HR: 08:15h
AN: U41A-02    [PDF]
TI: Progress in the Development of Techniques for Detection of Chemical Interactions Between the Core and Mantle
AU: * Walker, R J
EM: rjwalker@geol.umd.edu
AF: Richard J Walker, Department of Geology, University of Maryland, College Park, MD 20742 United States
AB: If some plumes arise from the core-mantle boundary and there is limited chemical interaction between the core and mantle within D", it is possible that these plumes could contain a unique chemical or iso-topic fingerprint that is characteristic of the core. Unequivocal identification of a core component in a plume could potentially settle a major question in geodynamics. The ideal tracers of a core component in a plume are elements that occur in very high abundance in the core relative to the mantle and crust. The most sensitive suite of elements for identifying possible core contributions to plumes that may arise from the core-mantle interface are the highly siderophile elements (HSE = Pt, Re, Os, Ir, Pd, Ru, Rh, Au ), and certain moderately siderophile elements such as Ag, W and Mo. Because of the extreme preference of the HSE for metal relative to sili-cates, the formation of the core nearly quantitatively sequestered the Earth's HSE, and also likely dominates the budget of moderately siderophile elements. Mass balance is potentially optimal for detection of core additions to the mantle. Isotopic systems are of greatest interest in prosecuting this task because characteristic isotopic signals may be immune to subsequent processing in the mantle or crust. Pros and cons in applications, and an overview of existing data will be presented, primarily focusing on the Pt-Re-Os coupled system and the short-lived $^{182}$Hf -$^{182}$W system. Although resolution of isotopic differences may currently be insufficient, W isotopes provide the best complement to Os isotopes in the search for a core component.
DE: 1000 GEOCHEMISTRY (New field, replaces Rock Chemistry)
DE: 1010 Chemical evolution
DE: 1025 Composition of the mantle
DE: 1040 Isotopic composition/chemistry
SC: U
MN: 2003 Fall Meeting