Geochemical and climatic controls on the sulfur cycle in volcanic settings: Implications for the origin of sulfur-rich deposits investigated by the Spirit and Opportunity rovers on Mars
On Earth, volcanic activity with elevated sulfur (S) degassing in the presence of water leads to the formation of hydrothermal deposits enriched in S-bearing minerals. Similar processes may have been an important source of S on Mars. The landing sites of Gusev crater and Meridiani Planum investigate...
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TRACE: Tennessee Research and Creative Exchange
2022
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| Online Access: | https://trace.tennessee.edu/utk_graddiss/7661 https://trace.tennessee.edu/cgi/viewcontent.cgi?article=9006&context=utk_graddiss |
| Summary: | On Earth, volcanic activity with elevated sulfur (S) degassing in the presence of water leads to the formation of hydrothermal deposits enriched in S-bearing minerals. Similar processes may have been an important source of S on Mars. The landing sites of Gusev crater and Meridiani Planum investigated by the Spirit and Opportunity rovers, respectively, showed elevated SO42- [sulfate] concentrations, suggesting high- and low-temperature aqueous processes. However, the SO42- contribution from subsequent aqueous weathering of hydrothermal S deposits has been poorly constrained, thus its importance to regional S cycling in the landing sites is unclear. In this study, geochemical and hydrological approaches were used to determine sediment and aqueous S sources in terrestrial volcanic terrains at local and regional scales. The results of local scale studies in Iceland and the U.S. showed that hydrothermal sediments are typically enriched in elemental S (~0.3-22 wt.% S) with minor sulfide (~0.1-3.9 wt.% S) and sulfate (~0.1-2.7 wt.% S), and their concentrations decrease in wet climates. Sulfur isotopes suggested that subsequent oxidation of elemental S and sulfide to SO42- is controlled by water-rock interactions under varied temperatures and oxidant availability (O2 [oxygen]/Fe3+ [ferric iron]). Despite the prevalence of sulfate minerals rather than elemental S/sulfides in the hydrothermal deposits of Gusev crater, the total S concentration is comparable to those formed in coastal Iceland. It is inferred that complete oxidation of Gusev hydrothermal deposits to SO42- took place later under low water-to-rock conditions with little S emission. The results of regional scale studies in Hawaii and Iceland showed that significantly higher SO42- loads (~20-260 tons/yr/km2) occur in aqueous systems on younger, wetter volcanic terrains with active hydrothermal S degassing and mineralization. Conversely, smaller SO42- loads (~2.1-10 tons/yr/km2) occur in older, drier and non-active terrains. Comparison of terrestrial SO42- loads ... |
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