The formation of alluvial platinum-group minerals: present knowledge and the way ahead

Abstract The weathering of platinum-group element (PGE) deposits presents unusual problems, especially in the very active environment lateritic under tropical conditions. There is clear evidence destruction minerals (PGM) to form PGE oxides, or fine intergrowths between relict PGM and iron oxides hydroxides, as an intermediate stage during weathering. released by are transported solution with more soluble Pd species remaining travelling further than less Pt species. presence laterite differing mineralogy, mineral assemblage size from those primary rock difficult explain, when they show secondary textures. Differing interpretations have created controversy. Are alluvial derived unaltered where rare and, therefore, not encountered standard petrographic examination? Is it possible that could developed some process we do yet fully understand? Some favourable genetic conditions been outlined debated. For 100 years authors reported ore textures recently proposed a biogenic origin. Frank Reith his co-workers provided involving metallophillic bacteria which, for first time, demonstrates growth laboratory supergene Their work shows mechanism (‘neoformation’) can occur, which offers new field study appropriate Eh, pH, $f_{{\rm O}_ 2}$ organic bacterial reactions permit growth.