Chalcophile-siderophile element systematics of hydrothermal pyrite from martian regolith breccia NWA 7533

Unlike other martian meteorites studied so far, Martian regolith breccia NWA 7533 and paired meteorites that have sampled 4.4 Ga-old impact lithologies show only sulfides of hydrothermal origin (mostly pyrite (1). The reasonably good positive correlation (R2 = 0.72) between Se and Ni reflects a temperature control on the solubility of both elements. Apart from the chalcogens S, Se and Te, pyrite appears to be a minor contributor (400 °C) temperature crystallization for NWA 7533 pyrite, as deduced from its Se and Ni contents, (ii) magmatic sulfide-depletion of brecciated early martian crust, (iii) precipitation from near neutral H2S-HS-H2O-rich hydrothermal fluids that did not provide halogen ligands for extensive transport of chalcophile-siderophile metals. It is suggested that the 1.4 Ga lithification event that precipitated hydrothermal pyrite left the chalcophile-siderophile element budget of the early martian crust nearly unmodified, except for S, Se and Te.