Development of the Himalayan Superstructure, Northwestern India

这项研究旨在确定喜马拉雅上层建筑从印度-亚洲缝合带到变形前陆的构造演化。上层建筑是指造山系统的低等级上层，与下面的高级基础设施形成对比。在喜马拉雅弧线的大部分地区，上层建筑岩石只保存了部分。它们出现在北部，但高品位的结晶岩占据了中部的狭长地带，最近的吸积物质主导了更南边的暴露。然而，在印度喜马拉雅西北部拉达克-尚巴东部地区，从缝合带到前陆褶皱冲断带，上层建筑岩石不断出露。保存在这些岩石中的变形记录可以用来解决两个问题：(1)关于基础结构岩石在上层建筑岩石和增生物质之间的侵位机制的长期争论，以及(2)最近认识到喜马拉雅岩石记录所保存的缩短可能远远小于板块电路重建所需的缩短。这些问题将通过一个结合测绘、分析工作和重建的研究计划来解决。使用ASTER数据的地面和遥感地质制图将建立横跨拉达克-尚巴上层建筑东部的地质框架。这些结果将得到通过微结构研究获得的运动学分析和通过40Ar/39Ar地质/热年代学确定的热历史的补充。新的和现有的构造、热和年代学数据将通过平衡的复古重建进行整合，以探索变形模式并确定缩短估计，从而提供能够测试挤压模型的变形历史和修订的地质缩短预算以测试缩短模型。初步分析表明，这项工作可能会使喜马拉雅山脉的缩短预算增加近500公里，这将意味着保存下来的地质缩短的增加超过50%。造山过程通常在阿尔卑斯山、安第斯山脉和喜马拉雅山脉等持续收缩的系统中进行探索。这些山脉带提供了良好的保存，直接限制了边界条件，并提供了同时询问古代和活动变形的机会。构造学工作者社区仍在研究这些系统许多部分的区域几何和运动学，特别是沿走向的构造变化。最近对喜马拉雅山脉的研究突显了我们对喜马拉雅山脉一阶知识的不完整性，这些研究对我们对最初的印度-亚洲碰撞及其高品位结晶核心的侵位的理解提出了各种激进的修正。目前的项目将帮助解决这两个问题，方法是利用该范围未得到充分开发的一个方面：在喜马拉雅西部保存一大片较低品位的壳层岩石。通过探索这些岩石的变形历史，这项研究有望为喜马拉雅运动学模型提供强有力的限制。这项工作的更广泛影响包括培训一名来自代表性不足群体的博士生，以及为多达六名本科生提供研究经验。研究小组将继续开展外联活动，通过创建维基百科页面，向当地和国际上的广大受众传播构造学。

This research seeks to determine the structural evolution of the Himalayan superstructure from the India-Asia suture zone to the deformed foreland. The term 'superstructure' refers to the low-grade upper level of an orogenic system, and contrasts with high-grade 'infrastructure' below. Along most of the Himalayan arc, superstructure rocks are only partially preserved. They occur in the north, but high-grade crystalline rocks occupy a central swath and recently accreted material dominates exposures farther south. However, across the eastern Ladakh - Chamba region of the northwestern Indian Himalaya, superstructure rocks are continuously exposed from the suture zone to the foreland fold-thrust belt. The deformation record preserved in these rocks can be used to address two problems: (1) long-standing controversy over the mechanism that emplaced infrastructure rocks between superstructure rocks and accreted materials, and (2) recent recognition that the Himalayan rock record may preserve far less shortening than that required by plate circuit reconstructions. These issues will be addressed by a research program combining mapping, analytical work, and reconstruction. Surface and remote sensing geological mapping using ASTER data will establish the geological framework across the eastern Ladakh - Chamba superstructure. These results will be complemented by kinematic analysis obtained via microstructural studies and thermal history determined via 40Ar/39Ar geo/thermochronology. New and existing structural, thermal, and chronological data will be integrated via balanced palinspastic reconstruction to explore deformation modes and determine shortening estimates, thereby providing a deformation history capable of testing extrusion models and a revised geological shortening budget to test shortening models. Preliminary analysis suggests that this work may add nearly 500 kilometers to the Himalayan shortening budget, which would represent a greater than 50% increase in preserved geological shortening.Mountain-building processes are commonly explored across systems with ongoing contraction such as the Alps, Andes, and Himalaya. These mountain belts offer good preservation, direct constraints on boundary conditions, and the opportunity to simultaneously interrogate ancient and active deformation. The community of tectonics workers is still working out the regional geometry and kinematics of many parts of these systems, particularly along-strike structural variations. The incompleteness of our first-order knowledge of the Himalaya is highlighted by recent studies of the Himalaya that propose a variety of radical revisions to our understanding of initial India-Asia collision and the emplacement of its high-grade crystalline core. The current project will help address both issues by utilizing an under-explored aspect of the range: the local preservation of a wide span of its lower grade carapace rocks in the western Himalaya. By exploring the deformation history of these rocks, this study is anticipated to provide strong limits on Himalayan kinematic models. Broader impacts of this work include training of a Ph.D. student from an underrepresented group, as well as providing research experience for as many as six undergraduate students. The research team will continue outreach activities to communicate tectonics to broad audiences locally, and internationally through creation of Wikipedia pages.