Gibbs Free Energy of Formation for Selected Platinum Group Minerals (PGM)

Abstract

Thermodynamic data for platinum group (Os, Ir, Ru, Rh, Pd and Pt) minerals are very limited. The present study is focused on the calculation of the Gibbs free energy of formation (ΔfG°) for selected PGM occurring in layered intrusions and ophiolite complexes worldwide, applying available experimental data on their constituent elements at their standard state (ΔG = G(species) − ΔG(elements)), using the computer program HSC Chemistry software 6.0. The evaluation of the accuracy of the calculation method was made by the calculation of (ΔGf) of rhodium sulfide phases. The calculated values were found to be ingood agreement with those measured in the binary system (Rh + S) as a function of temperature by previous authors (Jacob and Gupta (2014). The calculated Gibbs free energy (ΔfG°) followed the order RuS2 < (Ir,Os)S2 < (Pt, Pd)S < (Pd, Pt)Te2, increasing from compatible to incompatible noble metals and from sulfides to tellurides