Conditions, timescales and cosmochemical evolution during the early accretion of terrestrial planets

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The most important differentiation event to affect the terrestrial planets was their segregation into metallic Fe-rich cores and silicate mantles. The concentrations of a wide range of both siderophile and lithophile elements in planetary mantles provide major constraints on the conditions of core formation and the composition of the accreting material as a function of time. We have shown recently that a multi-stage model in which core formation occurs progressively, as the consequence of impacts between the proto-Earth and smaller differentiated bodies, can best reproduce mantle geochemistry. In this project we will further develop this preliminary model using a multi-disciplinary approach by (a) integrating it with the results of N-body accretion simulations, (b) including the Hf-W isotopic system in the model to provide additional constraints on timing and disequilibrium processes, and (c) obtaining new experimental partitioning data for silicon, oxygen and the volatile elements Sb, Pb, Cu, Sn, Ge, P, Ag and As. The latter studies will enable a large number of new elements to be included in the core formation/accretion models and will enable the mechanisms and timing of volatile element accretion to the terrestrial planets to be investigated.