts inherited from the mantle source that yielded their host magma. The second population is characterised by olivines that are sub- to euhedral, are significantly more forsteritic than expected from their host whole rock Mg#, and have Cr-spinel inclusons with relatively high Cr2O3 contents of ~50%. These are interpreted as xenocrysts. The composition of these high Cr2O3 spinels very closely resembles the composition of spinels within olivines in dunite sampled from the Dun Mountain Ophiolite on the South Island of New Zealand. The northward extension of the Dun Mountain complex beneath the North Island is defined by the Junction Magnetic Anomaly, marking a crustal terrane boundary that underlies the Auckland Volcanic Field. These data indicate that the magmas that have risen to produce the volcanoes of the Auckland Volcanic Field have carried crystals from an underlying ultramafic crust as well as from their asthenospheric source. Euhedral olivine crystals which do not contain Cr-spinel are also present in AVF lavas and these are interpreted as true phenocrysts that crystallised directly from their host magmas. The lack of reaction textures at crystal margins suggests rapid ascent rates. A crustal origin for the xenocrysts not only has large implications for ascent rate modelling of olivines, but also for the crustal structure of the Auckland area and possible magma ascent paths under the AVF.
Martian Dunite NWA 2737: Petrographic constraints on geological history, shock events, and olivine color
Allan H. Treiman; M. Darby Dyar; Molly McCanta; Sarah K. Noble; Carle M. Pieters
Meteorite Northwest Africa (NWA) 2737 is the second known chassignite, an olivine-rich igneous rock with mineral compositions and isotopic ratios that suggest it formed on Mars. NWA 2737 consists of ~85% vol. olivine (Mg#, molar Mg\\/(Mg + Fe), of 78.3 +\\/- 0.4%), which is notable because it is black in hand sample and brown in thin section. Other minerals include
Martian Dunite NWA 2737: Petrographic constraints on geological history, shock events, and olivine color
Allan H. Treiman; M. Darby Dyar; Molly McCanta; Sarah K. Noble; Carle M. Pieters
Meteorite Northwest Africa (NWA) 2737 is the second known chassignite, an olivine-rich igneous rock with mineral compositions and isotopic ratios that suggest it formed on Mars. NWA 2737 consists of ?85% vol. olivine (Mg#, molar Mg\\/(Mg + Fe), of 78.3 ▒ 0.4%), which is notable because it is black in hand sample and brown in thin section. Other minerals include
Martian Dunite NWA 2737: Petrographic Constraints on Geological History, Shock Events, and Olivine Color
Allan H. Treiman; M. Darby Dyar; Molly McCanta; Sarah K. Noble; Carle M. Pieters
Meteorite Northwest Africa (NWA) 2737 is the second known chassignite, an olivine-rich igneous rock with mineral compositions and isotopic ratios that suggest it formed on Mars. NWA 2737 consists of ?85% vol. olivine (Mg, molar Mg\\/(Mg + Fe), of 78.3 {+-} 0.4%), which is notable because it is black in hand sample and brown in thin section. Other minerals include
Characterization and petrologic interpretation of olivine-rich basalts at Gusev Crater, Mars
McSween, H.Y.; Wyatt, M.B.; Gellert, Ralf; Bell, J.F.; Morris, R.V.; Herkenhoff, K.E.; Crumpler, L.S.; Milam, K.A.; Stockstill, K.R.; Tornabene, L.L.; Arvidson, R.E.; Bartlett, P.; Blaney, D.; Cabrol, N.A.; Christensen, P.R.; Clark, B.C.; Crisp, J.A.; Des Marais, D.J.; Economou, T.; Farmer, J.D.; Farrand, W.; Ghosh, A.; Golombek, M.; Gorevan, S.; Greeley, R.; Hamilton, V.E.; Johnson, J.R.; Joliff, B.L.; Klingelhofer, G.; Knudson, A.T.; McLennan, S.; Ming, D.; Moersch, J.E.; Rieder, R.; Ruff, S.W.; Schrorder, C.; de Souza, P.A.; Squyres, S.W.; Wanke, H.; Wang, A.; Yen, A.; Zipfel, J.
Rocks on the floor of Gusev crater are basalts of uniform composition and mineralogy. Olivine, the only mineral to have been identified or inferred from data by all instruments on the Spirit rover, is especially abundant in these rocks. These picritic basalts are similar in many respects to certain Martian meteorites (olivine-phyric shergottites). The olivine megacrysts in both have intermediate compositions, with modal abundances ranging up to 20-30%. Associated minerals in both include low-calcium and high-calcium pyroxenes, plagioclase of intermediate composition, iron-titanium-chromium oxides, and phosphate. These rocks also share minor element trends, reflected in their nickel-magnesium and chromium-magnesium ratios. Gusev basalts and shergottites appear to have formed from primitive magmas produced by melting an undepleted mantle at depth and erupted without significant fractionation. However, apparent differences between Gusev rocks and shergottites in their ages, plagioclase abundances, and volatile contents preclude direct correlation. Orbital determinations of global olivine distribution and compositions by thermal emission spectroscopy suggest that olivine-rich rocks may be widespread. Because weathering under acidic conditions preferentially attacks olivine and disguises such rocks beneath alteration rinds, picritic basalts formed from primitive magmas may even be a common component of the Martian crust formed during ancient and recent times. Copyright 2006 by the American Geophysical Union.
Characterization and Petrologic Interpretation of Olivine-Rich Basalts at Gusev Crater, Mars
NASA Technical Reports Server (NTRS)
McSween, H. Y.; Wyatt, M. B.; Gellert, R.; Bell, J. F., III; Morris, R. V.; Herkenhoff, K. E.; Crumpler, L. S.; Milam, K. A.; Stockstill, K. R.; Tornabene, L. L.; Arvidson, R. E.; Bartlett, P.; Blaney, D.; Cabrol, N. A.; Christensen, P. R.; Clark, B. C.; Crisp, A.; DesMarais, D. J.; Economou, T.; Farmer, J. D.; Farrand, W.; Ghosh, A.; Golombek, M.; Gorevan, S.; Greeley, R.
Rocks on the floor of Gusev crater are basalts of uniform composition and mineralogy. Olivine, the only mineral to have been identified or inferred from data by all instruments on the Spirit rover, is especially abundant in these rocks. These picritic basalts are similar in many respects to certain Martian meteorites (olivine-phyric shergottites). The olivine megacrysts in both have intermediate compositions, with modal abundances ranging up to 20-30%. Associated minerals in both include low-calcium and high-calcium pyroxenes, plagioclase of intermediate composition, iron-titanium-chromium oxides, and phosphate. These rocks also share minor element trends, reflected in their nickel-magnesium and chromium-magnesium ratios. Gusev basalts and shergottites appear to have formed from primitive magmas produced by melting an undepleted mantle at depth and erupted without significant fractionation. However, apparent differences between Gusev rocks and shergottites in their ages, plagioclase abundances, and volatile contents preclude direct correlation. Orbital determinations of global olivine distribution and compositions by thermal emission spectroscopy suggest that olivine-rich rocks may be widespread. Because weathering under acidic conditions preferentially attacks olivine and disguises such rocks beneath alteration rinds, picritic basalts formed from primitive magmas may even be a common component of the Martian crust formed during ancient and recent times.
Single-Crystal Elasticity of San Carlos Olivine in the Earth's Mantle
NASA Astrophysics Data System (ADS)
Mao, Z.; Lin, J. F.; Fan, D.; Yang, J.; Zhuravlev, K. K.; Tkachev, S. N.
Olivine is the most abundant mineral in the Earth's upper mantle. Studies on the elasticity of olivine attracted extensive research interests in the past few decades and have provided important constraints on the composition and structure of the Earth's upper mantle. Of particular importance is the single-crystal elasticity of olivine which is essential for understanding the anisotropy structure of the upper mantle. However, previous experimental studies on the single-crystal elasticity of olivine are limited to high pressure and ambient temperature or high temperature and ambient pressure. Much of our current knowledge on the velocity and anisotropy structures of the upper mantle heavily relies on extrapolations of limited experimental results. Here, we have studied the single-crystal elasticity of San Carlos olivine, [(Mg0.9Fe0.1)2SiO4], up to 20 GPa and 900 K using Brillouin spectroscopy and X-ray diffraction in an externally-heated diamond anvil cell at GSECARS of the Advanced Photon Source, Argonne National Laboratory. The simultaneously high pressure-temperature experiments allow us to investigate the combined effect of pressure and temperature on the velocity and anisotropy of olivine. These results have been applied to model the velocity structure, Vp and Vs anisotropy, Vp/Vs ratio, and Poisson's ratio of the Earth's upper mantle. Comparing the modeling results with seismic observations allow us to have a more comprehensive understanding on the velocity and anisotropy structure of the Earth's upper mantle.
Charge Localization and Transport in Lithiated Olivine Phosphate Materials
Yu, Jianguo; Rosso, Kevin M.; Liu, Jun
We report density functional theory (DFT) calculations for olivine-type LiTMPO4 and TMPO4 (TM=Mn, Fe, Co, Ni) structures, using GGA+U and the B3LYP hybrid density functional that includes nonlocal Fock exchange. TM is typically characterized in terms of the formal oxide states of 2+ or 3+, corresponding to TM with localized charge in LiTMPO4 and TMPO4 structures, respectively, in which electron transport would take place by thermally activated hopping of electrons strongly localized on the transition metal (small polarons). In this work, we assess the validity of the concept of formal TM oxidation states in these materials, and conclude that the valence depends in large part on the strength of d-p hybridization. Stable small polaron formation, i.e., mixed 2+ and 3+ valence states, appears to require that the ratio of differences in the metal and oxygen ionic charges (dQTM/dQO) of the two end member phases is larger than 2, corresponding to the mixed-valence TM system. If the ratio of dQTM/dQO is smaller than 2, excess electrons prefer delocalization and the system behaves more single-valence like with charge transport more akin to metallic conduction. The critical ratio emerging from our analysis may turn out to be relevant to other transition metal systems as well, as a criterion to discriminate single-valence or mixed-valence characteristics and hence the predominant conduction mechanism.
Petrogenesis of olivine-phyric shergottite Larkman Nunatak 06319: Implications for enriched components in martian basalts
NASA Astrophysics Data System (ADS)
Basu Sarbadhikari, Amit; Day, James M. D.; Liu, Yang; Rumble, Douglas, III; Taylor, Lawrence A.
We report on the petrography and geochemistry of the newly discovered olivine-phyric shergottite Larkman Nunatak (LAR) 06319. The meteorite is porphyritic, consisting of megacrysts of olivine (?2.5 mm in length, Fo 77-52) and prismatic zoned pyroxene crystals with Wo 3En 71 in the cores to Wo 8-30En 23-45 at the rims. The groundmass is composed of finer grained olivine (<0.25 mm, Fo 62-46), Fe-rich augite and pigeonite, maskelynite and minor quantities of chromite, ulv÷spinel, magnetite, ilmenite, phosphates, sulfides and glass. Oxygen fugacity estimates, derived from the olivine-pyroxene-spinel geo-barometer, indicate that LAR 06319 formed under more oxidizing conditions (QFM -1.7) than for depleted shergottites. The whole-rock composition of LAR 06319 is also enriched in incompatible trace elements relative to depleted shergottites, with a trace-element pattern that is nearly identical to that of olivine-phyric shergottite NWA 1068. The oxygen isotope composition of LAR 06319 (? 17O = 0.29 ▒0.03) confirms its martian origin. Olivine megacrysts in LAR 06319 are phenocrystic, with the most Mg-rich megacryst olivine being close to equilibrium with the bulk rock. A notable feature of LAR 06319 is that its olivine megacryst grains contain abundant melt inclusions hosted within the forsterite cores. These early-trapped melt inclusions have similar trace element abundances and patterns to that of the whole-rock, providing powerful evidence for closed-system magmatic behavior for LAR 06319. Calculation of the parental melt trace element composition indicates a whole-rock composition for LAR 06319 that was controlled by pigeonite and augite during the earliest stages of crystallization and by apatite in the latest stages. Crystal size distribution and spatial distribution pattern analyses of olivine indicate at least two different crystal populations. This is most simply interpreted as crystallization of megacryst olivine in magma conduits, followed by eruption and subsequent crystallization of groundmass olivine. LAR 06319 shows close affinity in mineral and whole-rock chemistry to olivine-phyric shergottite, NWA 1068 and the basaltic shergottite NWA 4468. The remarkable features of these meteorites are that they have relatively similar quantities of mafic minerals compared with olivine-phyric shergottites (e.g., Y-980459, Dho 019), but flat and elevated rare earth element patterns more consistent with the LREE-enriched basaltic shergottites (e.g., Shergotty, Los Angeles). This relationship can be interpreted as arising from partial melting of an enriched mantle source and subsequent crystal-liquid fractionation to form the enriched olivine-phyric and basaltic shergottites, or by assimilation of incompatible-element enriched martian crust. The similarity in the composition of early-trapped melt inclusions and the whole-rock for LAR 06319 indicates that any crustal assimilation must have occurred prior to crystallization of megacryst olivine, restricting such processes to the deeper portions of the crust. Thus, we favor LAR06319 forming from partial melting of an "enriched" and oxidized mantle reservoir, with fractional crystallization of the parent melt upon leaving the mantle.
Experimental Partitioning of Cr(3+) and Sc(3+) into Olivine: Mechanisms and Implications
NASA Technical Reports Server (NTRS)
Jones, John; Mackwell, S. J.
Olivine (Mg, Fe)Si2O4 does not, by stoichiometry, accept cations such as Sc(3+) or Cr(3+). However, the partition coefficients of Sc and Cr between olivine and liquid are significant 0.2-1.0. We have measured Cr(3+) partition coefficients of near unity and have grown olivines with nearly 3 wt.% Sc2O3. Therefore, there must be a simple means of charge balancing 3+ ions in a crystal structure that was obviously not designed to receive other than 2+ ions on the olivine M sites. The simplest explanation is that two 3+ ions enter the olivine structure by displacing three 2+ ions and creating an M site vacancy. Even this explanation has difficulties. For minor elements in our experiments (1 wt.%) the odds of a minor element 3+ ion finding a second 3+ for charge balance are of the order of 100:1 against. Because of the reducing conditions of our experiments, Fe(3+) will not suffice; and Al(3+) is not in sufficient quantity in olivine for charge balance. Therefore, Cr or Sc must, in effect, charge balance itself. For true trace elements, the problem is compounded many times. For an ion at the 10 ppm level the chances of finding a second (for example) Sc ion is approx.10(exp 5):1 against. Of course, any other 3+ ion would suffice but comparisons between percent level doping experiments and trace level partitioning indicate that Henry s law is obeyed. This implies that the same substitution mechanism occurs at both the percent and tens of ppm levels. There are two simple solutions to this problem: (i) The electrical conductivity of olivine is such that charge balance need not be local. This requires substantial domains within the olivine crystal in electrical contact by migration of vacancies or electronic defects. (ii) The 3+ cation brings along its own charge-balancing ion because it existed as a dimer in the silicate liquid. Olivine is not a true insulator but is actually a p-type semiconductor. Even so, electrical communication by this means is unlikely over the tens or hundreds of unit cells that would be required for charge balance to be local. Therefore, we cautiously favor the idea that melt speciation is the means by which 3+ ions enter the olivine structure. Possibly this model might be tested by in situ XAFS measurements or by molecular dynamical calculations.
Role of olivine cumulates in destabilizing the flanks of Hawaiian volcanoes
Clague, D.A.; Denlinger, R.P.
The south flank of Kilauea Volcano is unstable and has the structure of a huge landslide; it is one of at least 17 enormous catastrophic landslides shed from the Hawaiian Islands. Mechanisms previously proposed for movement of the south flank invoke slip of the volcanic pile over seafloor sediments. Slip on a low friction de??collement alone cannot explain why the thickest and widest sector of the flank moves more rapidly than the rest, or why this section contains a 300 km3 aseismic volume above the seismically defined de??collement. It is proposed that this aseismic volume, adjacent to the caldera in the direction of flank slip, consists of olivine cumulates that creep outward, pushing the south flank seawards. Average primary Kilauea tholeiitic magma contains about 16.5 wt.% MgO compared with an average 10 wt.% MgO for erupted subaerial and submarine basalts. This difference requires fractionation of 17 wt.% (14 vol.%) olivine phenocrysts that accumulate near the base of the magma reservoir where they form cumulates. Submarine-erupted Kilauea lavas contain abundant deformed olivine xenocrysts derived from these cumulates. Deformed dunite formed during the tholeiitic shield stage is also erupted as xenoliths in subsequent alkalic lavas. The deformation structures in olivine xenocrysts suggest that the cumulus olivine was densely packed, probably with as little as 5-10 vol.% intercumulus liquid, before entrainment of the xenocrysts. The olivine cumulates were at magmatic temperatures (>1100??C) when the xenocrysts were entrained. Olivine at 1100??C has a rheology similar to ice, and the olivine cumulates should flow down and away from the summit of the volcano. Flow of the olivine cumulates places constant pressure on the unbuttressed seaward flank, leading to an extensional region that localizes deep intrusions behind the flank; these intrusions add to the seaward push. This mechanism ties the source of gravitational instability to the caldera complex and deep rift systems and, therefore, limits catastrophic sector failure of Hawaiian volcanoes to their active growth phase, when the core of olivine cumulates is still hot enough to flow. ?? 1994 Springer-Verlag.
CO2-induced small water solubility in olivine and implications for properties of the shallow mantle
NASA Astrophysics Data System (ADS)
Yang, Xiaozhi; Liu, Dingding; Xia, Qunke
H2O and CO2 are important components of fluids in the mantle at ?30-150 km depth, and may affect strongly water dissolution in nominally anhydrous olivine; however, available experimental hydrogenation of olivine has been nearly exclusively carried out in coexistence with H2O (CO2-free). In this study, the effect of CO2 on water solubility in olivine has been investigated by H-annealing natural olivine under peridotite- and fluid-saturated conditions. Experiments were conducted at 1.5-5 GPa and 1100-1300 ░C, with oxygen fugacity controlled by Ni-NiO and with either H2O or H2O-CO2 as buffering fluid. The olivine shows no change in composition during the experiments. The infrared spectra of the hydrated olivine are characterized by prominent OH bands from ?3650 to 3000 cm in all the runs, at both high frequency (>3450 cm) and low frequency (<3450 cm), and the H2O solubility is ?120-370 ppm for the olivine in coexisting with H2O, and ?65-180 ppm for the olivine in coexisting with H2O-CO2. When CO2 is present in the buffering fluid, the H2O solubility of olivine is reduced by a factor of ?2, due to effect on the partitioning of water between minerals and coexisting fluid, and the measured H2O solubility shows independence on fluid composition (the molar ratio of CO2 to CO2 + H2O at ?0.2-0.5) given pressure, temperature and oxygen fugacity. Olivine equilibrated in the shallow mantle is probably dominated by OH groups in the wavenumber ?3650-3000 cm, and the intensity of OH bands at low frequency may be higher than or comparable to those at higher frequencies. The storage capacity of water in the shallow mantle in previous estimates may have been overestimated by a factor of at least ?4 if the observed effect of CO2 on water solubility is correct. Our results have profound influence on understanding partial melting, electrical conductivity anomalies and metasomatism in the shallow mantle.
Experimental constraints on formation of hematite in olivine at high pressures and temperatures
NASA Astrophysics Data System (ADS)
Zhang, Yanfei; Wang, Chao; Wu, Yao; Liu, Wenlong; Jin, Zhenmin
Iron-rich oxides, such as magnetite or hematite, have been reported in olivine grains in many orogenic garnet peridotites from continental collision zones. Whether these iron-rich minerals originate from dry oxidation, dehydrogenation-oxidation or exsolution from a precursor wadsleyite phase is debatable. This paper explores high-pressure and high-temperature experiments in a hydrous harzburgite system, by taking advantage of electron backscattered diffraction (EBSD) analyses, to examine the formation of hematite in olivine. Experimental results show that hematite can be formed within olivine grains at pressures >6 GPa and temperatures in the 1073-1473 K range. EBSD analysis suggests that hematite rods (not associated with clinopyroxene) and host olivine have the following crystallographic relations: < 0001 > _{Hem} [100]_{Ol} , < 10{-}10> _{Hem} //[001]_{Ol} , < 11{-}20> _{Hem} //[010]_{{Ol}} , which are consistent with those observed in natural garnet peridotite from the Dabie-Sulu ultra-high-pressure (UHP) metamorphic terrane. It is postulated that both hydroxide (OH-) and hydrogen (H+) ions have the potential to oxidize Fe2+ to Fe3+, followed by rapid dehydrogenation and slow Fe diffusion, thus forming hematite within the olivine grains. It is proposed that dehydrogenation-oxidation is the most likely formation mechanism of hematite inclusions within olivine, with the following two requirements: an ample amount of H2O and specific P-T conditions (>6 GPa, at 1073 K). Such conditions are consistent with those calculated in natural garnet peridotites from the Dabie-Sulu UHP metamorphic terranes. The present study also indicates that hematite (or magnetite?) inclusions in olivine contain important clues about the tectonic evolution of UHP rocks in continental crust collision zones.
Influence of FeO and H on the electrical conductivity of olivine
NASA Astrophysics Data System (ADS)
Dai, Lidong; Karato, Shun-ichiro
The influence of Fe (iron) and H (hydrogen) on the electrical conductivity of olivine was investigated. Synthetic olivine aggregates with the XFe = Fe/(Fe + Mg) (molar ratio) = 21-64% with the water content of 84-620 ppm wt (Paterson calibration) were prepared and their electrical conductivity was measured at P = 4 GPa and T = 873-1473 K. The impedance spectroscopy was used to calculate the DC electrical conductivity. We found that electrical conductivity of samples increases with increasing FeO content in both anhydrous and hydrous olivine. However, the way in which FeO enhances electrical conductivity is different between anhydrous and hydrous olivine. In anhydrous sample, the activation energy is reduced with FeO content and hence the effect of FeO content is large at low temperatures, but its effect is small at mantle temperatures. In contrast, FeO content does not affect the activation energy in hydrous olivine, and consequently, the magnitude of FeO effect is nearly independent of temperature. For both anhydrous and hydrous olivine, the influence of FeO is only modest at high temperatures (increase in conductivity by a factor of ?2 for the increase in FeO by 20% (e.g., from 10 to 30%)). In contrast, the FeO content has relatively large effects at low temperatures for anhydrous olivine. However, the role of hydrogen is large at low temperatures and hydrogen mechanism dominates under most cases. Therefore the influence of FeO on electrical conductivity is small at all temperatures for a plausible range of water content. We conclude that the water (hydrogen) content in a terrestrial planet can be inferred from observed conductivity without substantial influence of FeO if the temperature is constrained. The present results provide a basis for the interpretation of electrical conductivity model of other planets with different FeO contents.
Partitioning of Ni between olivine and siliceous eclogite partial melt: experimental constraints on the mantle source of Hawaiian basalts
Zhengrong Wang; Glenn A. Gaetani
Olivine is abundant in EarthÆs upper mantle and ubiquitous in basaltic lavas, but rarely occurs in eclogite. Partial melts\\u000a of eclogite are, therefore, not in equilibrium with olivine, and will react with peridotite as they migrate through the upper\\u000a mantle. If such melts erupt at EarthÆs surface, their compositions will be highly modified and they may be olivine-saturated.\\u000a We investigated
Investigation into the Effect of H2O on Olivine-Ringwoodite Transformation Kinetics
NASA Astrophysics Data System (ADS)
Diedrich, T. R.; Sharp, T.; Leinenweber, K.; Hervig, R.
The rapid transformation of metastable olivine subducted into the transition zone has been proposed as a mechanism leading to deep focus earthquakes, as well as general rheological weakening of the subducting slab. In evaluation of this hypothesis, several experimental studies have derived olivine-ringwoodite transformation rates for dry systems. However, double-seismic zones in subducting slabs suggest significant hydration and serpentinization. This likely presence of H2O could be expected to significantly enhance the kinetics of the olivine-ringwoodite transformation, reducing the depth to which metastable olivine would persist in the transition zone. We have initiated a series of experiments to systematically investigate the effect of dissolved water on the transformation kinetics of olivine to its high-pressure polymorphs, ringwoodite and wadsleyite. Single crystals of San Carlos olivine were milled and sieved to produce spheres with a diameter of 450-500 microns. These crystals were then hot-pressed in a matrix of olivine and enstatite powder, and deuterated by welding liquid D2O inside the sample capsule during piston-cylinder experiments. The use of D2O as a proxy for H22O was made to ease SIMS analysis because of the high background for H2O. All deuteration experiments were conducted with a nickel/nickel oxide oxygen fugacity buffer. Run conditions ranged from 2-3.2 GPa and 1000-1050 oC. The single-crystal San Carlos olivine spheres in the run products were found to contain 150-400 ppm D2O by weight. The deuterated olivine spheres and hot-pressed matrix were cut into 1.5 mm cubes and are being used as starting material in experiments conducted in the wadsleyite and ringwoodite stability fields. These experiments are being performed in a multi-anvil apparatus for durations ranging from 30-240 minutes. Run products will be prepared as thin sections and the thickness of the reaction rims will be measured and related to run duration to infer transformation rates as a function of temperature, pressure, and water content. TEM analysis will be used to determine the effect of D2O on the transformation mechanisms.
Oxygen Isotopic Diversity in Olivine and Glass within the Volcanic Record of Klyuchevskoy Volcano, Kamchatka, Russia.
NASA Astrophysics Data System (ADS)
Auer, S. L.; Bindeman, I.; Ponomareva, V.
Klyuchevskoy volcano, Kamchatka, Russia, is one of the most active volcanoes in the world. Its 4750m edifice has formed in the last 7000 years. We present an oxygen isotope and major element study of glass, as well as individual and bulk phenocrysts of olivine in 16 samples of 14C and tephrochronologically-dated layers and lavas spanning the eruptive history of Klyuchevskoy. Whole rock analysis of these layers demonstrate that high-Mg (8-11 wt% MgO) and high-Al (17-19 wt% Al2O3, 3-6 wt% MgO) basalts and intermediate products erupted coevally over the course of Klyuchevskoy's eruptive history from both flank and central cones. The oxygen isotope record of Klyuchevskoy glass and olivine is also varied throughout its history. The ?18O individual and bulk olivine values range from a normal mantle 5.25 permil to a heavy 7.2 permil. Likewise, tephra and lava matrix glass gives a heavy 5.8 permil to 7.75 permil range. These values exhibit no systematic variation through time suggesting coeval eruption and mixing of normal, moderately-high, and ultra high-?18O melts. Glass ?18O values are heavier in high-Al basalts (6.9-7.6 permil) than in high-Mg basalts (6.2-6.6 permil), but even these high-Mg basalts are distinctly heavier than a normal mantle-derived basalts of 5.5-5.9 permil. These high and more normal olivines occur in both high-Mg and high-Al samples. However, olivines are not in oxygen isotopic equilibrium with their host glass and olivine-glass ?18O values range by 1 permil off equilibrium values. Olivines are also out of Fe-Mg equilibrium with the host glass, but to a lesser extent. In summary, oxygen isotope values indicate that complex olivine recycling and re-equilibration processes involving a multi-component non-primitive magma are involved at Klyuchevskoy Volcano. Further work will focus on establishing the role of oxygen and magnesium diffusion and solution re-precipitation in olivine and glass in order to put constraints on magma storage time and crustal recycling.
Space Weathering in Olivine and the Mineralogy of (Some) M-Class Asteroids
NASA Astrophysics Data System (ADS)
Britt, Daniel; Kohout, Tomas; Schelling, Patrick; Consolmagno, Guy J.
One aspect of space weathering of airless bodies is the production of nanophase iron (npFe0) from Fe bearing silicate minerals. The combined effects of low oxygen fugacity and solar-wind implanted H tend to result in strongly-reduced surfaces that can be chemically activated by heating due to micrometeorite impacts. The mineral kinetics of olivine makes it particularly vulnerable to reduction, decomposition, and npFe0 production. Kohout et al. has recently developed a new method of controlled npFe0 production on olivine powder grains that mimics the essential features of this weathering process and was developed to quantitatively evaluate spectral changes related to space weathering and presence of npFe0. Compared to fresh olivine the treated samples exhibit spectral characteristics of space weathering including spectral darkening, shallowing and attenuation of 1 Ąm olivine absorption band, and reddening. The attenuation of the 1 Ąm band significantly shrinks the band FWHM and shifts the much reduced band center to shorter wavelengths around 0.95 Ąm. These spectral changes are related to increasing amounts of npFe0 and the disruption of the crystal structure of the parent olivine. Significantly, the darkened, reddened, and band attenuated olivine spectra are a close match to a number of M-class asteroids. What is particularly interesting is the match with the weak absorption band near 0.95 Ąm seen in many M-class asteroids (i.e. 16 Psyche, 22 Kalliope, 55 Pandora to name a few). One of the major issues in asteroid science is the relative scarcity of olivine asteroids (the öGreat Dunite Shortageö coined by Bell et al in Asteroids II). One possibility worth further study is that asteroidal olivine may be hidden by the relative ease with which it weathers. The surface chemical and micrometeorite environment in the asteroid belt may produce over time a spectrum for an olivine-rich surface that is remarkably similar to that of an M-class asteroid.
Modal mineralogy of the surface of Vesta: Evidence for ubiquitous olivine and identification of meteorite analogue
NASA Astrophysics Data System (ADS)
Poulet, F.; Ruesch, O.; Langevin, Y.; Hiesinger, H.
The observations of the surface of 4 Vesta by the Visible and Infrared Mapping Spectrometer (VIR) onboard the Dawn spacecraft reveals that its composition is dominated by pyroxenes with olivine in very localized spots. To derive new constraints on the surface composition of the asteroid, we apply a scattering model to VIR reflectance spectra. The model is first calibrated by performing a non-linear deconvolution of laboratory spectra of mineral mixtures and howardite, eucrite, diogenite (HED) meteorites. Abundance estimates of minerals are accurate to within 15-25% for the analyzed samples, while the estimated particle sizes are within the intervals of actual sizes. Grain size effects complicate spectral deconvolution and estimation of modal abundances of samples (both HED and mineral mixtures) that contain olivine. The magnesium-rich olivine detection threshold is 10-20% for large grain sizes (100s ?m) and several 10s% for small grain sizes (<50 ?m). Major expected minerals (low-calcium pyroxenes, high-calcium pyroxenes, plagioclase and olivine) can provide satisfactory fits of VIR spectra with excellent residuals ?1%. Terrains with the strongest low-calcium pyroxene signatures are well representative of diogenites. The best fits of any unit are obtained by including Fo70 olivine at an abundance level of 10-20%, with an uncertainty of ?10%. Olivine is therefore likely to be ubiquitous over the whole surface of Vesta. Olivine is coarser grained (a few hundred ?m) than other minerals such as orthopyroxene and clinopyroxene (grain sizes typically smaller than 100 ?m). Both the grain size variance and the modal mineralogy are consistent with the lithologic size and mineral distributions of howardites containing olivine phenocryst-bearing melt. These howardites are the best petrologic analogues of Vesta. Such a surface assemblage could be the result of successive melting and mixing processes due to impacts. The compositional view confirms that Vesta underwent major homogenization processes, resulting in a relatively uniform modal mineralogy and explaining the lack of specific olivine enrichment in the Rheasilvia ejecta.
Seismic Properties and Acoustic Emission of Olivine and Molten Basalt: A Laboratory Study
NASA Astrophysics Data System (ADS)
Burlini, L.; Vinciguerra, S.; Meredith, P. G.; Zappone, A. S.; di Toro, G.
Here, we present the first results of petrophysical investigations on the system olivine + MORB up to 1473K and 300MPa confining pressure using an internally-heated Paterson gas apparatus especially designed for the measurements of physical properties of rocks. Both Vp and acoustic emissions were measured during heating and cooling of cold pressed synthetic aggregate of both San Carlos olivine and MORB powder (in the latter case till complete melting). The same measurements were also made on a layered sample comprising an olivine-MORB-olivine sandwich. Vp was measured using the pulse transmission technique, with 1 MHz piezoelectric transducers mounted on the end of ceramic buffer rods. The buffer rods were calibrated using a single crystal of sapphire cut parallel to the c-axis. The acoustic emissions were recorded using the same transducers. A significant decrease of both velocity and of the amplitude of the seismic signal were observed during experiments involving MORB at temperatures above 1273 K. BSE imaged that melt from the MORB layer had intruded into the olivine matrix, even under hydrostatic conditions. Higher acoustic activity recorded after the melting onset, characterized by short durations and very low amplitudes, confirms the melt migration, and suggests a brittle intrusive mechanism such as hydrofracturing. Importantly, this provides a unique experimental insight into magma migration in the lithosphere and the mechanism of dyke emplacement. The results support the presence of a low but distinguishable seismic output during this process.
Space weathering simulations through controlled growth of iron nanoparticles on olivine
NASA Astrophysics Data System (ADS)
Kohout, T.; ?uda, J.; Filip, J.; Britt, D.; Bradley, T.; Tu?ek, J.; Skßla, R.; Kletetschka, G.; KaÜlĒk, J.; Malina, O.; ŖiÜkovß, K.; Zbo?il, R.
Airless planetary bodies are directly exposed to space weathering. The main spectral effects of space weathering are darkening, reduction in intensity of silicate mineral absorption bands, and an increase in the spectral slope towards longer wavelengths (reddening). Production of nanophase metallic iron (npFe^{0}) during space weathering plays a major role in these spectral changes. A laboratory procedure for the controlled production of npFe^{0} in silicate mineral powders has been developed. The method is based on a two-step thermal treatment of low-iron olivine, first in ambient air and then in a hydrogen atmosphere. Through this process, a series of olivine powder samples was prepared with varying amounts of npFe^{0} in the 7-20-nm size range. A logarithmic trend is observed between the amount of npFe^{0} and darkening, reduction of 1-? m olivine absorption band, reddening, and the 1-? m band width. Olivine with a population of physically larger npFe^{0} particles follows spectral trends similar to other samples, except for the reddening trend. This is interpreted as follows: the larger, ś40-50-nm sized npFe^{0} particles do not contribute to the spectral slope change as efficiently as the smaller npFe^{0} fraction. A linear trend is observed between the amount of npFe^{0} and the 1-? m band center position, most likely caused by the Fe^{2+} disassociation from the olivine structure into npFe^{0} particles.
Space weathering simulations through controlled growth of iron nanoparticles on olivine
NASA Astrophysics Data System (ADS)
Kohout, TomßÜ; ?uda, Jan; Filip, Jan; Britt, Daniel; Bradley, Todd; Tu?ek, Ji?Ē; Skßla, Roman; Kletetschka, Gunther; KaÜlĒk, Josef; Malina, Ond?ej; ŖiÜkovß, KarolĒna; Zbo?il, Radek
Airless planetary bodies are directly exposed to space weathering. The main spectral effects of space weathering are darkening, reduction in intensity of silicate mineral absorption bands, and an increase in the spectral slope towards longer wavelengths (reddening). Production of nanophase metallic iron (npFe0) during space weathering plays major role in these spectral changes. A laboratory procedure for the controlled production of npFe0 in silicate mineral powders has been developed. The method is based on a two-step thermal treatment of low-iron olivine, first in ambient air and then in hydrogen atmosphere. Through this process, a series of olivine powder samples was prepared with varying amounts of npFe0 in the 7-20 nm size range. A logarithmic trend is observed between amount of npFe0 and darkening, reduction of 1 ?m olivine absorption band, reddening, and 1 ?m band width. Olivine with a population of physically larger npFe0 particles follows spectral trends similar to other samples, except for the reddening trend. This is interpreted as the larger, ?40-50 nm sized, npFe0 particles do not contribute to the spectral slope change as efficiently as the smaller npFe0 fraction. A linear trend is observed between the amount of npFe0 and 1 ?m band center position, most likely caused by Fe2+ disassociation from olivine structure into npFe0 particles.
Olivine in terminal particles of Stardust aerogel tracks and analogous grains in chondrite matrix
NASA Astrophysics Data System (ADS)
Frank, David R.; Zolensky, Michael E.; Le, Loan
The dearth of both major and minor element analyses of anhydrous silicate phases in chondrite matrix has thus far hindered their comparison to the Wild 2 samples. We present 68 analyses of olivine (Fa0-97) in the coarse-grained terminal particles of Stardust aerogel tracks and a comprehensive dataset (>103 analyses) of analogous olivine grains (5-30 ?m) isolated in CI, CM, CR, CH, CO, CV3-oxidized, CV3-reduced, C3-ungrouped (Acfer 094 and Ningqiang), L/LL 3.0-4, EH3, and Kakangari chondrite matrix. These compositions reveal that Wild 2 likely accreted a diverse assortment of material that was radially transported from various carbonaceous and ordinary chondrite-forming regions. The Wild 2 olivine includes amoeboid olivine aggregates (AOAs), refractory forsterite, type I and type II chondrule fragments and/or microchondrules, and rare relict grain compositions. In addition, we have identified one terminal particle that has no known compositional analog in the meteorite record and may be a signature of low-temperature, aqueous processing in the Kuiper Belt. The generally low Cr content of FeO-rich olivine in the Stardust samples indicates that they underwent mild thermal metamorphism, akin to a petrologic grade of 3.05-3.15.
In-situ XRD study of the olivine - ringwoodite transformation kinetics: application for effects of water on its growth kinetics
NASA Astrophysics Data System (ADS)
Ning, J.; Wang, S.; Kubo, T.; Higo, Y.; Funakoshi, K.
