Investigating the Kinematic History of the Kongur Shan Normal Fault System, Western Tibet

西藏西部公古尔山正断层系运动史研究

• 批准号: 0126122
• 负责人: An Yin
• 金额: $ 21.32万
• 依托单位: University of California-Los Angeles
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2002
• 资助国家: 美国
• 起止时间: 2002-02-15 至 2005-01-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0126122&HistoricalAwards=false
• 关键词: Investigating; Kinematic; History; Kongur; Shan

A first-order feature of the Tibetan Plateau is its triangular geometry on map view with itsnorth-south width increasing from ~500 km in the west to 1500 km in the east. This asymmetryhas been explained by either eastward extrusion of Tibet or partitioning of north-south shorteningin the Tian Shan and northern Tibet across the strong Tarim block. To quantify the role of lateralextrusion in accommodating intracontinental deformation during the Indo-Asian collision, wemust know the timing and magnitude of slip along major Cenozoic strike-slip faults in Asia. Thisgoal may be achieved by examining the termination structures of the strike-slip faults where theirmotion is transferred to dip-slip structures. In this proposal, we plan to investigate the temporaland spatial evolution of one of such structures: the 220-km long, north-trending Kongur Shanextensional system in the eastern Pamirs. In the lateral-extrusion model, the Kongur Shanextensional system is the northern termination of the ~1000-km long right-slip Karakorum fault,which is thought to have assisted Tibet to extrude hundreds of kilometers eastward. Because thesouthern end of the Kongur Shan system is assumed to link with the right-slip Karakorum fault,the extrusion model requires that the extensional system has progressively lengthened northwardand its total magnitude of extension decreases from south to north. Alternatively, the oroclinal-bendingmodel suggests that the development of the north-trending Kongur Shan system mayhave been related to pure bending of the Pamir-Nanga Parbat syntaxis system during Cenozoicnorthward indentation of the Pamir promontory. This hypothesis not only explains coeval east-westextension in the Pamirs and east-west contraction in the Nanga Parbat region in the westernHimalayan orogen, but also predicts specifically that the Kongur Shan extensional system shouldhave lengthened progressively southward and its total magnitude of extension decreases alongstrike to the south. The distinctive predictions regarding the extensional-magnitude distributionand propagation direction of the Kongur Shan extensional system by the two competing modelsform the basis of this proposal. We plan to conduct field mapping across the extensional systemin four different transects, each is about 20-40 km wide, which will allow us to construct a seriesof cross sections for estimating the magnitude of extension along individual segment of thesystem. Field mapping will focus on the question of whether the Kongur Shan extensionalsystem is actually linked with the Karakorum fault. We will integrate field mapping withthermobarometric, 40 Ar/39 Ar thermochronologic, and U-Th-Pb ion-microprobe geochronologicanalyses to constrain the P-T-t paths for both the hangingwall and footwall of the extensionalsystem. The results of this study will provide two important constraints on the tectonics of thewestern Himalayan orogen: (1) the timing and magnitude of eastward extrusion of Tibet, and (2)the dynamic cause for the initiation and development of coeval east-west extension andcontraction in the western syntaxis system.

藏族高原的一阶特征是其三角形几何形状在地图视图上，其北南宽度从西部的约500公里增加到东部的1500公里。这种不对称的人是通过向东挤出西藏的挤压或在强大的塔里姆（Tarim Block）横跨田山和西藏北部的南北缩短的。为了量化后期雷克斯在适应印度亚洲碰撞期间内大陆变形中的作用，Wemust知道沿亚洲主要的新生代滑滑断层沿主要的新生代滑滑断层的时机和幅度。可以通过检查将其运动转移到浸滑结构的终止断层的终止结构来实现这一目标。在此提案中，我们计划研究其中一种结构的颞空间演化：东部帕米尔人的220公里长，向北趋势的Kongur Shanextensional System。在横向排序模型中，Kongur Shanexensional System是〜1000公里长的右滑动karakorum断层的北部终止，据认为这有助于西藏挤出以东数百公里。由于假定Kongur Shan系统的Thesouthern端与右滑动karakorum断层联系在一起，因此挤出模型要求扩展系统逐渐延长了北向北向及其总延伸幅度从南部到北量减少。另外，口语前弯曲模型表明，北部趋势的Kongur Shan系统的发展可能与Pamir Promontory的Cenozoicnorth向凹痕期间的Pamir-Nanga Parbat语法系统的纯弯曲有关。该假设不仅解释了西部山基因造基因的北ga parbat地区的帕米尔和东西方收缩中的co eval，而且还专门预测，Kongur Shan的扩展系统应逐渐向南延长，并且其总幅度降低了向南的延伸。关于Kongur Shan伸展系统的延伸速度分布和传播方向的独特预测，这两个竞争模型将本提案的基础形成。我们计划在四个不同的样带上进行延伸系统的场映射，每个样带宽约20-40 km，这将使我们能够构造一个串联截面，以估计沿该系统各个段的扩展幅度。现场映射将集中于Kongur Shan扩展系统是否实际上与Karakorum故障相关的问题。我们将将现场映射与三杆计量学，40 AR/39 AR热力学学和U-TH-PB离子 - 微探针测量学测量学，以限制扩展系统的悬挂墙和脚壁的P-T-T路径。这项研究的结果将对西马拉扬基因造基因的构造提供两个重要的限制：（1）西藏的东挤出的时机和幅度，以及（2）西部语法系统中共同促进和发展的动态原因。