Collaborative Research: Orogen-parallel Mid-crustal Flow and Exhumation of Domes Along the Southern Margin of the Tibetan Plateau

地球上一些最大和最有趣的地质和地理特征，包括阿尔卑斯山/喜马拉雅山脉，是大陆碰撞的结果。因为大陆碰撞系统是地球大部分地区深刻地质变化的原因？在地球的历史上，了解它们复杂的动力学对地球科学具有根本的重要性。 地质研究的基础上保存在侵蚀核心的碰撞系统的岩石和结构提供了关键的见解，包括变质，熔融，变形和折返的基本过程的造山作用。 这项工作的结果将有助于完善我们的知识，不仅是个别过程，而且是在多大程度上，他们相互作用，以建设和破坏大型山脉。该项目的数据将成为编写课程材料的基础，这些材料将分发给中学教师，并将建立一个网站，专门介绍喜马拉雅山脉正在开展的地球科学项目。 该项目还将支持研究生和本科生的指导和教育，并在NSF国际科学与工程办公室的帮助下，将启动广泛的国际科学合作。 喜马拉雅山提供了一个特殊的机会，研究中地壳岩石在一个活跃的碰撞系统的演化。 沿着碰撞前沿，约束这些中地壳岩石的主要结构，下面的主中央逆冲断层和上面的藏南拆离断层，被年轻的变质圆顶（如本研究的重点Leo Pargil）抵消或重新激活。 这样的圆顶提供了一个重要的机会来研究部分熔融的产生，部分熔融和折返之间的潜在反馈，剪切带成核的影响，以及圆顶形成过程中地壳的流变学。 高品位的岩石的狮子座Pargil圆顶已被挖出的伸展和圆顶的形成过程中，在一个活跃的收敛设置沿着造山带平行逆冲断层和低角度拆离断层，一直活跃到中新世中期。 该项目将与美国和国际学术组织合作，采用野外和实验室为基础的跨学科研究，利用1）地质填图和详细的显微结构分析，2）同位素地质年代学（U/Pb，Ar/Ar，[U+Th]/He）和3）确定变质P-T-t路径来探索这些岩石的演化。 Leo Pargil的结果将与喜马拉雅前缘沿着的其他穹丘的结果进行对比，以生成一个高分辨率模型，用于研究自中新世中期以来青藏高原南缘沿着的造山带平行中地壳流和折返的时间和运动学。

Some of Earths largest and most intriguing geologic and geographic features, including the Alpine/Himalayan mountain chain, are the result of continental collision. Because continental collision systems are responsible for profound geologic change throughout a large portion of Earth?s history, understanding their complex dynamics is of fundamental importance to Earth Science. Geologic studies based on the rocks and structures preserved in eroded cores of collisional systems provide critical insights into the fundamental processes of mountain building including metamorphism, melting, deformation, and exhumation. Results of this work will help refine our knowledge, not only of individual processes, but also the extent to which they interact to both construct and destruct large mountain chains. Data from this project will form the basis for the development of curricular materials that will be distributed to middle school teachers and a website devoted to highlighting active geoscience projects in the Himalayas. This project will also support mentoring and education of graduate and undergraduate students, and with the help of the NSF Office of International Science and Engineering will initiate a wide-ranging international collaboration on the science. The Himalaya provide an exceptional opportunity to investigate the evolution of mid-crustal rocks in an active collisional system. Along the collisional front, the major structures that bound these mid-crustal rocks, the Main Central thrust below and South Tibetan detachment above, are offset or reactivated by young metamorphic domes like the Leo Pargil, the focus of this study. Such domes provide an important opportunity to study the generation of partial melt, the potential feedback between partial melt and exhumation, the affects of shear zone nucleation, and the rheology of the crust during dome formation. The high-grade rocks of the Leo Pargil dome have been exhumed during extension and dome formation within an active convergent setting along orogen-parallel thrust faults and low angle detachment faults that were active until the middle Miocene. In collaboration with US and international academic organizations this project will employ a field-and lab-based interdisciplinary investigation to explore the evolution of these rocks using 1) geologic mapping and detailed microstructural analysis, 2) isotope geochronology (U/Pb, Ar/Ar, [U+Th]/He), and 3) determination of metamorphic P-T-t paths. Results from Leo Pargil will be contrasted with that from other domes along the Himalayan front to generate a high-resolution model for the timing and kinematics of orogen-parallel mid-crustal flow and exhumation along the southern margin of the Tibetan plateau since the middle Miocene.