Dependence of water on the growth kinetics in San Carlos olivine phase transformation to ringwoodite was investigated with time-reserved X-ray diffraction method on BL04B1 station at SPring 8. The starting material is San Carlos olivine powder. Water is added by a mixture of Mg(OH)2 and SiO2. Single crystalline diamond or Ag-Pd is used as the sample capsule to prevent the escape of water. Pressure is generated by the double stage method in the SPEED 1500 system and measured by the gold pressure maker. After the annealing of the sample in the olivine stability field, we observed the olivine-ringwoodite transformation kinetics by time-reserved X-ray diffraction measurements with energy dispersive method using a solid-state detector. Kinetic data of the olivine phase transformation to ringwoodite, at about 16-20 GPa, 680-1050 C, and 500-2000 wt. ppm. H2O, were obtained. In previous kinetic studies, in-situ XRD experiments have been limited to the olivine-wadsleyite transformation. However, the kinetic data on the olivine-ringwoodite transformation is also indispensable to discuss the presence of the metastable olivine seismologically detected in some slabs. The kinetic data newly obtained here, combined with the previous published data, are used to study the effect of water on the olivine transformation to ringwoodite.. We will discuss the difference of the olivine transformation to ringwoodite and to wadsleyite, and the extent of metastable olivine in subduction zone under complicated water environment.
Olivine + halides: a recipe for iron mobilization in volcanic ash?
NASA Astrophysics Data System (ADS)
Hoshyaripour, G.; Hort, M. K.; Langmann, B.
During the last decade, scientific evidences strongly suggest that volcanic ash iron has fertilization impact upon the surface ocean. Still, it is not well constrained how the insoluble iron in ash (i.e., as a component in minerals and also glass) could be mobilized during volcanic eruptions and atmospheric transport. Here we investigate the volcanic plume controls on ash iron solubility. We develope a conceptual box model to simulate the high, mid and low temperature chemical, physical and thermodynamic processes in eruption plumes to better constrain the iron mobilization in volcanic ash. We take into account the interaction of different species in a solid-liquid-gas system representing various volcanic settings (convergent plate, divergent plate and hot spot). Results show that the hot core of a volcanic plume (T>600░C) does not produce soluble iron directly but significantly controls the Fe mineralogy and oxidation state at the ash surface. The final iron mineralogy at the ash surface (i.e. the ash's oxidation front with 1-100 nm thickness) is likely to be independent of temperature and oxygen fugacity and is closely correlated to the ratio of H2 and H2S content of the magmatic gas to the amount of entrained oxygen. As the plume continues rising and cooling, sulfuric acid condenses at about 150░C followed by water condensation at about 50░C which also dissociates sulfuric acid and produces H+ ions in the liquid phase. The aqueous phase scavenges the surrounding gas species (e.g. SO2, HCl, HF) and concurrently dissolves the ash surface constituents. Since HCl is about 4 orders of magnitudes more soluble than SO2, its dissolution mainly controls the pH of the liquid. Hence, high HCl concentrations in the gas phase results in lower pH in the aqueous phase (pH<0.5) and consequently an increase in the ash dissolution rate. Moreover reduced iron carrying minerals (e.g. fayalite) show a much higher dissolution rate in comparison with oxidized species (e.g. hematite). Thus, the presence of the reduced iron species in the mineral assemblage seems to be more favorable for the soluble iron production. We conclude that bio-available iron production is weakly correlated with the tectonic setting and is instead controlled by the halide content of the eruption plume and the oxidation state of the iron at the ash mineral assemblage (e.g. presence of olivine). This hypothesis could satisfactorily explain the extraordinary iron release from the ash of Hekla eruption in 2000 and also the fertilization impact caused by the ash erupted from Kasatochi in 2008.
Chemical zoning and diffusion of Ca, Al, Mn, and Cr in olivine of springwater pallasite
NASA Technical Reports Server (NTRS)
Zhou, Y.; Steele, Ian M.
The pallasites, consisting mainly of Fe-Ni metal and olivine, are thought to represent the interior of a planetary body which slowly cooled from high temperature. Although the olivines are nearly homogeneous, ion microprobe studies revealed variations of Ca, Ti, Co, Cr, and Ni near grain edges. These variations were thought to represent diffusion in response to falling temperature of the parent body. Pallasite cooling rates have been estimated based on kamacite taenite textures but results differ by x100. In principle elemental profiles in olivine can allow estimates of cooling rate if diffusion coefficients are known; in addition, given a cooling rate, diffusion coefficients could be derived. Data are presented which show that apparent diffusion profiles can be measured for Al, Ca, Cr, and Mn which qualitatively agree with expected diffusion rates and have the potential of providing independent estimates of pallasite cooling rates.
Near-infrared spectral reflectance of mineral mixtures - Systematic combinations of pyroxenes, olivine, and iron oxides
NASA Technical Reports Server (NTRS)
Singer, R. B.
Near-infrared spectral reflectance data are presented for systematic variations in weight percent of two component mixtures of ferromagnesium and iron oxide minerals used to study the dark materials on Mars. Olivine spectral features are greatly reduced in contrast by admixture of other phases but remain distinctive even for low olivine contents. Clinopyroxene and orthopyroxene mixtures show resolved pyroxene absorptions near 2 microns. Limonite greatly modifies pyroxene and olivine reflectance, but does not fully eliminate distinctive spectral characteristics. Using only spectral data in the 1 micron region, it is difficult to differentiate orthopyroxene and limonite in a mixture. All composite mineral absorptions were either weaker than or intermediate in strength to the end-member absorptions and have bandwidths greater than or equal to those for the end members. In general, spectral properties in an intimate mixture combine in a complex, nonadditive manner, with features demonstrating a regular but usually nonlinear variation as a function of end-member phase proportions.
Kinetics of evaporation of forsterite and Fe-Mg olivine in vacuum
NASA Astrophysics Data System (ADS)
Ozawa, K.; Nagahara, H.
Evaporation of forsterite, which plays an important role in chemical and isotope fractionation in the early solar nebula, is governed by surface kinetics strongly affected by surface conditions, such as surface roughness as well as density and orientation of dislocation outcrops. We have revealed anisotropies in evaporation rate and surface microstructure of forsterite and Fe-Mg olivine [1-3]. In order to better understand the kinetics of evaporation of forsteriete and olivine, we carried out experiments in a wider range of temperature and examined evaporation mode on the basis of temperature dependence of evaporation rates and surface microstructures. Experiments were carried out in a vacuum chamber internally heated by W mesh heater. Starting materials are single crystals of synthetic forsterite and natural Fe-Mg olivine (Fo~90), which are cut into crystallographically oriented rectangular parallelepipeds. The experimental temperature in the present and our previous studies ranged from 1300 to 1600 ░C for Fe-Mg olivine and from 1500 to 1800 ░C for forsterite. Surface microstructures of experimental residues were observed with SEM and EBSD, and face-specific evaporation rates were calculated from sample sizes and weight losses on at least three parallelepipeds with different [001]:[010]:[001] ratios. Development of Fe-Mg zoning due to preferential evaporation of Fe and Fe-Mg lattice diffusion in the sample was taken into consideration in rate estimation for olivine evaporation. The experimental results for both forsterite and olivine experiments demonstrated systematic temperature dependence of anisotropy in evaporation rate: (010)>(001)>(010) above ~1750░C, (001)>(100)>(010) at temperatures between ~1750 and ~1500░C, and (001)>(010)>(100) below ~1500░C. The maximum anistoropy in the evaporation rate is factor of 5 below ~1750░C, but the anisotropy is significantly suppressed above ~1750░C, where the differences among three evaporation rates are within 70% at ~1800░C. These crossovers in evaporation rate were intimately associated with changes in surface microstructures not directly related to surface morphologies originated from dislocation outcrops. Facets of (010) disappear on the (010) surface above ~1750░C, and (100) facets appear on the (100) surface below ~1500░C, which is consistently observed both for forsterite and olivine. The facets observed in SEM were confirmed to be atomistically flat consisting of stacking of layers with one or few unit-cells height through STM observations. On the contrary, non-facetted surfaces were confirmed to be atomistically rough. Therefore, the rate crossovers are attributed to rough-smooth transitions [4-5] at ~1500░C for (100) and at ~1750░C for (010). Such rough-smooth transition for the (001) surface is expected to exist below ~1500░C. The anisotropy in the rough-smooth transition temperature identified for forsterite and olivine cannot be explained solely by the differences in slice energy or attachment energy (anisotropy in bond stength) for the three crystallographic faces [6], which predicts that the transition temperture decreases in the order of (010), (001), and (100). The presence of Fe notably enhances stoichiometric evaporation of Fe-Mg olivine at 1500░C without forming any reaction product [3]. This suggests that stoichiometric evaporation from olivine or congruent evaporation from forsterite is controlled by removal of Mg2+ and Fe2+ from either the M1 or M2 site followed by spontaneous destruction of SiO4 tetrahedron at least above 1500░C, which is required not to result in incongruent evaporation forming enstatite layer. On the contrary, Fe-Mg olivine evaporates nonstoichiometrically to form enstatite at the forsterite surface at ~1300░C (Ozawa and Nagahara, 2002), where removal of Fe2+ or Mg2+ is not the rate-controlling process but Si removal or breaking Si-O bonds governs the overall reaction. The slow removal of Si results in nonstoichiometric evaporation via reaction with olivine residue to produce enstatite on the sur
Peridotite and pyroxenite components in the sources of Grande Comore lavas: evidence from olivine compositions
NASA Astrophysics Data System (ADS)
Weiss, Y.; Class, C.; Goldstein, S. L.
Grande Comore (Ngazidja) is the youngest Island of the Comores Archipelego in the Indian Ocean, located in the Somali Basin between Africa and Madagascar. The island formed by two volcanoes. Karthala is an active shield volcano, and La Grille is composed mainly of monogenetic cinder cones. The island represents interaction between a mantle plume and oceanic lithosphere and previous studies suggested, based on the major, trace elements and Sr-Nd-Pb-Os isotopic relationships of the lavas, that the alkali basalts of Karthala reflect mainly plume derived melts, while the basanites of La Grille are the products of interaction of plume melts with the metasomatized oceanic lithosphere. Here we report the chemical composition of olivine phenocrysts of Karthala lavas (5 samples), old Karthala (1) and La Grille (3) that were previously analyzed for their major, trace elements and Sr, Nd, Pb, Os and He isotopic compositions. Olivine phenocrysts from Karthala lavas have higher Mn and Ca, lower Al and slightly lower Ni content compared to olivines from La Grille at similar Mg#. Olivines from ';Old Karthala'are close in composition to those from La Grille and the content of Cr is similar between all three groups. The average Mn/Fe and Ca/Fe ratios of olivines of the samples positive correlate with the Sr-Pb-Os isotope ratios of the corresponding whole rocks, and Karthala has higher values than La Grille. These ratios negatively correlate with Nd-He isotope ratios, as well as with the La/Gd, Gd/Yb and Nb/K of the host lavas. The average Ni/Mg and Al/Mg ratios of the olivines correlate with the isotopic and trace element ratios of the whole rocks as well, but display trends in the opposite direction to the ones observed for Mn/Ca over Fe. Previous studies have proposed that the minor element (Ni, Mn and Ca) composition in olivine can be used to infer the proportions of peridotite vs pyroxenite and thus, the amount of recycled ocean crust in the source lithologies of magmas (Sobolev et al., 2007. The amount of recycled crust in sources of mantle-derived melts. Science, 306, 412-417). The Karthala olivines have high Mn/Fe and Ca/Fe and are similar in composition to olivines in MORB, suggesting 10-35% melt contribution from a pyroxenite source. La Grille and old Karthala olivines, on the other hand, are closer in composition to olivines from the Makapuu stage of the Koolau Island in Hawaii and represent 50-75% pyroxenite-derived melt. However, the Ni/Mg ratios in the Grande Comore lavas are relatively constant, unlike MORB, Koolau and other OIBs. Indeed the pyroxenite, which melts within the lithosphere to contribute to the La Grille and old Karthala lavas, most probably, due to metasomatic processes, differs from asthenospheric pyroxenite, which has been suggested to form by the interaction of recycled oceanic crust and peridotite in a rising plume. Thus, our data indicate that lithospheric pyroxenite formed by metasomatism of the lithospheric mantle can be distinguished from pyroxenite from mantle recycling from olivine phenocryst compositions in OIBs.
Elasticity of the olivine and spinel polymorphs of Ni 2 SiO 4
Jay D. Bass; Donald J. Weidner; N. Hamaya; M. Ozima; S. Akimoto
The single-crystal elastic moduli, cij x, of the olivine (a) and spinel (?) polymorphs of nickel orthosilicate have been measured at atmospheric pressure and 20░ C by Brillouin spectroscopy. The results are (Mbar), Ni2SiO4 olivine: c11=3.40(2), c22=2.38(2), c33=2.53(2), c44=0.71(1), c55=0.87(1), c66=0.78(1), c12=1.09(2), c13=1.10(4), c23=1.13(3), Ni2SiO4 spinel: c11=3.66(3), c44=1.06(1), c12=1.55(3). In comparing these results with extant elasticity data for olivine- and
The influence of bulk composition and dynamic melting conditions on olivine chondrule textures
NASA Technical Reports Server (NTRS)
Connolly, Harold C., Jr.; Hewins, Roger H.
The effects of the bulk composition and the dynamic melting conditions on the texture of olivine chondrules were investigated in a series of heating experiments. It is shown that variations in the olivine chondrule textures can be produced by varying the FeO/(FeO + MgO) ratio between the average Type IA and Type II chondrule compositions, could affect the texture of a chondrule at a constant initial melting temperature and heating time. A range of the heating times and the masses of precursor spheres caused variations in the degree of melting and in chondrule textures. Chondrule textures were distributed on a graph of initial temperatures vs. FeO/(FeO + MgO) ratios as bands parallel to the olivine disappearance curve. This graph could be used to predict chondrule textures from Fe/(FeO + MgO) ratios at specific initial melting temperatures.
Pressure dependence on partition coefficients for trace elements between olivine and the coexisting melts
NASA Astrophysics Data System (ADS)
Taura, Hiroshi; Yurimoto, Hisayoshi; Kurita, Kei; Sueno, Shigeho
Partition coefficients between olivine and melt at upper mantle conditions, 3 to 14 GPa, have been determined for 27 trace elements (Li, Be, B, Na, Mg, Al, Si, P, K, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Rb, Sr, Y, Zr, Cs, Ba, La and Ce) using secondary-ion mass-spectrometry (SIMS) and electron-probe microanalysis (EPMA). The general pattern of olivine/melt partitioning on Onuma diagrams resembles those reported previously for natural systems. This agreement strongly supports the argument that partitioning is under structural control of olivine even at high pressure. The partition coefficients for mono- and tri-valent cations show significant pressure dependence, both becoming larger with pressure, and are strongly correlated with coupled substitution into cation sites in the olivine structure. The dominant type of trace element substitution for mono- and tri-valent cations into olivine changes gradually from (Si, Mg)<-->(Al, Cr) at low pressure to (Si, Mg)<-->(Al, Al) and (Mg, Mg)<-->(Na, Al) at high pressure. The change in substitution type results in an increase in partition coefficients of Al and Na with pressure. An inverse correlation between the partition coefficients for divalent cations and pressure has been observed, especially for Ni, Co and Fe. The order of decreasing rate of partition coefficient with pressure correlates to strength of crystal field effect of the cation. The pressure dependence of olivine/melt partitioning can be attributed to the compression of cation polyhedra induced by pressure and the compensation of electrostatic valence by cation substitution.
Comet-like mineralogy of olivine crystals in an extrasolar proto-Kuiper belt.
de Vries, B L; Acke, B; Blommaert, J A D L; Waelkens, C; Waters, L B F M; Vandenbussche, B; Min, M; Olofsson, G; Dominik, C; Decin, L; Barlow, M J; Brandeker, A; Di Francesco, J; Glauser, A M; Greaves, J; Harvey, P M; Holland, W S; Ivison, R J; Liseau, R; Pantin, E E; Pilbratt, G L; Royer, P; Sibthorpe, B
Some planetary systems harbour debris disks containing planetesimals such as asteroids and comets. Collisions between such bodies produce small dust particles, the spectral features of which reveal their composition and, hence, that of their parent bodies. A measurement of the composition of olivine crystals (Mg(2-2x)Fe(2x)SiO(4)) has been done for the protoplanetary disk HD?100546 (refs 3, 4) and for olivine crystals in the warm inner parts of planetary systems. The latter compares well with the iron-rich olivine in asteroids (x???0.29). In the cold outskirts of the ??Pictoris system, an analogue to the young Solar System, olivine crystals were detected but their composition remained undetermined, leaving unknown how the composition of the bulk of Solar System cometary olivine grains compares with that of extrasolar comets. Here we report the detection of the 69-micrometre-wavelength band of olivine crystals in the spectrum of ??Pictoris. Because the disk is optically thin, we can associate the crystals with an extrasolar proto-Kuiper belt a distance of 15-45 astronomical units from the star (one astronomical unit is the Sun-Earth distance), determine their magnesium-rich composition (x = 0.01?▒?0.001) and show that they make up 3.6?▒?1.0 per cent of the total dust mass. These values are strikingly similar to those for the dust emitted by the most primitive comets in the Solar System, even though ??Pictoris is more massive and more luminous and has a different planetary system architecture. PMID:23038467
Water disequilibrium in olivines from Hawaiian peridotites: Recent metasomatism, H diffusion and magma ascent rates
NASA Astrophysics Data System (ADS)
Peslier, Anne H.; Bizimis, Michael; Matney, Mark
Constraining the distribution and mobility of H in olivine, the main mineral of the upper mantle, is crucial to our understanding of Earth's geodynamics because this trace element influences melting, rheology, and electrical and thermal conductivities of peridotite. For this purpose, the olivines from fresh and well-characterized peridotite xenoliths from Salt Lake Crater and Pali (Oahu, Hawaii), representing samples of the oceanic mantle lithosphere, were analyzed by FTIR. Water concentrations decrease from core to edge and near fractures of olivine grains, and are best interpreted as H loss during xenolith ascent to the surface in its host magma. Diffusion modeling of these profiles allowed the calculation of diffusion times, which were in turn used to estimate the average ascent rates of the xenolith host nephelinite at 0.2-25.3 m s-1. These rates are similar to those of continental basaltic magmas. Diffusion modeling further shows that the water contents at the core of olivines are preserved mantle values and are heterogeneous within each xenolith. In addition, the discrepant behavior of the 3225 cm-1 OH band (due to H in a Mg vacancy) relative to the other OH bands (in particular the Ti-H defect) along profiles evidences that H is heterogeneously distributed amongst olivine defects. These defect profiles are modeled to calculate that the diffusion rate of the Mg-H defect is about 1.3-6.8 times faster than that of the Ti-H defect. The heterogeneous distribution of H in the mantle between olivine cores in single xenoliths and within olivine grains testifies of a state of disequilibrium for water in these samples. The Salt Lake Crater peridotite olivines record two processes; recent metasomatism by a melt bringing water followed by water loss during ascent in the host magma, neither having lasted long enough for water to reach equilibrium. The observed decoupling between the heterogeneous distribution of H and the homogeneous distribution of lithophile elements suggests that the process of water addition to the peridotite via incipient melt metasomatism was likely interrupted by the host nephelinite removing the samples from the mantle and bringing them to the surface.
Bulk Diffusion and Isotopic Fractionation of Lithium in Olivine: an Experimental Study
NASA Astrophysics Data System (ADS)
Singletary, S.; Bell, D. R.
Lithium is the lightest of the lithophile elements, with high solid-state diffusivity (e.g. Giletti and Shanahan, 1997). Recent studies in synthetic and natural systems suggest that isotopic fractionation of lithium accompanies diffusion (Richter et al., 2003; Lundstrom et al., 2005; Beck et al., 2006; Teng et al., 2007; Jeffcoate et al., 2007). Lithium isotope variations therefore have the potential to constrain time scales of geological processes. We have performed a series of experiments to quantitatively assess the bulk diffusion of lithium in olivine and the degree of isotopic fractionation that can occur during diffusive transport. Single crystals of San Carlos olivine were surrounded by LiF and then held at temperature (800░C to 1000░C) for variable lengths of times (up to 20 hours at 800░C and as short as 2 hours at 1000░C). Measurements of the lithium concentration and isotopic composition of the experimental charges were conducted using the Cameca IMS 3f at Arizona State University. The lowest temperature experiments show no discernable diffusion of lithium into the olivine crystal, while in the highest temperature experiment, up to 650 ppm lithium is incorporated into the olivine. The lithium content in all experiments above 1000░C decreases smoothly from the crystal rim to the core; indicating diffusive transport of Li into the crystal. Lithium concentrations in the crystal cores range from background in the lowest temperature experiment, to ~100 ppm in the highest temperature experiment. Rim values, in contrast, vary from 650 ppm in the high temperature experiments to core concentrations in the low temperature experiment. All experiments in which diffusive transport into the olivine crystal occurred also display a fractionation of 6Li from 7Li. In the most extreme case, a variation of 50ē in ?7Li was observed across the diffusion profile, which was generated in just under 2 hours. As lithium content decreases toward the crystal center, the ?7Li values become increasingly negative, reaching values of -45ē in one experiment. These results confirm that solid state Li diffusion can be a major influence on the isotopic composition of Li in olivine, as shown previously for silicate melts (Richter et al., 2003). In one experiment, low ?7Li values were observed ahead of detectable changes in Li concentration, suggesting that isotopic exchange of Li in olivine may be more rapid than bulk Li diffusion. With experimentally determined values of Li diffusivity, it should be possible to place strict time constraints on geochemical processes that affect the lithium abundance and isotopic ratios in olivine.
Seismic evidence for olivine phase changes at the 410- and 660-kilometer discontinuities.
Lebedev, Sergei; Chevrot, Sķbastien; van der Hilst, Rob D
The view that the seismic discontinuities bounding the mantle transition zone at 410- and 660-kilometer depths are caused by isochemical phase transformations of the olivine structure is debated. Combining converted-wave measurements in East Asia and Australia with seismic velocities from regional tomography studies, we observe a correlation of the thickness of, and wavespeed variations within, the transition zone that is consistent with olivine structural transformations. Moreover, the seismologically inferred Clapeyron slopes are in agreement with the mineralogical Clapeyron slopes of the (Mg,Fe)2SiO4 spinel and postspinel transformations. PMID:12016311
Shock-Induced Transformation Exsolution Lamellae in Olivine in Black Veins of the Mbale Meteorite
NASA Astrophysics Data System (ADS)
Chen, M.; Wopenka, B.; El Goresy, A.
Mbale is a shocked L6 chondrite [1]. Some shock-induced veins of 0.1 to 2 mm width intersect the meteorite. The veins consist of diaplectic plagioclase glass, unmelted silicate fragments including olivines and pyroxenes, and the shock-induced melt materials consisting of metal-troilite intergrowths, microcrystalline pyroxene and olivine, and silicate glass. Here we report the first finding of shock-induced exsolutions in olivine that appear as compositionally different lamellae which presumably formed at high pressure by inversion of olivine (alpha) to the beta+gamma polymorphs. Olivine compositions in the chondritic part of Mbale range from Fa(sub)22.5 to Fa(sub)26 (average Fa(sub)24). In contrast, the exsolved olivines in the shock-induced veins (30 to 100 mm in diameter) consist of alternating Fe-rich (Fa(sub)22-32) and Fe-poor (Fa(sub)9.9-18.5) lamellae that range in width from less than 0.5 micrometers to up to 10 micrometers. Each individual lamella actually consists of microcrystals of less than 0.5 micrometers in diameter with rather diffuse borders within the lamella. The lamellae occur in ~30 micrometer segments which were formed by faulting and displacement. Micro-Raman spectroscopy confirms that both types of exsolution lamellae currently have the olivine (alpha) structure. The partially melted veins of Mbale may have reached a post-shock peak temperature of 1473 K >= T <= 1873 K. Based on the phase diagrams of the olivine(alpha)-wadsleyite(beta)-ringwoodite(gamma) transformations in the system Mg(sub)2SiO(sub)4-Fe(sub)2SiO(sub)4 at 1473 K [2], olivine of composition ~Fa(sub)24 should exsolve at equilibrium conditionsins to beta- + gamma-phases at P >12.7 GPa, and transform to a single gamma-phase at >15 GPa. Figure 1 shows that the determined compositions of the Fe-rich and Fe-poor lamellae in Mbale match perfectly the compositions at the beta + gamma/gamma and the beta + gamma/beta phase boundaries, respectively. Since these grains depict well ordered lamellar structure displaced by several faults, the exsolution lamellae of olivine must have nucleated before faulting. TEM studies of ringwoodite in black veins in other shocked chondrites indicate that the original olivine has transformed into a mosaic of ringwoodite grains in nano-meter size range [3,4]. The observed lamellar structure in Mbale olivines is indicative of exsolution transformation from single grains before faulting of the olivines and definitely before solidification of the silicate melt to glass in the vein. We therefore consider it unlikely that the shock-induced olivine lamellae were produced via retrograde exsolution from gamma to gamma + beta. Our findings strongly suggest that the exsolutions were produced from an originally homogeneous olivine (alpha) by the following mechanism: Original homogenous olivine exsolved at P>12.7 GPa and 1473 K >=T <= 1873 K into Fe-poor beta- and Fe-rich gamma-phases possibly along [001] which is the predominant dislocation orientation in olivine during deformation [4,5]. The dislocations in olivine may have provided the nucleation sites for the beta- and gamma-phases due to their reduced activation barrier to nucleation. The grains were then faulted to several segments of 30 micrometers in diameter. A cooling rate of >= 260 K/s during the solidification of the shock-induced melt was estimated in the interval of 1223-1673 K, based on the metallic dendrite arm spacing or cell width of ~14 micrometers [6]. The cooling of the veins after the solidification of metal and silicate melts should have been much slower than 260 K/s because of the homogeneous Ni-concentration within the metallic dendrites. We interpret the survival of the lamellar structure as due to a nonlinear cooling rate: (1) very fast cooling after pressure release thus inhibiting obliteration of the lamellae by diffusion; followed by (2) slow cooling <1223 K thus leading to inversion of gamma and beta lamellae to alpha without chemical homogenization. References: [1] Jenniskens P. et al. (1994) Meteoritics ,
Dehydration breakdown of antigorite and the formation of B-type olivine CPO
NASA Astrophysics Data System (ADS)
Nagaya, Takayoshi; Wallis, Simon R.; Kobayashi, Hiroaki; Michibayashi, Katsuyoshi; Mizukami, Tomoyuki; Seto, Yusuke; Miyake, Akira; Matsumoto, Megumi
Peridotite formed by contact metamorphism and dehydration breakdown of an antigorite schist from the Happo area, central Japan shows a strong olivine crystallographic preferred orientation (Ol CPO). The lack of mesoscale deformation structures associated with the intrusion and the lack of microstructural evidence for plastic deformation of neoblastic grains suggest that olivine CPO in this area did not form as a result of solid-state deformation. Instead, the good correspondence between the original antigorite orientation and the orientation of the newly formed olivine implies the CPO formed by topotactic growth of the olivine after antigorite. Ol CPO is likely to develop by a similar process in subduction zone environments where foliated serpentinite is dragged down to depths where antigorite is no longer stable. The Happo Ol CPO has a strong a-axis concentration perpendicular to the lineation and within the foliation-commonly referred to as B-type Ol CPO. Seismic fast directions parallel to the ocean trench are observed in many convergent margins and are consistent with the presence of B-type Ol CPO in the mantle wedge of these regions. Experimental work has shown that B-type CPO can form by dislocation creep under hydrous conditions at relatively high stresses. There are, however, several discrepancies between the characteristics of natural and laboratory samples with B-type Ol CPO. (1) The formation conditions (stress and temperature) of some natural examples with B-type CPO fall outside those predicted by experiments. (2) In deformation experiments, slip in the crystallographic c-axis direction is important but has not been observed in natural examples of B-type CPO. (3) Experimental work suggests the presence of H2O and either high shear stress or relatively low temperatures are essential for the formation of B-type CPO. These conditions are most likely to be achieved close to subduction boundaries, but these regions are also associated with serpentinization, which prevents strong olivine CPO patterns from forming. We show B-type Ol CPO can form as a result of static topotactic growth of olivine after high-temperature breakdown of foliated serpentinite. These results resolve the discrepancies between experimental and natural examples of B-type CPO and show the need to rethink the formation process of olivine CPO in convergent margins. Topotactic growth of olivine after antigorite can account for the inferred distribution of B-type Ol CPO in the mantle wedge more successfully than dislocation creep.
Short- and long-term olivine weathering in Svalbard: implications for Mars.
Hausrath, E M; Treiman, A H; Vicenzi, E; Bish, D L; Blake, D; Sarrazin, P; Hoehler, T; Midtkandal, I; Steele, A; Brantley, S L
Liquid water is essential to life as we know it on Earth; therefore, the search for water on Mars is a critical component of the search for life. Olivine, a mineral identified as present on Mars, has been proposed as an indicator of the duration and characteristics of water because it dissolves quickly, particularly under low-pH conditions. The duration of olivine persistence relative to glass under conditions of aqueous alteration reflects the pH and temperature of the reacting fluids. In this paper, we investigate the utility of 3 methodologies to detect silicate weathering in a Mars analog environment (Sverrefjell volcano, Svalbard). CheMin, a miniature X-ray diffraction instrument developed for flight on NASA's upcoming Mars Science Laboratory, was deployed on Svalbard and was successful in detecting olivine and weathering products. The persistence of olivine and glass in Svalbard rocks was also investigated via laboratory observations of weathered hand samples as well as an in situ burial experiment. Observations of hand samples are consistent with the inference that olivine persists longer than glass at near-zero temperatures in the presence of solutions at pH approximately 7-9 on Svalbard, whereas in hydrothermally altered zones, glass has persisted longer than olivine in the presence of fluids at similar pH at approximately 50 degrees C. Analysis of the surfaces of olivine and glass samples, which were buried on Sverrefjell for 1 year and then retrieved, documented only minor incipient weathering, though these results suggest the importance of biological impacts. The 3 types of observations (CheMin, laboratory observations of hand samples, burial experiments) of weathering of olivine and glass at Svalbard show promise for interpretation of weathering on Mars. Furthermore, the weathering relationships observed on Svalbard are consistent with laboratory-measured dissolution rates, which suggests that relative mineral dissolution rates in the laboratory, in concert with field observations, can be used to yield valuable information regarding the pH and temperature of reacting martian fluids. PMID:19191538
Reaction-induced fracturing during olivine serpentinization: A mechanistic investigation at the interface scale
NASA Astrophysics Data System (ADS)
Pl³mper, O.; R°yne, A.; Malthe-S°renssen, A.; King, H. E.; Jamtveit, B.
Serpentinization of the Earth's impermeable upper mantle is one of the most fundamental metamorphic hydration reactions. It governs lithospheric weakening, geochemical subduction zone input and possibly even the formation of life-essential building blocks. Serpentinization relies on fluid pathway generation due to low initial permeability and the large positive solid volume change associated with hydration. Although these pathways can be produced as a tectonic stress response, there is substantial evidence that the volume increase during olivine serpentinization itself generates stresses sufficient to fracture the rock. Nonetheless, the actual fracturing mechanism during olivine serpentinization is largely unexplored. Unconstrained batch experiments (Okamoto et al. 2011, this study) produce comparable hierachial fracture patterns to those found in natural samples demonstrating that no external forces (e.g., tensile stress) are required for fracturing to take place. Combining this with the observation that fluid-mediated mineral replacement advances via an interface-coupled dissolution-reprecipitation mechanism (e.g., Putnis 2009) without solid-state diffusion into the dissolving mineral indicates that classical (stress) corrosion cracking mechanisms cannot describe fracturing during olivine serpentinization. By uniting micro- and nanostructural characteristics ubiquitous to serpentinized olivine grains with a coupled diffusion-reaction-deformation model and crack growth theory this study explores the sub-critical fracturing mechanism at the interfacial scale. We present a new multistep reaction process and test the feasibility of a molecular wedge-assisted fracturing mechanism based on the following ubiquitously identified features: (1) no rotation of grain domains during fragmentation, (2) isotropic fracture orientation distribution with a uniform average width of individual finite length serpentine veins, (3) cumulative fragment area distribution with a log-normal scaling behavior following a hierachical fracturing model, (4) etch pit development at olivine-lizardite reaction interfaces, (5) crack initiation at these surface perturbations and (6) amorphous layer formation during olivine dissolution prior to serpentine nucleation (e.g., Rumori et al. 2004). Based on these observations we propose an entirely self-propagating reaction-driven fracturing process, where fractures nucleate at dissolution-induced surface perturbations assisted by a molecular wedge of amorphous 'gel', followed by further olivine dissolution and serpentine (▒brucite) reprecipitation coupled with the force of crystallization. This process results in the observed hierarchical fracture network. Our results suggest that the mechanical force needed to advance serpentinization at the grain-scale does not rely on external forces but is due to interface-coupled, chemomechanical feedback during olivine re-equilibration in the presence of a fluid phase. Nevertheless, the influence of tectonic forces will need to be accounted for at larger scales.
Olivine Composition of the Mars Trojan 5261 Eureka: Spitzer IRS Data
NASA Technical Reports Server (NTRS)
Lim, L. F.; Burt, B. J.; Emery, J. P.; Mueller, M.; Rivkin, A. S.; Trilling, D.
The largest Mars trojan, 5261 Eureka, is one of two prototype "Sa" asteroids in the Bus-Demeo taxonomy. Analysis of its visible/near-IR spectrum led to the conclusion that it might represent either an angritic analog or an olivine-rich composition such as an R chondrite. Spitzer IRS data (5-30 micrometers) have enabled us to resolve this ambiguity. The thermal-IR spectrum exhibits strong olivine reststrahlen features consistent with a composition of approximately equals Fo60-70. Laboratory spectra of R chondrites, brachinites, and chassignites are dominated by similar features.
BROWN AND CLEAR OLIVINE IN CHASSIGNITE NWA 2737: WATER AND DEFORMATION. A.H. , M. McCanta1
Hiroi, Takahiro
of vc lenses at right angles to each other and symmetric to the grains' optical extinction directions] chassignite is brown, with visually colorless (vc) lenses and ribbons of the same composition. VC olivine in thin section, not zoned in composition or color [3], and includes ribbons and lenses of vc olivine
Boyer, Edmond
939 STRUCTURE ET ENREGISTREMENT DES TRACES LATENTES D'IONS ARGON ET FER DANS L'OLIVINE ET LE MICA le mica muscovite. Dans les deux cas, il se forme des zones endommagķes qu'on caractķrise par leur and Ar ions (energy range : 1-7 MeV/a.m.u.) in olivine and muscovite mica. In both cases, zones
Lithium isotope analysis of olivine by SIMS: Calibration of a matrix effect and application to magmatic phenocrysts
Mcdonough, William F.
Lithium isotope analysis of olivine by SIMS: Calibration of a matrix effect and application-spatial resolution analysis of light element isotope variations by secondary-ion mass spectrometry (SIMS) has of this calibration to a suite of olivines separated from basaltic lavas from Ko'olau, Hawai'i demonstrates
Shock-compressed MgSiO3 glass, enstatite, olivine, and quartz: Optical emission, temperatures, and melting
Stewart, Sarah T.
Shock-compressed MgSiO3 glass, enstatite, olivine, and quartz: Optical emission, temperatures, enstatite, olivine, and quartz under shock wave compression was investigated with optical pyrometry coefficients (a) and blackbody spectral radiances (Llb) of shocked and unshocked materials were obtained
Sound velocities of hydrous olivine and the effects of water on the equation of state of nominally anhydrous minerals
S. D. Jacobsen; F. Jiang; J. R. Smyth; T. S. Duffy; Z. Mao; C. M. Holl; D. J. Frost
Here we report the sound velocities and elastic constants of olivine containing 0.8 wt% H2O. We will also summarize some emerging trends on the effects of water on the equation of state of nominally anhydrous mantle minerals as they pertain to seismological observation. Olivine is thought to be the most abundant mineral in the mantle to a depth of 410
Simultaneous precipitation of magnesite and lizardite from1 hydrothermal alteration of olivine under high-carbonate alkalinity2
Paris-Sud XI, Universitķ de
under high-carbonate alkalinity2 3 Romain Lafaya, b , German Montes-Hernandeza, *, Emilie Janotsb alkalinity 1M NaHCO3). Under these conditions, competitive precipitation olivine, the alteration reaction for olivine under high-carbonate alkalinity can be expressed as33 follows
Olivine LiCoPO4 phase grown LiCoO2 cathode material for high density Li batteries
Cho, Jaephil
Olivine LiCoPO4 phase grown LiCoO2 cathode material for high density Li batteries Hyunjung Lee olivine LiCoPO4, grown in LiCoO2 at 4.4 V, did not exhibit thermal runaway with a cell surface temperature
Reduced chromium in olivine grains from lunar basalt 15555 - X-ray Absorption Near Edge Structure (XANES)
NASA Technical Reports Server (NTRS)
Sutton, S. R.; Jones, K. W.; Gordon, B.; Rivers, M. L.; Bajt, S.; Smith, J. V.
The oxidation state of Cr in 200-micron regions within individual lunar olivine and pyroxene grains from lunar basalt 15555 was inferred using X-ray Absorption Near Edge Structure (XANES). Reference materials had previously been studied by optical absorption spectroscopy and included Cr-bearing borosilicate glasses synthesized under controlled oxygen fugacity and Cr-doped olivines. The energy dependence of XANES spectral features defined by these reference materials indicated that Cr is predominantly divalent in the lunar olivine and trivalent in the pyroxene. These results, coupled with the apparent f(02)-independence of partitioning coefficients for Cr into olivine, imply that the source magma was dominated by divalent Cr at the time of olivine crystallization.
