Osmium Isotope and Highly Siderophile Element Abundance Studies of Mantle Sources Sampled by Ocean Island Basalts

海洋岛玄武岩（OIB）地幔源样品的锇同位素和高亲铁元素丰度研究研究活动的知识价值：该项目将解决一个基本问题，即高亲铁元素（HSE = Os, Ir, Ru, Rh, Pt, Pd, Re, Au）和Sr-Nd-Os-Pb同位素的分选是否可用于确定某些海洋岛玄武岩（OIB）地幔源中存在的明确的回收或原始物质。夏威夷和西加那利岛熔岩的数据表明这是可能的，但需要更多的数据来充分验证这一假设。对地幔中的HSE行为，特别是OIB来源的了解有限，并且许多OIB样品缺乏Os同位素数据，而Sr-Nd-Pb同位素数据可用。因此，收集OIB熔岩的新的Os同位素和HSE丰度数据是更好地了解地幔非均质性的重要任务。该项目将；(1)进一步限定了OIB地幔源187Os/188Os的变化范围；(2)确定Os同位素和HSE丰度是否可以用来约束地壳和岩石圈回地幔的再循环；(3)较好地界定了OIB地幔源中HSE的分布。来自加那利群岛东部（戈梅拉岛、特内里费岛、大加那利岛、富埃特文图拉岛、兰萨罗特岛）、库克群岛（曼加亚岛、阿提乌岛、拉罗汤加岛）和马斯卡伦群岛（毛里求斯的r<s:1> union岛）的火山岩将使用最先进的分析技术系统地检查岩石学、矿物学、全岩主要元素和微量元素丰度、HSE （Os、Ir、Ru、Pt、Pd、Re）丰度和Sr-Nd-Os-Pb同位素系统。之所以选择这些岛屿进行研究，是因为有强有力的证据表明，它们的地幔来源中存在回收（加那利群岛、曼加亚岛、阿提乌岛）或原始（Mascarene群岛、拉罗汤加岛）的物质，而且本研究已经掌握了适当的样本。新的数据将用于评估地壳污染对地幔非均质性的影响，并模拟本地地幔源中再循环物质的性质和比例。建议活动的更广泛影响：培训和教学的组成部分是建议的一个强有力的主题，研究生和本科生直接参与。该项目将作为一名研究生博士论文的核心，并将为一些本科生提供高度可转移的定量分析和沟通技巧。参与该项目的学生将在几种最先进的分析技术方面获得丰富的经验，研究生将参加实地工作，接受实地方法的培训。该提案还将支持最近任命的早期职业非终身助理教授（开始日期，2011年1月）。研究成果将被纳入斯克里普斯海洋学研究所的课堂讲座和探究式学习活动。该项目的推广将包括在科学和公共领域的贡献，通过教育网站材料，在圣地亚哥地区的高中演讲和公共活动。

Osmium isotope and highly siderophile element abundance studies of mantle sources sampled by ocean island basaltsIntellectual merit of the proposed activity: This project will address the fundamental question of whether fractionation of highly siderophile element (HSE = Os, Ir, Ru, Rh, Pt, Pd, Re, Au) and Sr-Nd-Os-Pb isotopes can be used to identify unambiguously recycled or primitive materials present in some ocean island basalt (OIB) mantle sources. Data for Hawaiian and western Canary Island lavas suggest this is possible, but more data are required to test this hypothesis fully. Understanding of HSE behavior in the mantle, and in the sources of OIB in particular, is limited, and Os isotope data are lacking for many OIB samples for which Sr-Nd-Pb isotope data are available. Collection of new Os isotope and HSE abundance data on OIB lavas is therefore an important task for better understanding of mantle heterogeneity. The project will; (1) provide further constraints on the range of variation of 187Os/188Os in OIB mantle sources; (2) establish whether Os isotopes and HSE abundances can be used to constrain recycling of crust and lithosphere back into the mantle; and (3) better define the distribution of HSE in OIB mantle sources. Suites of lavas from the eastern Canary Islands (La Gomera, Tenerife, Gran Canaria, Fuerteventura, Lanzarote), Cook Islands (Mangaia, Atiu, Rarotonga), and Mascarene Islands (Réunion, Mauritius) will be systematically examined for petrology, mineralogy, whole-rock major- and trace-element abundances, HSE (Os, Ir, Ru, Pt, Pd, Re) abundances, and Sr-Nd-Os-Pb isotope systematics using state-of-the-art analytical techniques. These islands were selected for study because there is strong prior evidence for recycled (Canary Islands, Mangaia, Atiu) or primitive (Mascarene Islands; Rarotonga) material in their mantle sources, and appropriate samples are in hand for this study. New data will be used to assess effects of crustal contamination versus mantle heterogeneity, and to model the nature and proportions of recycled material in local mantle sources. Broader Impacts of the proposed activity: Components of training and teaching are a strong theme of the proposal, with direct involvement of graduate and undergraduate students. The project will serve as the core of a PhD thesis for a graduate student, and will equip a number of undergraduates with highly transferable quantitative analytical and communication skills. Students involved in this project will gain extensive experience in several state-of-the-art analytical techniques, and the graduate student will participate in fieldwork, receiving training in field methods. This proposal will also support a recently appointed early-career non-tenured Assistant Professor (start date, January, 2011). Research results will be incorporated into classroom lectures and in inquiry-based learning activities at Scripps Institution of Oceanography. Outreach for the project will include contributions at both scientific and public-domain levels, through educational website material, and in talks at high schools and public events in the San Diego area.