Os Isotopic Studies of Solid Earth Evolution

本提案要求支持继续将Re-Os同位素系统应用于有关地球壳-幔-核分异的广泛问题。 利用本项目所要求的资金，我们希望解决以下问题：（1）大陆岩石圈地幔的形成机制，特别关注跨克拉通的变化，克拉通边缘岩石圈物质的增加以及对太古代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a）随着时间的推移，海洋地壳与大陆地壳的生产比例发生变化，B）在早期地球历史期间，地球外输入地幔的铂族元素减少，以及c）地核与地幔之间的质量交换，和3）下地壳捕虏体的Os同位素特征，确定其初始地幔提取年龄，以评价岩浆底侵作用与大陆碰撞作用在增厚中的意义大陆地壳 这些研究都利用了Re-Os同位素体系的独特特征，当与Sr、Nd和Pb同位素数据结合使用时，这些特征为固体地球的年代学、构造和化学演化提供了新的见解。

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.