Field, Analytical, and Experimental Studies of Progressive Crustal Melting in the Himalaya

[9814497]霍奇斯喜马拉雅的变质核心区显示出由大陆地壳部分熔融产生的引人注目的浅花岗岩。随着造山带在晚渐新世至中新世中期的演化，这些熔体在各种压力和温度条件下产生。本研究将利用喜马拉雅山脉提供的机会，在时间和空间上更好地了解造山熔融作用的过程。在三年的时间里，将对尼泊尔东部珠穆朗玛峰-马卡鲁地区多代浅花岗岩进行综合野外、岩石学和地球化学研究。与以往的浅花岗岩石成因研究相比，该项目是独一无二的，因为它具有高分辨率的地质年代学，旨在探索融化过程的速率和间歇性。由于浅色花岗岩的成功定年依赖于对副矿物（锆石、独居石、xenotime和铀矿）的U-Th-Pb分析，因此了解浅色花岗岩的一个关键是了解副矿物在渐析过程中的行为。这需要在实验研究和地质实例的实地/分析研究之间进行直接和持续的反馈。该提案的实验部分建立在伦斯勒理工学院（Rensselaer Polytechnic Institute）沃森及其同事目前的研究基础上，重点研究了花岗岩熔体中的xenotime溶解度。

9814497HodgesThe metamorphic core region of the Himalaya displays spectacular exposures of leucogranites produced by partial melting of the continental crust. These melts were produced over a wide range of pressure and temperature conditions as the orogen evolved through Late Oligocene to Middle Miocene time. This research will capitalize on the opportunity presented by the Himalaya to better understand the process of orogenic anatexis in time and space. Over a three-year period, an integrated field, petrologic, and geochemical study of multiple generations of leucogranites in the Everest-Makalu region of eastern Nepal will be conducted. This project is unique, compared to previous studies of leucogranite petrogenesis, in that it features high-resolution geochronology designed to explore the rate and episodicity of the melting process. Since the successful dating of leucogranites relies on U-Th-Pb analyses of accessory minerals (zircon, monazite, xenotime, and uraninite), one key to understanding leucogranites is understanding the behavior of accessory minerals during the anatectic process. This requires direct and continual feedback between experimental studies and field/analytical studies of geologic examples. The experimental component of this proposal builds on current research by Watson and associates at the Rensselaer Polytechnic Institute by focusing on xenotime solubility in granitic melts.