Formation of silica by low-temperature acid alteration of Martian rocks: Physical-chemical constraints

Amy C. McAdam, Mikhail Zolotov, Mikhail V. Mironenko, Thomas Sharp

Research output: Contribution to journalArticle

35 Scopus citations

Abstract

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.

Original languageEnglish (US)
Article numberE08003
JournalJournal of Geophysical Research E: Planets
Volume113
Issue number8
DOIs
StatePublished - Aug 20 2008

ASJC Scopus subject areas

  • Geophysics
  • Forestry
  • Oceanography
  • Aquatic Science
  • Ecology
  • Water Science and Technology
  • Soil Science
  • Geochemistry and Petrology
  • Earth-Surface Processes
  • Atmospheric Science
  • Earth and Planetary Sciences (miscellaneous)
  • Space and Planetary Science
  • Palaeontology

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