Filling the Eastern Himalayan Gap: Structural Architecture and Kinematics of the Himalayan Orogen in Bhutan

填补喜马拉雅东部缺口：不丹喜马拉雅造山带的结构建筑和运动学

• 批准号: 0738552
• 负责人: Nadine McQuarrie
• 金额: $ 36.94万
• 依托单位: Princeton University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2008
• 资助国家: 美国
• 起止时间: 2008-01-01 至 2011-10-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0738552&HistoricalAwards=false
• 关键词: Filling; Eastern; Himalayan; Gap; Structural

The 2,400 km long Himalayan fold and thrust belt extends from the Nanga Parbat massif in northern Pakistan to the Namche Barwa syntaxis in eastern Tibet. There are only a handful of estimates that quantify the magnitude and geometry of shortening along this fold and thrust belt with no such estimates in the eastern portion of the range, a region characterized by fundamental changes in the geomorphic, geometric, and lithologic expression of the belt. In particular, the lack of information on the magnitude, style, and timing of shortening in the Lower Himalayan Series, a thick succession of early to middle Proterozoic-Paleozoic greenschist facies to unmetamorphosed metasedimentary rocks within the belt, inhibits understanding of the development of the Himalayan orogenic belt. The goal of this project is to determine the geometry, amount of shortening, and kinematic history of deformation in the Lower Himalayan Series as exposed in the Kingdom of Bhutan. Toward this end, a team of scientists from Princeton University and Bhutan are mapping the Lesser Himalayan Sequence from the Main Central Thrust to the Main Frontal Thrust. These field relationships and new U-Pb ages of detrital zircons are used to develop a regional stratigraphic framework. Balanced crustal-scale structural cross-sections are restored sequentially when combined with new thermochronologic and geochronologic ages in order to elucidate regional cooling patterns and to constrain timing of fault motion. These results allow evaluation of how deformation is partitioned in space and time, prediction of minimum shortening estimates, determination of minimum lateral and vertical erosion estimates compatible with both the balanced section and thermochronometers, and in the end, comparison of the timing and magnitude of deformation and exhumation between the Lesser and Greater Himalayan Series.The Himalayan mountain range is a consequence of the ongoing collision between India and Asia. During collision, the sedimentary cover that had blanketed northern India for the last 1.8 billion years became detached from the underlying basement. This deformed sedimentary cover, and the structures that developed within it, record the deformation history of the collision. Although it is one of the world's most famous mountain ranges, only a handful of estimates quantify this deformation and there are no such estimates for the eastern portion of the mountain belt. This study of the deformed rocks in the Kingdom of Bhutan will provide new estimates for this poorly understood portion of the range and, when compared to estimates for other portions of the Himalayan Range, will lead to a better understanding of the development of collisional mountain belts. The project fosters scientific collaboration between scientists from Bhutan and the United States and helps to build scientific infrastructure in Bhutan by training of Bhutanese students and an improved knowledge of the geology of the country, which in turn is important for understanding earthquake hazards and natural resources.

喜马拉雅褶皱冲断带长2400公里，从巴基斯坦北部的Nanga Parbat地块延伸到西藏东部的Namche Barwa构造带。只有为数不多的几个估计量化了沿该褶皱冲断带的缩短量和几何形状，而在该山脉的东部没有这样的估计，该地区的特点是该带的地貌、几何和岩性表达发生了根本性的变化。特别是，缺乏关于下喜马拉雅系缩短的规模、样式和时间的信息，下喜马拉雅系是早中元古代-古生代绿片岩相到带内未变质的变质沉积岩的厚实序列，阻碍了对喜马拉雅造山带发展的了解。该项目的目标是确定在不丹王国暴露的下喜马拉雅系的几何形状、缩短量和形变的运动学历史。为此，来自普林斯顿大学和不丹的一组科学家正在绘制从主要的中央逆冲到主要的前缘逆冲的小喜马拉雅序列。利用这些野外关系和碎屑锆石的U-Pb年龄建立了区域地层格架。当结合新的热年代学和地质年代学年龄时，平衡的地壳尺度结构截面被顺序地恢复，以阐明区域冷却模式和限制断层运动的时间。这些结果可以用来评估形变在空间和时间上的划分，预测最小的缩短量，确定与平衡剖面和温度计时器相适应的最小横向和垂直侵蚀估计值，最后比较小喜马拉雅和大喜马拉雅系列的变形和折返的时间和大小。喜马拉雅山脉是印度和亚洲持续碰撞的结果。在碰撞过程中，覆盖印度北部18亿年的沉积盖层从下面的基底中分离出来。这个变形的沉积盖层及其内部发育的构造记录了碰撞的变形历史。尽管它是世界上最著名的山脉之一，但只有少数几个估计数字对这种变形进行了量化，而且还没有对山脉带东部的这种估计。这项对不丹王国变形岩石的研究将对这一鲜为人知的山脉部分提供新的估计，与喜马拉雅山脉其他部分的估计相比，将有助于更好地了解碰撞山带的发展。该项目促进了不丹和美国科学家之间的科学合作，并通过培训不丹学生和增进对该国地质的了解，帮助在不丹建立科学基础设施，这反过来对了解地震灾害和自然资源也很重要。