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

大洋岛玄武岩采样的地幔源的锇同位素和高亲铁元素丰度研究

• 批准号: 1116089
• 负责人: James Day
• 金额: $ 26.31万
• 依托单位: University of California-San Diego Scripps Inst of Oceanography
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2011
• 资助国家: 美国
• 起止时间: 2011-07-01 至 2015-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1116089&HistoricalAwards=false
• 关键词: Osmium; Isotope; Highly; Siderophile; Element

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.

大洋岛屿玄武岩样品中地幔源的锇同位素和高度亲铁元素丰度研究这个项目将解决的基本问题是，是否分馏的高度亲铁元素（HSE = Os、Ir、Ru、Rh、Pt、Pd、Re，Au）和Sr-Nd-Os-Pb同位素可用于确定某些洋岛玄武岩（OIB）地幔源区中存在的明确的再循环或原始物质。夏威夷和加那利岛西部熔岩的数据表明这是可能的，但需要更多的数据来充分验证这一假设。对HSE在地幔中的行为，特别是OIB来源的理解是有限的，并且对于许多OIB样品缺乏Os同位素数据，其中Sr-Nd-Pb同位素数据是可用的。因此，收集新的Os同位素和HSE丰度数据的OIB熔岩是一个重要的任务，以更好地了解地幔非均质性。该项目将;（1）进一步限制OIB地幔源中187 Os/188 Os的变化范围;（2）确定Os同位素和HSE丰度是否可用于限制地壳和岩石圈再循环回地幔;（3）更好地确定OIB地幔源中HSE的分布。 加那利群岛东部的熔岩群（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（Mangaia、Atiu、Rarotonga）和马斯卡林群岛（毛里求斯留尼旺）将进行系统的岩石学、矿物学、全岩主要和微量元素丰度、HSE（Os，Ir，Ru，Pt，Pd，Re）丰度和Sr-Nd-Os-Pb同位素系统学。之所以选择这些岛屿进行研究，是因为先前有强有力的证据表明，这些岛屿的地幔来源中存在回收（加那利群岛，Mangaia，Atiu）或原始（Mascarene群岛，Rarotonga）物质，并且有适当的样品可用于本研究。新数据将用于评估地壳污染对地幔异质性的影响，并模拟当地地幔来源中再循环物质的性质和比例。拟议活动的更广泛影响：培训和教学部分是该提案的一个重要主题，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转移的定量分析和沟通技能。参与该项目的学生将获得几种最先进的分析技术的丰富经验，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生涯非终身助理教授（开始日期，2011年1月）。研究结果将纳入课堂讲座和斯克里普斯海洋研究所的探究式学习活动。该项目的推广将包括通过教育网站材料在科学和公共领域两个层面上做出贡献，并在圣地亚哥地区的高中和公共活动中进行演讲。