Multiple Approaches to Study of the Hafnium Isotope Evolution of the Crust and Mantle: 4.3 b.y. ago to Present

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The proposed work involves three parts aimed at the study of crust-mantle evolution from 4.3 Ga to present, all of which use Hafnium isotope variations as the common theme. The projects we have chosen reflect a balance between identification of key localities and sample suites and areas of research in which the PI and Co-PI have extensive experience. Our investigations of the sub-continental mantle focus on sites which represent major, rapidly- developed thermal anomalies in the mantle that involved various contributions from plume, depleted mantle, and lithospheric mantle. Work on the earliest differentiation of the Earth concentrates on integrated Nd, Hf, and U/Pb isotope work on the oldest terrestrial materials: 4.3 to 4.0 Ga zircons from western Australia and the 4.0 Ga Acasta Gneiss, NWT Canada. Investigations of crust-mantle recycling focus on the Penokean Orogen in Wisconsin through whole-rock/mineral Nd and Pb and combined Nd, Hf, and U/Pb isotope analysis of inherited, Proterozoic, and Archean zircons. This work represents a collaborative effort with 11 other researchers at seven institutions.