Physical Abrasion of Mafic Minerals and Basalt Grains: Application to Martian Aeolian Deposits
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Sediment maturity, or the mineralogical and physical characterization of sediment deposits, has been used to locate of sediment source, transport medium and distance, weathering processes, and paleoenvironments on Earth. Mature terrestrial sands are dominated by quartz, which is abundant in source lithologies on Earth and is physically and chemically stable under a wide range of conditions while immature sands, such as those rich in feldspars or mafic minerals, are composed of grains that are easily physically weathered and highly susceptible to chemical weathering. On Mars, which is predominantly mafic in composition, terrestrial standards of sediment maturity are not applicable. In addition, the martian climate today is cold, dry and sediments are likely to be heavily influenced by physical weathering instead of chemical weathering. Due to differences in weathering processes and composition, martian sediments require an alternate maturity index. Abrasion tests have been conducted on a variety of mafic materials and results suggest that mature martian sediments may be composed of very well sorted, well-rounded, spherical basalt grains with some volcanic glass and chemically altered products. A modified sediment maturity index is proposed that can be used in future studies to constrain sediment source, paleoclimate, mechanisms for sediment production, and surface evolution. This maturity index may also provide details about erosional and sediment transport systems and preservation processes of layered deposits.