Platinum-group element contents of chromites from mafic-ultramafic layered flows, Abitibi greenstone belt, Ontario: implications for geochemical fractionation and mineral exploration

Bill Stone, J.H. Crocket

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    The PGE contents of chromite separated from peridotite layers of Archaean maficultramafic 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.
    Original languageEnglish
    Pages (from-to)139-147
    JournalMineralogy and Petrology
    Publication statusPublished - 2003


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