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、最有趣的地质和地理特征，包括阿尔卑斯/喜马拉雅山脉，都是大陆碰撞的结果。由于大陆碰撞系统在地球历史的大部分时间里造成了深刻的地质变化，因此了解其复杂的动力学对于地球科学至关重要。 基于碰撞系统侵蚀核心中保存的岩石和结构的地质研究为造山的基本过程（包括变质作用、熔化、变形和折返）提供了重要的见解。 这项工作的结果将有助于完善我们的知识，不仅包括单个过程，还包括它们相互作用以构建和破坏大型山脉的程度。该项目的数据将构成开发课程材料的基础，这些材料将分发给中学教师和一个专门强调喜马拉雅山活跃的地球科学项目的网站。 该项目还将支持研究生和本科生的指导和教育，并在美国国家科学基金会国际科学与工程办公室的帮助下，启动广泛的国际科学合作。 喜马拉雅山为研究活跃碰撞系统中地壳岩石的演化提供了绝佳的机会。 沿着碰撞前缘，限制这些中地壳岩石的主要结构，即下方的主中央逆冲断层和上方的藏南脱离，被年轻的变质穹顶（如本研究的焦点）Leo Pargil 等所抵消或重新激活。 这种穹顶为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穹顶形成过程中地壳的流变学提供了重要的机会。 Leo Pargil圆顶的高品位岩石是在沿着造山带平行逆冲断层和低角度滑脱断层的活动汇聚环境中的伸展和圆顶形成过程中被挖出的，这些断层一直活跃到中中新世。 该项目将与美国和国际学术组织合作，采用基于现场和实验室的跨学科调查，利用 1) 地质测绘和详细的微观结构分析，2) 同位素地质年代学（U/Pb、Ar/Ar）来探索这些岩石的演化。 ，[U+Th]/He)，以及 3) 变质 P-T-t 路径的确定。 Leo Pargil 的结果将与喜马拉雅山前缘其他穹顶的结果进行对比，以生成中中新世以来沿青藏高原南缘平行造山带中地壳流动和折返的时间和运动学的高分辨率模型。