“…In some cases, sulfur is present in convergent zone magmas during various stages of their evolution beneath arc volcanoes [89,90], while on other occasions, sulfides are formed in differentiating arc melts through the assimilation of graphite-bearing crustal rocks and reduction in the initially oxidized arc basalt magma [87]. Under all these petrologic scenarios, gold is accumulated in differentiated arc basalts and late-stage residual magmatic liquids in subduction zone environments to the point of metal saturation during the advanced fractionation of convergent zone magmas, which may, in turn, trigger the formation of gold-rich globules and micro-nuggets [20,65,75] as well as the crystallization of gold-bearing intermetallic compounds [36,54] during late-stage magmatic differentiation processes in the upper island-arc crust. According to several experimental studies, the crystallization of noble metal compounds (assemblages) during crustal differentiation of convergent zone magmas occurs under oxidized conditions, which is inconsistent with our observations from natural systems in subduction-related environments within the Lesser Khingan and Stanovoy Ranges of the Russian Far East [19,36,65,75].…”