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

拟议活动的智力优点：该项目将解决以下基本问题：能否利用高度亲铁元素(HSe=Os、Ir、Ru、Rh、Pt、Pd、Re、Au)和锶-钕-Os-铅同位素的分馏来确定某些洋岛玄武岩(OIB)地幔来源中明确存在的循环或原始物质。夏威夷和加那利岛西部熔岩的数据表明，这是可能的，但需要更多数据来全面检验这一假设。对地幔中的HSE行为，特别是对OIB来源的了解有限，许多OIB样品缺乏Os同位素数据，但有锶-钕-铅同位素数据。因此，收集新的OIB熔岩的Os同位素和HSE丰度数据是更好地了解地幔不均质性的一项重要任务。该项目将：(1)进一步限制海洋大洋协会地幔来源中187Os/188Os的变化范围；(2)确定是否可以利用Os同位素和高硒元素丰度来限制地壳和岩石圈回流回地幔；以及(3)更好地确定高硒元素在大洋协会地幔来源中的分布。来自加那利群岛东部(La Gomera、Tenerife、Gran Canaria、Fuerteventura、Lanzarote)、库克群岛(Mangaia、Atiu、Rarotonga)和马斯卡林群岛(毛里求斯的留尼旺岛)的熔岩套装将利用最先进的分析技术进行系统的岩石学、矿物学、全岩常量和微量元素丰度、HSe(Os、Ir、Ru、Pt、Pd、Re)丰度和锶-Nd-Os-Pb同位素系统学研究。之所以选择这些岛屿进行研究，是因为有强有力的先前证据表明，这些岛屿的地幔来源中存在回收的(加那利群岛、曼加亚、阿提乌)或原始的(马斯卡林群岛；拉罗通加)物质，并且有适当的样品可用于这项研究。新的数据将被用来评估地壳污染与地幔不均质性的影响，并对当地地幔来源中回收材料的性质和比例进行建模。拟议活动的更广泛影响：培训和教学的组成部分是提议的一个重要主题，研究生和本科生直接参与。该项目将作为研究生博士论文的核心，并将为一些本科生提供高度可移植的定量分析和沟通技能。参与这个项目的学生将在几种最先进的分析技术方面获得广泛的经验，研究生将参与实地工作，接受现场方法培训。这项提议还将支持最近任命的一名职业早期非终身助理教授(开始日期，2011年1月)。研究成果将纳入斯克里普斯海洋研究所的课堂讲课和探究式学习活动。该项目的宣传活动将包括在科学和公共领域两个层面作出贡献，通过教育网站材料，以及在圣地亚哥地区的高中演讲和公共活动中作出贡献。

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.