Os Isotopic Studies of Solid Earth Evolution

9506713 Shirey该提案要求支持继续将Re-Os同位素系统应用于地球上有关壳-幔-核分异的广泛问题。我们希望利用本提案所要求的资金解决以下问题：1)大陆岩石圈地幔的形成机制，特别是克拉通的跨克拉通变异性，克拉通边缘岩石圈物质的添加及其对太古宙和元古代构造的影响；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以下影响：a)随着时间的推移，海洋与大陆地壳生产比例的变化；b)地球早期地球外输入到地幔的PGE的减少；c)地核与地幔之间的质量交换；3)对下地壳捕虏体进行Os同位素表征，确定其初始地幔提取年龄，以评价岩浆底沉积而非大陆碰撞对大陆地壳增厚的意义。这些研究都利用了Re-Os同位素系统的独特特征，当与Sr， Nd和Pb同位素数据结合使用时，可以为固体地球的年代学，构造和化学演化提供新的见解。

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.