Collaborative Research: Development of Extensional Systems in Regions of Hot, Thick Crust: Insight from Tibet

合作研究：热厚地壳区域伸展系统的发展：来自西藏的见解

• 批准号: 0809425
• 负责人: Brian Horton
• 金额: $ 7.52万
• 依托单位: University of Texas at Austin
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2008
• 资助国家: 美国
• 起止时间: 2008-08-15 至 2011-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0809425&HistoricalAwards=false
• 关键词: Collaborative; Research; Development; Extensional; Systems

This project will investigate how modern continental extensional systems and associated basins are developing in regions of hot, thick crust. Tibet is underlain by the thickest crust on Earth that is arguably flowing at mid-crustal levels, and is actively extending East-West at greater that one-third the total North-South convergence rate between India and Asia. Recent studies show that North-trending Tibetan normal faults and adjacent basins vary systematically in their characteristics as a function of extension magnitude, and may provide sequential snapshots of rift basin evolution during progressive extension. Nascent rifts are characterized by half-graben basins bounded by high-angle normal faults. In contrast, more evolved rifts are bounded by low-angle detachment faults characterized by basins undergoing incision with intrabasin drainage divides in areas of inferred maximum extension. The goal of this research is to test the hypothesis that Tibetan rifts initiate as high-angle normal faults and associated half-grabens that evolve into detachment faults active at uppermost crustal levels and above which rift basin fill is uplifted and eroded, in response to progressive tectonic unloading and isostatic rebound. This hypothesis, along with several alternatives, will be tested in this project along a well exposed in central Tibet by using geological and structural mapping, cosmogenic dating, basin analysis, and low-temperature thermochronology. The project is a multi-disciplinary and collaborative research effort between faculty and students at the University of Kansas, University of Arizona, University of Texas, Dalhousie University in Canada, and the Institute of Tibetan Plateau Research in China.Project findings will have a major scientific impact by documenting in detail how modern extensional systems develop in regions of active orogenesis that are underlain by hot, thick crust. The results will allow testing of contrasting models for the development of metamorphic core-complexes and low-angle normal faults, and may shed new light on the role of mid-crustal flow in enhancing isostatic rebound during continental extension.

该项目将调查现代大陆延伸系统和相关盆地如何在热厚的地壳区域发展。西藏是地球上最厚的地壳的底线，它可以说是在地壳中间的水平，并且正在积极地延伸东西方，比印度和亚洲之间的南北融合率更大。最近的研究表明，向北趋势的藏族正常断层和邻近的盆地的特征随着延伸幅度的函数而系统地变化，并且可以提供渐进式延伸过程中裂谷盆地进化的顺序快照。新生的裂痕的特征是半熟盆地受高角度正常断层界定的。相比之下，更多进化的裂纹是由盆地经受切口的低角度脱离断层的界定，并在推断的最大扩展区域中裂开，并具有内脊髓素的排水​​鸿沟。这项研究的目的是检验以下假设：藏族裂纹作为高角度正常断层和相关的半grabens启动，这些断层演变成在上皮水平上活跃的脱离断层，而高于裂谷盆地填充的高于该断层，以响应于进步的构造构造卸载和等静电折射。 该假设以及几种替代方法将在该项目中沿着西藏中央的一个良好暴露，使用地质和结构映射，宇宙基因测定，盆地分析和低温热量体来测试。该项目是堪萨斯大学，亚利桑那大学，德克萨斯大学，加拿大达尔豪斯大学的教师与学生之间的一项多学科和合作研究，以及中国的藏族高原研究所。项目的发现将通过详细地记录在现代扩展系统中，从而在厚实的地区中详细记录了一项重大的科学影响。该结果将允许测试对比模型，以开发变质核心复合物和低角度正常断层，并可能对中壳流动在增强大陆扩展期间等静态反弹方面的作用有了新的启示。