Exploring the Early History of the South Tibetan Fault System in Bhutan

探索不丹藏南断层系的早期历史

• 批准号: 0838112
• 负责人: Kip Hodges
• 金额: $ 27.97万
• 依托单位: Arizona State University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-04-01 至 2013-03-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0838112&HistoricalAwards=false
• 关键词: Exploring; Early; History; South; Tibetan

This research focuses on the South Tibetan fault system, one of the most enigmatic tectonic features of the Himalaya, and one that stirs much controversy in the Tectonics community. The South Tibetan fault system appears to be unique in that its kinematics are those of a low-angle, normal fault system while all other Himalayan fault systems with comparable displacements (many 10s to 100s of kilometers) have the more predictable kinematics of thrust fault systems typically found in mountain belts. The very existence of a feature like the South Tibetan fault system is indicating something fundamental about how the Himalaya, and mountain ranges in general, evolve. The PI and his colleagues work to clarify this message through their research. Unfortunately, in many parts of the Himalaya, the early history of the South Tibetan fault system has been obscured by late-stage deformation. This is not the case in Bhutan, where the PI and others have identified erosional remnants of early faults of the system that have been relatively undisturbed by younger deformation. This proposal describes targeted studies of these remnants. A broad array of techniques will be used to probe the early history of the fault system using these rare exposures. They include geologic mapping and structural analysis; quantitative element-partitioning thermobarometry; 40Ar/39Ar and (U-Th)/He thermochronology; and laser-ablation (U-Th)/Pb geochronology. Because the Himalaya and Tibetan Plateau are still evolving, studies of this natural laboratory provide critical information regarding the role that mountainous regions play in earth system function. For example, we know that the physiography of the Tibetan Plateau defines the weather patterns of the Asian monsoon climate, and this climate is the enabling mechanism for agriculture that feeds roughly 60% of the people on Earth. By detailing the processes that led to the establishment of the modern-day Himalaya and Tibetan Plateau, studies such as the one proposed here inform more effective strategies for the co-evolution of human societies and mountain landscapes.

这项研究的重点是藏南断层系，这是喜马拉雅山最神秘的构造特征之一，也是构造学界引起很大争议的一个。藏南断层系统似乎是独一无二的，因为它的运动学是低角度正断层系统的运动学，而所有其他具有可比位移（数十到数百公里）的喜马拉雅断层系统都具有更可预测的逆冲断层系统运动学通常发现于山区。像藏南断层系这样的特征的存在本身就表明了喜马拉雅山和整个山脉如何演化的一些基本特征。 PI 和他的同事致力于通过研究来澄清这一信息。不幸的是，在喜马拉雅山的许多地区，藏南断层系的早期历史已被晚期变形所掩盖。不丹的情况并非如此，PI和其他人已经发现了系统早期断层的侵蚀残留物，这些断层相对不受较新变形的干扰。该提案描述了对这些残留物的有针对性的研究。将使用一系列广泛的技术利用这些罕见的暴露来探测断层系统的早期历史。其中包括地质测绘和结构分析；定量元素分配热压法； 40Ar/39Ar 和 (U-Th)/He 热年代学；和激光烧蚀（U-Th）/Pb 地质年代学。由于喜马拉雅山和青藏高原仍在不断演化，对这个自然实验室的研究提供了有关山区在地球系统功能中所发挥作用的关键信息。例如，我们知道青藏高原的地貌决定了亚洲季风气候的天气模式，而这种气候是农业的有利机制，而农业养活了地球上大约 60% 的人口。通过详细描述导致现代喜马拉雅山和青藏高原形成的过程，本文提出的研究为人类社会和山地景观的共同进化提供了更有效的策略。