Physics
Scientific paper
Aug 2008
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2008jgre..11308003m&link_type=abstract
Journal of Geophysical Research, Volume 113, Issue E8, CiteID E08003
Physics
5
Geochemistry: Alteration And Weathering Processes (3617), Geochemistry: Geochemical Modeling (3610, 8410), Geochemistry: Planetary Geochemistry (5405, 5410, 5704, 5709, 6005, 6008), Planetary Sciences: Solid Surface Planets: Surface Materials And Properties, Planetary Sciences: Solid Surface Planets: Erosion And Weathering
Scientific paper
Theoretical geochemical modeling has been used to evaluate the formation conditions of amorphous silica during aqueous alteration of typical Martian igneous rocks at 0°C. The models show that some silica can form during low-temperature alteration of mafic to ultramafic rocks over a large range of pH and water/rock ratios. Silica-dominated deposits, like those found at the Columbia Hills in Gusev crater on Mars, could form at solution pH below ~2 and water/rock ratios of ~102-104. High-water/rock conditions could represent acid flow through rocks, solution discharge from an acid spring, and/or surface flow of released solutions. Low pH favors dissolution of silicates and saturation of solution with respect to relatively insoluble silica, which then precipitates. Partial evaporation or freezing of released solutions would also cause precipitation of amorphous silica. Modeling shows that Ti oxides are also present in silica-rich deposits. More soluble minerals (e.g., ferric oxides, phyllosilicates) could precipitate downstream from partially neutralized, evaporated, or frozen solutions. Temperatures above ~0°C are not required to form abundant silica through acid alteration of Martian rocks.
McAdam Amy Catherine
Mironenko Mikhail V.
Sharp Thomas G.
Zolotov Mikhail Yu.
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