Olivine Weathering and Sulfate Formation Under Cryogenic Conditions
NASA Astrophysics Data System (ADS)
Niles, P. B.; Golden, D. C.; Michalski, J. R.
High resolution photography and spectroscopy of the martian surface (MOC, HiRISE) from orbit has revolutionized our view of Mars with one of the most important discoveries being wide-spread layered sedimentary deposits associated with sulfate minerals across the low to mid latitude regions of Mars. The mechanism for sulfate formation on Mars has been frequently attributed to playa-like evaporative environments under prolonged warm conditions. An alternate view of the ancient martian climate contends that prolonged warm temperatures were never present and that the atmosphere and climate has been similar to modern conditions throughout most of its history. This view has had a difficult time explaining the sedimentary history of Mars and in particular the presence of sulfate minerals which seemingly need more water. We suggest here that mixtures of atmospheric aerosols, ice, and dust have the potential for creating small films of cryo-concentrated acidic solutions that may represent an important unexamined environment for understanding weathering processes on Mars. This study seeks to test whether sulfate formation may be possible at temperatures well below 0░C in water limited environments removing the need for prolonged warm periods to form sulfates on early Mars. To test this idea we performed laboratory experiments to simulate weathering of mafic minerals under Mars-like conditions. The weathering rates measured in this study suggest that fine grained olivine on Mars would weather into sulfate minerals in short time periods if they are exposed to H2SO4 aerosols at temperatures at or above -40░C. In this system, the strength of the acidic solution is maximized through eutectic freezing in an environment where the silicate minerals are extremely fine grained and have high surface areas. This provides an ideal environment despite the very low temperatures. On Mars the presence of large deposits of mixed ice and dust is undisputed. The presence of substantial sulfur-rich volcanism, and sulfur-rich surface deposits also makes it very likely that sul-fate aerosols have also been an important component of the martian atmosphere. Thus mixtures of ice, dust, and sulfate aerosols are likely to have been common on the martian surface. Given the fact that it is not difficult to achieve surface temperatures above -40░C on Mars throughout its history, it seems likely that sulfate formation on Mars is controlled by the availability of sulfate aerosols and not by the martian climate. The current polar regions of Mars and Earth provide interesting analogs. Large regions of sulfate-rich material have been detected on and around the modern north polar region of Mars. The prevalence of ice-dust mixtures in this region and the existence of sulfates within the ice cap itself are strong evidence for the origin of the sulfates from inside the ice deposits. In addition sulfates have been found in ice deposits in Greenland and Mount Fuji on Earth that have been attributed to forming within the ice deposit. These sulfates can form either through interaction with dust particles in the atmosphere or through weathering inside the ice itself.
American Mineralogist, Volume 81, pages 327-334, 1996 High-pressure crystal chemistry of LiScSi04: An olivine with
Downs, Robert T.
to the high-pressure behavior of olivine. INTRODUcrION The high-pressure behavior of olivine has been studied displays a significant decrease in polyhedral distortions with pressure, a behavior not observed in other. The behavior ofM~+SiH04 olivines contrasts with that of isostructural chrysoberyl AH+Be2+04,which is more
Deformation mechanisms of olivine single crystals compressed at 300 MPa and 800-1100░C
NASA Astrophysics Data System (ADS)
Cordier, Patrick; Demouchy, Sylvie; Mussi, Alexandre; Tommasi, Andrea
Rheology of mantle rocks at lithospheric temperatures remains poorly constrained, since most experimental studies on creep mechanisms of olivine single crystals ((MgFe)2SiO4, Pbnm) and polycrystalline olivine aggregates were performed at high-temperatures (T >> 1200oC). In this study, we have performed deformation experiments on oriented single crystals of San Carlos olivine and polycrystalline olivine aggregate at temperatures relevant of the uppermost mantle (ranging from 800o to 1090oC) in tri-axial compression. The experiments were carried out at a confining pressure of 300 MPa in a high-resolution gas-medium mechanical testing apparatus at various constant strain rates (from 7 ū 10-6 s-1 to 1 ū 10-4 s-1). Mechanical tests yield differential stresses ranging from 88 to 1076 MPa. All samples were deformed at constant displacement rate and for finite strains ranging from 4 to 23 %, to provide insight into possible effects of hardening, softening or stick-and-slip. The single crystals were compressed along several crystallographic directions to test the possibility of activating different slip systems (e.g. [100](001), [001](100), [001](010) and [100](010)). We will present the characterization of the dislocation microstructures performed in the TEM.
Pyroxenes and olivines: Structural implications of shock-wave data for high pressure phases
NASA Technical Reports Server (NTRS)
Jeanloz, R.; Ahrens, T. J.
The nature of the shock-induced, high-pressure phases of olivine and pyroxene rocks is examined in the light of data for the densities of a new class of perovskite-related silicate structures. Also examined are some new Hugoniot and release adiabat data for bronzite. Reexamining available shock data for magnesian pyroxenes and olivines leads to the conclusion that they define a mixed phase (or disequilibrium) region to about the 100 GPa range, related to the kinetics of phase transformation in these silicates. By recognizing this point, certain discrepancies in previous interpretations of shock data can be explained. A set of theoretical Hugonoits for pyroxene and olivine stoichiometry, perovskite-bearing assemblages was constructed based on their properties deduced from high-pressure work, showing that the shock data is compatible with transformations to perovskites in the 45-7GPa region. Finally, the shock data indicate very similar properties for olivine and pyroxene at high pressures making them both equally likely candidates for the lower mantle.
The elasticity of the upper mantle orthosilicates olivine and garnet to 3 GPa
Sharon L. Webb
The elastic moduli of single crystals of pyrope-rich garnet and San Carlos olivine have been measured over a 3 GPa pressure range at room temperature. The combination of improved ultrasonic techniques and this large pressure range provide for more reliable characterization of the pressure dependence of acoustic wave velocities than has previously been possible. First and second pressure derivatives of
The fate of fluid inclusions during high-temperature experimental deformation of olivine aggregates
NASA Astrophysics Data System (ADS)
Carter, Matthew J.; Zimmerman, Mark E.; Teyssier, Christian
Torsion experiments on initially wet and dry olivine aggregates at equivalent deformation conditions investigated the fate of fluid inclusions (FIs) during high-temperature deformation. Wet samples were produced by adding water to San Carlos olivine powders before hot pressing; those hot pressed without water are considered dry. After hot pressing, wet and dry aggregates have comparable grain sizes, but wet aggregates have more abundant primary FIs. Talc jackets were fitted around some wet and dry samples prior to deformation to hydrate samples during deformation via talc dehydration at elevated temperature, whereas other samples were deformed without talc. At similar strain rates (~1.0 ū 10-4 s-1), the peak shear stress for the dry sample (no talc) was 190-220 MPa, whereas all other samples reached 180 MPa; the strengths of wet (▒ talc) and dry (+ talc) specimens appear similar. Deformed samples reveal abundant FIs, reduced grain size, shape preferred orientation of olivine, and a pervasive low-angle fabric (C') to the shear plane defined by aligned FIs. Samples deformed with talc have FI-rich and FI-depleted domains; where FIs are abundant, the C' fabric is better developed and grain size is smaller. Electron backscatter diffraction pole figures suggest that olivine deformed in the dislocation creep regime via the (010)[100] slip system. Results of these experiments suggest that FIs are redistributed during dislocation creep, leading to the development of grain-scale, high-diffusivity pathways.
Effect of composition on adsorption of water on perfect olivine surfaces
Deymier, Pierre
Effect of composition on adsorption of water on perfect olivine surfaces M. STIMPFL 1 , M.J. DRAKE's water. We are investigating if adsorption of water onto mineral surfaces in the accretion disk could with radii gas and dust with high surface area, points
Spinel from Apollo 12 Olivine Mare Basalts: Chemical Systematics of Selected Major, Minor, and Trace Elements
NASA Technical Reports Server (NTRS)
Papike, J. J.; Karner, J. M.; Shearer, C. K.; Spilde, M. N.
Spinels from Apollo 12 Olivine basalts have been studied by Electron and Ion microprobe techniques. The zoning trends of major, minor and trace elements provide new insights into the conditions under which planetary basalts form. Additional information is contained in the original extended abstract.
Petrogenesis of olivine-phyric shergottite Larkman Nunatak 06319: Implications for enriched components in martian basalts
Perfect, Ed
components in martian basalts Amit Basu Sarbadhikari a , James M.D. Day b,*, Yang Liu a , Douglas Rumble III in mineral and whole-rock chemistry to olivine-phyric shergottite, NWA 1068 and the basaltic shergottite NWA and elevated rare earth element patterns more consistent with the LREE-enriched basaltic shergottites (e
Lithium isotopic signatures of peridotite xenoliths and isotopic fractionation at high temperature between olivine and pyroxenes
Hans-Michael Seitz; Gerhard P. Brey; Yann Lahaye; Soodabeh Durali; Stefan Weyer
We determined the Li isotopic composition of coexisting olivine, clinopyroxene, and orthopyroxene from spinel- and garnet-bearing peridotite xenoliths from San Carlos (Arizona), Vitim (Siberia), Dreiser Weiher (Eifel, Germany), and Kapfenstein (Austria). These samples represent the upper mantle that experienced varying degrees of partial melting followed by different metamorphic and metasomatic histories. Ultrasonic cleaning of handpicked mineral separates with Milli-Q water
Gochimie des olivines plantaires : une approche micro-analytique par EPMA et LA-ICPMS
Demouchy, Sylvie
G├®ochimie des olivines plan├®taires : une approche micro-analytique par EPMA et LA-ICPMS Directeur-louis BODINIER(G├®ochimie, Mod├®lisation, DR) + Andrea TOMMASI (texture et petrophysique), Claude MERLET (Sonde ├®lectronique et ionique, IR), Olivier BRUGUIER (LA-(HR)ICP-MS, IR) Th├®matique : Sciences de la Terre et des
Onset and Progression of Serpentinization and Magnetite Formation in Olivine-richTroctolite
Demouchy, Sylvie
are a reflection of Fe^Mg exchange between olivine and the brucite ■serpentine formed during early serpentini by oxidation of the Fe in brucite and serpentine, whereas addition of silica to the system converted the Mg-component of the brucite to serpentine. Magnetite forms one or more distinct bands in the interior of the vein and is never
Olivine hydration in the deep upper mantle: Effects of temperature and silica activity
J. R. Smyth; D. J. Frost; F. Nestola; C. M. Holl; G. Bromiley
Although water controls the biology and geology of the surface, hydrogen is perhaps the most poorly constrained compositional variable in the bulk Earth. Its concentration in the upper mantle appears to be controlled by its solubility as hydroxyl in the nominally anhydrous silicate phases, olivine, pyroxene, garnet, wadsleyite, and ringwoodite. Here we describe a series of experiments showing that the
Elasticity of Hydrous Olivine Polymorphs: Implications for Seismic Structure of the Transition Zone
T. S. Duffy; Z. Mao; S. D. Jacobsen; F. Jiang; J. R. Smyth; C. M. Holl; D. J. Frost
The presence of water in the upper mantle and transition zone has the potential to explain various phenomena such as shear velocity anomalies or uplift and broadening of the 410-km discontinuity. The presence of H2O in the transition zone has also been frequently invoked to reconcile laboratory elasticity data on olivine polymorphs with seismic data for the amplitude of the
Formation of H2 on an olivine surface: a computational study
T. P. M. Goumans; C. Richard; A. Catlow; Wendy A. Brown
The formation of H2 on a pristine olivine surface [forsterite (010)] is investigated computationally. Calculations show that the forsterite surface catalyzes H2 formation by providing chemisorption sites for H atoms. The chemisorption route allows for stepwise release of the reaction exothermicity and stronger coupling to the surface, which increases the efficiency of energy dissipation. This suggests that H2 formed on
INVITED REVIEW Thermal infrared (vibrational) spectroscopy of MgFe olivines: A review and
Hamilton, Victoria E.
in the minerals. Although band positions move to lower wavenumbers (longer wavelengths) across the forsterite common cations in olivine are Mg2 + and Fe2 + , forming a solid solution between forsterite (Mg2SiO4 of forsterite (Fo) and fayalite (Fa) (e.g., Fo90Fa10), or in shortened form, by just their forsterite number
Midinfrared spectroscopy of synthetic olivines: Thermal emission, specular and diffuse reflectance, and attenuated total reflectance
Glotch, Timothy D.
, and attenuated total reflectance studies of forsterite to fayalite Melissa D. Lane,1 Timothy D. Glotch,2 M. Darby] Synthetic olivine samples ranging in composition from forsterite to fayalite are analyzed in the midinfrared is identified of a specific emissivity maximum/reflectivity minimum (the flection position). From forsterite
Effects of hydration on the elastic properties of olivine Steven D. Jacobsen,1
Jacobsen, Steven D.
and single-crystal elastic constants of hydrous forsterite (hy-Fo100) and hydrous olivine (hy-Fo97 obtain KS0 = 124.4(▒0.4) GPa and G0 = 75.3(▒0.3) GPa. Compared with anhydrous forsterite, the combined
Iron Partitioning in the Lower Mantle: New Experimental Data from Al-Enriched Olivine
NASA Astrophysics Data System (ADS)
Piet, H.; Nabiei, F.; Gillet, P.; Badro, J.
The partitioning of iron between the major phases of the lower mantle has an important impact on their physical and chemical properties. A series of experimental studies of Fe-Mg exchange between bridgemanite (magnesium silicate perovskite) and ferropericlase have shown that stark differences in partitioning are observed if olivine [1, 2] or a pyrolitic [3, 4] starting composition are used. The discrepancy has been attributed to the presence of alumina, to that of ferric iron, to multiphase equilibria and even to the activity of FeO in the system. In order to mitigate the discrepancy, we synthesized a sample with San Carlos olivine composition that was doped in alumina. We then used this as starting material for experiments in the laser-heated diamond anvil cell at lower mantle (P,T) conditions along the geotherm. Samples were pressurized, heated, transformed to bridgemanite and ferropericlase, equilibrated, quenched, and decompressed. Thin sections were recovered from the hotspot using a focused ion beam microscope and the composition of the two phases was analyzed using analytical transmission electron microscopy. Iron partitioning in Al-rich olivine will be discussed through a detailed comparison with the Al-rich pyrolitic trend and the Al-free olivine trend. References [1] A-L. Auzende et al., Earth Planet. Sci. Lett., 2008. [2] R. Sinmyo et al., J. Geophys. Res., 2008.[3] R. Irifune et al., Science, 2010. [4] R. Sinmyo et al., Phys. Chem. Minerals, 2013.
Crystal orientation results in different amorphization of olivine during solar wind implantation
NASA Astrophysics Data System (ADS)
Li, Yang; Li, Xiongyao; Wang, Shijie; Li, Shijie; Tang, Hong; Coulson, Ian M.
Crystal orientation plays an important role in mineral amorphization during solar wind implantation. To discuss these effects, ion implantation experiments were carried out to irradiate natural olivine grains by 1 ū 1017 cm-2 50 keV He+. Based on the olivine grains irradiated in our experiment, residual crystal planes have been identified by reference to the crystal plane's spacing shown in diffraction images. It is found that He+ ions injected along [010] damages the olivine structure more effectively than with other orientations and that this possibly relates to the higher atomic density and the vertical impact of the flux on MO6 (where M commonly represents Fe2+ and Mg2+) octahedra chains. Crystal planes perpendicular or approximately perpendicular to [010] may be destroyed easily during the early stages of irradiation, particularly for (040). However, crystal planes, such as (041), (021), (022), (120), and (140), parallel to [100] or [001] may survive until the final stages of olivine amorphization. These different characteristics affected by crystal orientation in ion implantation might help researchers to better understand the process of solar wind weathering and in dating the exposure time of lunar and asteroidal soil grains as well as interplanetary dust particles affected by the solar wind.
In situ observation of texture development in olivine, ringwoodite, magnesiowqstite and silicate perovskite at high pressure
Shen, Guoyin
perovskite at high pressure H.-R. Wenka,*, I. Lonardellia , J. Pehla , J. Devineb , V. Prakapenkac , G. Shenc, perovskite and magnesiowqstite display transformation textures that are then modified by continuing towards h001i with increasing deformation. Perovskite, transforming from olivine, has a pronounced (100
IMPORTANCE OF OLIVINE IN S-ASTEROID SPACE WEATHERING. T. Hiroi1 and S. Sasaki2
Hiroi, Takahiro
IMPORTANCE OF OLIVINE IN S-ASTEROID SPACE WEATHERING. T. Hiroi1 and S. Sasaki2 , 1 Dept: Existence, cause, and process of space weathering on the S asteroids have been often discussed that S asteroids larger than about 120 km show much shallower absorption bands than the others [1], which could
Simultaneous precipitation of magnesite and lizardite from hydrothermal alteration of olivine under high-carbonate alkalinity
Montes-Hernandez, German
high-carbonate alkalinity Romain Lafay a,b , German Montes-Hernandez a, , Emilie Janots b , Rodica alteration High-carbonate alkalinity Magnesite Lizardite Crystal growth Hydrothermal systems The present = 15, olivine grain size b 30 m and high-carbonate alkalinity 1 M NaHCO3). Under these conditions
The role of olivine in the crystallization of the prehistoric Makaopuhi tholeiitic lava lake, Hawaii
James G. Moore; Bernard W. Evans
On eruption, the tholeiitic basalt lava of the prehistoric Makaopuhi lake contained nearly seven percent euhedral olivine phenocrysts of approximately Fa14 composition. In the center of the 225 foot vertical section of the lake, the lava became more than 90 percent solid at 1000░ C after about 30 years. At the surface the lava was quenched to air temperature, whereas,
Phosphorus-rich olivine overgrowths: Evidence for additional impact to the Main Group pallasite parent body
NASA Astrophysics Data System (ADS)
Fowler-Gerace, Neva; Tait, Kimberly
Phosphorus-rich olivine (1-7 wt% P2O5) is a metastable phase known from fewer than a dozen meteoritic or terrestrial occurrences. We have thoroughly examined P-rich olivine in the Springwater pallasite to characterise its distribution, textural relationships, and geochemical signature. P-rich olivine is abundant in Springwater as randomly distributed millimetre-scale partial overgrowths on the nominally P-free forsterite crystals. Geochemical analyses support the substitution mechanism of P into the tetrahedral Si site with octahedral site vacancies for charge balance; observed trace element variations, on the other hand, are not related to P substitution. Element mapping reveals fine-scale oscillatory P zoning in unusual serrate patterns, indicating rapid crystal nucleation from a melt and a subsequently variable rate of crystallisation. We constrain P-rich olivine formation in Springwater to at least 10-100 Myr subsequent to the introduction of the metal but before cooling below 700░C. Because the P-rich overgrowths overprint specific host grain boundary modifications, we suggest an impact to the Main Group pallasite parent body may have triggered the episode of extremely rapid cooling necessary to crystallise and preserve this rare phase.
Crystallographic preferred orientations and melt-rock interactions : olivine-rich troctolites from IODP Hole U1309D
NASA Astrophysics Data System (ADS)
Drouin, M.; Ildefonse, B.; Hirth, G.; Waters, C. L.; Godard, M.
IODP Expeditions 304-305 sampled the Atlantis Massif, an oceanic core complex located at 30░N in the inside corner of the intersection of the Mid-Atlantic Ridge with the Atlantis Fracture Zone. The most primitive end-members of the recovered gabbroic sequence, olivine-rich troctolites (ol > ~70%), have textures and geochemical compositions intermediate between those of mantle peridotites and primitive cumulates, indicative of melt impregnation processes (Drouin et al., 2009). Olivine-rich troctolites from Hole U1309D (about 5% of recovered rocks) display poikilitic textures, with olivine ranging from coarse-grained subhedral crystals, commonly containing well-developed subgrains, to medium-grained rounded crystals with fewer or no substructures. Olivine substructures reveal dislocation creep that is consistent with activation of the main high-temperature slip systems, dominantly (010)[100]. Olivine crystallographic preferred orientation is very weak, but generally shows a relatively stronger, uncommon [001] concentration (Drouin et al., 2010). These unusual olivine fabrics are interpreted as resulting from dunitisation and melt impregnation of a previously deformed olivine matrix; the solid olivine framework is eventually disrupted by olivine corrosion along grain and subgrain boundaries, and the high-temperature plastic fabric is modified in a liquid-dominated regime. Similar fabrics are described in impregnated peridotites from the mantle/crust transition zone in the Oman ophiolite. A reduction of fabric strength in the presence of melt is also documented in deformation experiments performed in a gas-medium high-pressure high-temperature vessel. Experiments were conducted with olivine + melt (10 to 30 wt%) isostatically hot-pressed initial material. The olivine crystallographic preferred orientation is weaker in deformed sampled than in the undeformed hot pressed material. We propose that very weak fabrics such as those measured in the Atlantis Massif olivine-rich troctolites, in this case with unusual preferred [001] maxima, are a common result of melt-rock interactions in melt-impregnated peridotites or ultramafic cumulates in mid-ocean ridge environments. The joint study of in situ crystal geochemistry and microstructures is needed to characterize complex crystallization histories in open system with percolation of large volume of MORB-type melt that postdate olivine crystal-plastic deformation. - Drouin, M., Godard, M., Ildefonse, B., Bruguier, O., and Garrido, C., 2009. Chem. Geol., doi:10.1016/j.chemgeo.2009.02.013 - Drouin, M., B. Ildefonse, and M. Godard, 2010. Geochem. Geophys. Geosyst., doi:10.1029/2009GC002995
Olivine Oxygen Isotope Evidence for Intracontinental Recycling of Continental Crust in the North China Craton
NASA Astrophysics Data System (ADS)
Xu, W.; Yang, D.; Pei, F.; Gao, S.
A suite of peridotite and pyroxenite xenoliths entrained by the Early Cretaceous high-Mg diorites and Feixian basalts in the eastern North China Craton provide direct evidence for recycling of dense lower continental crust in an intracontinental setting. Petrographic observations indicate that peridotite xenoliths include spinel-lherzolite, spinel-harzburgite, chromite-bearing dunite and wehrlite, and that pyroxenite xenoliths are olivine pyroxenite and websterite. The replacement of olivines by orthopyroxenes and in turn orthopyroxenes by clinopyroxenes can be found within the pyroxenite xenoliths. The ?18O values of olivines from the harzburgite and lherzolite xenoliths with Archean and Paleoproterozoic Re-depletion model ages (TRD) vary from 5.1 ▒ 0.1 ē to 5.8 ▒ 0.1 ē (average: 5.4 ▒ 0.2 ē, error = 2SD), which is typical of mantle values, whereas olivines from dunites and wehrlite xenoliths have ?18O ranging from 6.1 ▒ 0.2 ē to 7.7 ▒ 0.2 ē (averaging 6.45 ē), the latter are consistent with high incompatible element abundance (such as Ca, Ti, and Sc) in olivines and high initial 187Os/188Os ratios (0.16221-0.72715) of dunite xenoliths. The olivines from websterite xenoliths in Feixian basalts vary from 7.1 ē to 7.6 ē. These data, combined with positive correlations among Sr, Nd, and Os isotope ratios, Cr content of peridotite xenoliths, and the ?18O values of olivines, provide compelling evidence for the recycling of continental crust in an intracontinental setting. Therefore, our study shows that the intracontinental recycling of lower continental crust is a key factor not only to result in chemical and isotopic enrichment in the subcontinental lithospheric mantle (Xu et al., 2008), but also to result in compositonal variations of intracontinental basalts (Gao et al., 2008; Liu et al., 2008). This research was financially supported by National Basic Research Program of China (2009CB825005) and the NSFC (90814003 and 90714010). References Gao S. et al. (2008) Earth Planet. Sci. Lett. 270, 41-53. Liu Y S. et al. (2008) Geochim Cosmochim Acta 72, 2349-2376. Xu et al. (2008) Earth Planet. Sci. Lett. 265, 123-137.
Mineral Magnetism of Dusty Olivine: A Potential Carrier of Pre-Accretionary Remanence?
NASA Astrophysics Data System (ADS)
Harrison, R. J.; Lappe, S.; Feinberg, J. M.; Russell, S.; Bromiley, G.; Bastos da Silva Fanta, A.; Dunin-Borkowski, R.
The mechanism and location of chondrule formation is an important question in cosmochemistry. The remanent magnetisation of chondrules may provide clues to their formation environment, but requires magnetic carriers with extraordinary thermal and magnetic stability. Recently, the search for a suitable magnetic carrier has focussed on ædusty olivineÆ: relict grains that survived the chondrule heating event without fully melting. Dusty olivine grains contain submicron inclusions of metallic Fe-Ni, formed by sub-solidus reduction of the Fe-bearing olivine during heating. The Fe inclusions within dusty olivine potentially possess the ideal magnetic characteristics for acquiring and maintaining primary remanence. Here we describe a mineral magnetic characterisation of synthetic dusty olivine formed by laboratory reduction of terrestrial olivine. Crushed olivine grains were packed in a graphite crucible and reduced in a CO atmosphere at 1350░C for 10 minutes, before quenching into water. Samples were characterised by X-ray diffraction (XRD), optical microscopy, scanning electron microscopy (SEM), electron back scattered diffraction (EBSD), transmission electron microscopy (TEM), temperature-dependent magnetic susceptibility (?-T), and first-order-reveral-curve (FORC) diagrams. The results demonstrate the potential, as well as the pitfalls, of using dusty olivine for paleomagnetism. Microscopy reveals abundant Fe-Ni particles with sizes ranging from > 1 ?m to < 20 nm. ?-T reveals the presence of both a bcc-Fe phase with Tc = 770░C and bcc/fcc Fe-Ni phases with varying Ni content. The presence of Ni complicates the magnetic properties due to the effect of the bcc-fcc martensitic transition. Evidence for Fe-Ni redistribution within the particles at high temperature is found in the ?-T measurements, which leads to the formation of a ferromagnetic Ni-rich alloy with fcc structure and Tc = 200░C. Further complications arise due to the formation of magnetite above 300░C, and its subsequent transformation to wustite above 580 ░C. EBSD analysis reveals the presence of magnetite rims on the surface of some large Fe inclusions that have been exposed to air. FORC analysis demonstrates the presence of MD signals associated with > 1 ?m Fe particles, as well as an SD-like signal with broad coercivity distribution (extending to over 500 mT in some cases) and a narrow vertical spread. Comparison with TEM observations indicates that the coercivity distribution is consistent with SD particles dominated by shape anisotropy. This work highlights the combination of high magnetic stability and thermal stability that make dusty olivine a potential carrier of pre-accretionary remanence. It also demonstrates that a thorough characterisation of the Fe particles within natural dusty olivine and a detailed understanding of the mineral magnetic phase relations is necessary in order to design an effective paleointensity protocol capable of extracting the value of the paleofield.
Deformation mechanism maps of olivine and rheology of the continental upper mantle
NASA Astrophysics Data System (ADS)
Wang, Q.
The reliability of straightforward extrapolation of the laboratory-determined constitutive equations to the upper mantle depends on good quality of experimental data as well as the activation of same deformation mechanism at the much lower natural strain rates and stress. Recent laboratory studies have provided more accurate flow law parameters for olivine under both dry and wet conditions, which allow us to investigate deformation mechanisms of olivine and the mantle rheology more confidently. To compare rheology of the continental upper mantle in different geological settings, the western Superior Province (Canada), the Dabie Mountains and the North Jiangsu basin (China) are selected to represent an Archean craton, a Triassic continental collision zone and a Cenozoic intracratonic rift basin, respectively. Deformation mechanism maps of olivine were constructed under P-T conditions of the three tectonic units, and in a continental subduction zone characterized by P=6.28 GPa and T=900 ░C. For dry olivine, diffusion creep is the dominant mechanism in all the cases, which is contrary to the widely observed lattice-preferred orientation of olivine in peridotite xenoliths and tectonites. For wet olivine, a small amount of water (50 H/106Si) can remarkably decrease the stress of dislocation creep and increase contribution of dislocation creep to the deformation of olivine in the upper mantle. In contrast, the effect of water to diffusion creep is ignorable when water content is less than 100 H/106Si. Combined with a compilation of water contents of natural olivine, rheology of the continental upper mantle is controlled by power law creep of wet olivine, and diffusion creep is the dominant deformation mechanism in the asthenosphere, especially for fine-grained peridotites. The Lehmann discontinuity characterized by the rapid decrease in seismic anisotropy at depth of ~220 km can be attributed to the transition from dislocation creep to diffusion creep in most regions, or to the pressure-induced olivine fabric transition from [100] slip to [001] slip in cold subduction zones. The effective viscosity (?) profiles indicate remarkable rheological contrast among the three units at depth <120 km and a decreasing viscosity difference with depth. At depth >250 km, the values of effective viscosity are very similar in different units, implying that changes in water contents and composition will control rheological contrast of the deep upper mantle. The mechanical lithosphere-asthenosphere boundary (LAB) can be defined as the depth where d?/dP changes from the negative to positive (e.g., a sharp LAB beneath the Dabie Mountains and the North Jiangsu basin) or the absolute value of d?/dP is less than 5ū1012 s (e.g., a diffuse LAB beneath the western Superior Province). The LAB is about 250 km, 140 km and 75 km beneath the western Superior Province, the Dabie Mountains and the North Jiangsu basin, respectively. The sharp LAB (5-10 km thick) favors the lithosphere-asthenosphere decoupling beneath orogenic belts and rifts, while the diffuse LAB (~30 km thick) will lead to coherent deformation of the upper mantle and protect the continental roots from convective erosion. Hence the small pressure derivative of viscosity caused by cold and thick thermal lithosphere is the key to preserve continental roots.
Microstructural development in olivine aggregates during dislocation creep under hydrous conditions
NASA Astrophysics Data System (ADS)
Tasaka, M.; Zimmerman, M. E.; Kohlstedt, D. L.
Since hydrogen plays an important role in dynamic processes in the mantle, we conducted high-strain torsion experiments on aggregates of Fe-bearing olivine [(Mg,Fe)2SiO4; Fo50] under hydrous condition. Olivine with a composition of Fo50 was used because of its enhanced grain growth kinetics and low strength relative to Fo90. Two pieces of an oriented San Carlos olivine crystal were embedded in the aggregates to monitor water fugacity both before and after deformation. We deformed samples to high enough strain, ? ? 4, to achieve a steady-state microstructure. A non-linear, least-squares fit to the stress versus strain rate data yielded a stress exponent, n ? 3.5, indicative of deformation involving dislocations. The water content determined from Fourier transform infrared (FTIR) spectroscopy analyses of the single crystals demonstrate that the samples are water saturated after deformation. Fabric analyses of the polycrystalline olivine samples, determined using electron backscatter diffraction (EBSD), indicate that the strength of the lattice preferred orientation (LPO) increases with increasing strain. Further, at low strain, ? < 2, two slip systems contribute to deformation: (i) [100] axes parallel to the shear direction with the [001] axes normal to the shear plane, indicative of the (001)[100] slip system, plus (ii) [001] axes are parallel to the shear direction with the [100] axes normal to the shear plane, suggestive of the (100)[001] slip system. With increasing strain, the LPO evolves until (100)[001] becomes the dominant slip system at ? > 3. We interpret the observed fabric evolution to represent the competition between the two easiest slip systems in olivine, (100)[001] and (001)[100]. The evolution of fabric can be applied to investigations of upper mantle seismic anisotropy especially in a mantle wedge or in a shear zone, locations in which hydrous conditions prevail.
Solubility of hydrogen in olivine: dependence on temperature and iron content
NASA Astrophysics Data System (ADS)
Zhao, Yong-Hong; Ginsberg, S. B.; Kohlstedt, D. L.
The solubility of hydrogen in Mg-Fe olivines as a function of temperature and iron concentration was investigated by hydrothermally annealing single crystals of synthetic forsterite and San Carlos olivine. Experiments were performed at temperatures between 1,273 and 1,573 K on samples with compositions between Fa0 and Fa16.9 under a confining pressure of 300 MPa in a gas-medium apparatus with oxygen fugacity, fO_2, buffered by the Ni:NiO solid-state reaction and silica activity, aSiO_2, buffered by the presence of enstatite. Hydroxyl concentrations were determined from infrared spectra obtained from polished thin sections in crack-free regions <=50 Ąm in diameter. Hydroxyl solubility increases systematically with increasing temperature and with increasing iron content. Combined with published results on the dependence of hydroxyl solubility on water fugacity and pressure, the present results can be summarized by the relation COH = Af1H_2O [-(? Eo + P? Vo] (? XFa ) with A=90+/-10 H/106Si/MPa, ?=97+/-4 kJ/mol, ? Eo=50+/-2 kJ/mol, and ? Vo =(10.0+/-0.1)ū10-6 m3/mol. The subscript {} indicates that hydroxyl ions are incorporated primarily as defect pairs, probably of the type ( OH )O - V''Me - ( OH )3Ox ? ( 2H )x_Me. Under similar thermodynamic conditions, the water content in olivine in the martian mantle and in olivine from gabbros may be as much as 5 to 25 times larger than in the less iron-rich olivine dominant in Earth's mantle.
Microstructures, textures, and deformation mechanisms in highly sheared 2-phase aggregates: olivine - plagioclase
NASA Astrophysics Data System (ADS)
Stunitz, H.; Heilbronner, R.; Deronde, A.; Oesterling, N.
In the laboratory, processes of deformation of polyphase rocks were studied in synthetic olivine - plagioclase aggregates. Depending on the composition of the feldspar, the deforming aggregates undergo chemical reaction. The presence of metamorphic reaction greatly influences the deformation. Powders composed of olivine and labradorite (An60) or anorthite (An92) were placed between forcing blocks of dunite, pre-cut at 45 ░, and hot-pressed, yielding approx. 0.5 mm thick layers of solid material (porosity < 1%). Deformation was effected in a Griggs apparatus at 900░C, 1.0 or 1.5 GPa confining pressure, and a shear strain rate of 5Ę10-5 s-1. The deformed samples were cut parallel to the compression axis and the shape change of elongated intraclasts ("xenoliths" of fine grained fractions of the powder) was used to ascertain homogeneous and pervasive deformation (at the 100Ąm-scale). Localization of deformation (at the Ąm scale) within the matrix of the shear zones was studied using tesselations of the autocorrelation function (ACF). On SEM back scatter images, complete transects across the shear zone were recorded, with the olivine appearing grey, plagioclase dark and the reaction products white. The anisotropy and preferred orientation of the ACF of the olivine or olivine aggregates (thresholded at a specified level) was used as a measure of the deformation intensity. Calibrating the variations of the aspect ratio of the ACF against the applied shear strain revealed that there is a strain and strain rate ratio of up to 4:1 This variation closely correlates with the reaction progress, being highest where the reaction is complete.
Cross pressure and temperature derivatives of selected elastic moduli for olivine from gigahertz ultrasonic interferometry
NASA Astrophysics Data System (ADS)
Chen, Ganglin; Yoneda, Akira; Getting, Ivan C.; Spetzler, Hartmut A.
Techniques have been developed to measure the cross pressure and temperature dependence of elastic moduli of olivine using the gigahertz ultrasonic interferometric method in a gas pressure vessel (to 500 MPa) equipped with an internal heater (to 500 K). Special attention has been drawn to the effect of the bond which couples the sample to the buffer rod. We obtained ?2C22/?P?T = (2.8 ▒ 0.9) ū 10-3 K-1 for a San Carlos olivine sample with a lapped contact. Selective values of ?2KT/?P?T (0, 0.5 ū 10-3, 1.0 ū 10-3 K-1) are used to calculate their effect on cell volume, bulk modulus, and bulk sound velocity for olivine at pressures to 14 GPa and temperatures to 1800 K (410-km depth), using the high-temperature form of the Birch-Murnaghan equation of state. The largest difference between the cell volumes for ?2KT/?P?T = 1 ū 10-3 K-1 and for ?2KT/?P?T = 0 is about 0.6% at the highest pressure and the highest temperature (14 GPa, 1800 K). Therefore PVT data with precision at least better than 0.6% are required to distinguish between the extreme values of ?2KT/?P?T for olivine if the pressure and temperature data are free of errors. If the cross pressure and temperature derivative term is neglected (?2KT/?P?T = 0) in extrapolating laboratory elasticity data to mantle pressure and temperature conditions, the bulk modulus of olivine can be underestimated by as much as 10% and the bulk sound velocity by 3% at the 410-km seismic discontinuity. Thus the present study highlights the need to measure elastic properties of mantle candidate minerals at the P-T conditions of the mantle transition zone in order to establish a more precise model of the mantle mineralogy.
Distinguishing between Apollo 14 impact melt and pristine mare basalt samples by geochemical and textural analyses of olivine
NASA Astrophysics Data System (ADS)
Fagan, A. L.; Neal, C. R.; Simonetti, A.; Donohue, P. H.; O'Sullivan, K. M.
