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

Abstract

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.

Hydrothermal Alteration on Composite Volcanoes: Mineralogy, Hyperspectral Imaging, and Aeromagnetic Study of Mt Ruapehu, New Zealand

“…The abundance of goethite, and its confinement to higher flanks, can also be attributed to Ruapehu's extensive glacial history (Cole et al, 2020). The chemical weathering occurring beneath glaciers is primarily driven by microorganic activity, thriving on meltwater solution rich in oxidized pyrite, silica, and SO 4 2− anions (Mitchell et al, 2013; Rutledge et al, 2018), which can form extensive goethite by interacting with magnetite content of the host rocks on the surface.…”

Toward the geological significance of hydrated silica detected by near infrared spectroscopy on Mars based on terrestrial reference samples

“…Minitti et al, 2007;Chemtob et al, 2010, Seelos et al, 2010, coatings in proglacial environments (e.g. Hallet, 1975;Rutledge et al, 2018), and more opal-A/CT samples of geyserites and silica sinters from various locations (from geyser vents to discharge aprons). One crucial point will be to examine carefully the effect of temperature of formation of hydrated silica on its spectroscopic properties in a single geological context.…”

Nanoscale Variations in Natural Amorphous and Nanocrystalline Weathering Products in Mafic to Intermediate Volcanic Terrains on Earth: Implications for Amorphous Detections on Mars

“…The nature of the climate during the late Noachian/early Hesperian epochs on Mars is not well understood, and might have varied between "warm and wet" and "cold and icy/wet" periods (e.g., McLennan et al, 2019). In order to address the two potential climate endmembers, our sample suite consists of soils from "warm and wet" climates on the island of Hawai'i (Chadwick et al, 1999;Ziegler et al, 2003), "cold and wet" climate glacial sediments from the Three Sisters volcanic complex, Oregon (Rutledge et al, 2018;Scudder et al, 2021), and volcanic paleosols (lithified soil horizons) from the John Day Fossil Beds National Monument, Oregon SMITH AND HORGAN 10.1029/2020JE006769 weathered under a range of conditions from cool to warm (Retallack et al, 1999). The paleosol samples were chosen to test the hypothesis that amorphous and nanocrystalline materials do not survive diagenesis.…”