New bulk sulfur measurements of Martian meteorites and modeling the fate of sulfur during melting and crystallization - Implications for sulfur transfer from Martian mantle to crust-atmosphere system

Sulfur storage and transport between different reservoirs such as core, mantle, crust and atmosphere of Mars are tied to igneous processes. Martian meteorites carry a record of mantle melting and subsequent differentiation history of Martian magmas. Investigation of S geochemistry of Martian meteorites can thus provide an understanding of how S is transferred from the Martian interior to the exosphere. In this study we measured bulk S concentration of 7 Martian meteorites and modeled the behavior of S during both isobaric crystallization of primary Martian magmas and isentropic partial melting of Martian mantle. Comparisons between measured data and modeled results suggest that (1) sulfides may become exhausted at the source during decompression melting of the mantle and mantle-derived basalts may only become sulfide-saturated after cooling and crystallization at shallow depths and (2) in addition to degassing induced S loss, mixing between these differentiated sulfide-saturated basaltic melts and cumulus minerals with/without cumulate sulfides could also be responsible for the bulk sulfur contents in some Martian meteorites. In this case, a significant quantity of S could remain in Martian crust as cumulate sulfides or in trapped interstitial liquid varying from 2 to 95 percent by weight. Our modeling also suggests that generation of sulfide-undersaturated parental magmas requires that the mantle source of Martian meteorites contain <700-1000 ppm S if melting degree estimation of 2-17 wt.% based on compositions of shergottites is relevant.