Apollo 14 (A-14) impact melt olivine vitrophyres (OVs), composed of olivine phenocrysts in an opaque glass matrix with minor amounts of pyroxene and plagioclase, are petrographically similar to pristine quenched A-14 high-alumina (high-Al) and Apollo 12 (A-12) basalts. Textural and chemical analyses have been conducted on olivines within impact melt and pristine mare basalt clasts from A-14 breccia 14321 as well as various olivine-phyric Apollo 12 and 17 basalts to be able to distinguish between the petrographically similar samples. The A-14 high-Al basalts examined here represent samples from each of the three chemical groups (A, B, C). Examples from the three A-12 basalt suites (Ilmenite, Olivine, Pigeonite) and olivine-rich Apollo 17 (A-17) Type C basalt, 74275, have also been analyzed. As a complement to the chemical analyses, crystal size distributions (CSDs) were determined for approximately half of the samples investigated here (due to a small number of olivine crystals that did not produce statistically meaningful CSDs on half of the samples), and confirm that although similar, the basalts and impact melts are texturally distinct. Olivines from A-14 impact melts have the highest average forsterite contents (average Fo ś0.82) and generally the lowest average Co (37 ppm) and Mn (1544 ppm) abundances, thus chemically distinguishing them from the pristine basalts. In addition, chemical compositions obtained for olivine from 14321,1486 are most likely representative of an impact melt and thus contradict its previous classification as a high-Al basalt (Neal et al., 1988); olivine from, 1486 have similar average forsterite (average Fo ś0.82) and Ti/V-ratio to the OVs. Furthermore, on the basis of their chemical compositions, olivines have been identified within the impact melts that are likely inherited from basalts; these olivines are chemically distinct from the rest of the impact melt olivine population with lower forsterite (0.67-0.80) and low Ti/V (ś10), which are similar to olivine compositions from the A-14 high-Al basalts. In addition to distinguishing between sample types from A-14, olivine compositions can also be used to distinguish between pristine mare basalts from various missions. Olivine within the selected samples from the individual A-12 basalt suites can also be distinguished chemically from one another using the Ti/V ratio, where Olivine suite basalts have Ti/V <3 and Ilmenite suite basalts have Ti/V >3.5. The results indicate that combined use of CSDs and chemical analyses of olivine can be used to reliably distinguish between (1) impact melts and pristine Apollo 14 basalts, (2) basalts from different landing sites, and (3) individual basalt suites from a single site.
Low-pressure fractionation of strongly undersaturated alkaline ultrabasic magma: the olivine-melilite-nephelinite at Moiliili, Oahu, Hawaii
NASA Astrophysics Data System (ADS)
Wilkinson, J. F. G.; Stolz, A. J.
The olivine-melilite-nephelinite at Moiliili, a representative of the Honolulu Volcanic Series, experienced post-eruptive fractional crystallization which resulted in the formation of pegmatoids of restricted volume. The pegmatoids can be equated in composition with melilite-bearing nephelinite (?melilite-bearing titanaugite melteigite and titanaugite ijolite). Pegmatoid olivine, titaniferous Ca-rich pyroxene and melilite display mild decreases in their 100 Mg/(Mg + Fe) ratios, largely in response to olivine fractionation. Titanomagnetite Fe2TiO4 components increased with fractionation, mainly at the expense of Fe3O4. Nepheline and sodalite show only restricted compositional variation, although sodalite solid solution is more extensive than in plutonic analogues. Compared with the host olivine-melilite-nephelinite, the pegmatoids are highly depleted in Cr and Ni and enriched in Rb, Sr, Y, Zr, Nb and Ba. The Moiliili fractionation sequence confirms the low-pressure trend olivine-melilite-nephelinite?melilite-bearing nephelinite, previously defined on the basis of relationships in the synthetic system diopside-akermanite-nepheline, but it provides no support for the proposal that olivine-melilite-nephelinite ultimately may fractionate to phonolite. Phonolitic differentiates can be generated by the low-pressure fractionation of alkali feldspar-bearing olivine nephelinites but the relative volumes of the salic derivatives are minor. These volumetric and other constraints inherent in low-pressure fractionation models employing nephelinitic parents suggest that at least some phonolites may be the products of deep crustal or upper mantle anatexis.
Petrogenesis of Apollo 12 mare basalts. Part 1: Multiple melts and fractional crystallization to explain olivine and ilmenite basalt compositions
NASA Technical Reports Server (NTRS)
Neal, Clive R.; Taylor, Lawrence A.
Mare basalts returned by the Apollo 12 mission have been divided into 4 groups on the basis of mineralogy and whole-rock chemistry: olivine basalts; pigeonite basalts; ilmenite basalts; and feldspathic basalts. James and Wright and Rhodes et al. concluded that the olivine and pigeonite groups were co-magmatic and that the within group variations are due to fractional crystallization of olivine and minor Cr-spinel, with pigeonite replacing olivine in the pigeonite basalts. Rhodes et al. concluded that the parental compositions for these suites were probably represented by the vitrophyres, and the olivine basalts are comprised essentially of cumulates and the pigeonites of evolved end-members. However, Neal et al. have demonstrated, using trace-element considerations, that the Apollo 12 olivine and pigeonite suites are not related. The ilmenite basalts were studied extensively by Dungan and Brown who noted that both cumulates and evolved fractionates were present within this group. In their modeling, Dungan and Brown used the vitrophyre compositions as parents. Neal et al. demonstrated that the feldspathic suite was probably comprised of only one member - 12038. Herein, the ilmenite and olivine basalts are demonstrated to be the products of several non-modal partial melting events of a single source followed by closed-system fractional crystallization.
Olivine weathering in soil, and its effects on growth and nutrient uptake in Ryegrass (Lolium perenne L.): a pot experiment.
ten Berge, Hein F M; van der Meer, Hugo G; Steenhuizen, Johan W; Goedhart, Paul W; Knops, Pol; Verhagen, Jan
Mineral carbonation of basic silicate minerals regulates atmospheric CO(2) on geological time scales by locking up carbon. Mining and spreading onto the earth's surface of fast-weathering silicates, such as olivine, has been proposed to speed up this natural CO(2) sequestration ('enhanced weathering'). While agriculture may offer an existing infrastructure, weathering rate and impacts on soil and plant are largely unknown. Our objectives were to assess weathering of olivine in soil, and its effects on plant growth and nutrient uptake. In a pot experiment with perennial ryegrass (Lolium perenne L.), weathering during 32 weeks was inferred from bioavailability of magnesium (Mg) in soil and plant. Olivine doses were equivalent to 1630 (OLIV1), 8150, 40700 and 204000 (OLIV4) kg ha(-1). Alternatively, the soluble Mg salt kieserite was applied for reference. Olivine increased plant growth (+15.6%) and plant K concentration (+16.5%) in OLIV4. At all doses, olivine increased bioavailability of Mg and Ni in soil, as well as uptake of Mg, Si and Ni in plants. Olivine suppressed Ca uptake. Weathering estimated from a Mg balance was equivalent to 240 kg ha(-1) (14.8% of dose, OLIV1) to 2240 kg ha(-1) (1.1%, OLIV4). This corresponds to gross CO(2) sequestration of 290 to 2690 kg ha(-1) (29 10(3) to 269 10(3) kg km(-2).) Alternatively, weathering estimated from similarity with kieserite treatments ranged from 13% to 58% for OLIV1. The Olsen model for olivine carbonation predicted 4.0% to 9.0% weathering for our case, independent of olivine dose. Our % values observed at high doses were smaller than this, suggesting negative feedbacks in soil. Yet, weathering appears fast enough to support the 'enhanced weathering' concept. In agriculture, olivine doses must remain within limits to avoid imbalances in plant nutrition, notably at low Ca availability; and to avoid Ni accumulation in soil and crop. PMID:22912685
A review of water contents and ductile deformation mechanisms of olivine: Implications for the lithosphere-asthenosphere boundary of continents
NASA Astrophysics Data System (ADS)
Wang, Qin
Water plays an important role in the ductile deformation and evolution of the upper mantle. Water contents of natural olivine from 240 samples reveal a wide variation of 0-170 ppm H 2O, suggesting heterogeneous water distribution in the continental upper mantle. The average water contents (17 ▒ 13 ppm H 2O) in kimberlite nodules provide the best estimation of water concentrations in olivine in the lithosphere beneath cratons. The very low water contents (7 ▒ 9 ppm H 2O) of olivine from basalt xenoliths are caused by significant hydrogen loss during transport, while the high values (44 ▒ 34 ppm H 2O) in olivine megacrysts from kimberlites reflect restricted fluid-rich conditions in the upper mantle. To compare deformation in different tectonic environments, the western Superior Province (Canada), the Dabie Mountains and the North Jiangsu basin (China) are selected to represent an Archean craton, an orogenic belt and a rift basin, respectively. Using recent flow laws of olivine, deformation maps of dry and wet olivine are constructed under P- T conditions of the three tectonic units and in a continental subduction zone characterized by P = 6.28 GPa and T = 900 ░C. For dry olivine, diffusion creep is the dominant mechanism in all the cases, which is contrary to the widely observed crystal preferred orientation of olivine in peridotites and seismic anisotropy observations. For wet olivine, only a small amount of water (50 H/10 6 Si) can remarkably decrease the stress of dislocation creep and increase contribution of dislocation creep to the deformation of olivine. The strain rate profiles of olivine indicate a transition from dislocation creep to diffusion creep at a depth of ś 220 km, which can be related with the Lehmann discontinuity characterized by a rapid decrease in seismic anisotropy. However, the pressure-induced fabric transition from [100] slip to [001] slip may be responsible for the Lehmann discontinuity in subduction zones. Therefore rheology of the continental upper mantle is controlled by power-law creep of wet olivine, and diffusion creep is the dominant deformation mechanism in the deep upper mantle, especially for fine-grained peridotites. The mechanical lithosphere-asthenosphere boundary (LAB) can be defined by the characteristic pressure derivative of effective viscosity. The sharp LAB beneath the Dabie Mountains and the Sulu terrane favors the lithosphere-asthenosphere decoupling, while the diffuse LAB beneath the western Superior Province will protect the continental root from convective erosion and mantle metasomatism. The long-term preservation of the continental roots can be attributed to a large viscosity contrast (temperature contrast) at a depth of < 150 km, and a thick and diffuse LAB at a depth of > 150 km.
Chemical zonation in olivine-hosted melt inclusions: A record of syn-eruptive cooling
NASA Astrophysics Data System (ADS)
Newcombe, M. E.; Fabbrizio, A.; Zhang, Y.; Ma, C.; Le Voyer, M.; Guan, Y.; Eiler, J. M.; Saal, A. E.; Stolper, E. M.
During the last few minutes to hours of a volcanic eruption, olivine-hosted melt inclusions (MIs) cool and crystallize olivine on their walls, producing olivine-depleted boundary layers in the melt adjacent to their olivine hosts. Competition between diffusive relaxation of these boundary layers into the centers of the MIs and replenishment of the boundary layers by continued olivine crystallization produces concentration profiles that are preserved in glassy MIs. The concentration profile of a given element in a single MI depends on the diffusion coefficient of the element in the melt, its partition coefficient between melt and olivine, and the growth rate of the olivine. Concentration profiles thus differ from element to element in a single MI, and also from inclusion to inclusion depending on the size of the MI and its thermal history. An implication of this chemical zonation is that analyses of zoned MIs, even if made near the centers of the MIs, will be diffusively fractionated relative to a simple olivine extraction path (i.e., the diffusion of fast-diffusing elements such as Ca can extend to the center of a ~150 ?m radius MI). We have developed a model that uses measured MgO concentration profiles across compositionally zoned, naturally glassy, olivine-hosted MIs to constrain the thermal histories of the MIs in the last few minutes to hours of an eruption. We have applied this model to MIs sampled from three different magmatic settings: (1) glassy rims of pillow basalts sampled from the Siqueiros transform fault; (2) a hornito on Santiago Island, (Galapagos); (3) a lava flow on a submarine flank of Fernandina Island (Galapagos). Cooling rates of five MIs from the Siqueiros transform fault range from ~0.08-3 K/s. Most MIs from this sample suite require two-stage, linear cooling histories from liquidus temperatures to ~1000░C with a slower-cooling first stage followed by a faster-cooling second stage, over a time period of a few minutes to just over one hour. MgO profiles in eight MIs from the subaerial hornito on Santiago Island are well described by single-stage linear cooling histories, with cooling rates ranging from ~1-4 K/s and durations of < 2 mins. MgO profiles in the two MIs so far studied from the submarine Fernandina flow show different behaviors, with one being well described by a single-stage linear cooling history with a cooling rate of ~1 K/s and the other requiring a two-stage cooling history with the lowest recorded cooling rates of the entire sample set (0.02 K/s for ~1 hr, then 0.09 K/s for ~20 mins). The differences in thermal histories determined for the three different magmatic settings may reflect differences in their eruptive styles: The two-stage cooling histories required by most of the submarine MIs could reflect slow cooling of the MIs as they travel through a lava flow or pillow interior followed by rapid quenching of the MIs as the host phenocrysts near the melt-water interface. The short, single-stage cooling histories determined by the model for MIs from a subaerial hornito are consistent with the efficient fragmentation observed during this style of volcanic eruption.
Rock magnetic properties of dusty olivine: comparison and calibration of non-heating paleointensity methods
NASA Astrophysics Data System (ADS)
Lappe, S. L.; Harrison, R. J.; Feinberg, J. M.
The mechanism of chondrule formation is an important outstanding question in cosmochemistry. Magnetic signals recorded by Fe-Ni nanoparticles in chondrules could carry clues to their origin. Recently, research in this area has focused on 'dusty olivine' in ordinary chondrites as potential carriers of pre-accretionary remanence. Dusty olivine is characterised by the presence of sub-micron Fe-Ni inclusions within the olivine host. These metal particles form via subsolidus reduction of the olivine during chondrule formation and are thought to be protected from subsequent chemical and thermal alteration by the host olivine. Three sets of synthetic dusty olivines have been produced, using natural olivine (average Ni-content of 0.3 wt%), synthetic Ni-containing olivine (0.1wt% Ni) and synthetic Ni-free olivine as starting materials. The starting materials were ground to powders, packed into a 8-27 mm3 graphite crucible, heated up to 1350░C under a pure CO gas flow and kept at this temperature for 10 minutes. After this the samples were held in fixed orientation and quenched into water in a range of known magnetic fields from 0.2 mT to 1.5 mT. We present a comparison of all non-heating methods commonly used for paleointensity determination of extraterrestrial material. All samples showed uni-directional, single-component demagnetization behaviour. Saturation REM ratio (NRM/SIRM) and REMc ratio show non-linear behaviour as function of applied field and a saturation value < 1. Using the REM' method the samples showed approximately constant REM' between 100 and 150 mT AF-field. Plotting the average values for this field range again shows non-linear behaviour and a saturation value < 1. Another approach we examined to obtain calibration curves for paleointensity determination is based on ARM measurents. We also present an analysis of a new FORC-based method of paleointensity determination applied to metallic Fe-bearing samples [1, 2]. The method uses a first-order reversal curve (FORC) diagram to generate a Preisach distribution of coercivities and interaction fields within the sample and then physically models the acquisition of TRM as function of magnetic field, temperature and time using thermal relaxation theory. The comparison of observed and calculated NRM demagnetisation spectra is adversely effected by a large population of particles in the single-vortex state. Comparison of observed and calculated REM' curves, however, yields much closer agreement in the high-coercivity SD-dominated range. Calculated values of the average REM' ratio show excellent agreement with the experimental values - including the observed non-linearity of the remanence acquisition curve - suggesting that this method has the potential to reduce the uncertainties in non-heating paleointensity methods for extraterrestrial samples. [1] AR Muxworthy and D Heslop(2011) A Preisach method for estimating absolute paleofield intensity under the constraint of using only isothermal measurements: 1. Theoretical framework. Journal of Geophysical Research, 116, B04102, doi:10.1029/2010JB007843. [2] AR Muxworthy, D Heslop, GA Paterson, and D Michalk. A Preisach method for estimating absolute paleofield intensity under the constraint of using only isothermal measurements: 2. Experimental testing. Journal of Geophysical Research, 116, B04103, doi:10.1029/2010JB007844.
Origin of iron-rich olivine in the matrices of type 3 ordinary chondrites - an experimental study
NASA Astrophysics Data System (ADS)
Nagahara, H.; Kushiro, I.
The reaction of metallic iron and enstatite, with and without forsterite and SiO2, is experimentally studied at temperatures between 1150 and 800 C in order to investigate the origin of iron-rich olivine in the matrices of type 3 chondrites. The composition of olivine is shown to become more iron-rich with increasing silica/enstatite ratio. Possible scenarios for the origin of this olivine include: (1) free silica having been present if the iron-rich olivine was formed by solid-state reactions under oxidizing conditions in the solar nebula; and (2) the reaction of silicon-rich gas with metallic iron having taken place under oxidizing conditions in the solar nebula.
Olivine flotation and settling experiments on the join Mg2SiO4-Fe2SiO4
NASA Technical Reports Server (NTRS)
Herzberg, C. T.; Baker, M. B.; Wendlandt, R. F.
Results are presented of a study of some unusual density relations between olivine and coexisting liquid in the system fosterite-fayalite. At 1 atmosphere pressure it is found that olivine floats on its coexisting liquid for intermediate compositions on this binary because of extreme partitioning of Fe into the melt phase. At 20 kilobars, the usual behavior of olivine settling is found to occur because the partitioning of Fe in the melt is reduced, aided possibly by the dissolution of CO2 in the melt from the use of a graphite container. It is determined that olivine flotation and settling are rapid in a time period of only a few hours because viscosities are slightly greater than that of paraffin oil at room temperature. Some adcumulate textures with good triple junction grain boundaries are found to be developed. Observations of differentiated magmatic systems suggest that the mechanisms by which magmas can differentiate vary considerably in the ultramafic to tholeiitic compositional range.
Phospho-olivines as cathode materials for lithium ion battery: trends on microwave synthesis
NASA Astrophysics Data System (ADS)
Alarc¾n-Suesca, C. E.; Nilges, T.
In recently years, scientific research has been focused on finding new sources of efficient energy storage and lithium batteries are one of the most outstanding alternatives. Nowadays, investigation on cathode materials constitute one of the key factors of lithium rechargeable batteries studies. Recently, oxides with olivine structures has triggered the battery field, due to its excellent electrochemical properties, crystal stability, energy density, power capacity and are not expensive. However, the demand and development of more enhanced cathode materials can be achieved by the use of sophisticated synthetic methods. The purpose of this article is to provide a perspective to the materials community on the opportunities and limitations of nanostructured materials by highlighting examples in synthesis, fundamental studies and applications on microwave synthesis as novel route to obtain high voltage phospho-olivines.
Ar-Ar and Rb-Sr Ages of the Tissint Olivine-phyric Martian Shergottite
NASA Technical Reports Server (NTRS)
Park, J.; Herzog, G. F.; Nyquist, L. E.; Shih, C.-Y.; Turin, B.; Lindsay, F. N.; Delaney, J. S.; Swisher, C. C., III; Agee, C.
The fifth martian meteorite fall, Tissint, is an olivine-phyric shergottite that contains olivine macrocrysts (approximately 1.5 mm) [1]. [2] reported the Sm-Nd age of Tissint as 596 plus or minus 23 Ma along with Rb-Sr data that defined no isochron. [3] reported Lu-Hf and Sm-Nd ages of 583 plus or minus 86 Ma and 616 plus or minus 67 Ma, respectively. The cosmic-ray exposure ages of Tissint are 1.10 plus or minus 0.15 Ma based on 10Be [4], and 1.0-1.1 Ma, based on 3He, 21Ne, and 38Ar [5,6].We report Ar-Ar ages and Rb-Sr data.
Partition of Ni between olivine and sulfide: equilibria with sulfide-oxide liquids
M. E. Fleet; N. D. MacRae
The partition of Ni between olivine and monosulfide-oxide liquid has been investigated at 1300¢1395░ C, \\u000a$$f_{O_2 }$$\\u000a=10-8-9-10-6.8, and \\u000a$$f_{S_2 }$$\\u000a=10-2.0-10-0.9, over the composition range 20¢79 mol. % NiS. The product olivine compositions varied from Fo98 to Fo59 and from 0.06 to 3.11 wt% NiO. The metal\\/sulfur ratio of the sulfide-oxide liquid increases with increase in \\u000a$$f_{O_2 }$$\\u000a,
Magnetic petrology of eastern North America diabases. I - Olivine-normative dikes from western South Carolina
NASA Technical Reports Server (NTRS)
Warner, Richard D.; Wasilewski, Peter J.
The oxide mineralogy and the magnetic behavior of 15 olivine-normative samples obtained from South-Caroline diabase dikes were investigated using electron microprobe and SEM analyses and measurements of natural remanence magnetization (NRM), saturation isothermal remanence magnetization (SIRM), and anhysteritic remanence magnetization. It was found that chromite (which for these olivine-normative diabases is a sensitive petrologic indicator) constitutes up to 0.5 vol pct and that its abundance and composition correlate with bulk rock Cr. Microscopic analyses showed that titanomagnetite compositions were mostly between 0.4 and 0.55. The values of NRM and the NRM/SIRM ratios varied between 4 and 0.01 A sq m/kg and 0.0019 and 0.032, respectively. These properties inversely correlate with Cr content and demonstrably contrast Cr-rich and Cr-poor samples.
Olivine clasts from mesosiderites and howardites - Clues to the nature of achondritic parent bodies
NASA Technical Reports Server (NTRS)
Delaney, J. S.; Prinz, M.; Nehru, C. E.
The compositional ranges of olivine clasts from mesosiderites and most clasts from howardites (FO90-55 and FO89-45 respectively) overlap. Only one clast in howardite Allan Hills A78006,9 (FO16) differs significantly. Differences in FeO/MnO in olivines from the two groups may be explained by different redox states of their source regions. Whether the two meteorite groups were derived from the same parent body is not clear, but the lack of Fe-rich eucritic clasts in mesosiderites together with the lack of tridymite-phosphate rich gabbros and basalts in howardites, suggests that different bodies are required since both meteorite groups are near-surface polymict breccias, which have probably sampled significant portions of their parent body surfaces.
Origins and Distribution of Chondritic Olivine Inferred from Wild 2 and Chondrite Matrix
NASA Technical Reports Server (NTRS)
Frank, D. R.; Zolensky, M. E.
To date, only 180 particle impact tracks from Wild 2 have been extracted from the Stardust aerogel collector and even fewer have been thoroughly characterized. In order to provide a cohesive compositional dataset that can be compared to the meteorite record, we have made both major and minor element analyses (TEM/EDXS) of olivine and low-Ca pyroxene for 39 particles harvested from 26 tracks. However, the dearth of equivalent analyses for these phases in chondrite matrix hinders their comparison to the Wild 2 samples. To properly permit comparison of chondritic olivine and pyroxene to the Wild 2 samples, we have also provided a large, comprehensive EPMA dataset (greater than10(exp 3) analyses) of analogous grains (5-30 micrometers) isolated in L/LL3.0-4, CI, CM, CR, CH, CO, CV, Acfer 094, EH3, EL6, and Kakangari matrix
Unusual spin fluctuations and magnetic frustration in olivine and non-olivine LiCoPO4 detected by P31 and Li7 nuclear magnetic resonance
NASA Astrophysics Data System (ADS)
Baek, S.-H.; Klingeler, R.; Neef, C.; Koo, C.; B³chner, B.; Grafe, H.-J.
We report P31 and Li7 nuclear magnetic resonance (NMR) studies in new non-olivine LiZnPO4-type LiCoPO4tetra microcrystals, where the Co2+ ions are tetrahedrally coordinated. Olivine LiCoPO4, which was directly transformed from LiCoPO4tetra by an annealing process, was also studied and compared. The uniform bulk magnetic susceptibility and the P31 Knight shift obey the Curie-Weiss law for both materials with a high spin Co2+ (3d7, S =3/2), but the Weiss temperature ? and the effective magnetic moment ?eff are considerably smaller in LiCoPO4tetra. The spin-lattice relaxation rate T1-1 reveals a quite different nature of the spin dynamics in the paramagnetic state of both materials. Our NMR results imply that strong geometrical spin frustration occurs in tetrahedrally coordinated LiCoPO4, which may lead to the incommensurate magnetic ordering.
Origin of magnetite in oxidized CV chondrites: in situ measurement of oxygen isotope compositions of Allende magnetite and olivine
Byeon-Gak Choi; Kevin D. McKeegan; Laurie A. Leshin; John T. Wasson
Magnetite in the oxidized CV chondrite Allende mainly occurs as spherical nodules in porphyritic-olivine (PO) chondrules, where it is associated with Ni-rich metal and\\/or sulfides. To help constrain the origin of the magnetite, we measured oxygen isotopic compositions of magnetite and coexisting olivine grains in PO chondrules of Allende by an in situ ion microprobe technique. Five magnetite nodules form
Characterization of olivine fabrics and mylonite in the presence of fluid and implications for seismic anisotropy and shear localization
NASA Astrophysics Data System (ADS)
Jung, Sejin; Jung, Haemyeong; Austrheim, HÕkon
The LindÕs Nappe, Bergen Arc, is located in western Norway and displays two high-grade metamorphic structures. A Precambrian granulite facies foliation is transected by Caledonian fluid-induced eclogite-facies shear zones and pseudotachylytes. To understand how a superimposed tectonic event may influence olivine fabric and change seismic anisotropy, two lenses of spinel lherzolite were studied by SEM and EBSD techniques. The granulite foliation of the surrounding anorthosite complex is displayed in ultramafic lenses as a modal variation in olivine, pyroxenes and spinel, and the Caledonian eclogite-facies structure in the surrounding anorthosite gabbro is represented by thin (<1 cm) garnet-bearing ultramylonite zones. The olivine fabrics in the spinel bearing assemblage were E-type and B-type and a combination of A- and B-type LPOs. There was a change in olivine fabric from a combination of A- and B-type LPOs in the spinel bearing assemblage to B- and E-type LPOs in the garnet lherzolite mylonite zones. FTIR analyses reveal that the water content of olivine in mylonite is much higher (~600 ppm H/Si) than that in spinel lherzolite (~350 ppm H/Si), indicating that water caused the difference in olivine fabric. Fabric strength of olivine gets weaker as the grain size reduced, and as a result calculated seismic properties for the two deformation stages reveal that P- and S-velocity anisotropies are significantly weaker in the mylonite. Microtextures and LPO data indicate that the deformation mechanism changed from dominant dislocation creep in spinel lherzolite to dislocation creep accompanied by grain-boundary sliding in mylonite. Shear localization in the mylonite appears to be originated from the grain size reduction through (1) enhanced dynamic recrystallization of olivine in the presence of water and (2) Zener pinning of clinopyroxene, or (3) by ultracommunition during the pseudotachylyte stage.
Characterization of olivine fabrics and mylonite in the presence of fluid and implications for seismic anisotropy and shear localization
NASA Astrophysics Data System (ADS)
Jung, Sejin; Jung, Haemyeong; Austrheim, HÕkon
The LindÕs Nappe, Bergen Arc, is located in western Norway and displays two high-grade metamorphic structures. A Precambrian granulite facies foliation is transected by Caledonian fluid-induced eclogite-facies shear zones and pseudotachylytes. To understand how a superimposed tectonic event may influence olivine fabric and change seismic anisotropy, two lenses of spinel lherzolite were studied by scanning electron microscope (SEM) and electron back-scattered diffraction (EBSD) techniques. The granulite foliation of the surrounding anorthosite complex is displayed in ultramafic lenses as a modal variation in olivine, pyroxenes, and spinel, and the Caledonian eclogite-facies structure in the surrounding anorthosite gabbro is represented by thin (<1 cm) garnet-bearing ultramylonite zones. The olivine fabrics in the spinel bearing assemblage were E-type and B-type and a combination of A- and B-type lattice preferred orientations (LPOs). There was a change in olivine fabric from a combination of A- and B-type LPOs in the spinel bearing assemblage to B- and E-type LPOs in the garnet lherzolite mylonite zones. Fourier transform infrared (FTIR) spectroscopy analyses reveal that the water content of olivine in mylonite is much higher (approximately 600 ppm H/Si) than that in spinel lherzolite (approximately 350 ppm H/Si), indicating that water caused the difference in olivine fabric. Fabric strength of olivine gets weaker as the grain size reduced, and as a result, calculated seismic properties for the two deformation stages reveal that P- and S-velocity anisotropies are significantly weaker in the mylonite. Microtextures and LPO data indicate that the deformation mechanism changed from dominant dislocation creep in spinel lherzolite to dislocation creep accompanied by grain-boundary sliding in mylonite. Shear localization in the mylonite appears to be originated from the grain size reduction through (1) enhanced dynamic recrystallization of olivine in the presence of water and (2) Zener pinning of clinopyroxene or (3) by ultracomminution during the pseudotachylyte stage.
Mineralogy and petrology of the diabasic rocks in a differentiated olivine diabase sill complex, Sierra Ancha, Arizona
Douglas Smith
The Precambrian Sierra Ancha sill complex, more than 700 feet thick, is a multiple intrusion with a central layer of feldspathic olivine-rich diabase, and upper and lower layers of olivine diabase derived from a high-alumina basalt magma. Minor rock types include albite diabase and albite-diabase pegmatite. Deuteric alteration was extensive. Principal primary minerals are plagioclase (An72 to An16), augite (Wo43En44Fs13
Grafted NiO on natural olivine for dry reforming of methane
C. Courson; L Udron; C Petit; A Kiennemann
Natural olivine is used for gasification of biomass in a fluidised bed. Characterisations by X-ray diffraction and electron microscopies (SEM and TEM) have proved the presence of a (Mg,Fe)2SiO4 structure (Mg\\/Fe ratio: 9\\/1) with a rather broad distribution in elemental composition. Temperature programmed reduction has revealed equally the presence of iron oxides outside of this structure. The nature of free
Partitioning of phosphorus between olivine, clinopyroxene and silicate glass in a spinel lherzolite xenolith from Yemen
Fabrice Brunet; Gilles Chazot
The melting reaction: amphibole+apatite=olivine+cpx+spinel+liquid is documented in spinel lherzolite xenoliths found in Plio-Quaternary alkali basalts from Yemen (Ataq Volcano). All the phases involved in this reaction, including the melt, have been preserved within millimeter-size glassy melt pockets. In a previous study, ion microprobe analyses performed on these phases allowed determination of trace-element partition coefficients between apatite, clinopyroxene, amphibole and glass.
Diffusion-driven magnesium and iron isotope fractionation in Hawaiian olivine
Teng, F.-Z.; Dauphas, N.; Helz, R.T.; Gao, S.; Huang, S.
Diffusion plays an important role in Earth sciences to estimate the timescales of geological processes such as erosion, sediment burial, and magma cooling. In igneous systems, these diffusive processes are recorded in the form of crystal zoning. However, meaningful interpretation of these signatures is often hampered by the fact that they cannot be unambiguously ascribed to a single process (e.g., magmatic fractionation, diffusion limited transport in the crystal or in the liquid). Here we show that Mg and Fe isotope fractionations in olivine crystals can be used to trace diffusive processes in magmatic systems. Over sixty olivine fragments from Hawaiian basalts show isotopically fractionated Mg and Fe relative to basalts worldwide, with up to 0.4??? variation in 26Mg/24Mg ratios and 1.6??? variation in 56Fe/54Fe ratios. The linearly and negatively correlated Mg and Fe isotopic compositions [i.e., ??56Fe=(??3.3??0.3)????26Mg], co-variations of Mg and Fe isotopic compositions with Fe/Mg ratios of olivine fragments, and modeling results based on Mg and Fe elemental profiles demonstrate the coupled Mg and Fe isotope fractionation to be a manifestation of Mg-Fe inter-diffusion in zoned olivines during magmatic differentiation. This characteristic can be used to constrain the nature of mineral zoning in igneous and metamorphic rocks, and hence determine the residence times of crystals in magmas, the composition of primary melts, and the duration of metamorphic events. With improvements in methodology, in situ isotope mapping will become an essential tool of petrology to identify diffusion in crystals. ?? 2011 Elsevier B.V.
A Plagioclase-Olivine-Spinel-Magnetite Inclusion from Maralinga (CK): A Record of Sequential Condensation
E. Zinner; F. Brandstatter; G. Kurat
An unusual inclusion of triangular cross section (5 mm x 2.5 mm in size) from the Maralinga CK chondrite has a zonal structure, consisting of core, mantle, and crust. The core (2.5 x 1 mm) consists mainly of plagioclase-olivine intergrowth (troctolite) with ophitic texture, but also contains minor clinopyroxene and Cl-apatite, as well as some calcite, which partially fills pore
On high-temperature formation of iron-rich olivine in the early solar system
NASA Technical Reports Server (NTRS)
Dorofeyeva, V. A.; Makalkin, A. B.; Vityazev, A. V.
A kinetic restriction on the formation of fayalite-rich olivine in equilibrium with the cooling solar-composition gas appears to exist at the low temperature of approximately 500 K. We offer a high-temperature formation mechanism (different from simple condensation) which operates at high hydrogen depletion (up to 300 times) relative to solar abundance. We show how the necessary depletion rate decreases with temperature (thermodynamical equilibrium is suggested). The consequences for planet formation are considered.
Optical absorption spectra at high temperatures and radiative thermal conductivity of olivines
Yoshio Fukao; Hitoshi Mizutani; Seiya Uyeda
The absorption coefficient alpha of olivine crystals was measured in the range of wavelength from 0.3 mu-10 mu at various temperatures up to 1300 ░K. It was discovered that alpha in the pass-band (about 1.8 mu-3.0 mu) increases by a factor of about 100 in going from 300 ░K to 1300 ░K. The radiative thermal conductivity calculated from this result
Crystal melt partitioning of noble gases (helium, neon, argon, krypton, and xenon) for olivine and clinopyroxene
Veronika S. Heber; Richard A. Brooker; Simon P. Kelley; Bernard J. Wood
Mineral melt partition coefficients of all noble gases (min\\/meltDi) have been obtained for olivine (ol) and clinopyroxene (cpx) by UV laser ablation (213 nm) of individual crystals grown from melts at 0.1 GPa mixed noble gas pressure. Experimental techniques were developed to grow crystals virtually free of melt and fluid inclusions since both have been found to cause profound problems
Orthorhombic perovskite phases observed in olivine, pyroxene and garnet at high pressures and temperatures
Lin-Gun Liu
Ferromagnesian silicate olivines, pyroxenes and garnets with Mg\\/(Mg + Fe)>~0.3 (molar) have been found to transform to high-pressure phases characterized by the orthorhombic perovskite structure when compressed to pressures above 250 kbar in a diamond-anvil press and heated to temperatures above 1,000░C with a YAG laser. The zero-pressure density of the perovskite phase of (Mg,Fe)SiO3 is about 3-4% greater than
Effects of pressure on high-temperature dislocation creep in olivine
Shun-Ichiro Karato; Haemyeong Jung
Effects of pressure on high-temperature, dislocation creep in olivine ((Mg, Fe)2SiO4) aggregates have been determined under both water-poor ('dry') and water-saturated ('wet') conditions. New experimental data were obtained at pressures of 1-2 GPa under 'dry' and 'wet' conditions using a newly developed high-resolution dislocation density measurement technique to estimate the creep strength. These data are compared with previous data at
Serpentinization of sintered olivine during seawater percolation experiments AGU abstract N
Luquot, Linda
Serpentinization of sintered olivine during seawater percolation experiments AGU abstract N░ OS21C.% of serpentine, 4.3 wt.% of brucite and 0.8 wt.% of hematite were formed. The estimated total hydrogen content as follow: Fe2+ Fe3+ + e- 2H+ + 2e- H2 Log aSiO2 LogaMg2+ Talc Brucite Serpentine Mg[2+] -7 -6 -5 -4 -3 -2
Genesis of ilmenite rods and palisades along humite-type defects in olivine from Alpe Arami
A.-C. Risold; V. Trommsdorff; B. Grobķty
Rod-shaped ilmenite inclusions in olivine have been observed in numerous peridotite lenses of the Adula-Cima Lunga unit, Central Alps. The rods are elongated parallel to [010]ol and identical in size, shape and concentration to those reported from garnet peridotite at Alpe Arami (AA). TEM investigation of the rods at AA, Cima di Gagnone (CDG) and Monte Duria (MD) demonstrates that
First-principles calculations of equilibrium Mg isotope fractionations between garnet, clinopyroxene, orthopyroxene, and olivine: Implications for Mg isotope thermometry
NASA Astrophysics Data System (ADS)
Huang, Fang; Chen, Lijuan; Wu, Zhongqing; Wang, Wei
Equilibrium fractionation factors of Mg isotopes at high temperature and pressure are investigated for pyrope, majorite, clinopyroxene, orthopyroxene, and olivine using density functional theory. The calculated equilibrium fractionation factors are in good agreement with previous study (Schauble, 2011), suggesting that our calculations are reliable and accurate. The results reveal significant inter-mineral Mg isotope fractionations due to different coordination environment of Mg in minerals. Specifically, pyrope, where Mg is in eight-fold coordination, is more enriched in light Mg isotopes than olivine and pyroxene where Mg is in six-fold coordination. The calculated isotope fractionation for Mg isotopes between clinopyroxene and pyrope is consistent with observations from natural eclogites (Li et al., 2011; Wang et al., 2012). Our calculation also reveals substantial pressure effect on Mg isotope fractionations among garnet, pyroxene, and olivine. Equilibrium fractionation of Mg isotopes between pyrope and pyroxene (and olivine) could be used as a novel and independent thermometry with precision much better than the traditional garnet-clinopyroxene Fe-Mg exchange thermometry because such fractionation is significantly greater than the current uncertainties of Mg isotope analyses (ś0.05ē amu-1). These Mg isotope thermometries could have wide applications in high-temperature mafic igneous and metamorphic rocks where garnet co-exists with pyroxene or olivine. Equations for equilibrium Mg isotope fractionation factors between garnet (pyrope and majorite) and pyroxene and between garnet and olivine as a function of temperature and pressure are also presented in this study.
Extracting Olivine (Fo-Fa) Compositions from Raman Spectral Peak Positions
NASA Technical Reports Server (NTRS)
Kuebler, K.; Jolliff, B. J.; Wang, Alian; Haskin, L. A.
