The Role of Sulphur on the Melting of Ca-Poor Sediment and on Trace Element Transfer in Subduction Zones: An Experimental Investigation

Abstract We performed phase equilibrium experiments on a natural Ca-poor pelite at 3 GPa, 750–1000°C, under moderately oxidizing conditions, simulating the partial melting of such lithologies in subduction zones. Experiments investigated effect sulphur addition equilibria and compositions, with S contents up to ∼ 2.2 wt. %. Run products were characterized for their major trace element contents, order shed light role patterns melts produced by oceanic sediments. Results show that leads replacement phengite biotite along progressive consumption garnet, which is replaced an orthopyroxene-kyanite assemblage highest content investigated. All Fe-Mg silicate phases sulphur, including melt, have higher MgO/(MgO+FeO) ratios (relative S-free/poor conditions), owing Fe being primarily locked sulphide redox range. Secular infiltration mantle wedge MgO K2O-rich may contributed Mg K-rich character modern continental crust. Addition does not affect significantly stability main accessory controlling behaviour elements (monazite, rutile zircon), although our results suggest monazite solubility sensitive conditions The low temperature (∼ 800 °C) S-bearing sediment sourced slab Th La abundances, Th/La systematics HFSE signatures agreement characteristics sediment-rich arc magmas. Because high diminish garnet stabilities, S-rich Rb, B, Li (to lesser extent), HREE. La/Yb are observed sulphur-poor runs (with proportion retains HREE) beyond out curve (which LREE). Sulphides appear be relatively Pb-poor impart Pb/Ce ratio coexisting melts, even content. Overall, Phanerozoic magmas from flux margins owe geochemical signature terrigenous, sometimes S-rich, In contrast, during Archean appears unlikely or unrecorded.