Open system fluid-assisted sulfide dissolution reaction triggers explosive volcanic eruptions and can control production of metallogenic provinces

Abstract Explosive eruptions are frequently triggered by mixing of contrast-type magmas such as mantle-derived basaltic magmas with hydrous silica-rich magmas. Up to date, the mechanisms and rates of reaction of sulfide dissolution in hydrous silica-rich melt are unknown. I experimentally model dissolution of pyrrhotite mineral in water-saturated hydrous rhyolite melt at conditions corresponding to sulphate-sulfide transition field. The reaction results in production of FeO(melt) and SO42- and H2, H2S and di- and trisulfur radical ions, S2- or S3- in fluid/melt. The calculated diffusion coefficient for the oxidized sulfur dissolved in the hydrous rhyolitic melt implies extremely fast sulfur diffusion in the hydrous hybrid melt. Hybridization and magma mixing are controlled by the fastest ever recorded chemical diffusion of sulfur in the form of S2- or S3-, which is converted to [SO4]2- in the quenched glass and is associated with the production of hybrid fluid saturated magma. The dissolution reaction of the lower crust-to-mantle-crust transition zone-derived sulfides can trigger explosive volcanic eruptions not only in volcanic arcs but also in hot spot geodynamic settings. The fluid-assisted sulfide dissolution reaction can also control production of chalcophile (Au, Ag, Cu, Mo and Pt) metallogenic provinces.