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The shergottite meteorites are ultramafic to mafic igneous rocks whose parental magmas formed from partial melting of the martian mantle. This study reports in-situ laser ablation inductively coupled plasma mass spectrometry analyses for siderophile and chalcophile major and trace elements (i.e., Co, Ni, Cu, As, Se, Ag, Sb, Te, Pb, Bi, and the highly siderophile platinum-group elements, PGE: Os, Ir, Ru, Rh, Pt and Pd) of magmatic Fe-Ni-Cu sulfide assemblages from four shergottite meteorites. They include three geochemically similar incompatible trace element-(ITE-) depleted olivine-phyric shergottites (Yamato-980459, Dar al Gani 476 and Dhofar 019) that presumably formed from similar mantle and magma sources, and one distinctively ITE- enriched basaltic shergottite (Zagami). The sulfides in the shergottites have been variably modified by alteration on Earth and Mars, as well as by impact shock-shock related melting/volatilization during meteorite ejection. However, they inherit and retain their magmatic PGE signatures. The CI chondrite-normalized PGE concentration patterns of sulfides reproduce the whole-rock signatures determined in previous studies. These similarities indicate that sulfides exerted a major control on the PGE during shergottite petrogenesis. However, depletions of Pt ( and Ir) in sulfide relative to the other PGE suggest that additional phases such discrete Pt-Fe-Ir alloys have played an important role in the concentration of these elements. These alloys are expected to have enhanced stability in reduced and FeO-rich shergottite magmas, and could be a common feature in martian igneous systems. A Pt-rich PGM was found to occur in a sulfide assemblage in Dhofar 019. However, its origin may be related to impact shock-related sulfide melting and volatilisation during meteorite ejection. In the ITE-depleted olivine-phyric shergottites, positive relationships exist between petrogenetic indicators (e.g., whole-rock Mg-number) and most moderately to strongly siderophile and chalcophile elements in sulfides. These variations extend to incompatible elements like Te and Pd. The whole-rock concentrations of Pd derived from mass-balance calculations decrease by one order of magnitude in the order Y-980459, DaG 476 and Dhofar 019, and broadly overlap the trends in previously published whole-rock analyses. Mantle heterogeneities, and the timing of sulfide saturation as function of mantle melting and/or magma fractionation following ascent from the mantle, may have been the controlling factors of the siderophile and chalcophile element systematics in the analyzed shergottites.

Mantle-derived volcanic rocks on Mars display physical and chemical commonalities with mafic-ultramafic ferropicrite and komatiite volcanism on the Earth. Terrestrial komatiites are common hosts of massive sulfide mineralization enriched in siderophile-chalcophile precious metals (i.e., Ni, Cu, and the platinum-group elements). These deposits correspond to the batch segregation and accumulation of immiscible sulfide liquids as a consequence of mechanicalithermo-mechanical erosion and assimilation of sulfur-rich bedrock during the turbulent flow of high-temperature and low-viscosity komatiite lava flows. This study adopts this mineralization model and presents numerical simulations of erosion and assimilation of sulfide- and sulfate-rich sedimentary substrates during the dynamic emplacement of (channelled) mafic-ultramafic lava flows on Mars. For sedimentary substrates containing adequate sulfide proportions (e.g., 1 wt% S), our simulations suggest that sulfide supersaturation in low-temperature ( 1400 degrees C). The precious-metals tenor in the derived immiscible sulfide liquids may be significantly upgraded as a result of their prolonged equilibration with large volumes of silicate melts along flow conduits. The influence of sulfate assimilation on sulfide supersaturation in martian lava flows is addressed by simulations of melt-gas equilibration in the C-H-O-S fluid system. However, prolonged sulfide segregation and deposit genesis by means of sulfate assimilation appears to be limited by lava oxidation and the release of sulfur-rich gas. The identification of massive sulfide endowments on Mars is not possible from remote sensing data. Yet the results of this study aid to define regions for the potential occurrence of such mineral systems, which may be the large canyon systems Noctis Labyrinthus and Valles Marineris, or the Hesperian channel systems of Mars' highlands (e.g., Kasei Valles), most of which have been periodically draped by mafic-ultramafic lavas.

The Paleoproterozoic Baoule-Mossi domain of the southern West African Craton is regarded as the result of juvenile crust formation during the 2.3-1.9 Ga period. However, little is known about the complex processes that led to the formation of this highly metal endowed lithospheric block. Hence, in order to better constrain its geodynamic evolution, small catchments within modern drainage basins of the Niger and Bani Rivers were sampled for detrital zircons for U-Pb and Hf-isotope analyses, following TerraneChron (R) methodology. The study area stretches across southern Mali over 40,000 km(2) between the Yanfolila (west) and Syama (east) belts, from where more than 1000 zircons representing eight different sub-basins have been analyzed. The results of this study identified 2 main zircon age populations. The older population with ages between 3.6 and 2.7 Ga represents approximately 10% of the total of the analyzed zircons, and is mainly restricted to the western margin of the study area across the Yanfolila Belt sampling sites. The Hf-isotope data from this zircon population yielded model ages between 3.7 and 3.6 Ga and suggest a common evolution. Conversely, the main zircon population is dominated by Paleoproterozoic age zircons ranging between 2.4 and 2.1 Ga. Main peaks within this age group were identified at ca. 2161, 2121 and 2084 Ma, and minor peaks at ca. 2343, 2263 and 2200 Ma. The Hf-isotope data of this age group indicate that the zircons are derived from a mainly juvenile source, but were contaminated with crustal rocks potentially as old as 2.8 Ga. However, a group (approximately 10%) of Paleoproterozoic age zircons, which is interpreted to be the result of stream sediment transport from distal sources or the result of multiple cycles of sedimentation, displays a minor but significant older component, up to 4.0 Ga. This study also highlights the occurrence of >2.7 Ga detrital zircons, which are of an unknown source as no rock unit in the region has been identified to yield similar Archean ages. Moreover, some Paleoproterozoic zircons show Hf-isotope composition that indicates reworking of an older crustal component. Although zircons of the Baoule-Mossi domain generally confirm its juvenile origin, they also indicate reworking of an older crust at a much larger scale than previously recognized. The identification of Archean zircons in the region argues for greater interaction between the Baoule-Mossi domain and the Archean Kenema-Man domain.