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

合作研究：拉萨地块自上而下——亚洲前沿的岩石圈演化

• 批准号: 1111959
• 负责人: Donald DePaolo
• 金额: $ 48.54万
• 依托单位: University of California-Berkeley
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2011
• 资助国家: 美国
• 起止时间: 2011-09-01 至 2017-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1111959&HistoricalAwards=false
• 关键词: Collaborative; Research; Lhasa; Block; Top

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.

喜马拉雅-西藏造山系几十年来一直是广泛研究的对象，并将继续成为理解造山过程和大陆演化的富有成效的实验室。地质和地球物理研究对现代系统的结构和动力学提供了重要的见解，但对造山带的早期发育和可能影响后续演化的碰撞大陆的特征提供的信息较少。该项目的目标是研究西藏南部地壳和岩石圈厚度的变化，以便建立边界条件？关于印度-欧亚碰撞(约50年前)以及碰撞过程中和碰撞后岩石圈厚度的变化。岩石圈厚度定义了地壳和岩石圈的热状态和流变性，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。岩石圈厚度将结合地球化学、地质年代学、古海拔、地震学、构造学和模拟来了解南亚大陆边缘前缘的碰撞前结构和演化。拉萨街区？以及它在控制更广泛的造山带发展中的作用。他们试图回答两组相关的问题：？拉萨地块的地壳厚度是如何从碰撞演化到现在的？随着时间的推移，海拔和剥蚀史是如何变化的？变质作用在改变地壳流变性和密度，从而促进地表抬升和侵蚀方面起什么作用？岩石圈变形对该地区增厚的贡献是什么？这一组问题之所以相关，是因为地壳厚度和地表高度可以影响造山运动的机制。第二组相关问题涉及拉萨地块的后期演化：？碰撞后岩浆的起源是什么？？熔融在多大程度上促进了地壳的削弱和流动？岩浆和水流体及其分布的横向非均质性如何影响拉萨地块的演化和变形？为什么拉萨地块的高程相对均匀，尽管地质、折返和深部结构有很大的差异？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大小尺度变形方面所起的控制作用。