Metamorphic and Tectonic Evolution of the Tethyan Himalaya, Central Nepal

在这个项目中，正在开发新的岩石学方法，以帮助限制尼泊尔中部暴露的特提斯喜马拉雅层序变质岩的压力-温度-时间演化。这些岩石是了解喜马拉雅造山带早期历史和测试构造模型的关键岩性，但它们的钙质成分违背了以前的岩石学和年代学研究。然而，最近岩石学的进展表明，钛矿主元素、微量元素（Zr）和U-Pb同位素地球化学可以同时约束压力、温度和地层年龄。钛矿在喜马拉雅钙质岩石中极为常见。晶体表现出化学上和年代上不同的亚晶粒域，并在800°C左右的温度下保持结晶条件。通过确定这些不同区域的压力-温度-时间条件，我们可以首次绘制出这些岩石的压力-温度-时间演化图。这些数据将区分不同的碰撞造山模型，特别是中下地壳塑性流动的程度，并可能为喜马拉雅早期构造历史提供一个独特的窗口。研究结果还将广泛影响火成岩作用、热液和矿石系统的年龄和历史研究。所有的数据都将被永久的保存在MetPetDB中。这项研究解决了几个基本问题，即大陆地壳在板块碰撞期间的行为，特别是中下地壳的塑性流动程度，以及当整体力应该导致地壳变厚时，使地壳变薄的伸展系统是如何形成的。我们的工作还将开发新的解释方法，这将推动火成岩、热液和成矿过程的研究。除了该项目的研究目标之外，还将在加德满都的Tribhuvan大学举办一个为期两到三天的讲习班，以帮助培训尼泊尔科学家使用分析和解释方法，以及如何使用这些数据来区分相互竞争的假设。这项工作还将支持一名新的博士生和一名本科生的研究和培训，我们将从博伊西州立大学招聘一名本科生。s LSAMP程序。他在博伊西州立大学的本科和研究生课程中充分利用了教育机会，这里的学生群体与其他美国大学不同。

In this project, new petrologic methods are being developed to help constrain the pressure-temperature-time evolution of metamorphic rocks of the Tethyan Himalayan Sequence exposed in central Nepal. These rocks are key lithologies for understanding the early history of the Himalayan orogen and for testing tectonic models, but their calcareous compositions have defied previous petrologic and chronologic efforts. Recent petrologic advances, however, indicate that titanite major element, trace element (Zr), and U-Pb isotope geochemistry can simultaneously constrain pressure, temperature and age of formation. Titanite is extremely common in Himalayan calcareous rocks. Crystals exhibit chemically and chronologically distinct sub-grain domains and preserve crystallization conditions to temperatures of about 800 °C. By determining pressure-temperature-time conditions for these different domains, we can for the first time map out the pressure-temperature-time evolution of these rocks. These data will discriminate among models of collisional orogenesis, particularly the degree to which the middle and lower crust flows plastically, and may provide a unique window into the early tectonic history of the Himalaya. Results will also broadly impact investigations of igneous petrogenesis and ages and histories of hydrothermal and ore systems. All data will be permanently archived with MetPetDB. This research addresses several fundamental problems of how continental crust behaves during plate collisions, especially the degree to which the middle and lower crust flows plastically, and how extensional systems, which thin the crust, can form when the overall forces should cause thickening. Our work will also develop new interpretational methods that will advance research in igneous, hydrothermal and ore-forming processes. In addition to the research goals of the project, a two to three day workshop will be held at Tribhuvan University in Kathmandu to help train Nepalese scientists in analytical and interpretational methods and how these data can be used to discriminate among competing hypotheses. This work will also support the research and training of a new PhD student as well as an undergraduate, who we will seek to recruit from Boise State University?s LSAMP program. The PI leverages educational opportunities in his undergraduate and graduate courses at Boise State University, which reaches a different student demographic than other American universities.