Internal Flow, Extrusion and Exhumation History of the Greater Himalayan Slab

大喜马拉雅板片的内部流动、挤压和折返历史

• 批准号: 0711207
• 负责人: Richard Law
• 金额: $ 33.2万
• 依托单位: Virginia Polytechnic Institute and State University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2007
• 资助国家: 美国
• 起止时间: 2007-08-15 至 2012-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0711207&HistoricalAwards=false
• 关键词: Internal; Flow; Extrusion; Exhumation; History

The Greater Himalayan Slab is a 5-30 km thick northward-dipping tectonic unit of mid-crustal rocks that forms the crystalline core of the Himalaya and is bounded along its base by the Main Central Thrust Zone and along the top by the South Tibetan Detachment System of normal faults. Assuming simultaneous or overlapping movement along these crustal-scale bounding shear zones, the Greater Himalayan Slab is often modeled as a north-dipping channel or wedge/slab of mid-crustal rocks that, beginning in Early Miocene times, was extruded southward from beneath the Tibetan plateau. Identification of a pure shear component is critically important because a significant pure shear component will itself act as a driver for crustal extrusion and exhumation, resulting in: 1) thinning and dip-parallel extension of the slab itself, 2) relative to strict simple shear, an increase in both strain rates and extrusion/exhumation rates of the Himalayan crystalline core. Testing of channel flow/extrusion models requires that spatial and temporal distributions of vorticity domains be mapped out across the slab, and ultimately also requires a close integration between kinematic and pressure-temperature-time analyses in order to constrain progressive deformation and exhumation paths. Results from previous work the Mt. Everest region (along the top of the Greater Himalayan Slab) suggests that, in contrast to predictions from channel flow and extrusion models, the highest pure shear components are located towards the base of the slab, possibly indicating the importance of lithostatic loading. This project will complete transport-parallel sampling traverse across the Greater Himalayan Slab in the Everest region and undertake a series of similar transport-parallel traverses in key areas along the length of the Himalaya in order to make a first order assessment of: a) along-strike spatial and temporal variations in flow and, b) how these variations in flow may be related to along-strike changes in the structural evolution and exhumation history of the Greater Himalayan Slab. In each traverse suites of oriented samples will be collected for laboratory-based vorticity analyses using all appropriate microstructural and crystal fabric/strain techniques. Data provided by these different analytical techniques will be linked to deformation temperatures indicated by associated microstructures and crystal fabrics, hence enabling changes in vorticity of flow to be tracked during progressive exhumation/cooling.The Himalaya is frequently cited as the classic example of a mountain chain produced by continent-continent collision, with the chain progressively evolving as sheets of rock are stacked up on top of one another during continued collision between India and Asia. It has been proposed that rocks forming the metamorphic core of the Himalaya, originally located beneath the Tibetan Plateau, were being squeezed and extruded southwards as a slab-shaped body towards the Earth's surface, driving upwards the crest of the Himalaya, and that this movement is driven by horizontal gradients in vertical load. The greater the degree of vertical squeezing and shortening in this flowing channel, the greater the amount of material extruded towards the surface. If surface erosion cannot keep pace with extrusion, then the greater the amount of extrusion the greater the amount of surface uplift, hence explaining why the highest Himalayan peaks always coincide with the outcrop position of this slab of mid-crustal rocks. If the material is deforming by simple shear, a mechanism similar to shuffling a pack of playing cards, then the rocks won't lengthen parallel to the shearing motion, just as a playing card doesn't lengthen when the deck is shuffled. So, in simple shear, rocks from the middle crust won't move very far towards the surface. However, if material is both sheared and vertically shortened (pure shear) then the rocks will lengthen parallel to the shearing motion and move towards the surface. This research project aims to determine if the pure shear driven extrusion processes have operated along the length of the Himalaya, or if they are unique to the currently highest part of the mountain chain.

较大的喜马拉雅板是一个5-30 km厚的北向北深头岩石岩石，形成了喜马拉雅山的结晶芯，并沿其基部与正常断层的南藏族脱离系统沿着主要中央推力区域界定。假设沿着这些地壳尺度的边界剪切带同时或重叠运动，则较大的喜马拉雅板通常被建模为北倾通道或中壳中岩石的楔形通道或楔形/板，从中新世早期开始，从藏族高原下方挤出了南部。纯粹的剪切成分的识别至关重要，因为重要的纯剪切成分本身将充当地壳挤出和挖掘的驱动因素，从而：1）板本身的稀疏和浸入平行延伸，2）相对于严格的简单剪切，与他的紧张速率和挤出速率和挤出率的增加/挤出率的增加。通道流/挤出模型的测试要求将涡度结构域的空间和时间分布绘制在整个板上，最终还需要在运动学和压力温度时间分析之间进行密切的整合，以限制渐进式变形和挖掘路径。先前工作的结果珠穆朗玛峰区域（沿更大的喜马拉雅板的顶部）表明，与通道流量和挤出模型的预测相反，最高的纯剪切成分位于板的底部，可能表明岩性负载的重要性。该项目将完成珠穆朗玛峰地区大喜马拉雅板的横跨遍历的遍历，并在喜马拉雅山长度上进行一系列相似的运输 - 平行遍历，以进行一阶评估，以进行一阶评估：a）沿着流程和时间上的较大的流程和b）在流程中的较大变化以及b）在范围内的较大变化，并且b）与构建相关的变化相关，构成了沿着这些变化的范围，并且构成了沿着这些变化的变化。喜马拉雅板。在每个遍历套房中，将使用所有适当的微观结构和晶体织物/应变技术收集基于实验室的涡度分析。这些不同的分析技术提供的数据将与相关的微观结构和晶体织物所指示的变形温度有关，从而使在逐步挖掘/冷却过程中的流动涡度的变化发生变化，喜马拉雅山经常被认为是由临界的山连与canderivally contriment contriment contriment contrimenty contriment contriment contriment contrimation contriment contriment contrimation the rock的经典示例，而摇摆不定，则是摇摆不定的效果。在印度和亚洲之间。有人提出，最初位于藏族高原下方的喜马拉雅岩的变质核心的岩石被挤压和向南挤压，作为平板形的身体向地球表面，向上向上推动了喜马拉雅山脉的波峰，并且这种运动是由近水平梯度驱动的。在此流动通道中垂直挤压和缩短的程度越大，向表面挤出的材料量越大。如果表面侵蚀无法与挤压步伐保持同步，那么挤压量越大，表面隆起的量就越大，因此解释了为什么最高的喜马拉雅峰总是与中壳岩石板的露头位置相吻合。如果材料通过简单的剪切变形，这种机制类似于将一包扑克牌改装，那么岩石就不会延长与剪切运动的延长一样，就像当甲板被洗牌时扑克牌不会延长。因此，简单的剪切岩中的岩石不会向表面移动很远。但是，如果材料既剪切又垂直缩短（纯剪切），则岩石将平行于剪切运动并向表面移动。该研究项目旨在确定纯剪切驱动的挤出过程是否沿喜马拉雅省的长度进行，还是它们在山脉当前最高的部分是独特的。