How Does the Lower Crust Thicken and Grow During Continent Collisions? A Case Study of the Pamir

该奖项是根据2009年《美国复苏和再投资法案》(Public Law 111-5)资助的。大陆碰撞可能会形成像西藏这样的大高原，产生厚厚的地壳和影响气候变化的高地形。高原是如何变得如此大的还没有解决：要么是地壳的下部在温度较高的深处(30公里)流动，要么是地壳沿着横切整个地壳的断层以更脆的方式增厚。这项研究利用塔吉克斯坦帕米尔山脉下地壳的曝光量来研究这个问题。由于西藏和帕米尔高原的原型性质，这项研究的影响应该是相当大和广泛的。在三个假说的框架内，帕米尔下地壳增厚和剥离的PIS测试模型：新生代期间帕米尔下地壳被局部陆内缩短增厚和剥离，新生代新生代长距离流动增厚和陆内局部缩短剥离，或者主要在印度与亚洲碰撞之前增厚和剥离。这些假设将通过锆石U/Pb测年来确定深成岩体的结晶年龄，通过Lu-Hf和Sm-ND测年来测量地壳增厚年龄，通过温压测量来确定折返深度，通过40Ar/39Ar、裂变径迹和(U Th)/He年龄来确定热历史，并通过构造分析来确定变形历史。

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).Continent collisions can form large plateaus, like Tibet, producing thick crust and high topography that affects climate change. How plateaus grow to become so large is unresolved: either the lower parts of Earths crust flow at depths where the temperatures are high (30 km), or the crust thickens in a more brittle fashion along faults that transect the entire crust. This research focuses on this question using exposures of the lower crust in the Pamir Mountains of Tajikistan. The impact of this research should be considerable and broad because of the archetypal nature of the Tibetan and Pamir plateaus.The PIs test models for crustal thickening within the framework of three hypotheses: the Pamir lower crust was thickened and exhumed by local intracontinental shortening during the Cenozoic, thickened by Cenozoic long-distance flow and exhumed by local intracontinental shortening during the Cenozoic, or thickened and exhumed mostly before the collision between India and Asia. These hypotheses will be evaluated by U/Pb dating of zircon to determine crystallization ages of plutons, Lu-Hf and Sm-Nd dating to measure crustal thickening ages, thermobarometry to determine exhumation depths, 40Ar/39Ar, fission-track, and (U+Th)/He dating to constrain thermal histories, and structural analysis to determine deformation histories.