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

大陆碰撞期间下地壳如何增厚和生长？

• 批准号: 0838269
• 负责人: Bradley Hacker
• 金额: --
• 依托单位: University of California-Santa Barbara
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-08-01 至 2013-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0838269&HistoricalAwards=false
• 关键词: How; Does; Lower; Crust; Thicken

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.

该奖项是根据《2009 年美国复苏和再投资法案》（公法 111-5）提供资金的。大陆碰撞可以形成大高原，如西藏，产生影响气候变化的厚地壳和高地势。高原如何变得如此之大尚未解决：要么地壳的下部在高温（30公里）的深处流动，要么地壳沿着横断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暴露来重点解决这个问题。由于青藏高原和帕米尔高原的典型性质，这项研究的影响应该是相当大和广泛的。PIs在三个假设框架内对地壳增厚的测试模型：帕米尔下地壳在青藏高原期间由于局部陆内缩短而增厚和折返。新生代，新生代长距离流动增厚，新生代局部陆内缩短折返，或大部分在印度碰撞前增厚折返和亚洲。这些假设将通过锆石 U/Pb 测年来确定深成体的结晶年龄、Lu-Hf 和 Sm-Nd 测年来测量地壳增厚年龄、温压测量来确定折返深度、40Ar/39Ar、裂变径迹和（U +Th)/He 测定年代以约束热历史，并进行结构分析以确定变形历史。