This project is to investigate the accretion of the Earth and the separation of the Earth's core and crust from the Earth's mantle, by analyzing well characterized samples from different geochemical reservoirs with neutron activation analysis for the moderately siderophile and chalcophile trace elements Mo, W, As, and Sb, and by determination of metal/silicate partition coefficients for As and Sb. The varying depletion relative to elements with different affinities for Fe-metal or sulfide provide clues to the events involving accretion and metal segregation in the mantle, including the possibility of late veneers that accreted on the Earth after core formation, or the possibility of metal retention in the mantle during core formation. Determining the abundances and depletion of these elements un samples from terrains of different geological ages will also address the timing of core formation in the Earth, because the possibility of continued core formation through a substantial portion of geologic time has been invoked to explain some of the recent lead isotope results for samples from the mantle.
