Collaborative Research: Lhasa Block Top to Bottom-Lithospheric Evolution of Asia's Leading Edge

喜马拉雅山吗?几十年来，西藏造山系统一直是广泛研究的对象，并继续成为了解造山过程和大陆演化的富有成果的实验室。地质和地球物理研究为现代系统的结构和动力学提供了重要的见解，但对造山带的了解较少。碰撞大陆的特征可能会影响后来的演化。本项目的目的是研究藏南地区地壳和岩石圈厚度的变化情况，以建立藏南地区的地壳和岩石圈厚度。边界条件?印度-欧亚大陆碰撞（~50万年前）以及碰撞期间和碰撞后岩石圈厚度的变化。正如pi所指出的那样，岩石圈厚度决定了地壳和岩石圈的热状态和流变，这是理解碰撞过程中地壳和岩石圈变形性质所必需的重要边界条件和性质。pi将整合地球化学、地质年代学、古高程、地震学、构造学和建模，以了解南亚大陆边缘前缘的碰撞前结构和演化。拉萨街区？以及它在控制更广阔造山带发育中的作用。他们试图回答两组相关的问题：？拉萨地块的地壳厚度从碰撞到现在是如何演变的？？海拔和剥蚀历史是如何随时间变化的？？变质作用在改变地壳流变学和密度，从而促进地表隆起和侵蚀方面起什么作用？岩石圈变形对区域增厚的贡献是什么？这一系列问题是相关的，因为地壳厚度和地表高度可以影响造山带的力学。第二组相关问题涉及拉萨地块后来的演变：？碰撞后岩浆的起源是什么？融化在多大程度上导致了地壳的弱化和流动？岩浆流体和含水流体及其横向非均质性分布如何影响拉萨地块的演化和变形？为什么拉萨地块的海拔高度相对一致，尽管在地质、发掘和深部构造方面存在相当大的差异？这些问题的重要性源于流变学及其空间变化在决定造山带如何在大尺度和小尺度上变形方面所起的控制作用。

The Himalaya?Tibet orogenic system has been the subject of extensive research for decades, and continues to be a fruitful laboratory for understanding orogenic processes and continental evolution. Geological and geophysical studies have provided important insights into the structure and dynamics of the modern system, but imparted less information about the orogen?s early development, and the characteristics of the colliding continents that may affect subsequent evolution. The goal of this project is to investigate how crustal and lithospheric thickness changes in southern Tibet in order to establish the ?boundary conditions? for the India-Eurasia collision (~50 My ago) and how lithosphereic thickness changes during and after collision. As pointed out by the PIs, lithospheric thickness defines the thermal state and rheology of the crust and lithosphere, which are important boundary conditions and properties necessary for understanding the nature of crustal and lithospheric deformation during collision.The PIs will integrate geochemistry, geochronology, paleoelevation, seismology, tectonics, and modeling to understand the pre-collision structure and evolution of the leading edge of the southern Asian continental margin ? the Lhasa block ? and its role in controlling the development of the broader orogen. They seek to answer two sets of related questions:? How has the crustal thickness of the Lhasa block evolved from collision to the present?? How have the elevation and denudation histories changed through time?? What role does metamorphism play in altering crustal rheology and density and as a consequence facilitate surface uplift and erosion?? What is the contribution of lithospheric deformation to thickening of the region?This set of questions is relevant because of the way crustal thickness and surface elevation can influence the mechanics of an orogen.The second set of related questions addresses the later evolution of the Lhasa block:? What is the origin of post-collisional magmas?? To what extent has melting contributed to crustal weakening and flow?? How have magmatic and aqueous fluids and lateral heterogeneity in their distribution influenced evolution and deformation of the Lhasa block?? Why are elevations in the Lhasa block relatively uniform despite considerable variations in geology, exhumation, and deep structure?The importance of these questions derives from the control that rheology and its spatialvariations play in determining how orogens deform at large and small scales.