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

锂同位素比率是一种相对较新的示踪剂，有望用于跟踪地壳和地幔之间的物质循环。本研究项目是对南太平洋存在长寿命热点岩浆活动的海洋岛屿进行锂同位素变化的综合调查。目的是阐明洋岛玄武岩锂同位素组成的源组分和生成过程，并评估深地幔中锂同位素组成的非均质性程度。该方法将研究海洋岛屿中的锂同位素，这些岛屿代表由放射性成因同位素组成定义的地幔端成员。重点研究3组岛屿(1)Pitcairn岛（富地幔I）， (2) Samoan链（富地幔II）， (3) Mangaia和Tubuai（高U/Pb地幔，HIMU）。通过研究极端成分，我们有可能确定地幔同位素组成的全部范围。由此产生的数据库将允许测试关于主要地幔储层起源的新的工作假设，从而更好地了解地幔柱的来源物质，它与浅层储层的相互作用，以及俯冲过程在地幔地球化学和演化中的作用。这项研究涉及地幔地球化学，将对研究弧岩浆作用和地幔演化的研究人员产生广泛的兴趣。拟议的研究将与S. R. Hart（伍兹霍尔海洋研究所）和E. Hauri（华盛顿卡内基研究所）合作，并整合不同同位素和化学系统的研究。

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.