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

合作研究：青藏高原南缘造山带平行中地壳流动与穹窿折返

• 批准号: 0911416
• 负责人: John Cottle
• 金额: $ 4.14万
• 依托单位: University of California-Santa Barbara
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-10-01 至 2012-09-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0911416&HistoricalAwards=false
• 关键词: Collaborative; Research; Orogen; parallel; Mid

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.

地球上一些最大、最引人入胜的地质和地理特征，包括阿尔卑斯山脉/喜马拉雅山脉，都是大陆碰撞的结果。因为大陆碰撞系统导致了地球大部分地区的地质变化？因此，了解它们复杂的动力学对地球科学至关重要。基于在碰撞系统的侵蚀岩心中保存的岩石和结构的地质研究，为包括变质作用、融化、变形和挖掘在内的造山基本过程提供了关键的见解。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，而且在多大程度上它们相互作用，以建立和破坏大型山脉。这个项目的数据将成为课程材料的基础，这些材料将分发给中学教师，并建立一个网站，专门介绍喜马拉雅地区正在进行的地球科学项目。该项目还将支持研究生和本科生的指导和教育，并将在美国国家科学基金会国际科学与工程办公室的帮助下，开展广泛的国际科学合作。喜马拉雅山脉为研究活跃碰撞系统中地壳中部岩石的演化提供了绝佳的机会。这些圆顶为研究部分熔体的产生、部分熔体与掘出之间的潜在反馈、剪切带成核的影响以及圆顶形成过程中地壳的流变学提供了重要的机会。利奥帕吉尔穹隆的高品位岩石是在伸展和穹隆形成过程中，沿着与造山带平行的逆冲断层和低角度滑脱断层的活动辐合背景下发掘出来的，这些断层活动至中新世中期。在与美国和国际学术组织的合作下，该项目将采用实地和实验室为基础的跨学科调查，利用1)地质制图和详细的微观结构分析，2)同位素地质年代学（U/Pb, Ar/Ar, [U+Th]/He），以及3)确定变质P-T-t路径来探索这些岩石的演化。