Extrusion of the Greater Himalayan Crystalline in Himachal Pradesh, NW India

大喜马拉雅结晶(GHC)的挤压作用是关于印度-亚洲和世界其他碰撞带中下地壳变形机制的持续争论的话题，在喜马拉雅西北部横向结束。我建立了三种喜马拉雅西北部构造演化模式，它们是根据GHC中广泛韧性变形的涡度和变形的时间来区分的。为了考察这些模型的有效性，我提出了三种方法：(1)涡度和运动学分析；(2)多计时年代学；(3)变质独居石和尿晶石的原位Th/Pb定年。后者是一种相对较新的方法，这项工作将是朝着开发绿片岩级变质和同变质变形年龄的新工具迈出的重要一步。这项工作有助于理解碰撞造山过程中中下地壳的构造响应；具体地说，它研究了GHC的挤压及其边界断裂、藏南拆离和主要中央逆冲的相互作用。

Extrusion of the Greater Himalayan Crystalline (GHC), a topic of ongoing debate about mechanisms of middle to lower crustal deformation in the India-Asia and other collision zones worldwide, ends laterally in the NW Himalaya. I have developed three models for the tectonic evolution of the NW Himalaya, which are discriminated based on the vorticity of pervasive ductile deformation in the GHC and on timing of deformation. To investigate the validity of these models, I propose a threefold approach: (1) vorticity and kinematic analysis, (2) multi-chronometer thermochronology, and (3) in-situ Th/Pb dating of metamorphic monazite and allanite. The latter is a relatively new method and this work will be an important step towards developing a new tool for dating greenschist-grade metamorphism and syn-metamorphic deformation. This work contributes to the understanding of the tectonic response of the middle to lower crust during collisional orogeny; specifically, it investigates extrusion of the GHC and interaction of its bounding faults, the South Tibetan detachment and the Main Central thrust.