Jarosite formation in deep Antarctic ice provides a window into acidic, water-limited weathering on Mars

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Authors

Giovanni Baccolo , Barbara Delmonte, Paul B. Niles, Giannantonio Cibin, Elena Di Stefano, Dariush Hampai, Lindsay Keller, Valter Maggi, Augusto Marcelli, Joseph Michalski

Abstract

Many interpretations have been proposed to explain the presence of jarosite within Martian surficial sediments, including the possibility that it precipitated within paleo-ice deposits owing to englacial weathering of dust. But until now a similar mechanism was not observed on Earth nor in other planetary settings. We report the first multi-analytical indication of jarosite formation within deep ice. Below 1000 m depth, jarosite crystals adhering on residual silica-rich particles have been identified in the Talos Dome ice core (East Antarctica) and interpreted as products of weathering involving aeolian mineral dust and acidic atmospheric aerosols. The progressive increase of ice metamorphism and re-crystallization with depth favours the relocation and concentration of dust and acidic brines in isolated environments, allowing chemical reactions and mineral neo-formation to occur. This is the first described englacial diagenetic mechanism occurring in deep Antarctic ice. It supports the ice-weathering model for jarosite formation on Mars, highlighting the geologic importance of paleo ice-related processes on this planet. Additional implications concern the preservation of dust-related signals in deep ice cores with respect to paleoclimatic reconstructions and the englacial history of meteorites from Antarctic blue ice fields.

DOI

https://doi.org/10.31223/osf.io/gc469

Subjects

Cosmochemistry, Earth Sciences, Geochemistry, Physical Sciences and Mathematics, Planetary Geochemistry, Planetary Glaciology, Planetary Sciences

Keywords

Antarctica, Acidic weathering, Jarosite, Mars, Mineral dust, Post-depositional processes

Dates

Published: 2020-05-20 15:23

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License

CC BY Attribution 4.0 International

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