Mantle wedge oxidation from deserpentinization modulated by sediment-derived fluids

High-pressure dehydration of serpentinite during subduction generates fluids that flux and melt the overlying mantle wedge, forming primary arc basalts. These basalts are substantially more oxidized than their mid-ocean ridge counterparts. At slab surface current zones, these deserpentinization intrinsically oxidized, but, owing to low sulfur content subducted serpentinite, they only result in a wedge oxidation rate, which cannot account for source Here we show infiltration sediment-derived modulates can drastically change capacity fluids. The modulation mostly depends on stability abundance dissolved aqueous species redox-sensitive elements—notably sulfate—and not solely state sediment. Infiltration CH4-bearing derived from graphite-bearing sediment reduces high oxidant fluids, explaining relatively fO2 observed natural metaperidotite. sulfate-CO2-bearing, fluids—prevalent modern zones—generates with cold hot resulting global rate 3.5 km3 yr?1. Such will oxidize at similar arc-basalt generation thus nature volcanism. highly magmas may rely contain species—notably sulfate—into according thermodynamic modelling.