Rhenium-Osmium Isotope and Platinum Group Element Systematics of Lower Oceanic Crust

下洋地壳铼锇同位素和铂族元素系统学

• 批准号: 0337677
• 负责人: Bernhard Peucker-Ehrenbrink
• 金额: $ 29.97万
• 依托单位: Woods Hole Oceanographic Institution
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2004
• 资助国家: 美国
• 起止时间: 2004-01-01 至 2007-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0337677&HistoricalAwards=false
• 关键词: Rhenium; Osmium; Isotope; Platinum; Group

KelemenEAR-0337677Formation, alteration and subduction of oceanic crust are fundamental processes of Earth's ongoing chemical differentiation. The chemical transformations of oceanic crust from igneous accretion to subduction are of fundamental importance to constraining the chemical evolution of the Earth. While the chemical composition of upper oceanic crust has been studied using multiple shallow drill holes, our knowledge of middle and lower oceanic crust is limited to ophiolite sections and few drill holes into deeper oceanic crust. This project is aimed at investigating refractory cumulate gabbros and complementary lavas from well studied sections in the southernmost massifs in the Oman ophiolite, that overlap compositionally with the depleted end of the mid-ocean-ridge compositional spectrum. Two important hypothesis will be tested: 1) The lower oceanic crust is the main reservoir of platinum group elements (PGE) in the oceanic crust, and 2) The average rhenium/osmium in lavas is higher than that in corresponding cumulates. The project also aims at identifying important PGE carrier phases to better understand magmatic fractionation of these elements, and investigating the effects of hydrothermal alteration on the PGE budget of the oceanic crust. Complementary isotope, major and trace element, as well as petrographic and mineral analyses will be carried out to place the Re/Os/PGE data in a broader geochemical context. Results from this study will significantly improve our understanding of chemical interaction between the oceans, crust and mantle.

KelemenEAR-0337677洋壳的形成、蚀变和俯冲是地球持续化学分化的基本过程。 洋壳从火成岩增生到俯冲的化学转变对于限制地球的化学演化至关重要。 虽然已经使用多个浅钻孔研究了上洋壳的化学成分，但我们对中下洋壳的了解仅限于蛇绿岩部分，并且很少有深入洋壳的钻孔。 该项目旨在调查阿曼蛇绿岩最南端地块经过深入研究的难熔堆积辉长岩和补充熔岩，这些区域在成分上与洋中脊成分谱的贫化端重叠。 将测试两个重要的假设：1）下洋壳是洋壳中铂族元素（PGE）的主要储库，2）熔岩中的平均铼/锇含量高于相应堆积物中的平均铼/锇含量。 该项目还旨在确定重要的 PGE 载体相，以更好地了解这些元素的岩浆分馏，并研究热液蚀变对洋壳 PGE 预算的影响。 将进行补充同位素、主量元素和痕量元素以及岩相学和矿物分析，以将 Re/Os/PGE 数据置于更广泛的地球化学背景中。 这项研究的结果将显着提高我们对海洋、地壳和地幔之间化学相互作用的理解。