Olivine and pyroxene are two major basaltic minerals that have been identified at Gusev Crater and Meridiani Planum by the Mars Exploration Rovers. Full petrologic characterization of a sample (rock or soil), however, requires determining the range of mineral compositions, extent of zoning, range of grain sizes, mineral associations, presence of xenocrysts, etc. Information of this sort will aid the interpretation of sample crystallization and differentiation histories and help discriminate between lithologies. In Raman spectroscopic experiments, minerals are identified by their spectral patterns and mineral compositions can be inferred from the peak positions. Instruments currently in use or slated for impending surface exploration missions provide only average elemental compositions for relatively large rock or soil targets or bulk mineral analysis. No techniques currently in use or scheduled for flight can characterize both structure and composition of individual mineral grains, in-situ, like the Mars Microbeam Raman Spectrometer (MMRS). The MMRS is designed to take 100 spectra along a 1 cm linear traverse on the surface of a sample, with contributions from one or a few mineral phases per spectrum. We presented a method to extract structural and compositional information from the Raman spectra of quadrilateral pyroxenes. The pyroxene calibration was applied to a Raman spectroscopic study of Martian meteorite EETA79001 along with a preliminary olivine calibration, where we demonstrated the capability to discriminate related lithologies using Raman point counts. This paper presents an improved olivine calibration that will further aid sample characterization and the study of alteration processes.
Two-Stage Deformation of Olivine Aggregates with Changing Deformation Kinematics
NASA Astrophysics Data System (ADS)
Mahan, B. M.; Skemer, P. A.; Griera, A.
Two-stage deformation experiments have been conducted on synthetic olivine aggregates to investigate the influence of pre-existing fabric on the evolution of lattice-preferred orientation (LPO), seismic anisotropy, and grain morphology. This study is motivated by recent work on naturally and experimentally deformed peridotites, which suggest that the alignment of olivine axes with the shear plane requires more strain in samples with a strong pre-existing LPO than in samples with weak or random LPO. In the first stage of deformation, aggregates synthesized from San Carlos olivine are deformed at P = 1 GPa and T = 1500 K in a triaxial geometry to produce axi-symmetric LPOs of varying strength. In a second stage of deformation, the aggregates are re-deformed in simple shear to varying shear strains. Microstructural analyses are performed after each step (synthesis, triaxial deformation, simple shear deformation) using optical microscopy and electron backscatter diffraction (EBSD). These results are compared to numerical models of microstructural evolution. Our results provide constraints on the evolution of LPO and consequent seismic signature as a function of preexisting rock fabric. These data are necessary to interpret seismic anisotropy in settings where kinematics are complex, such as mid-ocean ridges and subduction zones.
In situ observation of texture development in olivine, ringwoodite, magnesiow³stite and silicate perovskite at high pressure
NASA Astrophysics Data System (ADS)
Wenk, H.-R.; Lonardeli, I.; Pehl, J.; Devine, J.; Prakapenka, V.; Shen, G.; Mao, H.-K.
Magnesium silicates are the dominant minerals in the earth's mantle. Their preferred orientation is important for understanding the rheology and seismic anisotropy in the deep earth. Here we report results of radial synchrotron diffraction diamond anvil cell (DAC) experiments on San Carlos olivine, axially compressed to 50 GPa. Experiments were performed at room temperature, except for brief laser heating to induce phase transformations. High stresses and development of preferred orientation were observed in diffraction images. Quantitative texture information was obtained by analyzing the images with the Rietveld method. With increasing pressure (between 9 and 43 GPa) olivine develops a texture with [001] axes perpendicular to the compression direction that is compatible with {hk0}[001] pencil glide. Ringwoodite (between 20 and 50 GPa) develops weak preferred orientation with {011} lattice planes perpendicular to the compression direction. After the phase transformation, perovskite and magnesiow³stite display transformation textures that are then modified by continuing deformation. Magnesiow³stite has a weak <111> maximum parallel to the compression direction that changes towards <001> with increasing deformation. Perovskite, transforming from olivine, has a pronounced (100) transformation texture and with increasing deformation a {012} maximum develops. The transformation texture is probably produced by mechanical {110} twinning and nucleation in orientations that minimize elastic strain energy. The deformation texture of perovskite is due to slip.
A high precision EPMA data of olivine: comparison with LA ICP-MS
NASA Astrophysics Data System (ADS)
Batanova, V. G.; Sobolev, A. V.; Kuzmin, D.
Composition of olivine provides critical information on the composition and origin of primary mantle derived melts and their sources. Especially informative are minor and trace elements Ni, Mn, Ca, Al, Cr, Co, Ti, Zn, P, Na [1, 2], which being in the concentration range over 10 ppm are assessable by EPMA. The analytical protocol built up on new JEOL JXA 8230 EPMA in ISTerre, UJF, Grenoble, France. Facility has tungsten source gun, is equipped by five WDS and one SDD EDS and placed in the environment with controlled temperature (22+/-0.3 degrees C) and humidity (50+/-3%). The analytical conditions are the following: acceleration voltage 25kV, 900 nA beam current, WDS recording for trace elements (Ni, Mn, Ca, Al, Cr, Co, Ti, Zn, P, Na) and EDS recording for Si, Mg, Fe, total counting time 12 minutes, ZAF correction. Instrumental drift during analytical sessions is monitored by repeated measurements of olivine standards. For trace elements this protocol yields detection limits from 3 to 10 ppm and average precision of individual analysis of 10 ppm (2 standard errors). For Fo of olivine precision is 300 ppm (2 standard errors). Comparison of EPMA and LA ICP-MS data for the large range of olivine compositions suggests that accuracy of EPMA is similar to precision noted above. For elements with concentration over 100 ppm the obtained EPMA precision and accuracy are better than these of LA ICP-MS. For the concentration of elements between 50-100 ppm both methods show similar precision and accuracy; and for concentration between 10-50 ppm LA ICP-MS yields better precision and accuracy. Spatial resolution of EPMA, however, is significantly better: 3-5 micrometres compared to 30-50 for LA ICP-MS. This makes our new EPMA protocol of great advantage for measurement of zoned or small olivine grains. [1] Sobolev et al., 2007. Science 316 (5823), p.412-417. [2] De Hoog et al., 2010. Chemical Geology 270, p. 196-2015
Rheological contrast between serpentines and olivine and weakening of a subducting plate interface
NASA Astrophysics Data System (ADS)
Hirauchi, K.; Katayama, I.
Recent seismic observations have suggested that water released by dehydration reactions within a subducting slab is transported through the base of the overlying mantle, thereby causing serpentinization. The degrees of viscous coupling between the serpentinite layer and the overlying mantle wedge might influence the style of mantle convection and the thermal state of a subduction zone (Wada et al., 2008). Serpentine minerals (lizardite, chrysotile, and antigorite) are hydrous phyllosilicates (13 wt% H2O). In subduction zone environments, lizardite and chrysotile seem to form at temperatures below 300-400░C, whereas antigorite is stable at higher temperatures of 300 to 600░C. Previous deformation experiments have revealed that the low- and high-temperature serpentine species display intracrystalline plastic flow in the mantle wedge (e.g., Hilairet et al., 2007; Hirauchi et al., 2010). In particular, Hilairet et al. (2007) indicated that the strength of antigorite is an order of magnitude lower than that of olivine at geological time scales: however, the rheological contrast between lizardite/chrysotile and antigorite under the mantle wedge conditions is not directly constrained. We therefore conducted two-layer shear deformation experiments on serpentines and olivine under P-T conditions (P = 1 GPa, T = 250, 300░C) that correspond to the forearc mantle wedge in subduction zones. The experimental results show that strain rates in lizardite/chrysotile are approximately an order of magnitude higher than those in olivine, whereas strain rates in antigorite is only 1 to 2 times higher than those in olivine. The contrasts in strain rates between lizardite/chrysotile and antigorite is represented by a factor of 5 to 6. Based on the results of our experiments, we suggest that the rheology of lizardite/chrysotile can only explain strong decoupling on the subducting plate interface. Our experiments also show that antigorite is not significantly weaker than olivine in the dislocation-accommodated creep regime, as compared to Hilairet et al. (2007), resulting in weak decoupling at the plate interface. Therefore, we suggest that the degrees of viscous coupling in subduction zones are strongly controlled by the serpentine species stable in the base of the mantle wedge, depending on various parameters (e.g., cool vs. warm subduction zones, change with depth).
The effect of conductive grain boundary impurities on electrical conductivity in polycrystalline olivine
NASA Astrophysics Data System (ADS)
Watson, H. C.; Roberts, J. J.; Tyburczy, J. A.
Grain boundaries affect the rheological, mechanical, diffusive, and electrical properties of polycrystalline materials. In crustal and mantle rocks, they may provide a ōfast conduction pathö explaining areas of anomalously high electrical conductivity without necessitating intra-granular hydrogen or an interconnected melt or fluid phase. Conductive impurities on grain boundaries such as graphite or sulfide have been suggested to explain some field-based high-conductivity anomalies, but direct experimental studies have been few. Studies on grain boundary conductivity in polycrystalline monomineralic, dry olivine exist, but a systematic understanding of impure grain boundary conductivity remains unrealized. Bulk electrical conductivity and impedance spectroscopy of single crystal and polycrystalline San Carlos olivine and polycrystalline olivine with carbon or iron sulfide on grain boundaries were measured at 1GPa and 350o C-1200o C in a piston cylinder apparatus. Sometimes, impedance spectroscopy is the only tool that yields definitive evidence of a secondary (grain boundary) conduction mechanism. We demonstrate that grain boundary conductivity in series with grain interiors is more apparent in the presence of small amounts of carbon grain boundary impurities, whereas the presence of quenched iron sulfide melt on grain boundaries can enhance bulk conductivity even if full melt interconnectivity is not established. Specifically, the addition of 0.1 wt% (~0.16 vol%) C has no significant effect on bulk conductivity. In contrast, the addition of ~1.0 vol% Fe67S33 melt results in conductivity much higher than that of pure olivine, but lower than what is expected for a fully interconnected sulfide phase. We infer that the sulfide is partially connected on the grain boundaries and edges and has reached the electrical percolation threshold, but not the fluid percolation threshold. The effect of the addition of sulfide to the grain boundaries on electrical conductivity is similar to the effect of adding 0.01%-0.1% H to pure olivine. It may not always be necessary to have hydrogen or connected melt or fluid to account for anomalously high conductivity in some parts of the mantle or crust. This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.
Elasticity of Hydrous Olivine Polymorphs: Implications for Seismic Structure of the Transition Zone
NASA Astrophysics Data System (ADS)
Duffy, T. S.; Mao, Z.; Jacobsen, S. D.; Jiang, F.; Smyth, J. R.; Holl, C. M.; Frost, D. J.
The presence of water in the upper mantle and transition zone has the potential to explain various phenomena such as shear velocity anomalies or uplift and broadening of the 410-km discontinuity. The presence of H2O in the transition zone has also been frequently invoked to reconcile laboratory elasticity data on olivine polymorphs with seismic data for the amplitude of the 410-km discontinuity (Li et al., 2001; Chambers et al., 2005). Recently, we have measured the single-crystal elastic properties of hydrous olivine (Jacobsen et al., 2006) and a suite of hydrous wadsleyites (Mao et al., 2007a) at ambient conditions and one hydrous wadsleyite composition (0.84 wt% H2O) up to 12 GPa (Mao et al., 2007b). These data provide new constraints on elastic moduli and their pressure derivatives for hydrous olivine and wadsleyite. Using this data, we first examine the effect of H2O on bulk sound velocities under transition zone conditions because anelastic effects can be neglected in this case. At 410 km depth (~13.8 GPa, along a 1400░C adiabat), the bulk sound velocity of wadsleyite with 1 wt% H2O is 3.1% lower than for dry wadsleyite. Comparison of the seismic velocity jump across the 410-km discontinuity with the measured velocity contrast between wadsleyite and olivine provides a means to estimate the olivine abundance at 410-km depth. For mantle wadsleyite with 0.1-0.2 wt% H2O (Huang et al., 2005) and using experimentally determined olivine- wadsleyite H2O partition coefficients, the olivine abundance is found to be 40%, much lower than a pyrolite model. In order for a pyrolite composition to satisfy the seismic data, 1.2 wt. % H2O is needed in wadsleyite- a value greater than its maximum solubility under these conditions. The anomalously steep seismic gradient in the transition zone has been another feature of the region that has long defied explanation. We show that the seismic gradient can be matched if there is a gradient in H2O concentration across the transition zone such that the H2O content drops, for example, from 0.3 wt% at 410 km to 0.1 wt% at 520 km dpeth. For compressional and shear wave velocities, 0.1 wt% H2O in wadsleyite would lead to 0.3% and 0.4% reductions in VP and VS, respectively, neglecting any anelasticity. If the water content of wadsleyite was instead 1.0 wt. %, then the corresponding velocity reductions would be 3.3% and 3.6%. Following the work of Karato and Jung (1998), we have implemented a preliminary model accounting for the effect of H2O on anelasticity. This model indicates that 0.1 wt% H2O in wadsleyite could be responsible for reductions in shear velocities up to 1.0%.
Reaction Progress of Olivine Alteration as a Function of Time and CO2 Supply at 150░C - An Experimental Study
NASA Astrophysics Data System (ADS)
Prikryl, J.; Stefansson, A.
Increased anthropogenic CO2 emissions have caused an imbalance in the Earth's carbon cycle causing climate changes. Interaction of CO2 with water and rock plays important role in geochemical cycle of carbon and among potential ways of reducing atmospheric CO2 by sequestration into carbonates. Olivine, among the main constituents of mafic and ultramafic rocks, is rich in Mg and Fe that can react with CO2 to form Mg-Fe carbonates like siderite and magnesite. Laboratory experiments were performed in batch-type titanium reactors to study the interaction between CO2-rich water and olivine under hydrothermal conditions. The experimental were conducted at 150░C, for 1 to 4 weeks, the CO2 concentration was 5 to 30 mmol/kg and the initial pH was around neutral. The olivine used was forsterite 93% from ┼heim Olivine Pit-Norway. The alteration products and fluid chemistry were monitored as a function of time. Moreover, the results were supported with reaction path modeling to further constrain the olivine alteration and carbonate mineral formation mechanism. Initially forsterite dissolved releasing elements into solution. During this stage limited alteration products were formed and the solution pH was buffered by H+ uptake by olivine dissolution and CO2 concentration. Upon further reactions secondary phases started to form including chrysotile, brusite and mainly solid solution of iron-containing magnesite. This resulted in decrease of CO2 concentrations and eventually increased solution pH. Experiments with higher initial CO2 concentrations required longer period until CO2was consumed. Furthermore experiments with longer duration had quantitatively larger amount of precipitated minerals. Findings of this research represent platform for kinetic numerical simulations of olivine alteration and therefore provide insight into carbon storage in mafic rocks under in-situ conditions.
Crustal origin for coupled 'ultra-depleted' and 'plagioclase' signatures in MORB olivine-hosted melt inclusions: evidence from the Siqueiros Transform Fault, East Pacific Rise
Leonid V. Danyushevsky; Michael R. Perfit; Stephen M. Eggins; Trevor J. Falloon
Geochemical data from melt inclusions in olivine phenocrysts in a picritic basalt from the Siqueiros Transform Fault on the northern East Pacific Rise provide insights into the petrogenesis of mid-ocean ridge basalts (MORB). The fresh lava contains ~10% of olivine phenocrysts (Fo89.3-91.2) and rare, small (80-90, An57-63). Melt inclusions in olivine phenocrysts are glassy, generally rounded in shape and vary
Fayalite-rich rims, veins, and halos around and in forsteritic olivines in CAIs and chondrules in carbonaceous chondrites - Types, compositional profiles and constraints of their formation
X. Hua; J. Adam; A. El Goresy; H. Palme
Fayalitic intergrowths in different olivine-bearing objects in the Allende and Groznaya CV3 chondrites were studied in reflected light and with the backscattered-electron-imaging technique and the concentration profiles were measured quantitatively with an automated EMPA. The information was discussed in the framework of the possible conditions and the mechanism of fayalitic olivines formation. The results suggest that the fayalitic olivine was
P-rich olivines in a melt vein of a composite mantle xenolith: implications for crystal growth and kinetics
NASA Astrophysics Data System (ADS)
Baziotis, Ioannis; Asimow, Paul D.; Ntaflos, Theodoros; Koroneos, Antonios; Perugini, Diego; Stolper, Edward M.
The mineral chemistry of mantle xenoliths, and in particular the presence of phosphorus (P) - a moderately incompatible and slowly diffusing element - may preserve the history of mineral growth and constrain timescales of pre-eruption petrogenetic processes (Boesenberg & Hewins 2010). P-rich zones in olivine may reflect incorporation of P in excess of equilibrium partitioning during rapid growth, in which case zoning patterns primarily record crystal growth rate variations (Milman-Barris et al. 2008; Stolper et al. 2009). We investigated using EMP analyses and X-ray maps a composite amphibole-bearing, mantle xenolith (sample: Ci-1-196) from Cima Volcanic Field (California, USA) that contains second generation P-rich olivines. The xenolith contains multiple lherzolite, websterite, and dunite layers. The host magma (not preserved in our hand-specimen) is thought to be a hawaiite (Wilshire et al. 1988). A thin (average ~200 ?m width), dark layer is present along the contact between lherzolite and websterite. Interpreted as a rapidly crystallized melt, this layer consists of olivine + glass + plagioclase + spinel + clinopyroxene + apatite + ilmenite. The layer contains olivines (Fo83-89.3) with 0.03-0.52 wt.% P2O5; the P-rich olivines (P2O5 >0.1 wt.%) are Fo85 to Fo89.3. Apatite inclusions are present near the rim of P-rich olivine (Fo85) and in plagioclase (An54). Glass is widespread (~15 vol.%) in the layer, having variable composition with P2O5 up to 1.2 wt.%. Plagioclase occurs as prismatic, flow-oriented crystals, parallel to the elongation of the layer or intergranular crystals between olivine and/or clinopyroxene. Clinopyroxene formed either as crystallized products within the melt layer or by reaction at the interface between melt and matrix olivine. Spinel occurs as inclusions in the olivine or associated with plagioclase and glass, showing anhedral shape and linear edges; spinel composition varies from chromite to Ti-chromite from core to rim, with an outer rim rich in ulv÷spinel. Ilmenite occurs as idiomorphic crystals within the layer or as thin rims (
Highly impregnated slow-spread lithosphere : microstructure and geochemistry of olivine-rich troctolites from IODP Hole U1309D
NASA Astrophysics Data System (ADS)
Ildefonse, B.; Drouin, M.; Godard, M.
IODP Expeditions 304-305 sampled the Atlantis Massif, an oceanic core complex located at 30░N in the inside corner of the intersection of the Mid-Atlantic Ridge with the Atlantis Fracture Zone. IODP Hole U1309D was drilled to 1415.5 meters below seafloor; it is the second deepest hole in slow-spreading crust, after Ocean Drilling Program (ODP) Hole 735B on the Southwest Indian Ridge. The recovered rocks are mostly gabbroic. We present a petrostructural (EBSD) and in-situ geochemical (EPMA, LA-ICPMS and LA-HR-ICPMS) study of olivine-rich troctolites (ol > 70%; 5.5 % of recovered section) and associated gabbros. Olivine-rich troctolites from Hole U1309D display poikilitic textures, with olivine ranging from coarse-grained subhedral crystals to medium-grained rounded crystals, embedded in large, undeformed clinopyroxene and plagioclase poikiloblasts. Trace element compositions of clinopyroxene and plagioclase poikiloblasts indicate that they crystallized from the same depleted MORB melt in both olivine-rich troctolites and associated gabbros. Olivine trace element compositions appear too depleted in light REE to be in equilibrium with plagioclase and clinopyroxene. Olivine crystallographic preferred orientations are weak, and misorientations are consistent with deformation by dislocation creep with activation of the high-temperature (010) [100] slip system, commonly described in asthenospheric mantle. The fabrics also display a relatively strong uncommon [001] concentration that we interpret as resulting from abundant melt impregnation. The joint study of geochemical processes and microstructures in these rocks suggest a complex crystallization history in an open system with percolation of large volume of MORB-type melt that postdate olivine crystal-plastic deformation. Although the mantle origin of the olivine is difficult to demonstrate unequivocally, we propose that olivine-rich troctolites represent the ultimate residue of melt-mantle reaction processes. Our results are consistent with the formation of oceanic core complexes associated with relatively strong magmatic activity, and with the crystallization of most of melt in the Atlantis Massif lithosphere without basaltic counterpart erupted on the seafloor.
Microstructural evidence for complex formation histories of amoeboid olivine aggregates from the ALHA77307 CO3.0 chondrite
NASA Astrophysics Data System (ADS)
Han, Jangmi; Brearley, Adrian J.
The microstructures and compositions of olivine and refractory components in six amoeboid olivine aggregates (AOAs) in the Allan Hills A77307 CO3.0 chondrite have been characterized in detail using the focused ion beam sample preparation technique with transmission electron microscopy. In the AOAs, refractory components (perovskite, melilite, spinel, anorthite, and Al-Ti-bearing diopside) provide evidence of a high degree of textural and compositional heterogeneity, suggesting that these phases have formed by disequilibrium gas-solid condensation at high temperatures under highly dynamic conditions. We infer different possible reactions of early-condensed solid minerals (perovskite and spinel) with a nebular gas, forming diopside with wide ranges of Al and Ti contents and/or anorthite. The progressive, incomplete consumption of spinel in these reactions may have resulted in the Cr enrichment in the remaining, unreacted spinel in the AOAs. In contrast to the refractory components, olivines in the AOAs have equilibrated textures with 120░ triple junctions, indicating that the AOAs were subjected to high-temperature annealing after agglomeration of olivine and refractory components. Because the AOAs consist of fine-grained olivine grains with numerous pores, the annealing is constrained by experimental data to have occurred for a short duration of the order of a few hours to tens of hours depending on the annealing temperature. In comparison, the effects of annealing on the refractory components are minimal, probably due to pinning of grain boundaries in the multiphase assemblages that inhibited grain growth.
Natural dissociation of olivine to (Mg,Fe)SiO3 perovskite and magnesiowustite in a shocked Martian meteorite.
Miyahara, Masaaki; Ohtani, Eiji; Ozawa, Shin; Kimura, Makoto; El Goresy, Ahmed; Sakai, Takeshi; Nagase, Toshiro; Hiraga, Kenji; Hirao, Naohisa; Ohishi, Yasuo
We report evidence for the natural dissociation of olivine in a shergottite at high-pressure and high-temperature conditions induced by a dynamic event on Mars. Olivine (Fa(34-41)) adjacent to or entrained in the shock melt vein and melt pockets of Martian meteorite olivine-phyric shergottite Dar al Gani 735 dissociated into (Mg,Fe)SiO(3) perovskite (Pv)+magnesiow³stite (Mw), whereby perovskite partially vitrified during decompression. Transmission electron microscopy observations reveal that microtexture of olivine dissociation products evolves from lamellar to equigranular with increasing temperature at the same pressure condition. This is in accord with the observations of synthetic samples recovered from high-pressure and high-temperature experiments. Equigranular (Mg,Fe)SiO(3) Pv and Mw have 50-100 nm in diameter, and lamellar (Mg,Fe)SiO(3) Pv and Mw have approximately 20 and approximately 10 nm in thickness, respectively. Partitioning coefficient, K(Pv/Mw) = [FeO/MgO]/[FeO/MgO](Mw), between (Mg,Fe)SiO(3) Pv and Mw in equigranular and lamellar textures are approximately 0.15 and approximately 0.78, respectively. The dissociation of olivine implies that the pressure and temperature conditions recorded in the shock melt vein and melt pockets during the dynamic event were approximately 25 GPa but 700?░C at least. PMID:21444781
Octahedral cation ordering in Mg, Fe2+-olivine: an optical absorption spectroscopic study
NASA Astrophysics Data System (ADS)
Taran, Michail N.; Koch-M³ller, Monika
Polarized optical absorption spectra of natural olivine, Fa10Fo90, were measured before and after annealing/quenching experiments performed at 650, 800, 1,000 and 1,200░C under controlled oxygen fugacity. It was found that the annealing induces weak but definite changes in the olivine spectra. The intensity of the spin-allowed Z > X-polarized band at 9,560 cm-1 and shoulder at ś8,300 cm-1 attributed to Fe2+(M2), continuously decreases with annealing temperature, whereas a weaker band at ś11,600 cm-1 assigned to electronic spin-allowed transitions of Fe2+(M1), increases. This evidently shows that annealing treatments cause a redistribution of Fe2+ from M2 to M1. The fractionation increases with increasing temperature. This observation is in good correspondence with many diffraction structural studies of natural and synthetic olivines, as well as with recent Raman and M÷ssbauer investigations by Kolesov and Geiger (Mitt ųsterr Mineral Ges 149:48, 2004) and Morozov et al. (Eur J Mineral 17:495 500, 2005) evidencing a weak tendency of Fe to order into the M1 site with increasing temperature. However, this deduction is incompatible with the results of the in situ neutron power diffraction study of synthetic FeMgSiO4 by Redfern et al. (Phys Chem Minerals 27:630 637, 2000). Polarization properties of the UV absorption edge, attributed to ligand-to-metal charge-transfer transitions in Fe3+, changes from Y > X ? Z in natural samples to a weak Y ? X ? Z-pleochroism in annealed ones. This may be due to redistribution of a small content of Fe3+ among M1 and M2 structural sites.
Low-high temperature behaviour of olivine: implication for Mercury surface
NASA Astrophysics Data System (ADS)
Nestola, Fabrizio; Ferrari, Sabrina; Massironi, Matteo; Cremonese, Gabriele; Visona, Dario; Bruno, Marco; Fioretti, Anna Maria; Redhammer, Gunther J.
Under variable temperature conditions minerals may significantly change their crystal struc-ture (e.g. change of the atomic positions) and consequently their spectral signatures. This could limits our capability of inferring compositions and rheological properties of geological materials from remote sensing acquisition of extraterrestrial surfaces. When (a) the temper-ature conditions are not well constrained and (b) the properties of the material as a function of temperature are not characterized there is actually a high probability of misinterpreting the acquired data. In particular, MESSENGER (NASA) and Bepi-Colombo (ESA) missions will record spectral images of the Mercury surface, which experiences extreme temperature varia-tions (T between 85 and 700 K) due to its long rotational period, small heliocentric distance and eccentric orbit. Within such a wide range of temperatures the minerals constituting the surface of Mercury could undergo marked structural changes due to processes which are totally reversible (thermal expansion, polymorphic phase transformations) but would strongly affect the resulting spectral signatures. This could make the spectral interpretation very complex and could potentially lead to erroneous geological interpretations. In this work we investigated the low-high temperature evolution of the crystal structure of a natural olivine (solid solution between forsterite and fayalite end-members) extracted from a meteorite. Olivine is in fact one of the hypothesized constituents of Mercury crust. In order to determine its thermal expansion and possible phase transformations X-ray diffraction data will be collected on olivine between 80 and 700 K, the temperature range of the Mercury surface. This work wants to be the starting point in understanding which kind of change we could expect in the spectral signatures.
Oxygen diffusion in olivine: Effect of oxygen fugacity and implications for creep
Ryerson, F. J.; Durham, W. B.; Cherniak, D. J.; Lanford, W. A.
Oxygen self-diffusion experiments on single crystals of San Carlosolivine (/similar to/Fo/sub 92/) at 1200/degree/less than or equal to/ital T/less than or equal to1400 /degree/C, oxygen fugacities(/ital f//sub O2/) along the Ni-NiO and Fe-FeO buffers, and silica activityat the olivine-orthopyroxene buffer yielded results that follow therelationship /ital D/=2.6/times/10/sup /minus/10//ital f/ /sub O2//sup 0.21+-0.03/ exp (/minus/266+-11)(kJ mol/sup /minus/1///ital RT/), where/ital D/ is the diffusion coefficient in m/sup 2/ s/sup /minus/1/ and /ital f//sub O2/ is givenin pascals. The activation energy compares reasonably well with results forpure forsterite. The positive dependence of /ital f//sub O/sub 2// implies that theoxygen defect responsible for diffusion is an interstitial rather than a morestericaly reasonable oxygen vacancy. Diffusion of oxygen in other close-packedoxides has also shown a positive dependence on /ital f//sub O2/. The rate ofcreep of single-crystal olivine at fixed orthopyroxene activity also showsa positive /ital f//sub O2/ dependence. If oxygen interstitials should be shown tobe unimportant in oxygen diffusion in oxides, then coupled mechanisms such ascountervacancy diffusion must be appealed to in order to explain the positive/ital f//sub O2/ dependence. Such processes are rate-limited by the diffusion ofmetal vacancies which also display a positive /ital f//sub O2/ dependence inolivine. Compared with data for silicon diffusion in forsterite, our dataindicate that oxygen is not the slowest diffusing species in olivine.
Comparison and calibration of nonheating paleointensity methods: A case study using dusty olivine
NASA Astrophysics Data System (ADS)
Lappe, Sophie-Charlotte L. L.; Harrison, Richard J.; Feinberg, Joshua M.; Muxworthy, Adrian
We present a comparative study of nonheating paleointensity methods, with the aim of determining the optimum method for obtaining paleointensities from "dusty olivine" in chondritic meteorites. The REM method, whereby thermoremanent magnetization (TRM) is normalized by saturation isothermal remanent magnetization (SIRM), is shown to "over normalize" TRM in dusty olivine due to the transformation of stable single-vortex (SV) states to metastable single-domain (SD) states in a saturating field. The problem of over normalization is reduced in the REMc and REM' methods, which more effectively isolate the high-coercivity stable SD component of remanence. A calibration factor of f = 1600 (1000 < f < 2900) is derived for the REM' method. Anhysteric remanent magnetization (ARM) is shown to be a near perfect analogue of TRM in the stable SD component of dusty olivine. ARM normalization of the high-coercivity (100-150 mT) remanence with a calibration factor fARM = 0.91 (0.7 < fARM < 1.2) yields paleofield estimates within ▒ 30% of the actual field values for SD dominated samples. A Preisach method for simulating TRM acquisition using information extracted from first-order reversal curve (FORC) diagrams is shown to work well for SD dominated samples, but fails when there is a large proportion of SV remanence carriers. The failure occurs because (1) SV states are not properly incorporated into the Preisach distribution of remanence carriers, and (2) the acquisition of TRM by SV states is not properly modeled by the underlying SD thermal relaxation theory.
Alteration of Al-rich inclusions inside amoeboid olivine aggregates in the Allende meteorite
Hoshimoto, A.; Grossman, L.
Lightly-altered Al-rich inclusions in amoeboid olivine aggregates have cores containing primary melilite + fassaite + spinel + perovskite and no secondary alteration products. In moderately altered inclusions, whose cores now contain only fassaite + spinel + perovskite, melilite was replaced by a fine-grained mixture of grossular + anorthite + feldspathoids and perovskite was partially replaced by ilmenite. In heavily altered inclusions, fassaite has been replaced by a mixture of phyllosilicates + ilmenite and the remaining primary phases are spinel +/- perovskite. In very heavily altered inclusions, no primary phases remain, the spinel having reacted to form either phyllosilicates of a mixture of olivine + feldspathoids. This sequence of alteration reactions may reflect successively lower solar nebular equilibration temperatures. During alternation, SiO/sub 2/, Na/sub 2/O, K/sub 2/O, FeO, Cr/sub 2/O/sub 3/, H/sub 2/O and Cl were introduced into the inclusions and CaO was lost. MgO may have been lost during the melilite reaction and added during formation of phyllosilicates. Electron microprobe analyses indicate that the phyllosilicates are a mixture of Na-rich phlogopite and chlorite or Al-rich serpentine. Thermodynamic calculations suggest that, at a solar nebular water fugacity of 10/sup -6/, Na-rich phlogopite could have formed from fassaite at approx. 470K and chlorite from Na-rich phlogopite at approx. 328 K. Olivine mantling Al-rich inclusions is not serpentinized, suggesting that these objects stopped equilibrating with the nebular gas above 274 K.
Dislocation-accommodated grain boundary sliding - from olivine to ice (Invited)
NASA Astrophysics Data System (ADS)
Kohlstedt, D. L.; Hansen, L. N.; Goldsby, D. L.; Zimmerman, M. E.
Dislocation-accommodated grain boundary sliding is likely the dominant mechanism of deformation throughout much of the upper mantle, within major portions of glaciers and ice sheets on Earth, and in icy planetoids. In this creep regime, strain rate depends non-linearly on stress, similar to dislocation creep, and exhibits a marked dependence on grain size, similar to diffusion creep. Furthermore, a strong crystallographic preferred orientation (CPO) develops during deformation in this creep regime. We explored the evolution of rheological behavior and grain-scale microstructure of olivine aggregates in this regime with a series of high-strain torsion experiments on thin-walled cylindrical samples. Hot-pressed specimens with a starting grain size of ~40 ?m were deformed under anhydrous conditions at 1200oC to shear strains of ? > 5 at constant strain rates between 1x10-4 and 3x10-3 s-1. Each sample underwent a period of strain weakening prior to reaching steady-state flow. Post-deformation grain sizes ranged from 27 to 7 ?m with grain size decreasing with increasing strain rate (i.e., with increasing shear stress). All samples exhibited a strong CPO characteristic of dislocation glide on the (010)[100] (easy) slip system. The evolution of stress as a function of strain for each sample is well explained by the combined effects of grain size reduction and CPO development. The stress exponent, n ? 4, and grain size exponent, p ? 1, obtained from the steady-state flow behavior are characteristic of deformation occurring by dislocation-accommodated grain boundary sliding. Observations of dislocation-accommodated grain boundary sliding in olivine are similar to those in other geological materials, indicating that this mechanism is important in a variety of natural environments. For both olivine and ice, extrapolation of the laboratory-derived flow laws for dislocation-accommodated grain boundary sliding, dislocation creep, and diffusion creep indicates that dislocation-accommodated grain boundary sliding is the primary deformation mechanism over a wide range of geological conditions in the mantle as well as in ice sheets, glaciers, and icy satellites. Importantly, the CPOs developed in olivine and ice in the dislocation-accommodated grain boundary sliding regime are similar to those observed in nature, allowing confident extrapolation of our laboratory-derived flow laws to the larger temporal and spatial scales important to modeling the dynamic behavior of planetary interiors and the Earth's cryosphere.
The influence of magma degassing on entrapment pressures recorded in olivine-hosted melt inclusions
NASA Astrophysics Data System (ADS)
Gaetani, G. A.
The concentrations of H2O and CO2 in olivine-hosted melt inclusions provide estimates for the pressures at which they were entrapped, and represent an important source of information on the depths at which basaltic magmas crystallize [1]. Results from recent dehydration experiments demonstrate that diffusive loss of H2O from melt inclusions, driven by degassing of the external magma, leads to significant decreases to pressure within the inclusion [2, 3]. This, in turn, lowers the solubility of CO2 in the included melt causing a vapor to exsolve and form a bubble. This process has the potential to significantly modify estimates of entrapment pressures derived from volatile concentrations in olivine hosted melt inclusions. I have developed a quantitative model that describes this process, allowing the influence of degassing on entrapment pressures to be rigorously evaluated. Diffusive loss of H2O from the inclusions was determined using the model of [3]. An equation of state (EOS) for the silicate melt was taken from the results of [4] and [5], while the EOS for H2O-CO2 vapor was taken from [6]. The solubilities of H2O and CO2 in the silicate melt were derived from VolatileCalc [7]. Modeling results demonstrate that degassing of H2O-rich magma produces significant pressure drops, so that entrapment pressures never exceed crustal values and always represent a minimum. Conversely, degassing of H2O-poor magma does not significantly perturb the H2O content of olivine-hosted melt inclusions. Therefore, these inclusions preserve reliable records of the pressures at which they were entrapped. These results are consistent with a global compilation of olivine-hosted melt inclusion entrapment pressures presented by [3]. References: [1] Wanless, VD, and Shaw, AM, Nature Geosci, 5, 651-655 (2012); [2] Gaetani, GA, et al., Geology, 40, 915-918 (2012); [3] Bucholz, CE, et al., Earth Planet Sci Lett, 374, 145-155 (2013); [4] Lange, R. A., and Carmichael, ISE, Geochim Cosmochim Acta, 51, 2931-2946, (1987); [5] Kress, VC, and Carmichael, ISE, Contrib Mineral Petrol, 108, 82-92 (1991); [6] Duan, Z, and Zhang, Z, Geochim Cosmochim Acta, 70, 2311-2324 (2006); [7] Newman, S, and Lowenstern, JB, Comput Geosci, 28, 597-604 (2002).
Petrology and Mineral Chemistry of New Olivine-Phyric Shergottite RBT04262
NASA Technical Reports Server (NTRS)
Dalton, H. A.; Peslier, A. H.; Brandon, A. D.; Lee, C.-T. A.; Lapen, T. J.
RBT04262 was found by the 2004-2005 ANSMET team at the Roberts Massif in Antarctica. It is paired with RBT04261 and is classified as an olivine-phyric shergottite. RBT04261 is 4.0 x 3.5 x 2.5 cm and 78.8 g, and RBT04262 is 6.5 x 5.5 x 3.5 cm and 204.6 g. Both were partially covered by a fusion crust [1]. Chemical analysis and mapping of this meteorite was performed using the Cameca SX100 electron microprobe at NASA Johnson Space Center.
Chemical and morphological changes during olivine carbonation for CO2 storage in the presence of NaCl and NaHCO3.
