{'fraction_non_alphanumeric': 0.036513951085084394, 'fraction_numerical': 0.022390630382363073, 'mean_word_length': 5.482142857142857, 'pattern_counts': {'":': 0, '<': 2, '<?xml version=': 0, '>': 1, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 1, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Calcification rate and carbon-isotope fractionation in coccolithophore calcite through laboratory culture experiments

Hydrothermal fluids are major mass transport agents in the lithosphere and reactive fluid flow underlies alteration and ore-forming mechanisms in diverse settings. In contrast to our advanced knowledge of alteration mineralogy and geochemistry, little is known about the volume of fluids responsible for specific mineralization or about the nature of replacement, i.e. dissolution-precipitation reactions on the microscale. We use alteration zoning of cassiterite-bearing greisens from the Kru2né hory (Erzgebirge) Mts. in Central Europe as model example to interpret the fluid-mineral reaction mechanisms and calculate the time-integrated fluid fluxes. The greisen veins and swarms are hosted by highly evolved Li-F-P-rich biotite and zinnwaldite granites with topaz and tourmaline. Magmatic plagioclase (An<10) and Kfeldspar (Or>84Ab<16) exchanged Na and K prior to greisenization. Dark micas are represented by lithian annite continuosly evolving to zinnwaldite, whereas white mica corresponds to lithian Fe-bearing muscovite. Greisenization occurs in several stages: (i) breakdown of feldspars to quartz and sericite or muscovite. Silicification and muscovite formation are spatially decoupled and represent dissolutionprecipitation process, which requires local transport of Al, (ii) replacement of dark mica by celadonitic muscovite under volume-conserved conditions. This reaction requires significant Al addition and Mg, Fe release, (iii) breakdown of muscovite to topaz and quartz. This is a dissolutionprecipitation reaction under Al-conserved conditions but declining fugacity of HF, and (iv) hydraulic fracturing and open-space filling by quartz greisens and monomineralic veins. Thermodynamic simulation of fluid-mineral interaction during disequilibrium infiltration in a pressure-temperature gradient reveals that the formation of mica-quartz and topazquartz greisens requires time-integrated fluid fluxes 102 to 103 m3 fluid per m2 rock, and the corresponding fluid flow rate of 10-10 to 10-8 m s-1. The formation of a single greisen vein with a typical volume of 103–5·104 m3 would thus require 105–3·107 m3 aqueous fluid that must have exsolved from an intrusion measuring 80-700 m in each dimension. This approach illustrates use of reaction stoichiometries and non-equilibrium transport theory in estimating fluid fluxes in hydrothermal oreforming processes. Calcification rate and carbon-isotope fractionation in coccolithophore calcite through laboratory culture experiments M. HERMOSO1,*, F. MINOLETTI2, Y. CANDELIER2, H. MCCLELLAND1, G. ALOISI3 AND R.E.M. RICKABY1 1 University of Oxford, Dept. Earth Sciences, Oxford, UK, michael.hermoso@earth.ox.ac.uk (* presenting author). 2 Univ. Paris 06 and 7193, Paris, France. 3 Univ. Paris 06 and 7159, Paris, France.