Comprehensive Study of the Platinum-Group Elements (PGE) in Normal and Hotspot Affected Mid Ocean Ridge Basalts

将对从URI疏浚岩石收集的大洋中脊玄武岩玻璃中选定的一组高度亲铁和亲铜元素进行全面的记录和研究，重点是相对分馏和系统的地理变化。URI的疏浚岩石收集集中在异常升高的洋中脊附近的热点和底层地幔柱的影响。 到目前为止，文献报道的MORB中PGE含量非常有限，不是很系统，主要是由于它们的丰度非常低，导致分析困难。 高分辨率、高灵敏度、电感等离子体质谱（HR-ICP-MS）的使用提供了新的分析机会。 同位素稀释/ HR-ICP-MS分析方法的Ir，Ru，Pt，Pd，Re，Ag，Cd和Te将被开发和测试，然后分析大量的MORB玻璃。 同样的玻璃也将分析S（用电子探针）和Se（通过放射化学中子活化分析）。 重点将是划定全方位的亲铁/亲铜元素变化的MORB，其相对分馏，并寻求可能的相关性，或去耦，这些元素和铅，锶，钕，和他的同位素系统，S，Se和Te，和其他地球化学参数以前建立在同一玄武岩玻璃。其目的是在大洋地壳和下伏地幔的铂族元素含量、地幔铂族元素不均匀性的长度尺度、熔融条件、地幔柱来源和地幔动力学等方面获得新的认识。

A comprehensive documentation and study of a selected group of highly siderophile and chalcophile elements in mid-ocean ridge basalt (MORB) glasses from the URI dredge rock collection will be conducted, with emphasis on relative fractionations and systematic geographical variations. The URI dredged rock collection has focused on unusually elevated mid-ocean ridge affected by nearby hotspots and underlying mantle plumes. So far, PGE contents in MORB reported in the literature have been very limited and not very systematic, primarily due to their very low abundances and resulting analytical difficulties. The use of high resolution, high sensitivity, inductive plasma-mass spectrometry (HR-ICP-MS) is providing new analytical opportunities. An isotopic dilution / HR-ICP-MS method of analysis for Ir, Ru, Pt , Pd, Re, Ag, Cd, and Te will be developed and tested initially, and followed by analyses of a large number of MORB glasses. The same glasses will also be analyzed for S (with the electron microprobe) and Se (by radiochemical neutron activation analysis). The focus will be on delineating the full range of siderophile/chalcophile element variations of MORBs, their relative fractionation and seek possible correlations, or decoupling, between these elements and the Pb, Sr, Nd, and He isotope systems, S, Se and Te, and other geochemical parameters previously established on the very same basalt glasses. The purpose is to gain new and greater insights in our understanding of the PGE content of the oceanic crust and underlying mantle, length-scales of mantle heterogeneities in PGE, melting conditions, sources of mantle plumes and mantle dynamics.