Slab-derived devolatilization fluids oxidized by subducted metasedimentary rocks

Abstract Metamorphic devolatilization of subducted slabs generates aqueous fluids that ascend into the mantle wedge, driving partial melting produces arc magmas. These magmas have oxygen fugacities some 10–1,000 times higher than generated at mid-ocean ridges. Whether this oxidized magmatic character is imparted by slab or acquired during ascent and interaction with surrounding crust debated. Here we study petrology metasedimentary rocks from two Tertiary Aegean subduction complexes in combination reactive transport modelling to investigate oxidative potential sedimentary cover slabs. We find preserve evidence for fluid-mediated redox reactions could be highly oxidized. Furthermore, demonstrates layers these less about 200 m thick capacity oxidize ascending dehydration flux via remove H 2 , CH 4 and/or S fluids. can then overlying wedge rates comparable magma generation rates, primarily involving sulfur species. Oxidized need not generate large amounts fluid themselves but instead through them. Proposed Phanerozoic increases fugacity may reflect recycling weathering products following Neoproterozoic–Palaeozoic marine atmospheric oxygenation.