The redistribution of platinum-group elements and platinum-group minerals in the weathered chromitites of the Lower and Middle Group chromitites of the Bushveld Complex and the mineralogical siting of Ru

The chromitite seams of the Lower Group (LG) and Middle Group (MG) of the Bushveld Complex in South Africa contain elevated Pt and Pd concentrations. So far, only limited work has been done on the distribution of platinum-group elements (PGE) and platinum-group minerals (PGM) in these ores. In particular, the knowledge about the effects of weathering of PGM and the redistribution of PGE in these ores are rare. Previous studies showed that the main PGM are PGE-sulfides (cooperite-braggite, malanite, laurite), followed by PGE-sulfarsenides, sperrylite and Pt-Fe alloys. During weathering PGM are largely destroyed and only relict PGM are observed. Platinum-group minerals are weathered along small cracks and neo-formation of PGM may take place. Additionally, the mineralogical siting of Ru within chromitites is studied here. It was shown by LA-ICP-MS work that chromite can host some 100s-ppb of Ru.