A Thermal-Mechanical and Hafnium Isotope View of the Interplay Between Continental Extension and Magmatism -The Death Valley Volcanic Field and Adjacent Volcanic Sequences

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9506612 Johnson The proposed work will develop new thermal and mechanical melting models to explain the mantle dynamics that occur during continental extension, and tie these to new observations on the chemical, isotopic, and temporal evolution of extension related lavas (ERL) in the Death Valley volcanic field and adjacent areas. Recent work has cast doubt on simple, previously proposed models of crust-mantle evolution during large-scale extension of the crust. Preliminary isotope data, including Hf isotope analyses, provide important constraints on the depths of ancient and modern melting, metasomatism, and depletion events, and these data will be used to constrain thermal-mechanical models. The large and highly extended volcanic field at Death Valley provides an exceptional opportunity to constrain and evaluate extensional thermal/melting models of the mantle.