In situ determination of platinum properties in sulfur-rich carbonate melts

Chalcophile metals are bonded to sulfur (S) in magmas, which is the key player in mass transfers of these elements between the Earth’s major silicate reservoirs (mantle and crust). Geochemical studies of mantle-derived magmas suggest S recycling processes from the surface to the mantle and back again. Geophysical methods indicate the widespread occurrence of potentially S-rich, carbonate magmas in the mantle. Yet, a major gap in our knowledge concerns the properties of metals and S in carbonate melts (i.e. speciation and solubility), which control geochemical transport. We propose to shed light on metal and S cycling on Earth, using unprecedented X-ray spectroscopic measurements to determine these properties in situ. The results will provide novel quantitative constraints on the modes and extents of metal and S transfer in the mantle. They will modify our current views of these cycles and the processes forming critical metal deposits in the crust.