Highly siderophile element geochemistry of mantle pyroxenites

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Abundances of highly siderophile elements (HSE, which include rhenium, gold and the plati-num group elements) in the Earth’s mantle may yield constraints on the influence of core formation and late accretion processes. This approach, however, requires a good understanding of the distribution and behaviour of these elements during magmatic processes in the Earth’s mantle such as partial melting, melt migration and crystal fractionation. Pyrox-enites are a minor lithology in the mantle, but may play a key role in understanding mantle evolution and formation of basaltic magmas. Elevated abundances of some HSE in mantle pyroxenites indicate their relevance for redistribution of these elements in the mantle. Here we propose to study the abundance systematics of HSE and the composition of radiogenic isotopes (187Os, 87Sr, 143Nd) in pyroxenites in order to shed light on the processes that control HSE abundances in basalts, how HSE redistribute during magma transport in the mantle, to evaluate the relative partitioning of different HSE, and to assess the role of sulfide in HSE fractionation during the formation of mantle pyroxenites.