Seminar Antoine Bénard

Abstract

The magmatic transfer of sulfur and the chemically bonded chalcophile metals between the upper mantle and the crust is poorly understood. These are complex processes associated with redox reactions, especially in the case of platinum-group elements (PGE). I will show that sulfate liberated from the slab exerts a key control on metal release from the mantle wedge during magma generation at subduction zones. This view is supported by geochemical analyses of sub-arc mantle peridotites and numerical models. These results, however, question the origin of the PGE-depleted nature of the continental crust generated at subduction zones. Alkaline and carbonated magmas formed in an intraplate tectonic setting offer a window for further studies of sulfur and metal transport in the deeper mantle. I will present recent analytical and experimental data unveiling the conditions of a favorable transport of sulfur and metals in alkaline and carbonated magmas. This ongoing research requires new high pressure and high temperature experiments to determine key physicochemical properties, such as redox reactions and the solubility of sulfur and metals in magmas.