Gadikota, Greeshma; Matter, Juerg; Kelemen, Peter; Park, Ah-Hhyung Alissa
The increasing concentrations of CO2 in the atmosphere are attributed to the rising consumption of fossil fuels for energy generation around the world. One of the most stable and environmentally benign methods of reducing atmospheric CO2 is by storing it as thermodynamically stable carbonate minerals. Olivine ((Mg,Fe)2SiO4) is an abundant mineral that reacts with CO2 to form Mg-carbonate. The carbonation of olivine can be enhanced by injecting solutions containing CO2 at high partial pressure into olivine-rich formations at high temperatures, or by performing ex situ mineral carbonation in a reactor system with temperature and pressure control. In this study, the effects of NaHCO3 and NaCl, whose roles in enhanced mineral carbonation have been debated, were investigated in detail along with the effects of temperature, CO2 partial pressure and reaction time for determining the extent of olivine carbonation and its associated chemical and morphological changes. At high temperature and high CO2 pressure conditions, more than 70% olivine carbonation was achieved in 3 hours in the presence of 0.64 M NaHCO3. In contrast, NaCl did not significantly affect olivine carbonation. As olivine was dissolved and carbonated, its pore volume, surface area and particle size were significantly changed and these changes influenced subsequent reactivity of olivine. Thus, for both long-term simulation of olivine carbonation in geologic formations and the ex situ reactor design, the morphological changes of olivine during its reaction with CO2 should be carefully considered in order to accurately estimate the CO2 storage capacity and understand the mechanisms for CO2 trapping by olivine. PMID:24469156
Catalytic reforming of toluene as tar model compound: effect of Ce and Ce-Mg promoter using Ni/olivine catalyst.
Zhang, Ruiqin; Wang, Huajian; Hou, Xiaoxue
Tar produced by biomass gasification as a route of renewable energy must be removed before the gas can be used. This study was undertaken using toluene as a model tar compound for evaluating its steam reforming conversion with three Ni-based catalysts, Ni/olivine, Ni-Ce/olivine and Ni-Ce-Mg/olivine. Effects of Ce and Mg promoters on the reaction activity and coke deposition were studied. Overall the performance of Ce and Mg promoted Ni/olivine catalysts is better than that of only Ce promoter and Ni/olivine alone. The experimental results indicate that Ni-Ce-Mg/olivine catalysts could improve the resistance to carbon deposition, enhance energy gases yield and resist 10ppm H2S poison at 100mLmin(-1) for up to 400min. Furthermore, the activity of catalysts was related to the steam/carbon (S/C) ratios; at S/C ratio=5, T=790░C, space velocity=782h(-1) and t=2h, the Ni-Ce-Mg/olivine system yielded 89% toluene conversion, 5.6Lh(-1) product gas rate, 62.6mol% H2 content and 10% (mol useful gas mol(-1) toluene) energy yield. Moreover, at low S/C ratio, it had higher reaction activity and better ability to prevent coking. There is a small amount of carbon deposition in the form of amorphous carbon after 7h. Various characterization techniques such as XRD, FTIR and thermogravimetric were performed to investigate the coke deposition of Ni/olivine, Ni-Ce/olivine and Ni-Ce-Mg/olivine. It is suggested that 3% Ni-1% Ce-1% Mg/olivine was the most promising catalyst due to its minimum coke amount and the lower activation energy of coke burning. PMID:24275153
Recycling bacteria for the synthesis of LiMPO4 (M = Fe, Mn) nanostructures for high-power lithium batteries.
Zhou, Yanping; Yang, Dan; Zeng, Yi; Zhou, Yan; Ng, Wun Jern; Yan, Qingyu; Fong, Eileen
In this work, a novel waste-to-resource strategy to convert waste bacteria into a useful class of cathode materials, lithium metal phosphate (LiMPO4; M = Fe, Mn), is presented. Escherichia coli (E. coli) bacteria used for removing phosphorus contamination from wastewater are harvested and used as precursors for the synthesis of LiMPO4. After annealing, LiFePO4 and LiMnPO4 nanoparticles with dimensions around 20 nm are obtained. These particles are found to be enveloped in a carbon layer with a thickness around 3-5 nm, generated through the decomposition of the organic matter from the bacterial cell cytoplasm. The battery performance for the LiFePO4 is evaluated. A high discharge capacity of 140 mAh g(-1) at 0.1 C with a flat plateau located at around 3.5 V is obtained. In addition, the synthesized particles display excellent stability and rate capabilities. Even under a high C rate of 10 C, a stable discharge capacity of 75.4 mAh g(-1) can still be achieved. PMID:24930375
Comment on ōDehydration breakdown of antigorite and the formation of B-type olivine CPOö by Nagaya et al. (2014)
NASA Astrophysics Data System (ADS)
Nozaka, Toshio
Recently, Nagaya et al. (2014) have reported the B-type crystallographic preferred orientation (CPO) of olivine in thermally metamorphosed serpentinites from the Happo ultramafic complex, central Japan, and interpreted the CPO as a result of topotactic growth of olivine after antigorite. Their conclusions require the reconsideration of the genesis of B-type olivine CPO, which is generally believed to be formed by plastic deformation of hydrous peridotites, and could have an impact on structural models of supra-subduction zones. I appreciate the detailed observations by Nagaya et al. (2014) but have to point out that they committed significant misinterpretation of facts and failed to show robust evidence and rationale for their argument.
Origin of ultra-nickeliferous olivine in the Kevitsa Ni-Cu-PGE-mineralized intrusion, northern Finland
NASA Astrophysics Data System (ADS)
Yang, Sheng-Hong; Maier, Wolfgang D.; Hanski, Eero J.; Lappalainen, Markku; Santaguida, Frank; Mõõttõ, Sanna
The 2,058 ▒ 4 Ma mafic-ultramafic Kevitsa intrusion is located in the Central Lapland greenstone belt, northern Finland. It is hosted by a Paleoproterozoic volcano-sedimentary sequence that contains komatiitic volcanic rocks and sulfide- and graphite-rich black schists. Economic Ni-Cu-(PGE) sulfide mineralization occurs in the middle part of the ultramafic lower unit of the intrusion. Two main types of ore are distinguished, "normal" and "Ni-PGE" ores. The normal ore is characterized by ~2 to 6 vol% disseminated sulfides and average Ni and Cu grades of 0.3 and 0.42 wt %, respectively (Ni/Cu < 1). The Ni-PGE ore has broadly similar sulfide contents, but a higher Ni grade and lower Cu grade. As a result, the Ni/Cu ratio reaches 15, much higher than in the normal ore. The Ni-PGE ores occur as irregular, discontinuous, lense-like bodies in the ultramafic rocks. Notably, the olivines in the Ni-PGE ore contain extremely high Ni contents of up to 14,000 ppm, which is significantly higher than the Ni content of olivine in other mafic-ultramafic igneous rocks globally (up to ~5,000 ppm) and in harmony with the associated Ni-rich sulfide assemblage containing pentlandite, millerite and pyrite. Microprobe mapping of olivine from the Ni-PGE ore suggests relatively low and homogeneous S contents and homogeneous distribution of Ni, Mg, Fe, which is inconsistent with the presence of sulfide inclusions in the olivine grains, or diffusion of Ni from interstitial sulfides into the olivine grains. We therefore conclude that Ni substitutes for Mg in the olivine lattice. The clinopyroxenes from the Ni-PGE ore also have unusually high Ni concentrations reaching 1,500 ppm and show a positive correlation with the nickel content of the associated olivine. The Nicpx/Niolivine is ~0.1 to 0.2 corresponding to high T partitioning of Ni between clinopyroxene and olivine. K D of 20 can account for the partitioning of nickel between olivine and the sulfide phase, consistent with magmatic equilibration. These data suggest that the olivine, clinopyroxene, and sulfides all crystallized from a basaltic magma with an unexceptionally high Ni content ranging from 300 to 1,100 ppm. The Ni-PGE ores are spatially associated with ultramafic xenoliths. Olivine in these ultramafic xenoliths have relatively high Fo contents (up to 90 mol %) and high Ni contents (up to 5,200 ppm) suggesting that the xenoliths formed from a komatiitic parental magma. It is proposed that assimilation by the Kevitsa magma of massive or semi-massive sulfides associated with komatiitic rocks elevated the Ni content of the magma and resulted in the formation of Ni-PGE ores and related extremely Ni-rich olivines.
Evidence for fractional crystallization of wadsleyite and ringwoodite from olivine melts in chondrules entrained in shock-melt veins.
Miyahara, Masaaki; El Goresy, Ahmed; Ohtani, Eiji; Nagase, Toshiro; Nishijima, Masahiko; Vashaei, Zahra; Ferroir, Tristan; Gillet, Philippe; Dubrovinsky, Leonid; Simionovici, Alexandre
Peace River is one of the few shocked members of the L-chondrites clan that contains both high-pressure polymorphs of olivine, ringwoodite and wadsleyite, in diverse textures and settings in fragments entrained in shock-melt veins. Among these settings are complete olivine porphyritic chondrules. We encountered few squeezed and flattened olivine porphyritic chondrules entrained in shock-melt veins of this meteorite with novel textures and composition. The former chemically unzoned (Fa(24-26)) olivine porphyritic crystals are heavily flattened and display a concentric intergrowth with Mg-rich wadsleyite of a very narrow compositional range (Fa(6)-Fa(10)) in the core. Wadsleyite core is surrounded by a Mg-poor and chemically stark zoned ringwoodite (Fa(28)-Fa(38)) belt. The wadsleyite-ringwoodite interface denotes a compositional gap of up to 32 mol % fayalite. A transmission electron microscopy study of focused ion beam slices in both regions indicates that the wadsleyite core and ringwoodite belt consist of granoblastic-like intergrowth of polygonal crystallites of both ringwoodite and wadsleyite, with wadsleyite crystallites dominating in the core and ringwoodite crystallites dominating in the belt. Texture and compositions of both high-pressure polymorphs are strongly suggestive of formation by a fractional crystallization of the olivine melt of a narrow composition (Fa(24-26)), starting with Mg-rich wadsleyite followed by the Mg-poor ringwoodite from a shock-induced melt of olivine composition (Fa(24-26)). Our findings could erase the possibility of the resulting unrealistic time scales of the high-pressure regime reported recently from other shocked L-6 chondrites. PMID:18562280
Evidence for fractional crystallization of wadsleyite and ringwoodite from olivine melts in chondrules entrained in shock-melt veins
Miyahara, Masaaki; El Goresy, Ahmed; Ohtani, Eiji; Nagase, Toshiro; Nishijima, Masahiko; Vashaei, Zahra; Ferroir, Tristan; Gillet, Philippe; Dubrovinsky, Leonid; Simionovici, Alexandre
Peace River is one of the few shocked members of the L-chondrites clan that contains both high-pressure polymorphs of olivine, ringwoodite and wadsleyite, in diverse textures and settings in fragments entrained in shock-melt veins. Among these settings are complete olivine porphyritic chondrules. We encountered few squeezed and flattened olivine porphyritic chondrules entrained in shock-melt veins of this meteorite with novel textures and composition. The former chemically unzoned (Fa24¢26) olivine porphyritic crystals are heavily flattened and display a concentric intergrowth with Mg-rich wadsleyite of a very narrow compositional range (Fa6¢Fa10) in the core. Wadsleyite core is surrounded by a Mg-poor and chemically stark zoned ringwoodite (Fa28¢Fa38) belt. The wadsleyite¢ringwoodite interface denotes a compositional gap of up to 32 mol % fayalite. A transmission electron microscopy study of focused ion beam slices in both regions indicates that the wadsleyite core and ringwoodite belt consist of granoblastic-like intergrowth of polygonal crystallites of both ringwoodite and wadsleyite, with wadsleyite crystallites dominating in the core and ringwoodite crystallites dominating in the belt. Texture and compositions of both high-pressure polymorphs are strongly suggestive of formation by a fractional crystallization of the olivine melt of a narrow composition (Fa24¢26), starting with Mg-rich wadsleyite followed by the Mg-poor ringwoodite from a shock-induced melt of olivine composition (Fa24¢26). Our findings could erase the possibility of the resulting unrealistic time scales of the high-pressure regime reported recently from other shocked L-6 chondrites. PMID:18562280
Disclinations and grain boundary migration: evidence for a new deformation mechanism in olivine-rich rocks (Invited)
NASA Astrophysics Data System (ADS)
Cordier, P.; Demouchy, S. A.; Beausir, B.; Taupin, V.; Fressengeas, C.
The rheology of olivine-rich rocks remains poorly understood. In particular, the ability of orthorhombic olivine to bear large strains represents an apparent violation of the von Mises criterion due to a lack of slip systems. In this study we show that a more general description of the deformation process including the motion of rotational defects referred to as disclinations can solve the olivine deformation paradox. Disclinations were proposed together with dislocations by Volterra (1907) to account for elastic distorsions (distorzione) in solids. They have recently been experimentally evidenced from orientation maps in several polycrystalline metallic alloys (Beausir & Fressengeas, 2013). Using high-resolution EBSD orientation maps we show that disclinations decorate grain boundaries in olivine samples deformed experimentally and in nature. We present a disclination-based model of a high-angle tilt boundary in olivine, which demonstrates that an applied shear induces grain boundary migration through disclination motion. This new approach allows further understanding of grain boundary-mediated plasticity in polycrystalline aggregates. By providing the missing mechanism for describing plastic flow in olivine, the present work allows multiscale modeling of the rheology of the upper mantle, from the atomic scale to the scale of the flow. Beausir, B. & Fressengeas, C., Disclination densities from EBSD orientation mapping. International Journal of Solids and Structures 50 (1), 137-146 (2013). Volterra, V., Sur l'ķquilibre des corps ķlastiques multiplement connexes. Annales scientifiques de l'╔cole Normale Supķrieure 24, 401-517 (1907). Acknowledgement for support: ERC grant RheoMan, Marie Curie fellowship PoEM and ANR NanoMec.
Thermal properties of olivine- and diogenite-rich sites on Vesta
NASA Astrophysics Data System (ADS)
Tosi, F.; Capria, M. T.; De Sanctis, M. C.; Buczkowski, D. L.; Palomba, E.; Zambon, F.; Ammannito, E.; Titus, T. N.; Russell, C. T.; Raymond, C. A.
Olivine-rich deposits were discovered locally on Vesta's surface. Unexpectedly, these deposits occur far away from the prominent Rheasilvia basin: they were rather found in the northern hemisphere as a layer exposed in walls and in ejecta of two craters, scattered more diffusely over a broad area [1]. Furthermore, while diogenite was firmly identified at southern latitudes [2], mineralogical data acquired by VIR suggest diogenite-rich howardite at equatorial latitudes, namely on the top of Brumalia Tholus hill and in the nearby Teia crater's ejecta, which is consistent with the hill being the surface representation of a magmatic intrusion (dike) [3,4]. Dawn's Visible and Infrared Mapping Spectrometer (VIR) [5] hyperspectral images can be used to retrieve surface temperatures, with high accuracy (< 1 K) as long as temperatures are greater than ~180 K. In this work, we present temperature maps and emissivity spectra of olivine-rich deposits found on Vesta, and temperature maps of crater Teia's ejecta. Thermal emission, especially when measured at different points in time, can provide clues to the physical structure of such peculiar sites, which complements the mineralogical investigation based on VIR data collected at shorter wavelengths.
State of stress in the lithosphere: Inferences from the flow laws of olivine
Kirby, S.H.
The experimental flow data for rocks and minerals are reviewed and found to fit a law of the form {Mathematical expression} where {Mathematical expression} This law reduces to the familiar power-law stress dependency at low stress and to an exponential stress dependency at high stress. Using the material flow law parameters for olivine, stress profiles with depth and strain rate are computed for a representative range of temperature distributions in the lithosphere. The results show that the upper 15 to 25 km of the oceanic lithosphere must behave elastically or fail by fracture and that the remainder deforms by exponential law flow at intermediate depths and by power-law flow in the rest. A model computation of the gravitational sliding of a lithospheric plate using olivine rheology exhibits a very sharp decoupling zone which is a consequence of the combined effects of increasing stress and temperature on the flow law, which is a very sensitive function of both. ?? 1977 Birkha??user Verlag.
In-situ X-ray Synchrotron Microtomography: Real Time Pore Structure Evolution during Olivine Carbonation
NASA Astrophysics Data System (ADS)
Zhu, W.; Fusseis, F.; Lisabeth, H. P.; Xiao, X.
Mineral carbonation has been proposed as a promising method for long-term, secure sequestration of carbon dioxide. In porous rocks, fluid-rock interactions can significantly alter the pore space and thus exert important controls over the rate and extent of carbonation. We constructed an x-ray transparent pressure cell [Fusseis et al., 2013] to investigate the real time pore structure evolution during mineral carbonation in porous olivine aggregates. In each experiment, a sintered olivine sample was subjected to a confining pressure of 13 MPa and a pore pressure of 10 MPa, with a sodium bicarbonate solution (NaHCO3 at 1.5 M) as pore fluid. At these pressure conditions, the cell was heated to 473 K. Constant pressure and temperature conditions were maintained during the length of the experiments, lasting 72-120 hours. Using a polychromatic beam in the 2-BM upstream hutch at the Advanced Photon Source, 3-dimensional (3-D) microtomography data were collected in 20 seconds with 30-minute interval. A novel phase retrieval reconstruction algorithm [Paganin et al., 2002] was used to reconstruct microtomographic datasets with a voxel size of ~1.1 micron. The microtomography images at different stages of the carbonation process reveal progressive growth of new crystals in the pore space. Integration of a x-ray transparent pressure vessel with flow through capacity and 3-D microtomography provides a novel research direction of studying the coupled chemo-hydro-thermal-mechanical processes in rocks.
Reaction-driven cracking during retrograde metamorphism: Olivine hydration and carbonation
NASA Astrophysics Data System (ADS)
Kelemen, Peter B.; Hirth, Greg
Retrograde metamorphism (mineral hydration, carbonation and oxidation) is important in controlling the composition and rheology of the Earth's crust and upper mantle, particularly along tectonic plate margins, and in proposed mechanisms for geothermal power generation and engineered, geological carbon storage. Retrograde processes can lead to an increase in solid mass and volume, or can be balanced by host phase dissolution at constant solid volume. In turn, solid volume changes could reduce permeability and reactive surface area, and/or lead to host rock deformation, via fracture and frictional sliding or viscous flow. Which of these outcomes emerges in specific cases is determined in part by the ōcrystallization pressureö, which creates local gradients in pressure around growing crystals, and thus a differential stress. We develop thermodynamic and mineral physics estimates of the crystallization pressure and differential stress resulting from volume changes during olivine hydration (serpentinization) and carbonation. Because olivine is so far from equilibrium with fluids near the surface, the stress due to serpentinization and/or carbonation may exceed 300 MPa at temperatures up to 200 ░C or more, greater than required to fracture rocks and cause frictional failure in the upper 10 km of the Earth. Provided that fluid access is initiated, for example along pre-existing fractures, the volume change due to hydration and carbonation can cause fracture formation and dilation, maintaining or increasing permeability and reactive surface energy in a positive feedback mechanism.
A Plagioclase-Olivine-Spinel-Magnetite Inclusion from Maralinga (CK): A Record of Sequential Condensation
NASA Astrophysics Data System (ADS)
Zinner, E.; Brandstatter, F.; Kurat, G.
An unusual inclusion of triangular cross section (5 mm x 2.5 mm in size) from the Maralinga CK chondrite has a zonal structure, consisting of core, mantle, and crust. The core (2.5 x 1 mm) consists mainly of plagioclase-olivine intergrowth (troctolite) with ophitic texture, but also contains minor clinopyroxene and Cl-apatite, as well as some calcite, which partially fills pore space. The mantle varies in thickness (0.1-1.5 mm) and consists of a dense intergrowth of green spinel and plagioclase with abundant dispersed magnetite grains of widely varying sizes (1-100 micrometer) and shapes. The spinel-plagioclase intergrowth has, in places, symplectitic texture and variable plag/sp ratios and grain-sizes. The mantle is frequently cut by plagioclase-rich veins connecting the core with the crust. Minor phases in the mantle are ilmenite (exsolution lamellae in magnetite) and calcite (in rare pore space). The thin (^about10 micrometer) discontinuous crust consists mainly of plagioclase with some olivine and magnetite and is commonly intimately intergrown with the chondrite matrix. An indentation contains an olivine-plagioclase intergrowth with subophitic texture in places. A super-crust of calcite almost continuously covers the inclusion. Phase compositions, as determined by EMP, are: Olivine - Fa = 33.1, NiO = 0.62 wt%, plagioclase - An 55-74 with high-An compositions in the mantle, clinopyroxene - Fs 10, Wo 46.7, spinel - Fe/Fe+Mg = 0.55, NiO = 1.53 wt%, and magnetite - TiO2 = 0.50 wt%, NiO = 0.57 wt%. Abundances of up to 37 trace elements were determined by secondary ion mass spectrometry[1]. Most phases are rich in trace elements and have group II REE patterns[2] with depletions of the refractory HREEs, a strong positive Tm anomaly and, commonly, a negative Eu anomaly. The exceptions are olivine, which has LREE depletions relative to the HREEs, and calcite, which does not show any significant REE fractionation at the 1xCI abundance level. Thus, trace element abundances in most phases are determined by volatility[3] and not by interphase distribution coefficients, and only olivine appears to have lost the LREEs. This suggests formation of the Maralinga inclusion by condensation from a gas depleted in the superrefractory REEs. Similar patterns have been reported from spinel-hibonite inclusions in Murchison[4], spinel-rich inclusions in Mighei[5], grossite-hibonite inclusions in Acfer 182[6], and spinel inclusions in micrometeorites[7]. The essentially unfractionated REE abundances in calcite must represent an independent reservoir. A search for ^26Al in plagioclase was mostly negative, with only one measurement giving a small ^26Mg excess. The Ti isotope ratios in ilmenite are normal, as expected. The formation history of the inclusion appears to be the following: plagioclase and olivine condensed simultaneously from a gas depleted in superrefractory elements, forming the igneous-looking troctolite core. Plagioclase continued to condense and was joined by spinel and magnetite (or a phase that was subsequently replaced by magnetite). Finally, plagioclase was again joined by olivine, forming the crust. Subsequently, metasomatic exchange reactions under oxidizing conditions in a volatile-rich gas added Fe^2+ and Na (among others) to the phases and led to the formation of phosphate (from phosphide ?) and magnetite (from a reduced precursor ?). Continuing oxidizing conditions caused mobilization of Ca from inside (and probably also outside) the inclusion that precipitated calcite into available pore spaces and at the inclusion's surface. References: [1] Zinner E. and Crozaz G. (1986) Int. J. Mass Spectr. Ion Processes, 69, 17-38. [2] Mason B. and Martin P. M. (1974) Nature, 249, 333-334. [3] Boynton W. V. (1975) GCA, 39, 569-584. [4] Ireland T. R. et al. (1988) GCA, 52, 2841-2854. [5] MacPherson G. J. and Davis A. M. (1994) GCA, 58, 5599-5625. [6] Weber D. et al. (1995) GCA, 59, 803-823. [7] Kurat G. et al. (1994) LPS XXV, 763-764.
Experimental study of the incorporation of Li, Sc, Al and other trace elements into olivine
NASA Astrophysics Data System (ADS)
Grant, Kevin J.; Wood, Bernard J.
We performed a series of synthesis experiments at 1 atm pressure to investigate the substitution mechanisms of 1+ and 3+ ions into olivine. Forsterite crystals were grown from bulk compositions that contained the element of interest (e.g. Li) and different amounts of additional single trace elements. By working at constant (major element) liquid composition and temperature we eliminated all compositional effects other than those due to the trace elements. Mineral-melt pairs were then analysed to determine the compositional-dependence of the partition coefficient ( D), which corresponds to {[element]}/{[element]}, and where [element] refers to weight concentration of the element in the respective phase. We find that Li forms a stable coupled substitution with Sc and, at above ś500 ppm Sc in the crystal, Li + and Sc 3+ ions form an ordered neutral complex ([LiSc]). This complex dissociates at lower trace element concentrations and a second, concentration-independent, mechanism begins to dominate. This second solution mechanism is most likely 2Li + ? Mg 2+ where one of the Li atoms is in an interstitial position in the crystal lattice. Natural olivines show Li contents slightly greater than Sc (on an atomic basis), indicating that both substitution mechanisms are significant. Unlike Sc, Al does not appear to form a stable complex with Li in the olivine structure. Sodium is highly incompatible in olivine with DNaFo-melt of ś0.00015-0.03. Olivine-liquid partitioning of Na + is independent of Sc 3+ or Al 3+ concentration. This indicates that the coupled substitution of Na + with any 3+ ions is unlikely. Instead, the relevant substitution mechanism appears to be 2Na + ? Mg 2+. Although independent of 3+ ion concentration, DNaFo-melt is inversely correlated with the Li concentration of both melts and crystals, implying that Na competes (unsuccessfully) with Li to replace Mg in the olivine structure. Aluminium is highly incompatible in forsterite DAlFo-melt=0.006▒0.0005n=7. Values DAlFo-melt of are similar for all phase pairs synthesised from starting materials containing between 10 and 100,000 ppm Al. This suggests that Al is principally incorporated in forsterite by replacing one Mg and one Si atom MgMgx+SiSix?AlMgĢ+AlSi', where the Al atoms on octahedral (Mg) and tetrahedral (Si) sites are dissociated from one another. The incorporation of gallium into forsterite is influenced by the presence of Li. Where Li concentration in the crystal is much greater than that of Ga (on an atomic basis) we find an excellent correlation between DGaFo-melt and melt Li content. This relationship indicates that Ga 3+ and Li + replace 2Mg 2+ on octahedral sites and that the Ga and Li atoms are, like Sc and Li, strongly associated in the crystal structure. The mechanism by which scandium is incorporated into forsterite is strongly governed by the presence Li. As discussed above, ordered LiMg'ScMgĢ complexes form readily in forsterite in Li-rich experiments. Under Li-absent but Sc-rich conditions (Sc in the crystal >ś500 ppm), DScFo-melt is proportional to the concentration of Sc in the melt. This indicates that Sc incorporation is charge-balanced by the formation of magnesium vacancies 3MgMgx?2ScMgĢ+VMg?, and that both species are associated [ScMgĢVMg?]. At lower Sc concentrations (<500 ppm in the crystal), the concentration-dependence of partitioning indicates that the ScMgĢVMg? complexes dissociate. Our results demonstrate that partitioning of 1+ and 3+ ions into olivine is complex and involves a range of point defects which yield strongly composition-dependent crystal-melt partition coefficients. Since physical and chemical properties of natural olivine, such as diffusion of 6Li and 7Li and H 2O solubility, depend on the concentrations of the defects identified in this study, our results provide an important insight into how determining substitution mechanisms can improve our understanding of large-scale mantle processes and properties.
High and highly anisotropic electrical conductivity of the asthenosphere due to hydrogen diffusion in olivine
NASA Astrophysics Data System (ADS)
Dai, Lidong; Karato, Shun-ichiro
Experimental studies on electrical conductivity in hydrated olivine had been made only at relatively low temperatures. The extrapolation of these data to asthenosphere temperatures shows that explaining high and highly anisotropic conductivity by hydrogen is difficult. We present new experimental results on the electrical conductivity in hydrated olivine single crystals measured under a broader temperature range than before (T (temperature) = 573-1373 K at P (pressure) = 4 GPa). The new results agree well with the previous results at low temperatures (T < 900 K), whereas at higher temperatures (T > 1000 K) substantial deviations from the previous results are observed: (i) anisotropy in conductivity increases with temperature, and (ii) activation energies at high temperature regime are substantially higher than those at lower T. The high temperature behavior is consistent with a model invoking diffusion of two-protons at M-site vacancy, whereas the low temperature behavior suggests conduction by more mobile species such as free proton. The present results (i) explain the discrepancy between different previous studies conducted under different temperature regimes, and (ii) show that most of geophysical observations on the electrical conductivity in the asthenosphere including the high and highly anisotropic conductivity can be explained by high water content in the asthenosphere that is consistent with the geochemical model. Combining with a previous model of low seismic wave velocity of the asthenosphere, a subsolidus model invoking the role of hydrogen provides a unified explanation for the geophysical anomalies of the asthenosphere.
Suppression of Phase Separation in LiFePO 4 Nanoparticles During Battery Discharge
Bai, Peng
Using a novel electrochemical phase-field model, we question the common belief that LiXFePO? nanoparticles always separate into Li-rich and Li-poor phases during battery discharge. For small currents, spinodal decomposition ...
Materials Data on LiFePO4 (SG:62) by Materials Project
Kristin Persson
Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations
Anisotropic surface reaction limited phase transformation dynamics in LiFePO4
G. K. Singh; M. Z. Bazant; G. Ceder
A general continuum theory is developed for ion intercalation dynamics in a single crystal of a rechargeable battery cathode. It is based on an existing phase-field formulation of the bulk free energy and incorporates two crucial effects: (i) anisotropic ionic mobility in the crystal and (ii) surface reactions governing the flux of ions across the electrode\\/electrolyte interface, depending on the
Anisotropic surface reaction limited phase transformation dynamics in LiFePO4
G. K. Singh; M. Z. Bazant; G. Ceder
A general continuum theory is developed for ion intercalation dynamics in a\\u000asingle crystal of a rechargeable battery cathode. It is based on an existing\\u000aphase-field formulation of the bulk free energy and incorporates two crucial\\u000aeffects: (i) anisotropic ionic mobility in the crystal and (ii) surface\\u000areactions governing the flux of ions across the electrode\\/electrolyte\\u000ainterface, depending on the
Plastic deformation of wadsleyite and olivine at high-pressure and high-temperature using a rotational Drickamer apparatus (RDA)
Yu Nishihara; David Tinker; Takaaki Kawazoe; Yousheng Xu; Zhicheng Jing; Kyoko N. Matsukage; Shun-Ichiro Karato
Large-strain plastic deformation experiments of wadsleyite and olivine were conducted using a rotational Drickamer apparatus (RDA) up to pressure and temperature conditions corresponding to the Earth's mantle transition zone. Sintered ring-shaped (Mg,Fe)2SiO4 wadsleyite and olivine samples were deformed at P?16GPa and T=1600 and 1800K, and P?11GPa and T=1800K, respectively, with equivalent strain rate of ??E?6ū10?5?s?1. In situ observations of deforming
Bacterial Oxidation of Iron in Olivine: Implications for the Subsurface Biosphere, Global Chemical Cycles, and Life on Mars
NASA Astrophysics Data System (ADS)
Fisk, M. R.; Popa, R.; Smith, A. R.; Popa, R.; Boone, J.
We isolated 21 species of bacteria from subseafloor and terrestrial basalt environments and which thrive on olivine at neutral pH. Cell numbers increase four to five orders of magnitude over three weeks in media where the only metabolic energy comes from the oxidation of Fe(II) in olivine. The subseafloor bacteria were isolated from a borehole on the flank of Juan de Fuca Ridge in the northeast Pacific basin where the temperature ranged from 4 up to 64 ░C over four years. Terrestrial isolates originated from the basalt-ice boundary in a lava tube on the flank of Newberry Caldera in the Cascades of Oregon. The borehole water was either seawater or seawater plus subseafloor formation water and the lava tube ice was frozen meteoric or ground water. Although microorganisms capable of oxidizing iron for growth are known, microbes that oxidize iron from silicate minerals at neutral pH have not previously been cultured. The 21 species in this study are the first neutrophilic, iron-oxidizing bacteria (nFeOB) to be isolated and cultured that grow on olivine. These nFeOB are primary producers and we believe that they are a widespread component of the subsurface biosphere. In addition to their ability use iron from olivine, these microbes assimilate carbon from bicarbonate in solution and can grow when oxygen pressures are low. They also use nitrate as an alternative electron acceptor to oxygen in anaerobiosis. Since basalt is the most common rock in the Earth's crust and iron is the fourth most abundant element in the crust, we believe nFeOB are likely to be a significant portion of the subsurface biosphere. They are likely to affect, and perhaps in some environments control, the weathering rate of olivine and possibly of pyroxene and basalt glass. Olivine is a component of Mars's surface and it is present on other rocky bodies in the solar system. The ability of these bacteria to use Fe(II) from olivine, to assimilate carbon, to grow at low temperature, and to use low levels of oxygen and nitrate as oxidants would allow them to survive below the surface of Mars. These cultured organisms, which are the first known to oxidize iron from olivine at neutral pH, may be a major component of the subsurface biosphere, may affect global chemical cycles of elements in basalt, and could potentially, live in the Martian subsurface.
Deducing Wild 2 Components with a Statistical Dataset of Olivine in Chondrite Matrix
NASA Technical Reports Server (NTRS)
Frank, D. R.; Zolensky, M. E.; Le, L.
Introduction: A preliminary exam of the Wild 2 olivine yielded a major element distribution that is strikingly similar to those for aqueously altered carbonaceous chondrites (CI, CM, and CR) [1], in which FeO-rich olivine is preferentially altered. With evidence lacking for large-scale alteration in Wild 2, the mechanism for this apparent selectivity is poorly understood. We use a statistical approach to explain this distribution in terms of relative contributions from different chondrite forming regions. Samples and Analyses: We have made a particular effort to obtain the best possible analyses of both major and minor elements in Wild 2 olivine and the 5-30 micrometer population in chondrite matrix. Previous studies of chondrite matrix either include larger isolated grains (not found in the Wild 2 collection) or lack minor element abundances. To overcome this gap in the existing data, we have now compiled greater than 10(exp 3) EPMA analyses of matrix olivine in CI, CM, CR, CH, Kakangari, C2-ungrouped, and the least equilibrated CO, CV, LL, and EH chondrites. Also, we are acquiring TEM/EDXS analyses of the Wild 2 olivine with 500s count times, to reduce relative errors of minor elements with respect to those otherwise available. Results: Using our Wild 2 analyses and those from [2], the revised major element distribution is more similar to anhydrous IDPs than previous results, which were based on more limited statistics (see figure below). However, a large frequency peak at Fa(sub 0-1) still persists. All but one of these grains has no detectable Cr, which is dissimilar to the Fa(sub 0-1) found in the CI and CM matrices. In fact, Fa(sub 0-1) with strongly depleted Cr content is a composition that appears to be unique to Kakangari and enstatite (highly reduced) chondrites. We also note the paucity of Fa(sub greater than 58), which would typically indicate crystallization in a more oxidizing environment [3]. We conclude that, relative to the bulk of anhydrous IDPs, Wild 2 may have received a larger contribution from the Kakangari and/or enstatite chondrite forming regions. Alternatively, Wild 2 may have undergone accretion in an anomalously reducing region, marked by nebular condensation of this atypical forsterite. In [4], a similar conclusion was reached with an Fe-XANES study. We will also use similar lines of reasoning, and our previous conclusions in [5], to constrain the relative contributions of silicates that appear to have been radially transported from different ordinary and carbonaceous chondrite forming regions to the Kuiper Belt. In addition, the widespread depletion of Cr in these FeO-rich (Fa(sub greater than 20)) fragments is consistent with mild thermal metamorphism in Wild 2.
Composition of komatiite melts from Abitibi and Belingwe inferred from melt inclusions in olivine phenocrysts.
NASA Astrophysics Data System (ADS)
Asafov, Evgeny; Sobolev, Alexander; Arndt, Nicholas; Batanova, Valentina
Komatiites are the products of extreme amounts of partial melting and hence are best indicators of the composition of their mantle sources. However, the most known komatiites are highly altered, and this prevents the use of their compositions to estimate the volatile and mobile element contents of the mantle. To estimate the concentrations of these elements, we analyzed melt inclusions in high-Mg olivine phenocrysts from two 2.7 Ga sample suites, one from Abitibi greenstone belt, Canada and the other from the Belingwe greenstone belt, Zimbabwe. Fresh olivine grains 0.2-0.5 mm across were heated for 5 minutes and quenched at 1350░C in a C-O-H atmosphere with oxygen fugacity corresponding to quartz-fayalite-magnetite buffer. Homogenized melt inclusions were exposed at the surface of grains and analyzed by electron probe micro-analyzer for concentrations of Mg, Si, Ti, Al, Fe, Mn, Ca, Na, Cr, P, K, Cl and S. The size of melt inclusions ranges from 20 to 80 Ąm. The measured compositions were adjusted to equilibrium with host olivine with iron loss correction using Petrolog3 software (Danyushevsky & Plechov, G-cubed 12, 2011). Cracked inclusions were filtered out using their low S contents. Data on the volatile components Cl and S were thus obtained for the first time for the melt inclusions in Abitibi komatiites. Calculated melt compositions range from 19.5 to 27.1 wt.% MgO in Abitibi samples and from 18.9 to 22 wt.% in Belingwe samples. Other elements, except Cl and K, show strong negative correlation with MgO and follow an olivine fractionation trend. Concentrations of Si, Ti, Al, and Ca are consistent with the corresponding compositions of whole rocks. Variations of Cl and K cannot be explained by fractionation of olivine and are attributed to the variations in parental melt. The melt inclusion compositions from Abitibi and Belingwe komatiites have similar Ca, Na, K and S concentrations at the same concentration of Mg but Al and Ti are lower in Belingwe samples, and Si and Cl are higher. In Abitibi samples, Cl correlates strongly with K2O with a constant ratio (Cl/K2O= 0.7); in Belingwe samples the correlation is weak with Cl/K2O=1.4. In general, Cl/K2O ratios are a factor of 10-20 higher than in estimated Phanerozoic mantle reservoirs. Possible explanations of obtained data including crustal contamination of parental melt; presence of recycled components in the mantle sources or specific composition of Archean mantle sources will be discussed. This study has been founded by Russian Science Foundation grant 14-17-00491.
