9316129 Mathez The large layered mafic complexes are important because they contain evidence for fundamental processes in igneous petrology and because several contain economic deposits of various metals, including the platinum group elements (PGEs). The essential question addressed by this project is what is the role of post-cumulus, magmatic processes, in particular metasomatism, in the formation of PGE-rich horizons. In order to investigate this question, two related studies will be conducted. The first involves a detailed study of trace element contents of pyroxene and other major phases of the Merensky reef and adjacent rocks in the Atok area, northeast Bushveld Complex. A second study involves the PGE-rich horizon of the Great Dyke. The horizon, which is known as the MSZ, exhibits a characteristic geochemical stratigraphic profile whereby the maximum concentrations of Ni, Cu, S and Au are found approximately 15 to 30 cm higher in the stratigraphy than the maximum concentrations of Pt, Pd and the other PGEs. A relationship will be sought between the profiles for the chalcophile elements and incompatible element contents of pyroxene, which again will be determined by ion probe. Se/S, As/S and Te/S ratios may help to distinguish whether the sulfides were concentrated by mainly cumulate or metasomatic processes.
