Melt Generation Below Continents in Diffuse Igneous Provinces

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Intellectual merit. A comprehensive uranium-series (U-series) isotope study is proposed to understand the origins of young (10,000 years, or, 10 kyr) continental lavas from East Asia. Widely dispersed intraplate volcanism in East Asia is distinct from large-volume basaltic eruptions at Large Igneous Provinces by virtue of its greater compositional diversity, lower rate of melt production, and lack of evidence for deep mantle plumes. Preliminary U-Th disequilibrium data of the young lavas from East Asia suggest that the young lavas from East China display significant 230Th excesses whereas the young lavas from SE Tibet show strong 238U excesses. We propose to analyze U-Th disequilibrium in additional samples to test the generality of these results. U-Pa and Th-Ra disequilibria, together with Nd, Sr and Pb isotopic compositions and trace element concentrations, will also be measured. Modelling of these data will help constrain process of melt generation and transportation. The proposed research addresses fundamental questions concerning the mechanisms of melt generation below continents in diffuse igneous provinces, and specifically the relative roles of lithosphere and asthenosphere mantle sources in the context of active geodynamic settings in East China and SE Tibet.Broader impacts. These include collaborations between UCLA, WHOI, and Chinese Bureau of Seismology. Secondly, this project will support the research of an early-career principal investigator, and would foster the educational development of one or two UCLA undergraduates. Third, quantitative geochemical models developed from the project are going to be available to the community of petrology and geochemistry.