Platinum group element geochemistry of submarine arc lavas associated with Cu-Au mineralization: Implications for modern VMS deposit exploration

Abstract

We investigated platinum group element (PGE) geochemistry of the two submarine lavasuites, which are related to magmatic hydrothermal mineralization, in order to understandtheir variations during magma differentiation and identify the timing of sulfide saturation.Both of the submarine lava suites show similar PGE geochemistry. Palladium behavesincompatibly during the early stage of magma differentiation whereas Pt, Rh, Ru and Irbehave compatibly, showing positive correlations with MgO (fractionation index). Thesetrends can be attributed to co-crystallization of Pt-alloy and Cr spinel. After prolongedmagma evolution, the concentrations of all of the PGE as well as Pd/Cu and Pd/Ptdecrease abruptly at ~3 % MgO, correlative with sulfide saturation. Late sulfide saturationresulted in the magmatic systems becoming enriched in ore metals such as Cu and Au bythe time of volatile saturation, which allowed the ore metals to partition into the exsolvedmagmatic gas and form magmatic hydrothermal deposits on the seafloor.iming of sulfide saturation.Both of the submarine lava suites show similar PGE geochemistry. Palladium behavesincompatibly during the early stage of magma differentiation whereas Pt, Rh, Ru and Irbehave compatibly, showing positive correlations with MgO (fractionation index). Thesetrends can be attributed to co-crystallization of Pt-alloy and Cr spinel. After prolongedmagma evolution, the concentrations of all of the PGE as well as Pd/Cu and Pd/Ptdecrease abruptly at ~3 % MgO, correlative with sulfide saturation. Late sulfide saturationresulted in the magmatic systems becoming enriched in ore metals such as Cu and Au bythe time of volatile saturation, which allowed the ore metals to partition into the exsolvedmagmatic gas and form magmatic hydrothermal deposits on the seafloor.