Accomplishment-Based Renewal (ABR) - Rhenium-Osmium Isotope Study of the Mantle

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9909197WalkerThe proposed research is directed towards a better understanding of the geochemical behaviors of Re and Os in ultramafic-mafic systems, and examining and interpreting the Os isotopic compositions of reservoirs within both the modern and ancient mantle. Specific issues that Re-Os isotopes may be particularly useful in elucidating are: 1) the nature of material added to the Earth via late accretion, 2) the rate at which late accreted materials were homogenized throughout the mantle, 3) the nature and rate at which oceanic crust has been recycled back into certain plume sources, 4) the existence of, and level of chemical exchange between the mantle and outer core, 5) the chronology of the development of subcontinental lithospheric keels, and 6) the distribution of highly siderophile elements in various modern and ancient reservoirs. Much effort will be directed towards the assessement of, and use of separated phases as a means of determining primary magmatic Re-Os systematics. The resulting information should lead to a better understanding of how Os isotopic heterogeneities have developed in the mantle, and also further our knowledge about the evolution of highly siderophile elements in the Earth's mantle. These results may also provide additional constraints on the nature of highly siderophile elements in the mantle and early mantle mixing rates.