EXPLORING THE CHEMICAL BEHAVIOR OF PLATINUM GROUP ELEMENTS

Currently, two competing hypotheses describe how the platinum group elements (PGEs) are deposited as ore in large igneous bodies deep, known as layered mafic intrusions, in Earth's crust. The first model calls upon the precipitation of sulfides which sequester PGEs from the melt and settle gravitationally to the bottom of the magma chamber where they form laterally extensive stratabound PGE deposits. The second model calls upon the exsolution of an aqueous fluid which scavenges PGEs from the melt and then the aqueous fluid ascends buoyantly through the magma where precipitation of PGEs occurs owing to water-rock reaction and changes in pressure and temperature. Both theories suffer from a lack of data about the diffusivity and partitioning of PGEs in silicate magmas at the pressures and temperatures found in nature. In this study we are experimentally determining the diffusivity of platinum, as a proxy for other PGEs, in order to understand better the mobility of PGEs in the melt and how this affects the two models for PGE-deposit formation.