Did Channel Flow Drive the Thermo-mechanical Evolution of the Eastern Himalaya? A Field-based Test in Northeast Bhutan

喜马拉雅山脉和青藏高原代表着世界上S最高的山脉和最大的高地面积，是大陆-大陆碰撞形成的山带的典型例子。这一系统仍在积极发展；因此，对这些山脉的研究提供了一个独特的机会，可以了解在这种类型的板块碰撞期间地壳是如何演化的。在喜马拉雅山脉的大部分地区，今天在地球表面观察到的岩石被埋在地球表面以下约35公里处，并被带到足以部分融化的温度。喜马拉雅山脉的许多地方都对这些岩石进行了研究，目前关于这些岩石是如何被挖掘到地表的，存在着激烈的争论。渠道流模型预测，这些深埋的岩石在部分熔融后失去了大部分强度，然后向南转移到地表。相比之下，其他提出的模型认为，断层和剪切带是它们折返的原因，而较少关注岩石软弱的驱动力。在这个项目中，我们打算测试这些不同模型对位于喜马拉雅山脉东部的不丹王国岩石的适用性。我们将通过在实地考察期间收集岩石样本，并确定它们所经历的压力、温度、时间和变形的演变来做到这一点。过去，对于地质研究人员来说，不丹相对孤立，因此不丹暴露的大部分岩石都没有得到很好的研究。该项目的结果将对碰撞造山过程中大陆地壳如何演化的争论做出有价值的贡献。此外，还将对多名研究生进行实地和实验室培训，其中包括一名不丹公民和不丹地质调查局的现任雇员。完成学位后，他将返回不丹，在自然资源、自然灾害和公共政策研究方面担任领导角色。本科生还将参与实验室分析，并将获得培训、教育和研究经验。最后，这项研究将支持两名早期职业研究人员的研究努力，并促进联合国研究所与不丹？S地质调查局的科学家之间有价值的国际合作。

The Himalayan range and Tibetan Plateau represent the world?s tallest mountain range and largest area of elevated land, and are the type-example of a mountain belt that formed as a result of continent-continent collision. This system is still actively growing; therefore, study of these mountains provides a unique opportunity to understand how the crust evolves during this type of plate collision. Across much of the Himalayan range, rocks that have been buried to depths as much as approximately 35 km below Earth's surface and taken to temperatures hot enough to partially melt are observed at the surface today. These rocks have been studied in many parts of the Himalaya, and there is currently a vigorous debate over how these rocks were exhumed to the surface. The channel flow model predicts that these deeply buried rocks lost much of their strength after partially melting, and were then translated southward and towards the surface. In comparison, other proposed models argue that faults and shear zones were responsible for their exhumation, and are less focused on the driving force being the weakness of the rocks. In this project, we propose to test the applicability of these different models to rocks in the kingdom of Bhutan, which lies in the eastern part of the Himalayan range. We will do this by collecting rock samples during field expeditions, and determining the pressure, temperature, timing, and evolution of deformation that they experienced. In the past, Bhutan has been relatively isolated for geologic researchers so the majority of the rocks exposed in Bhutan have not been well studied.The results of this project will make a valuable contribution to the debate over how continental crust evolves during collisional mountain building. In addition, multiple graduate students will be trained in the field and laboratory, including one Bhutanese citizen and current employee of Bhutan's geologic survey. After he finishes his degree, he will return to Bhutan to take on a leadership role in the study of natural resources, natural hazards, and public policy. Undergraduate students will also be involved with laboratory analyses and will obtain training, education, and research experience. Finally, this study will support the research efforts of two early career researchers, as well as foster valuable international collaboration between UNR and scientists at Bhutan?s geological survey.