Silica Dissolution and Precipitation in Galciated Volcanic Environments and Implications for Mars

Rutledge, A M ; Horgan, B H N ; Havig, J R ; Rampe, E B[Point of Contact] ; Scudder, N A ; Hamilton, T L

关键词: GEOCHEMISTRY;    GLACIERS;    ICE ENVIRONMENTS;    MARS SURFACE;    SEDIMENTARY ROCKS;    SILICON DIOXIDE;    VOLCANOES;    WATER;    WEATHERING;   

RP-ID  :  JSC-E-DAA-TN59509

学科分类：天文学(综合)

美国|英语

来源: NASA Technical Reports Server

【 摘 要 】

The surface of Mars exhibits strong evidence for a widespread and long-lived cryosphere. Observations of the surface have identified phases produced by water-rock interactions, but the contribution of glaciers to the observed alteration mineralogy is unclear. To characterize the chemical alteration expected on an icy early Mars, we collected water and rock samples from terrestrial glaciated volcanics. We related geochemical measurements of meltwater to the mineralogy and chemistry of proglacial rock coatings. In these terrains, water is dominated by dissolved silica relative to other dissolved cations, particularly at mafic sites. Rock coatings associated with glacial striations on mafic boulders include a silica-rich component, indicating that silica precipitation is occurring in the subglacial environment. We propose that glacial alteration of volcanic bedrock is dominated by a combination of high rates of silica dissolution and precipitation of opaline silica. On Mars, cryosphere-driven chemical weathering could be the origin of observed silica-enriched phases.