Development of the Himalayan Superstructure, Northwestern India

本研究旨在确定从印度-亚洲缝合带到变形前陆的喜马拉雅上部结构的构造演化。“上层建筑”一词指的是造山系统的低级上层，与下面的高级“基础设施”形成对比。沿着喜马拉雅弧的大部分，上部结构岩石仅部分保存。它们出现在北部，但高级结晶岩占据了中央地带，最近增生的物质在更南部的暴露中占主导地位。然而，在印度喜马拉雅西北部的拉达克-昌巴地区东部，从缝合带到前陆褶皱冲断带，上部结构岩石不断出露。保存在这些岩石中的变形记录可以用来解决两个问题：（1）长期存在的争议机制，侵位的基础结构岩石之间的上部结构岩石和增生物质，（2）最近认识到，喜马拉雅岩石记录可能保存远小于缩短所需的板块电路重建。这些问题将通过一项结合绘图、分析工作和重建的研究计划来解决。利用ASTER数据进行的地表和遥感地质测绘将建立横跨拉达克东部-昌巴上层建筑的地质框架。这些结果将得到补充的运动学分析，通过微结构研究和热历史确定通过40 Ar/39 Ar地质/热年代学。新的和现有的结构，热，年代学数据将通过平衡palmostastic重建整合，以探索变形模式，并确定缩短估计，从而提供一个变形历史能够测试挤压模型和修订的地质缩短预算测试缩短模型。初步分析表明，这项工作可能会增加近500公里的喜马拉雅山缩短预算，这将意味着超过50%的增加保存的地质缩短。造山过程通常是探索跨系统与持续收缩，如阿尔卑斯山，安第斯山脉，喜马拉雅山。这些山脉带提供了良好的保存，直接限制边界条件，并有机会同时询问古老的和活跃的变形。构造学界仍在研究这些系统的许多部分的区域几何学和运动学，特别是沿走向的构造变化。最近对喜马拉雅山的研究突出了我们对喜马拉雅山的一级知识的不完整性，这些研究对我们对最初的印度-亚洲碰撞及其高级结晶核的定位的理解提出了各种根本性的修正。目前的项目将有助于解决这两个问题，利用一个未充分开发的方面的范围：当地保存的宽跨度的低等级甲壳岩石在喜马拉雅山西部。通过探索这些岩石的变形历史，这项研究预计将提供强有力的限制喜马拉雅运动学模型。这项工作的更广泛影响包括培养一名博士。学生从一个代表性不足的群体，以及提供研究经验，多达六个本科生。研究团队将继续开展外展活动，通过创建维基百科页面，向当地和国际上的广大受众传达构造学。

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.