Distribution of cations and vacancies and the structure of defects in oxidized intermediate olivine by atomic-resolution TEM and image simulation
The Fe, Mg, and vacancy distributions in oxidized olivine of intermediate composition and the crystal structures of associated planar defects were examined by a combination of atomic-resolution transmission electron microscopy, image analysis, and image simulation. Simulated images using various structures and site occupancies show that the defects are not laihunite-like layers within an essentially normal olivine, but instead are integral
Hiroi, Takahiro
THERMAL INFRARED SPECTROSCOPY OF A SYNTHETIC OLIVINE SERIES (FORSTERITE- FAYALITE the solid solution series between Mg2SiO4 (forsterite [Fo100]) to Fe2SiO4 (fayalite [Fo0]). Changes. Synthetic olivine samples, ranging in composition from forsterite to fayalite [1], have been analyzed us
Lunar highland rocks - Element partitioning among minerals. II - Electron microprobe analyses of Al, P, Ca, Ti, Cr, Mn and Fe in olivine
NASA Technical Reports Server (NTRS)
Smith, J. V.; Hansen, E. C.; Steele, I. M.
Lunar olivines from anorthosites, granulitic impactites, and rocks in the Mg-rich plutonic trend were subjected to electron probe measurements for Al, P, Ca, Ti, Cr and Mn, which show that the FeO/MnO ratio for lunar olivines lies between 80 and 110 with little difference among the rock types. The low values of Ca in lunar olivines indicate slow cooling to subsolidus temperatures, with blocking temperatures of about 750 C for 67667 and 1000 C for 60255,73-alpha determined by the Finnerty and Boyd (1978) experiments. An important paradox is noted in the low Ti content of Fe-rich olivines from anorthosites, although both Ti and Fe tend to become enriched in liquid during fractional distillation. Except for Ca and Mn, olivine from anorthosites has lower minor element values than other rock types. Formation from a chemically distinct system is therefore implied.
Olivine or impact melt: Nature of the ōOrangeö material on Vesta from Dawn
NASA Astrophysics Data System (ADS)
Le Corre, Lucille; Reddy, Vishnu; Schmedemann, Nico; Becker, Kris J.; O'Brien, David P.; Yamashita, Naoyuki; Peplowski, Patrick N.; Prettyman, Thomas H.; Li, Jian-Yang; Cloutis, Edward A.; Denevi, Brett W.; Kneissl, Thomas; Palmer, Eric; Gaskell, Robert W.; Nathues, Andreas; Gaffey, Michael J.; Mittlefehldt, David W.; Garry, William B.; Sierks, Holger; Russell, Christopher T.; Raymond, Carol A.; De Sanctis, Maria C.; Ammanito, Eleonora
NASAÆs Dawn mission observed a great variety of colored terrains on asteroid (4) Vesta during its survey with the Framing Camera (FC). Here we present a detailed study of the orange material on Vesta, which was first observed in color ratio images obtained by the FC and presents a red spectral slope. The orange material deposits can be classified into three types: (a) diffuse ejecta deposited by recent medium-size impact craters (such as Oppia), (b) lobate patches with well-defined edges (nicknamed ōpumpkin patchesö), and (c) ejecta rays from fresh-looking impact craters. The location of the orange diffuse ejecta from Oppia corresponds to the olivine spot nicknamed ōLeslie featureö first identified by Gaffey (Gaffey, M.J. [1997]. Icarus 127, 130-157) from ground-based spectral observations. The distribution of the orange material in the FC mosaic is concentrated on the equatorial region and almost exclusively outside the Rheasilvia basin. Our in-depth analysis of the composition of this material uses complementary observations from FC, the visible and infrared spectrometer (VIR), and the Gamma Ray and Neutron Detector (GRaND). Several possible options for the composition of the orange material are investigated including, cumulate eucrite layer exposed during impact, metal delivered by impactor, olivine-orthopyroxene mixture and impact melt. Based on our analysis, the orange material on Vesta is unlikely to be metal or olivine (originally proposed by Gaffey (Gaffey, M.J. [1997]. Icarus 127, 130-157)). Analysis of the elemental composition of Oppia ejecta blanket with GRaND suggests that its orange material has ?25% cumulate eucrite component in a howarditic mixture, whereas two other craters with orange material in their ejecta, Octavia and Arruntia, show no sign of cumulate eucrites. Morphology and topography of the orange material in Oppia and Octavia ejecta and orange patches suggests an impact melt origin. A majority of the orange patches appear to be related to the formation of the Rheasilvia basin. Combining the interpretations from the topography, geomorphology, color and spectral parameters, and elemental abundances, the most probable analog for the orange material on Vesta is impact melt.
Volatile Contents of Olivine-Hosted Melt Inclusions From the Central Oregon High Cascades
NASA Astrophysics Data System (ADS)
Ruscitto, D.; Johnson, E.; Wallace, P.; Kent, A.; Mercer, C.; Bindeman, I.
The young (~ 16 Ma) and slowly subducting (~ 5 cm/a NNW) Juan de Fuca plate should be mostly dehydrated at typical arc magma generation depths (~ 100 km) beneath the Central Oregon High Cascades, resulting in small amounts of slab-derived fluids infiltrating the overlying mantle wedge (Green and Harry, 1999; Peacock, 2003). To investigate this hypothesis, we analyzed olivine-hosted melt inclusions in mafic tephra deposits from five volcanic centers (Blue Lake Crater, Yapoah Crater, Twin Crater, Palagonite Tuff, and North Sister Volcano) by FTIR, LA-ICPMS, and electron probe to characterize the pre-eruptive volatile contents (H2O, CO2, S, F, Cl) and their relationship to major and trace element compositions. Host olivine phenocrysts (Fo79-84) have ?18O values of 5.35 ▒0.2 ē. The melt inclusions have compositions of 49 - 54 wt. % SiO2 and 4.9 - 5.5 wt. % MgO. H2O contents for the entire dataset vary from ~ 0.2 to 4.0 wt. % and CO2 contents vary from below detection up to 2000 ppm, implying maximum pressures of entrapment between 1.7 and 3.9 kbar during ascent and degassing (Newman and Lowenstern, 2002). Additionally, within-cone averages for inclusions range from 800 - 1500 ppm F, 900 - 1400 ppm S, and 350 - 1000 ppm Cl. For the set of inclusions from each cone, we assume that the highest H2O content is least affected by degassing and therefore represents the minimum amount of H2O in the parent magma. Highly fluid mobile to less fluid mobile element ratios (e.g., Ba/La and Sr/La) correlate positively with maximum H2O/La ratios for Cascades melt inclusions (r2 ~ 0.60; n = 5 volcanic centers). High incompatible element abundances relative to NMORB closely correspond to an EMORB-type source mantle, overprinted with even higher abundances of incompatible and fluid mobile elements (e.g., Ba, U, Pb), resulting in a distinct, negative Nb-Ta anomaly. The volatile data, taken together with olivine ?18O values, trace element abundances and conservative element ratios (e.g., Nb/Y ~ 0.29 - 0.60), suggest partial melting of an EMORB-type mantle source that has been fluxed by an H2O-rich slab component even in this hot, dry end-member subduction zone.
Doped LiFePO? cathodes for high power density lithium ion batteries
Bloking, Jason T. (Jason Thompson), 1979-
Olivine LiFePO4 has received much attention recently as a promising storage compound for cathodes in lithium ion batteries. It has an energy density similar to that of LiCoO 2, the current industry standard for cathode ...
CONTROL ID: 1191197 TITLE: Mineral Magnetism of Dusty Olivine: A Credible Recorder of Pre-Accretionary Remanence
Dunin-Borkowski, Rafal E.
NAME, LAST NAME): Richard J Harrison1, Sophie Lappe1, Nathan S Church1, Takeshi Kasama2 , Alice Bastos da Silva Fanta2, Geoff Bromiley3, Rafal Dunin-Borkowski2, Joshua M Feinberg5, Sara Russell4. SPONSOR NAME: Richard Harrison ABSTRACT BODY: The magnetic properties of olivine-hosted Fe-Ni particles
Materials Science and Engineering A 442 (2006) 170174 Contrasting viscoelastic behavior of melt-free and melt-bearing olivine
-free and melt-bearing olivine: Implications for the nature of grain-boundary sliding Ian Jacksona,, Ulrich H Abstract Melt-free and basaltic (complex alumino-silicate) melt-bearing specimens of fine oscillation and microcreep, display markedly different behavior. For the melt-bearing materials, superimposed
Materials Science and Engineering A 442 (2006) 170174 Contrasting viscoelastic behavior of melt-free and melt-bearing olivine
-free and melt-bearing olivine: Implications for the nature of grain-boundary sliding Ian Jacksona,, Ulrich H bstract Melt-free and basaltic (complex alumino-silicate) melt-bearing specimens of fine oscillation and microcreep, display markedly different behavior. For the melt-bearing aterials, superimposed
Temperature effects on the 1585 mm spectra of olivines and pyroxenes J. E. Bowey,1,2P
Bowey, Janet
Temperature effects on the 15Ł85 mm spectra of olivines and pyroxenes J. E. Bowey,1,2P C. Lee,1 C at wavelengths .20 mm are likely to be at temperatures below ,150 K. In order to investigate the effect absorbances of spectral peaks are also observed. The temperature dependence of lpk and bandwidth shows promise
Single-crystal Brillouin Spectroscopy with Laser Heating and Variable q: Design, Demonstration and New Results on Olivine
NASA Astrophysics Data System (ADS)
Zhang, J.; Bass, J. D.
We have developed a novel Brillouin spectroscopy system integrated with CO2 laser heating and Raman spectroscopic capabilities. High-pressure laser heating experiments on liquid water compressed in a diamond-anvil cell up to 2500 ▒ 150 K demonstrate the flexibility and performance of the system. Temperature is determined from the grey-body thermal radiation of the heated samples,. New single-crystal laser heating Brillouin measurements were made on San Carlos Olivine in the (111) plane at pressures up to ~13 GPa, and T~1300 ▒ 200 K. We obtain quantitative values for the thermal pressure in the diamond cell. Using KCl and KBr and pressure-transmitting media, we show that pressure gradients in the sample chamber are small at high P-T conditions based on observations of the olivine-wadsleyite transition. This system is additionally designed for continuously varying scattering angles from near forward scattering (0║ scattering angle) up to near back scattering (~141║). Our results on the sound velocities of olivine at high pressure-temperature conditions have implications for the nature of the 410 km discontinuity and the olivine content of the upper mantle.
Sound velocities of olivine and beta polymorphs of Mg2SiO4 at Earth's transition zone pressures
NASA Astrophysics Data System (ADS)
Li, Baosheng; Gwanmesia, Gabriel D.; Liebermann, Robert C.
Sound velocities of olivine (?) and beta (?) polymorphs of Mg2SiO4 are measured to P > 12 GPa at room temperature on polycrystalline samples in a multi-anvil apparatus using ultrasonic interferometry. The new velocity data for olivine are lower by 1% for P waves and 2% for S wave at transition zone pressures than extrapolations of low pressure (<1 GPa) data. However, the elastic bulk (KS) and shear (G) moduli for the polycrystalline olivine exhibit good agreement to 10 GPa with recent Brillouin scattering and ultrasonic data for single crystals. The velocity data for the polycrystalline beta phase at 12 GPa agree within 1% with Eulerian finite strain extrapolations of previous data by Gwanmesia et al. (1990b) for similar specimens. The pressure derivatives of the elastic moduli calculated by linear fittings to KS and G vs. pressure yield K0? = 4.4 and G0? = 1.3 for the olivine and K0? = 4.2 and G0? = 1.5 for the beta phases. The isothermal velocity contrast at room temperature between these two phases, (V?-V?rpar/V? decreases systematically with increasing pressure, reaching 8.0% for P wave and 11.3% for S wave at pressures equivalent to 410 km depth.
The effect of dynamic recrystallization on olivine fabric and seismic anisotropy: Insight from a ductile shear zone, Oman ophiolite
Kanagawa, Kyuichi
a ductile shear zone, Oman ophiolite Katsuyoshi Michibayashi a,, Toshiki Ina a , Kyuichi Kanagawa b a shear zone in a sinistral sense of shear within the northern Fizh mantle section of the Oman ophiolite ophiolite; porphyroclastic texture; olivine crystal-preferred orientation; dynamic recrystallization
Appendix 2: Photomicrographs and back scattered electron images (BEI) of selected samples showing characteristic textures. ol = olivine, opx = orthopyroxene, cpx =
Simon, Nina
characteristic textures. ol = olivine, opx = orthopyroxene, cpx = clinopyroxene, gt = garnet, sp = spinel, ilm) Magnification of Fig. 2a and b, with crossed polars, showing spinel-opx symplectites ('fingerprint textures I sample K27. Note the #12;difference in texture to garnet-free samples. Garnets often occur on opx
Reply to comment by Nozaka (2014) on ōDehydration breakdown of antigorite and the formation of B-type olivine CPOö
NASA Astrophysics Data System (ADS)
Nagaya, Takayoshi; Wallis, Simon R.; Kobayashi, Hiroaki; Michibayashi, Katsuyoshi; Mizukami, Tomoyuki; Seto, Yusuke; Miyake, Akira; Matsumoto, Megumi
We would like to thank Dr. Nozaka for his interest in our work and also for supplying some of the crystal orientation data that we used in our study. He presents a detailed discussion of differences in interpretation between our two studies. The main difference is whether the strong B-type olivine CPO developed as a result of topotactic static growth after breakdown of antigorite (Nagaya et al., 2014) or if it developed due to homoepitaxial growth on a limited number of olivine grains that already showed a general B-type CPO (Nozaka, 2014). In both of our studies static growth of olivine due to the breakdown of antigorite is key in the strengthening or formation of B-type olivine CPO. This conclusion has potentially far reaching implications for the interpretation of mantle seismic anisotropy in subduction zones and is the most important take home message. However, the details of interpretation are also important. In our reply, we focus on what we consider to be the 5 main points of disagreement. We refer to Fig. 1 to explain different microstructural domains.
Steam reforming of tar from a biomass gasification process over Ni\\/olivine catalyst using toluene as a model compound
D. ?wierczy?ski; S. Libs; C. Courson; A. Kiennemann
A Ni\\/olivine catalyst, previously developed for biomass gasification and tar removal during fluidized bed steam gasification of biomass, was tested in a fixed bed reactor in toluene steam reforming as a tar destruction model reaction. The influence of the catalyst preparation parameters (nickel precursor, calcination temperature and nickel content) and operating parameters (reaction temperature, steam to carbon S\\/C ratio and
An experimental study of the solubility and partitioning of iridium, osmium and gold between olivine and silicate melt
Mcdonough, William F.
= An experimental study of the solubility and partitioning of iridium, osmium and gold betweenŁmelt partitioning experiments to understand the behaviour of iridium, osmium and gold during crust; osmium; iridium; gold; partitioning; olivine 1. Introduction Owing to their refractory nature, and unique
Crystallization, melt inclusion, and redox history of a Martian meteorite: Olivine-phyric shergottite Larkman Nunatak 06319
NASA Astrophysics Data System (ADS)
Peslier, A. H.; Hnatyshin, D.; Herd, C. D. K.; Walton, E. L.; Brandon, A. D.; Lapen, T. J.; Shafer, J. T.
The Larkman Nunatak (LAR) 06319 olivine-phyric shergottite is composed of zoned megacrysts of olivine (Fo 76-55 from core to rim), pyroxene (from core to rim En 70Fs 25Wo 5, En 50Fs 25Wo 25, and En 45Fs 45Wo 10), and Cr-rich spinel in a matrix of maskelynite (An 52Ab 45), pyroxene (En 30-40Fs 40-55Wo 10-25,), olivine (Fo 50), Fe-Ti oxides, sulfides, phosphates, Si-rich glass, and baddeleyite. LAR 06319 experienced equilibration shock pressures of 30-35 GPa based on the presence of localized shock melts, mechanical deformation of olivine and pyroxene, and complete transformation of plagioclase to maskelynite with no relict birefringence. The various phases and textures of this picritic basalt can be explained by closed system differentiation of a shergottitic melt. Recalculated parent melt compositions obtained from melt inclusions located in the core of the olivine megacrysts (Fo >72) resemble those of other shergottite parent melts and whole-rock compositions, albeit with a lower Ca content. These compositions were used in the MELTS software to reproduce the crystallization sequence. Four types of spinel and two types of ilmenite reflect changes in oxygen fugacity during igneous differentiation. Detailed oxybarometry using olivine-pyroxene-spinel and ilmenite-titanomagnetite assemblages indicates initial crystallization of the megacrysts at 2 log units below the Fayalite-Magnetite-Quartz buffer (FMQ - 2), followed by crystallization of the groundmass over a range of FMQ - 1 to FMQ + 0.3. Variation is nearly continuous throughout the differentiation sequence. LAR 06319 is the first member of the enriched shergottite subgroup whose bulk composition, and that of melt inclusions in its most primitive olivines, approximates that of the parental melt. The study of this picritic basalt indicates that oxidation of more than two log units of FMQ can occur during magmatic fractional crystallization and ascent. Some part of the wide range of oxygen fugacities recorded in shergottites may consequently be due to this process. The relatively reduced conditions at the beginning of the crystallization sequence of LAR 06319 may imply that the enriched shergottite mantle reservoir is slightly more reduced than previously thought. As a result, the total range of Martian mantle oxygen fugacities is probably limited to FMQ - 4 to - 2. This narrow range could have been generated during the slow crystallization of a magma ocean, a process favored to explain the origin of shergottite mantle reservoirs.
A- to B-Type Olivine Fabric Transitions Associated with Hydration, Dehydration and Shear Above the Farallon Flat Slab
NASA Astrophysics Data System (ADS)
Behr, W. M.; Smith, D.
We investigate mantle rocks associated with hydration, dehydration and shear above the Farallon flat-slab at its contact with the base of North America. The rocks we focus on are ultramafic inclusions hosted within serpentinized ultramafic microbreccia diatremes of the Navajo Volcanic Field (New Mexico) that erupted to the surface at the waning stages of the Laramide orogeny. A large number of petrological and geochronological studies have pinpointed the origin of these rocks to the hydrated mantle wedge above the Farallon slab as well as tectonically eroded and entrained fragments of the plate interface. We combine petrological observations and EBSD measurements of olivine grainsize and LPO to examine the effects of hydration on olivine fabric development in different parts of the supra-subduction zone mantle. The rocks examined include weakly deformed to strongly foliated tectonites we interpret to represent partially hydrated fragments of the upper plate mantle; and mylonites and ultramylonites we interpret to represent deformed fragments of the plate interface. The rocks deformed at temperatures ranging from 500-900░C based on thermometry, and olivine compositions in some record heating just before incorporation in the diatreme mix. We observe the following: Tectonites exhibit A-type bulk olivine LPOs, but show transitions to B-type LPO in local, fine-grained, dynamically recrystallized regions associated with hydrous minerals. Mylonites and ultramylonites with stable chlorite and/or antigorite and recrystallized grainsizes of less than 10?m show strong B-type olivine LPOs. A single mylonite with recrystallized grainsizes of ~35?m shows evidence for prograde metamorphism and dehydration through the chlorite breakdown reaction at temperatures above ~770░C. It contains no hydrous minerals and shows a strong A-type olivine LPO. Together these rocks demonstrate a strong correlation between hydration under high stress conditions, and B-type olivine LPO, consistent with experimental studies that indicate this fabric forms at high water contents and high stress. If interpreted in terms of supra-subduction zone seismic anisotropy, these rocks are consistent with a transition from trench-parallel fast directions close to the trench to trench-perpendicular fast directions away from the trench.
Chemically fractionated olivine-wadsleyite-ringwoodite assemblages in Grove Mountains meteorites: Constraints on formation mechanism of ringwoodite
NASA Astrophysics Data System (ADS)
Feng, L.; Miyahara, M.; Nagase, T.; Ohtani, E.; Hu, S.; Lin, Y.
A crucial issue in the olivine (Ol)-ringwoodite (Rgt) transformation mechanisms is whether they formed via incoherent crystallization along grain boundaries or coherent intracrystalline nucleation and growth. Discovery of ringwoodite lamellae in olivine [1,2] was interpreted as evidence for coherent crystallization [1]. However, recent FIB-TEM studies revealed that they are polycrystalline assemblages (incoherent mechanism) [3]. In addition, some ringwoodite show a large compositional gap with coexisting wadsleyite (Wd), suggestive of a new mechanism of fractional crystallization from olivine melts [4,5]. Abundant Ol-Wd-Rgt assemblages were found in heavily shocked L5-6 Grove Mountains (GRV) chondrites. Ringwoodite and coexisting olivine show different compositions and textures, shedding light on Ol-Wd-Rgt transformation mechanism. Here we report textures and compositions of these assemblages from the shock-induced melt vein mainly in GRV 050249 (L5). Ringwoodite in the entrained Ol-Wd-Rgt assemblages occur as: (1) Polycrystalline ringwoodite rims (up to 10?m wide), and polycrystalline ringwoodite rounded or band-like objects inside the fragments. The ringwoodite crystallites (most ~1?m) are Fa36-82 and show 120░triple junctions; the cores of the fragments are Mg-rich (Fa8-14) submicron-sized Ol-Wd coexistence intermingling with the ringwoodite rims. The compositional gap is up to 74 mol% of Fa (the largest value reported), indicative of extreme fractionation (the host rock olivine is homogeneous, Fa24-25); (2) Submicron-sized irregular grains of ringwoodite in the Ol-Wd cores, consisting of Mg-rich lathes (probably wadsleyite) and Fe-rich matrix (probably olivine) with various proportions. The ringwoodite grains are exclusively embedded in the matrix. Repetitions of concentric zoning (Fa13-17 and Fa26-28) were observed on several entrained olivine fragments depicting polycrystalline ringwoodite rims and inclusions. Each zone exhibits different proportions of the Mg-rich lathes and Fe-rich matrix. The sharp boundaries of ringwoodite-rimmed olivine fragments entrained in the melt veins suggest that the whole fragments were not completely molten. This is supported by the repeated concentric zoning of the ringwoodite-bearing olivine grains. However, the huge compositional gap between ringwoodite and olivine indicates crystallization of ringwoodite from liquid of partial melting. The Rgt-Wd-Ol coexistence superimposed on the repeated concentric zoning suggests that crystallization of Rgt-Wd-Ol might postdate than the latter. In addition, The 120░triple junctions of ringwoodite polycrystalline assemblages indicate annealing under high pressure. Detailed information of the assemblages is expected by the going on FIB-TEM work. References: [1] Chen M., et al. 2004. PNAS 101: 15033-15037. [2] Ohtani E., et al. 2004. EPSL 227: 505-515. [3] Chen M., et al. 2007. EPSL 264: 277-283. [4] El Goresy A. 2006. AGU Fall Meeting Abstracts 54: 08. [5] Miyahara M., et al. 2008. PNAS 105: 8542-8547.
CCMR: Growth of Olivine Single Crystals for Point Defect and Transport Investigations
NSDL National Science Digital Library
Maier, Mitchell
Using the float-zone technique and an image furnace, single crystals of the olivine compound Mn2SiO4 were grown to be used for defect-related properties analysis. The crystals grown so far are not of high enough quality to perform this analysis on; however, the crystals are well suited for producing oriented seed crystals for later high quality crystal growth. The crystals were grown with the aid of a ceramic afterheater. This type of afterheater proved effective at growing crack-free single crystals, and the use of an afterheater is planned to be implemented for all further growth of high-quality single crystals of Mn2SiO4.
Retention of ion-implanted-xenon in olivine: Dependence on implantation dose
NASA Technical Reports Server (NTRS)
Melcher, C. L.; Tombrello, T. A.; Burnett, D. S.
The diffusion of Xe in olivine, a major mineral in both meteorites and lunar samples, was studied. Xe ions were implanted at 200 keV into single-crystal synthetic-forsterite targets and the depth profiles were measured by alpha particle backscattering before and after annealing for 1 hour at temperatures up to 1500 C. The fraction of implanted Xe retained following annealing was strongly dependent on the implantation dose. Maximum retention of 100% occurred for an implantion dose of 3 x 10 to the 15th power Xe ions/sq cm. Retention was less at lower doses, with (approximately more than or = 50% loss at one hundred trillion Xe ions/sq cm. Taking the diffusion coefficient at this dose as a lower limit, the minimum activation energy necessary for Xe retention in a 10 micrometer layer for ten million years was calculated as a function of metamorphic temperature.
The primary liquid condensation model and the origin of barred olivine chondrules
NASA Astrophysics Data System (ADS)
Varela, M. E.; Kurat, G.; Zinner, E.
Barred olivine (BO) chondrules are some of the most striking objects in chondrites. Their ubiquitous presence and peculiar texture caught the attention of researchers and, as a consequence, considerable effort has been expensed on unraveling their origin(s). Here we report on a detailed study of two types of chondrules: the Classic and the Multiple-Plate Type of BO chondrules from the Essebi (CM2), Bishunpur (LL3.1), Acfer 214 (CH3) and DAG 055 (C3-UNGR) chondrites, and discuss the petrographic and chemical data of their major mineral phases and glasses. Glasses occur as mesostasis or as glass inclusions, the latter either enclosed inside the olivine bars (plates) or still connected to the mesostasis. The chemical composition of all glasses, characterized by being Si-Al-Ca-rich and free of alkali elements, is similar to those of the constituents (the building blocks, such as chondrules, aggregates, inclusions, mineral fragments, etc.) of CR and CV3 chondrites. They all have high trace element contents ( ś10ūCI) with unfractionated CI-normalized abundances of refractory trace elements and depletions in moderately volatile and volatile elements with respect to the refractory trace elements. The presence of alkali elements (Na + K + Rb) is coupled with a low Ca content and is only observed in those glasses that have behaved as open systems. This result supports the previous finding that Ca was replaced by alkalis (e.g., Na-Ca exchange), presumably through a vapor-solid reaction. The glasses apparently are the quenched liquid from which the olivine plates crystallized. However, they do not show any chemical fractionation that could have resulted from the crystallization of the olivines, but rather have a constant chemical compositions throughout the formation of the chondrule. In a previous contribution we were able to demonstrate the role of these liquids in supporting crystal growth directly from the vapor. Here we extend application of the primary liquid condensation model to formulate a new model for the origin of BO chondrules. The primary liquid condensation model is based on the ability of dust-enriched solar-nebula gas to directly condense into a liquid, provided the gas/dust ratio is sufficiently low. Thus, we propose that chondrules can be formed by condensation of a liquid droplet directly from the solar nebula. The extensive variability in chemical composition of BO chondrules, which ranges from alkali-poor to alkali-rich, can be explained by elemental exchange reactions with the cooling nebula. We calculate the chemical composition of the initial liquid droplet from which BO chondrules could have formed and speculate about the physical and chemical conditions that prevail in the specific regions of the solar nebula that can promote creation of these objects.
Cosmogenic Be-10, Al-26, and He-3 in olivine from Maui lavas
NASA Technical Reports Server (NTRS)
Nishiizumi, K.; Craig, H.; Klein, J.; Middleton, R.
This paper reports the presence of cosmogenic Be-10 and Al-26 in olivines from the Maui Haleakala basalts in which cosmogenic He-3 and Ne-21 were discovered. Based on production-rate calibrations in quartz crystals from late Pleistocene granite exposures in the Sierra Nevada, the Haleakala crater erosion rates derived from Be-10 and Al-26 concentrations agree within 10 percent and give a mean rate of 12 m/Myr, about 40 percent greater than the rate of 8.5 m/Myr previously derived from He-3 measurements. These results establish the feasibility of the simultaneous use of radioactive and stable cosmogenic nuclides for studies of exposure-ages and erosion-rates in basaltic and andesitic terrains.
Deformation of olivine under mantle conditions: An in situ high-pressure, high-temperature study using monochromatic synchrotron radiation
Hilairet, NadĶge; Wang, Yanbin; Sanehira, Takeshi; Merkel, Sķbastien; Mei, Shenghua (CNRS-UMR); (UC); (UMM)
Polycrystalline samples of San Carlos olivine were deformed at high-pressure (2.8-7.8 GPa), high-temperature (1153 to 1670 K), and strain rates between 7.10{sup -6} and 3.10{sup -5} s{sup -1}, using the D-DIA apparatus. Stress and strain were measured in situ using monochromatic X-rays diffraction and imaging, respectively. Based on the evolution of lattice strains with total bulk strain and texture development, we identified three deformation regimes, one at confining pressures below 3-4 GPa, one above 4 GPa, both below 1600 K, and one involving growth of diffracting domains associated with mechanical softening above {approx}1600 K. The softening is interpreted as enhanced grain boundary migration and recovery. Below 1600 K, elasto-plastic self-consistent analysis suggests that below 3-4 GPa, deformation in olivine occurs with large contribution from the so-called 'a-slip' system [100](010). Above {approx}4 GPa, the contribution of the a-slip decreases relative to that of the 'c-slip' [001](010). This conclusion is further supported by texture refinements. Thus for polycrystalline olivine, the evolution in slip systems found by previous studies may be progressive, starting from as low as 3-4 GPa and up to 8 GPa. During such a gradual change, activation volumes measured on polycrystalline olivine cannot be linked to a particular slip system straightforwardly. The quest for 'the' activation volume of olivine at high pressure should cease at the expense of detailed work on the flow mechanisms implied. Such evolution in slip systems should also affect the interpretation of seismic anisotropy data in terms of upper mantle flow between 120 and 300 km depth.
Olivine water contents in the continental lithosphere and the longevity of cratons.
Peslier, Anne H; Woodland, Alan B; Bell, David R; Lazarov, Marina
Cratons, the ancient cores of continents, contain the oldest crust and mantle on the Earth (>2 Gyr old). They extend laterally for hundreds of kilometres, and are underlain to depths of 180-250 km by mantle roots that are chemically and physically distinct from the surrounding mantle. Forming the thickest lithosphere on our planet, they act as rigid keels isolated from the flowing asthenosphere; however, it has remained an open question how these large portions of the mantle can stay isolated for so long from mantle convection. Key physical properties thought to contribute to this longevity include chemical buoyancy due to high degrees of melt-depletion and the stiffness imparted by the low temperatures of a conductive thermal gradient. Geodynamic calculations, however, suggest that these characteristics are not sufficient to prevent the lithospheric mantle from being entrained during mantle convection over billions of years. Differences in water content are a potential source of additional viscosity contrast between cratonic roots and ambient mantle owing to the well-established hydrolytic weakening effect in olivine, the most abundant mineral of the upper mantle. However, the water contents of cratonic mantle roots have to date been poorly constrained. Here we show that olivine in peridotite xenoliths from the lithosphere-asthenosphere boundary region of the Kaapvaal craton mantle root are water-poor and provide sufficient viscosity contrast with underlying asthenosphere to satisfy the stability criteria required by geodynamic calculations. Our results provide a solution to a puzzling mystery of plate tectonics, namely why the oldest continents, in contrast to short-lived oceanic plates, have resisted recycling into the interior of our tectonically dynamic planet. PMID:20811455
Enhanced olivine carbonation within a basalt as compared to single-phase experiments: reevaluating the potential of CO2 mineral sequestration.
Sissmann, Olivier; Brunet, Fabrice; Martinez, Isabelle; Guyot, Franńois; Verlaguet, Anne; Pinquier, Yves; Daval, Damien
Batch experiments were conducted in water at 150 ░C and PCO2 = 280 bar on a Mg-rich tholeiitic basalt (9.3 wt % MgO and 12.2 wt % CaO) composed of olivine, Ti-magnetite, plagioclase, and clinopyroxene. After 45 days of reaction, 56 wt % of the initial MgO had reacted with CO2 to form Fe-bearing magnesite, (Mg0.8Fe0.2)CO3, along with minor calcium carbonates. The substantial decrease in olivine content upon carbonation supports the idea that ferroan magnesite formation mainly follows from olivine dissolution. In contrast, in experiments performed under similar run durations and P/T conditions with a San Carlos olivine separate (47.8 wt % MgO) of similar grain size, only 5 wt % of the initial MgO content reacted to form Fe-bearing magnesite. The overall carbonation kinetics of the basalt was enhanced by a factor of ca. 40. This could be explained by differences in the chemical and textural properties of the secondary silica layer that covers reacted olivine grains in both types of sample. Consequently, laboratory data obtained on olivine separates might yield a conservative estimate of the true carbonation potential of olivine-bearing basaltic rocks. PMID:24735106
The geochemical effects of olivine slurry replenishment and dolostone assimilation in the plumbing system of the Franklin Large Igneous Province, Victoria Island, Arctic Canada
NASA Astrophysics Data System (ADS)
Hayes, Ben; Lissenberg, C. Johan; Bķdard, Jean H.; Beard, Charlie
The Neoproterozoic (~723-716 Ma) Franklin Large Igneous Province exposed on Victoria Island in the Canadian Arctic is comprised of a sill-dominated magma plumbing system overlain by the coeval Natkusiak flood basalts. We have investigated three sections, separated by a total of >50 km of distance, of a sill (the Fort Collinson Sill Complex) emplaced just above a prominent sedimentary marker unit. The sill is characterized by a basal olivine-enriched layer (OZ: up to 55 % olivine) and an upper gabbroic unit. The observed diversity of olivine compositions in the OZ implies that bulk-rock MgO versus FeO arrays reflect accumulation of a heterogeneous olivine crystal cargo. We suggest that the OZ was formed as a late olivine slurry replenishment in a partially crystallized gabbroic sill, propagating for over 50 km along strike. This interpretation is consistent with Pb-isotope data, which show that at least three geochemically distinct magmas were emplaced into the Fort Collinson Sill Complex. The OZs exhibit a gradual westward evolution toward more Fe-rich bulk compositions. This is best explained by progressive mixing of the replenishing olivine slurry with a resident gabbroic mush during westward flow. Pb-isotopic signatures suggest that magmas near the inferred conduit feeder assimilated small amounts (<10 %) of dolostone country rock, which may have locally buffered olivine compositions to high-Fo contents.
Lattice preferred orientation of olivine found in diamond-bearing garnet peridotites in Finsch, South Africa and implications for seismic anisotropy
NASA Astrophysics Data System (ADS)
Lee, Jaeseok; Jung, Haemyeong
Seismic anisotropy in the upper mantle provides important constraints on mantle dynamics, continental evolution and global tectonics and is believed to be produced by the flow-induced lattice-preferred orientation (LPO) of olivine. Recent experimental studies at high pressure and temperature have suggested that the LPO of olivine is affected by pressure in addition to water and stress. However, there has been no report yet for the pressure-induced LPO of natural olivine because samples from the deep upper mantle are rare and often unsuitable for study due to ambiguous foliation and lineation. Here we show evidence of the pressure-induced LPO of natural olivine in diamond-bearing garnet peridotites from Finsch, South Africa. We found that the [010] axes of olivine are aligned subnormal to foliation and that the [001] axes are aligned subparallel to lineation, which is known as B-type LPO of olivine. The equilibrium pressure of the samples, as estimated using geobarometer, was greater than 4 GPa, indicating that the samples originated from a depth greater than ~120 km. In addition, FTIR spectroscopy of the olivine showed that the samples are dry, with a water content of less than 90▒20 ppm H/Si (5.5▒1.2 ppm wt. H2O). These data suggest that the samples are the first natural examples of olivine displaying B-type LPOs produced due to high pressure under dry condition. Our data indicate that the trench-parallel seismic anisotropy observed in many subduction zones in and below subducting slabs at depths greater than ~90 km under dry condition may be attributed to the pressure-induced olivine fabrics (B-type LPO) and may be interpreted as the entrainment of the sub-lithospheric mantle in the direction of subduction rather than anomalous trench-parallel flow.
Fayalite-rich rims, veins, and halos around and in forsteritic olivines in CAIs and chondrules in carbonaceous chondrites: Types, compositional profiles and constraints of their formation
Hua, X.; Adam, J.; Palme, H.; Goresy, A. E. (Max-Planck-Institut fuer Kernphysik, Heidelberg (Germany, F.R.))
Fayalite-rich rims, veins, and halos around and in forsteritic olivines are a wide-spread phenomenon in chondrules, Ca, Al-rich inclusions (CAIs), and single grains in carbonaceous chondrites. The presence of fayalite rod-like crystals and laths in rims, veins, in wall of pores, and as fluffy network bridging neighboring olivines, pyroxenes, feldspars, etc. is strongly suggestive that the fayalitic olivine was formed by condensation presumably from the solar nebula gas. The formation of the fayalitic olivine was probably caused by an increase in the H{sub 2}O/H{sub 2} ratio (to a ratio between 0.1-1) subsequent to condensation of forsterite. At that stage, FeNi inclusions in olivine were also oxidized and fayalitic halos around the metal were then formed Fe diffusion along with addition of SiO{sub 2} from the solar gas or loss of M{sub g}O to the solar gas. The Fa-rich olivine rims and veins display a narrow compositional variation between Fa{sup 34} and Fa{sup 46}. Subsequent to condensation of Fa-rich olivine and oxidation of FeNi metal, Fe diffused in forsterite. This diffusion was probable enhanced due to the presence of point defects in olivine or the formation of a nonstoichiometric phase analogous to laihunite enriched in Al{sub 2}O{sub 3} and Cr{sub 2}O{sub 3}. However, the presence of Al{sub 2}O{sub 3{minus}} and Cr{sub 2}O{sub 3{minus}} rich discrete domains cannot by excluded. Cooling rates calculated by modeling of the diffusion profiles are indicative of rapid cooling subsequent to the condensation of fayalitic olivines. The authors obtain cooling rates ranging from 2000{degree}/day and 10{degree}C/day at an initial temperature of 1200C{degree} and 900C{degree}, respectively.
Rock magnetic properties of dusty olivine: a potential carrier of pre-accretionary remanence in unequilibrated ordinary chondrites
NASA Astrophysics Data System (ADS)
Lappe, S. C. L. L.; Harrison, R. J.; Feinberg, J. M.
