Os Isotopic Studies of Solid Earth Evolution

9506713 Shirey这项建议要求支持继续应用Re-Os同位素系统来解决有关地球壳-地幔-核分异的各种问题。利用这项提案所要求的资金，我们希望解决以下问题：1)大陆岩石圈地幔的形成机制，特别是跨克拉通变异性、克拉通边缘岩石圈物质的增加以及对太古宙和元古界构造的影响；2)对流地幔Os同位素组成的长期变化，可能揭示地幔是否记录了a)洋壳与陆壳生产比率随时间变化的影响，b)早期地球历史期间地外对地幔的PGE输入的减少，c)核幔之间的质量交换，3)下地壳捕虏体的Os同位素特征，以确定其初始地幔提取年龄，以评价岩浆底侵作用的意义，而不是大陆碰撞在增厚的陆壳中的意义。这些研究都利用了Re-Os同位素体系的独特特征，当与锶、钕和铅同位素数据结合使用时，可以提供对固体地球的年代学、构造和化学演化的新见解。

9506713 Shirey This proposal requests support to continue application of the Re-Os isotopic system to a wide range of problems concerning crust-mantle-core differentiation on the Earth. With the funding requested in this proposal we hope to address the following topics: 1) the mechanisms of formation of continental lithospheric mantle, focusing especially on across-craton variability, addition of lithospheric material at craton margins and the implications for Archean and Proterozoic tectonics; 2) secular changes in the Os isotopic composition of the convecting mantle that may reveal if the mantle records the effects of a) changing ratios of oceanic to continental crust production through time, b) decline in extraterrestrial input of PGE's to the mantle during early Earth history and c) mass exchange between core and mantle, and 3) Os isotopic characterization o lower crustal xenoliths to determine their initial mantle extraction ages in order to evaluate the significance of magmatic underplating as opposed to continental collision in thickening continental crust. These studies all make use of the unique characteristics of the Re-Os isotopic system that when used in conjunction with Sr, Nd, and Pb isotopic data offers the potential of new insights into the chronological, tectonic, and chemical evolution of the solid earth.