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Silica coatings on the 1974 Kilauea flow: new SEM and SIMS results and implications for Mars

Despite the predominately mafic character of martian 
surface rocks, silica-rich materials have long been predicted to occur on Mars; recently, those predictions 
have been validated. CRISM spectra from numerous regions of Mars have revealed H_2O and OH-bearing phases most consistent with amorphous silica. Additionally, the detection of high-silica materials at Home Plate by MER Spirit implied aqueous alteration and leaching in a volcanic environment [3]. In order to fully understand the environments in which silica-rich materials are formed on Mars, it is useful to study silica in analogous terrestrial settings. We focus on silica and Fe-Ti oxide coatings in the Ka’u Desert on the island of Hawaii, an analog to Mars characterized by low levels of rainfall and strong acid-sulfate alteration processes [4]. Many formation mechanisms for these coatings have been proposed, including dissolution of wind-blown tephra [5], leaching of volcanic 
glass [6], and vapor deposition [7]. We focus on a suite 
of samples from the 1974 Kilauea pahoehoe flow, collected 
in 2003. The chemistry and morphology of these coatings were previously presented [8]. Here we present new morphological, spectral and isotopic analyses of the coating suite. The goal of the study is to characterize the coatings and their formation mechanism and describe the implications for silica mobility on Mars.