The mechanism of chondrule formation is an important outstanding question in cosmochemistry. Magnetic signals recorded by Fe-Ni nanoparticles in chondrules could carry clues to their origin. Recently, research in this area has focused on 'dusty olivine' grains within ordinary chondrites as potential carriers of pre-accretionary remanence. Dusty olivine is characterised by the presence of sub-micron Fe-Ni inclusions within the olivine host. These metal particles form via subsolidus reduction of the olivine during chondrule formation and are thought to be protected from subsequent chemical and thermal alteration by the host olivine. Three sets of synthetic dusty olivines have been produced, using natural olivine (average Ni-content of 0.3 wt%), synthetic Ni-containing olivine (0.1wt% Ni) and synthetic Ni-free olivine as starting materials. The starting materials were ground to powders, packed into a 2-3 mm3 graphite crucible, heated up to 1350 ░C under a pure CO gas flow and kept at this temperature for 10 minutes. After this the samples were held in a fixed orientation and quenched into water in a range of known magnetic fields, ranging from 0.2 mT to 1.5 mT. We present here for the first time an analysis of a new FORC-based method of paleointensity determination applied to metallic Fe-bearing samples [1, 2]. The method uses a first-order reversal curve (FORC) diagram to generate a Preisach distribution of coercivities and interaction fields within the sample and then physically models the acquisition of TRM as a function of magnetic field, temperature and time using thermal relaxation theory. The comparison of observed and calculated NRM demagnetisation spectra is adversely effected by a large population of particles in the single-vortex state. Comparison of observed and calculated REM' curves, however, yields much closer agreement in the high-coercivity SD-dominated range. Calculated values of the average REM' ratio show excellent agreement with the experimental values - including the observed non-linearity of the remanence acquisition curve - suggesting that this method has the potential to reduce the uncertainties in non-heating paleointensity methods for extraterrestrial samples. [1] AR Muxworthy and D Heslop(2011) A Preisach method for estimating absolute paleofield intensity under the constraint of using only isothermal measurements: 1. Theoretical framework. Journal of Geophysical Research, 116, B04102, doi:10.1029/2010JB007843. [2] AR Muxworthy, D Heslop, GA Paterson, and D Michalk. A Preisach method for estimating absolute paleofield intensity under the constraint of using only isothermal measurements: 2. Experimental testing. Journal of Geophysical Research, 116, B04103, doi:10.1029/2010JB007844.
The magnetic properties of natural and synthetic (Fe x, Mg 1 - x) 2 SiO 4 olivines
NASA Astrophysics Data System (ADS)
Belley, France; Ferrķ, Eric C.; MartĒn-Hernßndez, Fßtima; Jackson, Michael J.; Dyar, M. Darby; Catlos, Elizabeth J.
Olivine is an abundant orthosilicate in the solar system, in the upper mantle of rocky planets, in meteorites and interstellar dust. The magnetic properties of (Fe x, Mg 1 - x) 2 SiO 4 olivines result from the silicate matrix and its iron-rich inclusions and have not always been separated in previous studies. The properties of the matrix are important to understand mantle rocks' anisotropy and their deformation, both in xenoliths and peridotite massifs, while the inclusions are potential paleomagnetic and paleointensity recorders. In this study, we performed new measurements on 7 natural and 23 synthetic ferromagnesian olivines, covering the whole range from forsterite Mg 2SiO 4 (Fo 100) to fayalite Fe 2SiO 4 (Fo 0) and from 4 to 310 K. Many of our specimens contain ferromagnetic inclusions (magnetite or maghemite), with magnetic sizes ranging from superparamagnetic to multidomain. The respective contributions of the matrix and the inclusions are systematically isolated using magnetic fields large enough to saturate the ferromagnetic component due to inclusions. At room temperature, as predicted by molecular field theory, while the forsterite end-member is diamagnetic ( XHF = - 6.8 10 - 10 m 3/kg) and the fayalite end-member is paramagnetic ( XHF = 1.10 10 - 6 m 3/kg), their magnetic properties do not vary linearly with iron content. These olivines also exhibit one or two magnetic transitions at composition-dependent low temperatures. At the Nķel temperature ( TN), olivines exhibit a first magnetic transition from paramagnetic to antiferromagnetic behavior, indicated by negative paramagnetic Curie temperatures ( ?). A second transition ( Tt) occurs at lower temperatures for specimens with x ? 0.1, and could be attributed to a change from collinear to canted antiferromagnetic state. In the range Fo 83-Fo 93, corresponding to the Earth's upper mantle, the anisotropy of magnetic susceptibility (AMS) is directionally consistent, with the AMS principal axes K1, K2 and K3 respectively corresponding to the a, c and b crystallographic axes. At room temperature, the degree of anisotropy increases from 1.028 to 1.302 with decreasing iron content. The presence of small and submicroscopic iron-rich inclusions significantly complicates the investigation of olivine physical properties but also constitutes opportunities to record paleomagnetic field intensities.
Low strength of Earth's uppermost mantle inferred from tri-axial deformation experiments on dry olivine crystals
NASA Astrophysics Data System (ADS)
Demouchy, Sylvie; Tommasi, Andrķa; Boffa Ballaran, Tiziana; Cordier, Patrick
We have performed tri-axial compression experiments on single crystals of San Carlos olivine with various orientations at temperatures relevant for the uppermost mantle, between 800 and 1090 ░C. The experiments were carried out at a confining pressure of 300 MPa in a high-resolution gas-medium mechanical testing apparatus at various constant strain rates (from 7 ū 10-6 s-1 to 1 ū 10-4 s-1); they yield differential stresses ranging from 88 to 754 MPa. Unpolarized infrared spectroscopy analyses indicate that hydrogen concentration in the olivine lattice is very low (<0.5 ppm wt H2O) both before and after deformation. Transmission electron microscopy confirms plastic deformation by dislocation glide. [0 0 1] glide dominates regardless of the orientation of the crystals, even if very marginal [1 0 0] glide has also been activated in some samples. Orientation mapping by electron backscatter diffraction highlights significant local deviations from the original orientation in some samples associated with bending and deformation bands. These strain localizations suggest a heterogeneous mechanical behavior in this temperature range, which is favored by the strong mechanical anisotropy of the olivine crystal. The present experiments confirm that previous published high-temperature flow laws (i.e., power flow law) overestimate the strength of lithospheric mantle, since all samples deformed under stresses significantly lower than predicted by these flow laws. Based on the present results and on a compilation of previously published data on olivine deformation between 500 and 1000 ░C, we propose a new semi-empirical exponential flow law applicable to the uppermost mantle: ??=1▒0.2ū106exp-{450▒60ū103}/{RT}12 where T is the absolute temperature, R is the gas constant, and ? is the differential stress in GPa. Subsequently, small fractions of melt or incorporation of hydrogen in olivine may not be required to reconcile natural observations indicating a limited strength of Earth's uppermost mantle lithosphere (<1 GPa) and experimental data on the rheology of olivine.
doi:10.1016/j.gca.2003.08.012 Northwest Africa 773: Lunar mare breccia with a shallow-formed olivine-cumulate
is an olivine-rich cumulate (Fagan et al., 2001, Korotev et al., 2002, Bridges et al., 2002). A lunar origin was determined by Fagan and coworkers (Fagan et al., 2001, 2003) from noble-gas contents, oxygen isotopes
CONSTRAINTS ON THE GEOCHEMICAL VARIATIONS AND EVOLUTION OF THE LUNAR CRUST AND MANTLE AS REVEALED BY FE, MN, CR CONCENTRATIONS IN OLIVINE. J. Gross1
Treiman, Allan H.
is a polymict, anorthositic regolith breccia from the lunar highlands [8,9] and is thought to come from the far 81005, olivines in anorthosites, granulites, mafic clasts, basaltic clasts (low Ti and VLT) and isolated
Comparison of Small Polaron Migration and Phase Separation in Olivine LiMnPO? and LiFePO? using Hybrid Density Functional Theory
Ong, Shyue Ping
Using hybrid density functional theory based on the Heyd-Scuseria-Ernzerhof (HSE06) functional, we compared polaron migration and phase separation in olivine LiMnPO? to LiFePO?. The barriers for free hole and electron ...
Helium Isotopes in Basalt-Hosted Olivines From the Yellowstone Plateau: Implications on Volcanic Processes
NASA Astrophysics Data System (ADS)
Abedini, A. A.; van Soest, M.; Hurwitz, S.; Kennedy, B. M.
The Yellowstone Plateau volcanic field is the youngest part of a magmatic system that began its northeastward propagation along the path of the eastern Snake River Plain in the mid-Miocene. Previous noble gas isotopic studies in Yellowstone have focused on samples from hydrothermal features. Such samples are often subject to shallow crustal contamination that may mask a deeper magmatic component. Most of the reported He-isotope ratios within the Yellowstone caldera perimeter are ~7 ▒ 1 RA, with peaks occurring around Mud Volcano (~16 RA) and Gibbon Geyser Basin (~13 RA). Outside the caldera, the He-isotope ratios generally drop to <3 RA. The elevated helium isotope data from Mud Volcano and Gibbon Geyser Basin was interpreted as unequivocal evidence for the presence of a deep mantle plume underlying the Yellowstone volcanic field (Craig et al., 1978; Kennedy et al., 1985). However, in an attempt to reconcile the available geochemical and geophysical data some researchers argue solely for a shallow mantle source for the magmatism related to Yellowstone (Christiansen et al., 2002). To gain a better understanding of the helium isotope composition of the mantle source below Yellowstone and its possible changes in time, we have started a study of helium isotopes in basalt-hosted olivines from the Yellowstone volcanic field. A total of 28 samples representing most basalt units from Yellowstone's three eruptive cycles were collected. All of the exposed basalts are located outside the Yellowstone caldera, mainly near Mammoth Hot Springs and Tower Junction to the north and in the Island Park area to the southwest. Most basalts contain 46-52 wt% SIO2, 8-12 wt% FeO, and 0.16-0.23 wt% MgO. Helium was released from aliquots of ~1.5 g olivine by crushing in vacuo, and initial helium isotope results, corrected for 10-15% procedural blank include: 1. The Gerrit basalt from Island Park, with a ratio of 15.7 ▒ 2.2 RA; 2. Falls River basalt from Island Park, 15.1 ▒ 0.8 RA; 3. Warm River basalt from Island Park, 18.6 ▒ 4.0 RA; 4. Osprey basalt from north of the caldera, 25.3 ▒ 4.4 RA. These ratios are all within the range of OIB and suggest that the preponderance of lower, ~7 RA values in fluid samples involves crustal contamination. Christiansen et al., 2002, Geol. Soc. Amer. Bull., 114 (10), 1245-1256. Craig et al., 1978, Geophys. Res. Lett. 5, 897-900. Kennedy et al., 1985, Geochim Cosmochim. Acta, 49 (5), 1251-1261.
Mineralogical and Raman spectroscopy studies of natural olivines exposed to different planetary environments
NASA Astrophysics Data System (ADS)
Weber, I.; B÷ttger, U.; Pavlov, S. G.; Jessberger, E. K.; H³bers, H.-W.
New lander missions to bodies of our solar system are coming up and thus new techniques are desirable for the in-situ investigation of planetary surface and near surface materials. During the last decade Raman spectroscopy has been developed to become an excellent laboratory tool for fast petrological and mineralogical investigation of terrestrial and extraterrestrial rocks. Consequently, Raman spectroscopy has successfully been proposed for operation on planetary surfaces. In the joint ESA and Roscosmos mission ExoMars a Raman Laser Spectrometer (RLS) will for the first time be applied in space to identify minerals and organic compounds in Martian surface rocks and soils. The present study aims to investigate the possible response of various environmental conditions to Raman spectra in preparation for the ExoMars mission, as well as other space missions in future. For our study we selected five natural olivines with different forsterite (Mg2SiO4) and fayalite (Fe2SiO4) compositions. Olivine as an important rock forming mineral of the Earth upper mantle and an abundant mineral in Martian meteorites is one of the key planetary mineral. The spectra were taken in various environmental conditions that include vacuum down to 10-6 mbar, 8 mbar CO2 atmosphere, and temperatures ranging between room temperature and~8 K resembling those on Mars as well as on the Moon and on asteroids. We have found that forsterite shows only small temperature-related shifts in Raman spectra at very low temperatures indicating relatively weak changes in the lattice modes. Fayalite demonstrates, in addition to temperature dependent changes in the lattice modes found for forsterite, modification of Raman spectra at low Stokes frequencies. This is an effect in the SiO4 internal modes that most probably is caused by the high amount of iron in the mineral structure, which triggers antiferromagnetic transition at low temperatures. No influence of a CO2 atmosphere on Raman spectra for the investigated rock-forming minerals has been observed at any pressure from ambient 1 bar down to a few mbar.
Partitioning of siderophile and chalcophile elements between sulfide, olivine, and glass in a naturally reduced basalt from Disko Island, Greenland
NASA Technical Reports Server (NTRS)
Klock, W.; Palme, H.
Major and trace elements in coexisting glass, olivines, and metal-sulfide spherules from a chilled margin sample of a strongly reduced basaltic dike from Disko Island, Greenland have been investigated. Three sets of partition coefficients are obtained, olivine/silicate liquid and metal-sulfide liquid/silicate liquid partition coefficients established at magmatic temperatures, and FeNi/FeS partition coefficients at lower temperatures. High metal-sulfide liquid/silicate liquid partition coefficients are found for Ni, Sb, As, Mo, Cu, Co, and W. The significance of the present results for planetary evolution and the formation of metal-rich or sulfide-rich metal cores is considered in terms of P, W, and Mo abundances in the mantles of the earth, moon, the Shergotty parent body, and the Eucrite parent body.
Destabilization of olivine by 30keV electron irradiation: a possible mechanism of space weathering affecting interplanetary dust particles and planetary surfaces
L. Lemelle; L. Beaunier; S. Borensztajn; M. Fialin; F. Guyot
Electron irradiation experiments were performed using a 30-keV electron beam on single crystals of olivine in a scanning electron microscope (SEM) and in an electron microprobe (EMP). We determined that, under certain conditions, structural damage is caused to the irradiated surface of iron-bearing olivines. The irradiated areas comprise spherules with sizes of hundreds of nanometers and micrometer-sized holes. In the
A laser-ablation ICP-MS study of Apollo 15 low-titanium olivine-normative and quartz-normative mare basalts
Darren W. Schnare; James M. D. Day; Marc D. Norman; Yang Liu; Lawrence A. Taylor
Apollo 15 low-Ti mare basalts have traditionally been subdivided into olivine- and quartz-normative basalt types, based on their different SiO2, FeO, and TiO2 whole-rock compositions. Previous studies have reconciled this compositional diversity by considering the olivine- and quartz-normative basalts as originating from different lunar mantle source regions. To provide new information on the compositions of Apollo 15 low-Ti mare basalt
Calorimetric study of olivine solid solutions in the system Mg 2 SiO 4 Fe 2 SiO 4
H. Kojitani; M. Akaogi
Solution enthalpies of synthetic olivine solid solutions in the system Mg2SiO4-Fe2SiO4 have been measured in molten 2PbOĘB2O3 at 979 K. The enthalpy data show that olivine solid solutions have a positive enthalpy of mixing and the deviation from ideality is approximated as symmetric with respect to composition, in contrast to the previous study. Applying the symmetric regular solution model to
Mg tracer diffusion in synthetic forsterite and San Carlos olivine as a function of P, T and fO 2
Sumit Chakraborty; John R. Farver; Richard A. Yund; David C. Rubie
We present new experimental data on Mg tracer diffusion in oriented single crystals of forsterite (Fo100) and San Carlos olivine (Fo92) between 1000¢1300░ C. The activation energies of diffusion are found to be 400 (▒60) kJ\\/mol (ś96 kcal\\/mol) and 275 (▒25) kJ\\/mol (ś65 kcal\\/ mol) in forsterite and San Carlos olivine, respectively, along [001] at a fO2 of 10-12 bars.
Plastic deformation of olivine-rich diogenites and implications for mantle processes on the diogenite parent body
NASA Astrophysics Data System (ADS)
Tkalcec, Beverley J.; Brenker, Frank E.
Numerous petrologic and geochemical studies so far on the howardite, eucrite, and diogenite (HED) meteorites have produced various crystallization scenarios for their parent body, believed to be the differentiated asteroid 4 Vesta. Structural analyses of diogenites can reveal important insights into postcrystallization deformation on the parent body. Recently published results (Tkalcec et al.) of structural analysis on the olivine-rich diogenite NWA 5480 reveal that it underwent solid-state plastic deformation, although not at the base of a magma chamber. Dynamic mantle downwelling has been proposed as a plausible deformation mechanism (Tkalcec et al.). The purpose of this study is to investigate whether the plastic deformation found in NWA 5480 is an isolated case. We expand the structural analysis on NWA 5480 and extend it to NWA 5784 and MIL 07001,6, two other samples of rare olivine-rich diogenites, using electron-backscattered-diffraction (EBSD) techniques. Our EBSD results show that the diogenites analyzed in this study underwent solid-state plastic deformation, confirming that the observed deformation of NWA 5480 was not an isolated case on the diogenite parent body. The lattice-preferred orientations (LPOs) of olivine in NWA 5784 and NWA 5480 are clearly distinct from that typical for cumulate rocks at the base of magma chambers, indicating a different stress environment and a different deformation mechanism. The LPO of olivine in MIL 07001 is less conclusive. The structural results of this study suggest that plastic deformation occurred on the diogenite parent body at high temperatures (1273 < T ? 1573 K) in the solid state, i.e., after crystallization of the diogenites themselves, in a dynamic environment with active stress fields.
Recycled Crust in the Mantle: Is High-Ni Olivine the Smoking Gun or a Red Herring?
C. Li; E. M. Ripley
It is widely accepted that small amounts of recycled crustal components are present in some mantle-derived mafic and ultramafic magmas. This concept is supported by many isotopic and trace element studies of basalts, picrites and komatiites in the last 30 years. Recently Sobolev et al. [1,2] used olivine compositions such as Ni content and Mn\\/Fe ratio to demonstrate that the
Effect of the heterotrophic bacterium Pseudomonas reactans on olivine dissolution kinetics and implications for CO2 storage in basalts
NASA Astrophysics Data System (ADS)
Shirokova, L. S.; Bķnķzeth, P.; Pokrovsky, O. S.; Gerard, E.; Mķnez, B.; Alfredsson, H.
This work is aimed at quantification of forsteritic olivine (Fo92) dissolution kinetics in batch and mixed-flow reactors in the presence of aerobic gram-negative bacteria (Pseudomonas reactans HK 31.3) isolated from an instrumented well located within a basaltic aquifer in Iceland. The release rate of mineral constituents was measured as a function of time in the presence of live and dead cells in constant-pH (4-9), bicarbonate-buffered (0.001-0.05 M), nutrient-rich and nutrient-free media in batch reactors at 0-30 atm of CO2 partial pressure (pCO2). In batch reactors at 30 atm pCO2, 0.1 M NaCl and 0.05 M NaHCO3 the rates were weakly affected by the presence of bacteria. In nutrient media, the SEM observation of reacted grains revealed the presence of biofilm-like surface coverage that does not modify Mg and Si release rate at the earlier stages of reaction but significantly decreased the dissolution after prolonged exposure. Olivine dissolution rates measured in flow-through reactors are not affected by the presence of dead and live bacteria at pH ?9 in 0.01 M NaHCO3 solutions. In circumneutral, CO2-free solutions at pH close to 6, both live and dead bacteria increase the dissolution rate, probably due to surface complexation of exudates and lysis products. In most studied conditions, the dissolution was stoichiometric with respect to Mg and Si release and no formation of secondary phases was evidenced by microscopic examination of post-reacted grains. Obtained results are consistent with known molecular mechanism of olivine dissolution and its surface chemistry. Overall, this work demonstrates negligible effect of P. reactans on olivine reactivity under conditions of CO2 storage in the wide range of aqueous fluid composition.
Suitability of chondrules for studying the magnetic field of the early solar system: an examination of synthetically produced dusty olivine
NASA Astrophysics Data System (ADS)
Hu, Y.; Feinberg, J. M.; Church, N.; Bromiley, G.; Bowles, J.; Jackson, M.; Moskowitz, B. M.; Harrison, R. J.
Chondritic meteorites are rare, yet incredibly valuable windows into the geophysical and geochemical environment of the early solar system. Dusty olivine grains containing exsolved nanometer-scale iron-nickel alloy inclusions are present in many chondritic meteorites and their remanent magnetization may give insight into the strength of the solar dynamo at the time of chondrule formation. Laboratory methods for determining the paleointensity of these rare materials must be optimized prior to conducting experiments on actual meteorite samples. To this end, we have used high temperature recrystallization techniques to produce synthetic dusty olivine samples with textures remarkably similar to those observed in chondritic meteorites. The olivine grains used in these annealing experiments are from the 13 kya Haleyjabunga picritic basalt flow in Iceland and have compositions of Fo90, which closely resembles the olivine composition observed in chondritic meteorites. Samples were annealed at 1350░C either under vacuum in the presence of graphite or under controlled oxygen fugacity using pure CO gas. The laboratory-produced magnetic mineral assemblages in two sets of samples have been characterized using low and high temperature remanence and susceptibility measurements, hysteresis loops, FORC diagrams, and scanning electron microscopy. The room-temperature remanence properties of these materials have been explored using stepwise IRM and ARM acquisition and alternating field demagnetization. These synthesis techniques allow us to produce a wide rage of iron-nickel grain sizes with correspondingly large variations in coercivity (between 0 and 500 mT). High temperature measurements of saturation magnetization show that both samples reach their Curie temperatures at ~760░C, consistent with kamacite, a low-Ni high-Fe metal alloy. Multiple experiments have shown that care must be taken to rigorously control the atmosphere in which the samples are heated and cooled in order to avoid forming trace amounts of magnetite on the surface of the samples. Future research will explore the feasibility of using modified Thellier protocols to determine the paleointensity of laboratory-induced thermoremanent magnetizations.
A More Reduced Mantle Source for Enriched Shergottites; Insights from the Olivine-Phyric Shergottite Lar 06319
NASA Technical Reports Server (NTRS)
Peslier, A. H.; Hnatyshin, D.; Herd, C. D. K.; Walton, E. L.; Brandon, A. D.; Lapen, T. J.; Shafer, J.
A detailed petrographic study of melt inclusions and Cr-Fe-Ti oxides of LAR 06319 leads to two main conclusions: 1) this enriched oxidized olivine- phyric shergottite represents nearly continuous crystallization of a basaltic shergottite melt, 2) the melt became more oxidized during differentiation. The first crystallized mineral assemblages record the oxygen fugacity which is closest to that of the melt s mantle source, and which is lower than generally attributed to the enriched shergottite group.
Partitioning of samarium and nickel between olivine, orthopyroxene, and liquid; preliminary data at 20 kbar and 1025░C
Bj°rn Mysen
Olivine (ol) and aluminous enstatite (opx) coexist with a hydrous liquid (liq) of haplobasaltic composition in the system Fo-An50Ab50-SiO2-H2O at 20 kbar and 1025░C. Concentrations of Ni and Sm in these three phases have been determined by mapping beta tracks in nuclear emulsions using 63Ni and 151Sm as sources of beta particles. Partition coefficients defined as Kialpha-beta = Cialpha\\/Cibeta (concentrations
DTA, FTIR and impedance spectroscopy studies on lithium¢iron¢phosphate glasses with olivine-like local structure
P. Jozwiak; J. E. Garbarczyk; M. Wasiucionek; I. Gorzkowska; F. Gendron; A. Mauger; C. M. Julien
Amorphous analogs of lithium¢iron¢phosphates (LFP) with olivine-like local order were prepared by standard press-quenching method and their thermal stabilities as well as structural and electric properties were studied for the first time. Glass transition temperature Tg determined by DTA method is equal to 492¢523Ā░C depending on the glass composition. Fourier transform infrared (FTIR) absorption spectroscopy was used to study local
The partitioning of Fe and Mg between olivine and carbonate and the stability of carbonate under mantle conditions
NASA Astrophysics Data System (ADS)
Dalton, John A.; Wood, Bernard J.
We have investigated the effect of Fe on the stabilities of carbonate (carb) in lherzolite assemblages by determining the partitioning of Fe and Mg between silicate (olivine; ol) and carbonates (magnesite, dolomite, magnesian calcite) at high pressures and temperatures. Fe enters olivine preferentially relative to magnesite and ordered dolomite, but Fe and Mg partition almost equally between disordered calcic carbonate and olivine. Measurement of K d ( X {Fe/carb} X {Mg/ol}/ X {Fe/ol} X {Mg/carb}) as a function of Fe/ Mg ratio indicates that Fe-Mg carbonates deviate only slightly from ideality. Using the regular solution parameter for olivine W{FeMg/ol}of 3.7▒0.8 kJ/mol (Wiser and Wood 1991) we obtain for (FeMg)CO3 a W{FeMg/carb}of 3.05▒1.50 kJ/mol. The effect of Ca-Mg-Fe disordering is to raise K d substantially enabling us to calculate W {CaMg/carb}- W {CaFe/carb}of 5.3▒2.2 kJ/mol. The activity-composition relationships and partitioning data have been used to calculate the effect of Fe/Mg ratio on mantle decarbonation and exchange reactions. We find that carbonate (dolomite and magnesian calcite) is stable to slightly lower pressures (by 1 kbar) in mantle lherzolitic assemblages than in the CaO-MgO-SiO2(CMS)-CO2 system. The high pressure breakdown of dolomite + orthopyroxene to magnesite + clinopyroxene is displaced to higher pressures (by 2 kbar) in natural compositions relative to CMS. CO2. We also find a stability field of magnesian calcite in lherzolite at 15 25 kbar and 750 1000░C.
Crystal¢melt partitioning of noble gases (helium, neon, argon, krypton, and xenon) for olivine and clinopyroxene
Veronika S. Heber; Richard A. Brooker; Simon P. Kelley; Bernard J. Wood
Mineral¢melt partition coefficients of all noble gases (min\\/meltDi) have been obtained for olivine (ol) and clinopyroxene (cpx) by UV laser ablation (213nm) of individual crystals grown from melts at 0.1GPa mixed noble gas pressure. Experimental techniques were developed to grow crystals virtually free of melt and fluid inclusions since both have been found to cause profound problems in previous work.
Crystallographic preferred orientations and melt-rock interactions : olivine-rich troctolites from IODP Hole U1309D
M. Drouin; B. Ildefonse; G. Hirth; C. L. Waters; M. Godard
IODP Expeditions 304-305 sampled the Atlantis Massif, an oceanic core complex located at 30░N in the inside corner of the intersection of the Mid-Atlantic Ridge with the Atlantis Fracture Zone. The most primitive end-members of the recovered gabbroic sequence, olivine-rich troctolites (ol > ~70%), have textures and geochemical compositions intermediate between those of mantle peridotites and primitive cumulates, indicative of
Accretion of arc-oceanic lithospheric mantle in the Mediterranean: Evidence from extremely high-Mg olivines and Cr-rich spinel inclusions in lamproites
NASA Astrophysics Data System (ADS)
Prelevi?, D.; Foley, S. F.
Si-rich Mediterranean type lamproites (48-56 wt.% SiO 2) are olivine-phyric, mantle-derived volcanics, in which both phenocrystic and xenocrystic olivine are present. Here we demonstrate the phenocrystic origin of the most extremely NiO-MgO enriched olivine in lamproites with Mg# up to 0.95, that host Cr-rich (Cr# around 0.95) spinels. Our comprehensive study of olivine-spinel pairs from Mediterranean lamproites enables us to constrain the extent of depletion of their mantle source. Olivine-spinel pairs from primitive Mediterranean lamproites plot in the most refractory part of the olivine-spinel mantle array diagram, showing even more refractory character than mineral pairs from boninites and cratonic mantle xenoliths. This indicates involvement of an ultra-depleted mantle component which had previously lost up to 40% basaltic components. These characteristics would fit the involvement of depleted subcratonic lithospheric mantle which underwent komatiite extraction in the Archaean, but mantle of such composition and age is known neither from ultramafic xenolith suites nor in tectonically emplaced ultramafic massifs in western and central Europe. Here, we explore the possibility that the extremely depleted component of the mantle source of Mediterranean lamproites is derived from an island-arc oceanic lithosphere accreted during Alpine collisional processes. This may provide compelling evidence for recent accretion of oceanic lithospheric blocks during Mesozoic subduction-collision processes in the Mediterranean.
Rb-Sr and Sm-Nd Studies of Olivine-Phyric Shergottites RBT 04262 and LAR 06319: Isotopic Evidence for Relationship to Enriched Basaltic Shergottites
NASA Technical Reports Server (NTRS)
Nyquist, L.E.; Shih, C.-Y.; Reese, Y.
RBT 04262 and LAR 06319 are two Martian meteorites recently discovered in Antarctica. Both contain abundant olivines, and were classified as olivine-phyric shergottites. A detailed petrographic study of RBT 04262 suggested it should be reclassified as a lherzolitic shergottite. However, the moderately LREE-depleted REE distribution pattern indicated that it is closely related to enriched basaltic shergottites like Shergotty, Zagami, Los Angeles, etc. In earlier studies of a similarly olivinephyric shergottite NWA 1068 which contains 21% modal olivine, it was shown that it probably was produced from an enriched basaltic shergottite magma by olivine accumulation . As for LAR 06319, recent petrographic studies suggested that it is different from either lherzolitic shergottites or the highly LREE-depleted olivine-phyric shergottites. We performed Rb-Sr and Sm-Nd isotopic analyses on RBT 04262 and LAR 06319 to determine their crystallization ages and Sr and Nd isotopic signatures, and to better understand the petrogenetic relationships between them and other basaltic, lherzolitic and depleted olivine-phyric shergottites.
Ar-40/Ar-39 Ages for Maskelynites and K-Rich Melt from Olivine-Rich Lithology in (Kanagawa) Zagami
NASA Technical Reports Server (NTRS)
Park, J.; Herzog, G. F.; Nyquist, L. E.; Lindsay, F.; Turrin, B.; Swisher, C. C., III; Delaney, J. S.; Shih, C.-Y.; Niihara, T.; Misawa, K.
We report Ar/Ar release patterns for small maskelynite grains and samples of a K-rich phase separated from the basaltic shergottite Zagami. The purpose of the work is to investigate the well-known discrepancy between published Ar/Ar ages of Zagami, >200 Ma, and its age of approx. 170 Ma as determined by other methods [1-6]. Niihara et al. [7] divide less abundant darker material present in Zagami into an olivine-rich lithology (ORL), from which most of our samples came, and a pyroxene-rich one (Dark Mottled-Lithology: DML) [8, 9]. ORL consists of vermicular fayalitic olivine, coarse-grained pyroxene, maskelynite, and a glassy phase exceptionally rich in K (up to 8.5 wt%), Al, and Si, but poor in Fe and Mg. The elemental composition suggests a late-stage melt, i.e., residual material that solidified late in a fractional crystallization sequence. Below we refer to it as "K-rich melt." The K-rich melt contains laths of captured olivine, Ca-rich pyroxene, plagioclase, and opaques. It seemed to offer an especially promising target for Ar-40/Ar-39 dating.
Electrical, optical and magnetic investigations on LiNiPO{sub 4} based olivines synthesized by solution combustion technique
Vijayan, Lakshmi [St. Aloysius College, Edathua, Alappuzha (District), Kerala 689573 (India); Cheruku, Rajesh [Department of Physics, School of Physical, Chemical and Applied Sciences, Pondicherry University, R.V. Nagar, Kalapet, Pondicherry 605 014 (India); Govindaraj, G., E-mail: firstname.lastname@example.com [Department of Physics, School of Physical, Chemical and Applied Sciences, Pondicherry University, R.V. Nagar, Kalapet, Pondicherry 605 014 (India)
Highlights: Ģ Solution combustion technique and preparation of nanocrystalline olivine materials. Ģ Olivine type LiNiPO{sub 4} based nanocrystalline materials and characterization. Ģ AC electrical studies on olivine type LiNi{sub 1?x}M{sub x}PO{sub 4}(M = Cu{sup 2+}/Mg{sup 2+})based materials. Ģ Enhancement of ionic conductivity in the nanocrystalline phase of LiNiPO{sub 4} material. - Abstract: Citric acid assisted solution combustion technique is explored for synthesis of supervalent Cu{sup 2+}/Mg{sup 2+} ion doped LiNiPO{sub 4} system. XRD, FT-IR and microscopy studies confirmed the formation of a well crystallized material at low concentration of dopants. Ionic conductivity increases for lower concentrations of dopants due to the increased channel size for Li{sup +} diffusion. Owing to inherent anti-site defects, ionic conductivity decreases with increase of dopant concentration. Magnetic studies are explored for confirmation of antiferromagnetic nature of ions. Wagner polarization method is used to elucidate the negligible contribution of electrons to total conductivity.
Improved texture measurement during deformation of polycrystalline olivine at high pressure
NASA Astrophysics Data System (ADS)
Dixon, N. A.; Durham, W. B.; Kohlstedt, D. L.; Hunt, S. A.
Unresolved issues in geodynamics demand a better understanding of the bulk mechanical properties of mantle minerals, and also careful analysis of the complex lattice-scale physics behind these properties. Instead of probing the mechanical properties of a material by testing the relationship between "bulk" stress and strain rate in a sample at a variety of conditions (varying P, T, water content, and other environmental variables), synchrotron x-ray diffraction now allows us to observe, in situ, the active deformation physics in much greater detail. This includes in situ monitoring of plastic anisotropy and local stress heterogeneity, grain size, the development of lattice-preferred orientation (LPO), and even the partitioning of stress between multiple phases in the same polycrystalline sample. Here, we present results obtained with the use of the MTEX toolbox for Matlab and energy-dispersive x-ray diffraction, showing the in situ development of LPO in deforming dry San Carlos olivine samples, at pressures from 2-7 GPa. These measurements hint at the active dislocation mechanisms for these conditions. The ability generate a broad range of mantle conditions in the D-DIA, while precisely measuring the structure and conditions within our sample at the grain and lattice scale, demonstrates the promising future of deformation experiments as a means to understanding the evolution of the deep Earth.
Markov chain Monte Carlo inversion for the rheology of olivine single crystals
NASA Astrophysics Data System (ADS)
Mullet, Benjamin G.; Korenaga, Jun; Karato, Shun-Ichiro
We present major modifications to the Markov chain Monte Carlo inversion method of Korenaga and Karato (2008), which was developed to analyze rock deformation data and determine a corresponding flow law and its uncertainty. The uncertainties of state variables, e.g., temperature, pressure, and stress, are now taken into account by data randomization, to avoid parameter bias that could be introduced by the original implementation of the cost function. Also, it is now possible to handle a flow law composed of both parallel and sequential deformation mechanisms, by using conjugate gradient search to determine scaling constants. We test the new inversion algorithm extensively using synthetic data as well as the high-quality experimental data of Bai et al. (1991) on the deformation of olivine single crystals. Our reanalysis of this experimental data set reveals that a commonly adopted value for the stress exponent (ś3.5) is considerably less certain than previously reported, and we offer a detailed account for the validity of our new estimates. The significance of fully reporting parameter uncertainties including covariance is also discussed with a worked example on flow law prediction under geological conditions.
Pyroxenes and olivines from a Galapagos spreading center (GSC) rhyodacite record crystal fractionation and magma mixing
Mattson, S.R.; Byerly, G.R.; Carpenter, P.
Phenocrysts and xenocrysts of augite, subcalcic augite, pigeonite, orthopyroxene, and olivine in two glassy rhyodacite dredge samples from 95/sup 0/W on the GSC reflect a complex history of fractional crystallization and magma mixing. The pyroxene compositions can be grouped into clusters reflecting three major sources: a) Fenumber approx. 0.2 from basalt, b) Fenumber approx. 0.5 from rhyodacite, and c) Fenumber approx. 0.6 from rhyolite. Pyroxene Ti/Al ratios of 1:14, 1:7 and 1:3 have Fenumbers suggesting original crystallization from basalt, rhyodacite, and rhyolite melts respectively. These general compositional groups are typical of those produced during fractional crystallization of basalt to rhyolite. At relatively constant Fenumber the augites in any group display a wide spectrum of variation in Wo, Al, and Ti. Basaltic augite core to rim variations exhibit both increases and decreases in Ti at nearly constant Fenumber. A continuous variation in subcalcic augites is present from Fe-augite to Fe-pigeonite. These effects are likely kinetic, perhaps due to rapid cooling rates, but possibly due to supersaturation produced during mixing. Magma mixing may have played an important role in bringing together these contrasting components. The abundance of very-fine-grained basaltic xenoliths and xenocrysts, the glassy rhyolitic inclusions and associated xenocrysts, along with major reverse zoning in Fenumber or major discontinuities in Fenumber in the ferromagnesian phases all point to coexisting melts of radically differing composition.
Mineralogy of Stardust Track 112 Particle: Relation to Amoeboid Olivine Aggregates
NASA Technical Reports Server (NTRS)
Komatsu, M.; Fagan, T.; Mikouchi, T.; Miyamoto, M.; Zolensky, M.; Ohsumi, K.
The successful analysis of comet 81P/Wild 2 particles returned by the Stardust mission has revealed that the Wild 2 dust contains abundant silicate grains that are much larger than interstellar grains and appear to have formed in the inner regions of the solar nebula [1]. Wild 2 particles include minerals which are isotopically and mineralogically similar to CAIs [e.g., 2, 3] and chondrules [e.g., 4] in chondrites. In addition, particles similar to amoeboid olivine aggregates (AOAs) also have been discovered [5, 6,7]. C2067,2,112,1 is a terminal particle recovered from track #112 (T112). Nakamura-Messenger et al. [7] showed that the forsterite grain in T112 has O-16 enrichment of approximately 40 0/00 (vs. SMOW) and possibly formed together with AOAs. In this study, we have examined the mineralogy of the T112 particle and compared the possible relationships between T112 and AOAs in primitive meteorites.

subset: commoncrawl