Zircon Geochronology and REE Geochemistry of High- and Ultrahigh-Pressure Metamorphic Rocks: North Qaidam and South Altun Terranes, Northwest China

超高压变质作用(深度80公里)是大陆俯冲和碰撞的产物。研究超高压变质岩及其在地表折返和暴露的过程有助于我们理解大陆演化和壳幔地球化学过程。本研究采用锆石U-Pb年代学方法，结合稀土元素地球化学、矿物包裹体分析和温压测量，结合压力、温度和矿物共生作用，研究了中国西北部柴北超高压地体和南阿尔金超高压地体的变质年龄及其榴辉岩-麻粒岩和角闪岩相减压的折返速率。这一结果将大大提高我们对柴达木地体和阿尔金地体地质历史的认识，并将评估它们之间的地质年代学对比。此外，这项研究还将有助于我们对超高压过程的总体理解，特别是那些负责超高压岩石在折返过程中和随后暴露在地球表面上的保存过程的过程。PI、研究生Chris Mattinson、合作者J.L.Wood、J.S.Yang和Mattinson的论文联合导师J.G.Liou拥有解决所提出问题所需的现场和实验室经验，所需资源可在斯坦福大学获得。这项研究是研究生克里斯·马丁森博士研究的组成部分，将在同行评议的期刊上发表多篇文章，并在国内和国际会议上发表演讲。这项研究的核心是与中国同事的合作，从而加强国际科学交流与合作。在初步研究期间开发的REE分析程序支持并增强了最先进的、多用户的斯坦福-美国地质勘探局SHRIMP-RG设施，从而加强了研究和教育的基础设施。

Ultra-high pressure (UHP) metamorphism (at depths 80 km) is a product of continental subduction and collision. Investigation of UHP metamorphic rocks and the processes responsible for their exhumation and exposure at the Earth's surface aids our understanding of continental evolution and crust/mantle geochemical processes. This study will employ zircon U-Pb geochronology, linked to pressure, temperature, and mineral paragenesis by REE geochemistry, mineral inclusion analysis, and thermobarometry, to study the ages of metamorphism in the North Qaidam and South Altun UHP terranes in northwest China, as well as the exhumation rates associated with their eclogite- to granulite- and amphibolite-facies decompression. The results will significantly advance our knowledge of the geologic history of the N. Qaidam and S. Altun terranes, and will evaluate the geochronological correlation proposed between them. In addition, this study will also aid our general understanding of UHP processes, especially those responsible for the preservation of UHP rocks during exhumation and subsequent exposure at the Earth's surface.The proposed research addresses significant questions both in the field of metamorphic petrology, as well as central Asian tectonics. The PI, graduate student Chris Mattinson, together with collaborators J.L. Wooden, J.S. Yang, and Mattinson's thesis co-advisor J.G. Liou have both the field and laboratory experience necessary to address the questions posed, and the required resources are available at Stanford University. This research is an integral part of graduate student Chris Mattinson's doctoral research, and will result in multiple publications in peer-reviewed journals and presentations at national and international meetings. Central to this research is collaboration with Chinese colleagues, thereby enhancing international scientific exchange and cooperation. The REE analysis routine developed during the preliminary study supports and enhances the state-of-the-art, multi-user Stanford-USGS SHRIMP-RG facility, thereby enhancing the infrastructure for research and education.