Lithium Isotope Variation in Ocean Island Basalts: A Study of Magma Source and Mantle Heterogeneity

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Lithium isotope ratio is a relatively novel tracer that shows promise for tracking material recycling between crust and mantle. This research project is a comprehensive investigation to determine the lithium isotope variation in ocean islands of the south Pacific Ocean which harbors long-lived hotspot magmatism. The goal is to elucidate the source components and processes that generate the lithium isotope compositions of ocean island basalts and assess the degree of compositional heterogeneity in the deep mantle. The approach will be to study lithium isotopes in ocean islands that represent mantle end members as defined by radiogenic isotope compositions. The investigation will focus on three groups of islands (1) Pitcairn Island (Enriched Mantle I), (2) Samoan chain (Enriched Mantle II), and (3) Mangaia and Tubuai (high U/Pb mantle, HIMU). By studying the compositional extremes, we are likely to define the full range of isotopic composition of the mantle. The resulting database will permit testing of new working hypotheses in regard to the origin of the major mantle reservoirs, leading to a better understanding of the source material of the mantle plume, its interaction with shallow reservoirs, and the role of subduction process in mantle geochemistry and evolution. This study, which deals with mantle geochemistry, will be of broad interest to the researchers interested in arc magmatism and mantle evolution. The proposed research will be a collaborative effort with S. R. Hart (Woods Hole Oceanographic Institution) and E. Hauri (Carnegie Institute of Washington), and integrate research on different isotope and chemical systems.