COH-fluid induced metasomatism of peridotites in the forearc mantle

Abstract Devolatilization of subducting lithologies liberates COH-fluids. These may become partially sequestered in peridotites the slab and overlying forearc mantle, affecting cycling volatiles fluid mobile elements subduction zones. Here we assess magnitudes, timescales mechanism channelized injection COH-fluids doped with $${\mathrm{Ca}}_{\mathrm{aq}}^{2+}$$ Ca aq 2 + , $${\mathrm{Sr}}_{\mathrm{aq}}^{2+}$$ Sr $${\mathrm{Ba}}_{\mathrm{aq}}^{2+}$$ Ba into dry mantle by performing piston cylinder experiments between 1–2.5 GPa 600–700 °C. Cylindrical cores natural spinel-bearing harzburgites were used as starting materials. Based on mineral assemblage composition three reaction zones are distinguishable from rim towards core primary olivine orthopyroxene grains. Zone 1 contains carbonates + quartz ± kyanite zone 2 talc chlorite. Olivine is further replaced 3 either antigorite magnesite or within above stability, respectively. Orthopyroxene Mineral assemblages compositions secondary minerals depend silicate. The extent alteration depends CO content fluid/rock-ratio, promoted permeable driven cracking. Our results show that COH-fluid induced metasomatism self-perpetuating efficient at sequestering 2aq newly formed carbonates. This process fast 90% available C nearly 50% initial altered 650 °C, 55 h. dissolution silicates under high COH-fluid/rock-ratios, flow, enriches SiO fluid, while In an open system, remaining -depleted, Si-enriched aqueous cause Si-metasomatism away peridotite.