Glacial weathering of geologic materials contributes to the solute flux in meltwater, provides feedback in the global carbon cycle, and is a potential source of energy to chemotrophic microbes. It is important to understand the weathering processes occurring in these environments and to identify the composition of associated alteration products at local and regional scales. The majority of past glacial alteration studies have focused on weathering of silicic or carbonate bedrock, leading to a gap in our knowledge of how glaciers interact with mafic rock such as basalt and basaltic andesite. Understanding mafic rock alteration is particularly important when studying planetary processes, such as the chemical effects of ice on the surface of Mars.
This talk will report on new field studies of glacial weathering in volcanic environments in the Oregon Cascade Range. We utilize aqueous geochemistry, field spectroscopy, and remote sensing to understand the alteration processes occurring on mafic bedrock. We propose that weathering in climates dominated by snow melt, glacial, and periglacial processes produces distinctive water chemistries and mineral assemblages dominated by silica and amorphous mineraloids, which are highly relevant to planetary studies.