Magmatic and supergene evolution of the unconventional pirogues Pt mineralization in the New Caledonia ophiolite

Abstract : The New Caledonia ophiolite presents an unconventional Pt-Cr mineralization, located at the base of a magma chamber, itself presenting specific differences compared to the other cumulate sequences of the ophiolite. The primary mineralization and its magmatic environment are presented. The strong weathering having affected the mineralized zone has provoked a decoupling between the Cr and the Pt mineralization, with dissolution of the Pt minerals and their redistribution in the profile owing to heterogeneities in the porosity of the weathered profile. Moreover, weathering conditions having affected the PGM have locally provoked the formation of oxygen-bearing Pt-Fe grains according to a mechanism that will be proposed.