The behaviour of platinum-group elements during magmatic differentiation in Hawaiian tholeiites

Concentrations of platinum-group elements (PGEs) and gold in basalts from K ilauea and Mauna Loa, Hawaii, were determined by ICP-MS, using an improved fire-assay and tellurium coprecipitation technique for preconcentrating the metals. Major and trace elements, together with Pb-Sr isotope compositions of basalt samples confirmed that these samples are typical Hawaiian tholei ites. The abundances of the PGEs and Au in Hawaiian tholeiites are rather c onstant during magmatic differentiation processes, whereas MORBs show stron g fractionation of those elements. The distinctive behaviour of these PGEs in Hawaiian tholeiites cannot be explained solely via, fractionation of tho se elements by separation of crystallizing phases such as chromite, olivine and clinopyroxene. Oversaturation of sulfur and separation of sulfides fro m magmas are required for elucidating PGEs and Au concentrations in Hawaiia n tholeiites.