Platinum-group element contents of chromites from mafic–ultramafic layered flows, Abitibi greenstone belt, Ontario: implications for geochemical fractionation and mineral exploration |
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| Authors: | W E Stone J H Crocket |
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| Institution: | (1) Centre for Global Metallogeny, Department of Geology and Geophysics, University of Western Australia, Crawley, Australia, AU;(2) School of Geography and Geology, McMaster University, Hamilton, Ontario, Canada, CA |
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| Abstract: | Summary ?The PGE contents of chromite separated from peridotite layers of Archaean mafic–ultramafic flows, Abitibi belt (Canada),
indicate enrichment in Os–Ir–Ru (600 ppb) relative to Pd–Au (<5 ppb). Evidently, chromite was a sink for Ir–Os–Ru during melt-chromite
fractionation in each of the flows. However, an additional phase, probably olivine, is required to explain the bulk Ir content
of the sulphide-poor peridotites. In contrast, the chromite Pt contents range from <10 ppb to 400 ppb, with large variation
in Pt/Ru (0.02–2.76) and Pt/Pd (5–400) ratios. The Pt enrichment may be related to the presence of Pt spinel structure compounds
in oxidised melt, reflecting Fe–Ti spinel-related mineralisation in higher pyroxenite-gabbro layers.
Received December 5, 2002; revised version accepted January 7, 2003 |
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