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

海岛玄武岩锂同位素变化：岩浆源与地幔异质性研究

• 批准号: 0439960
• 负责人: Lui-Heung Chan
• 金额: $ 15.98万
• 依托单位: Louisiana State University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2005
• 资助国家: 美国
• 起止时间: 2005-01-01 至 2007-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0439960&HistoricalAwards=false
• 关键词: Lithium; Isotope; Variation; Ocean; Island

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.

锂同位素比率是一种相对新颖的示踪剂，在追踪地壳和地幔之间的物质循环方面表现出了希望。本研究项目是对南太平洋长期存在热点岩浆活动的海岛的锂同位素变化进行的综合调查。目的是阐明产生洋岛玄武岩锂同位素组成的来源成分和过程，并评估地幔深部成分的不均匀程度。办法将是研究海洋岛屿中的锂同位素，这些岛屿代表由放射性同位素组成界定的地幔末端成员。调查将集中在三组岛屿(1)皮特凯恩岛(富集地幔一号)，(2)萨摩亚链(富集地幔二号)，和(3)曼加亚和图布艾岛(高U/铅地幔，HIMU)。通过对组成极端的研究，我们有可能确定地幔的全部同位素组成。由此产生的数据库将能够检验有关主要地幔储集层起源的新的工作假说，从而更好地了解地幔热柱的来源物质、其与浅层储集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。这项涉及地幔地球化学的研究将引起对弧岩浆作用和地幔演化感兴趣的研究人员的广泛兴趣。这项拟议的研究将与伍兹霍尔海洋研究所(S.R.Hart)和华盛顿卡内基研究所(E.Hauri)合作，整合不同同位素和化学系统的研究。