Structural & metamorphic evolution of the Zanskar Himalaya in the Suru Valley region(India), from crustal thickening through to melting and exhumation

结构性

• 批准号: 2099916
• 金额: --
• 依托单位: University of Oxford
• 依托单位国家: 英国
• 项目类别: Studentship
• 财政年份: 2018
• 资助国家: 英国
• 起止时间: 2018 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=studentship-2099916
• 关键词: Structural; metamorphic; evolution; Zanskar; Himalaya

The Himalaya is one of the best orogenic belts to understand orogenic processes involved in continental collisions because it is the youngest, still ongoing, best exposed and most intensively studied mountain belt on Earth. Unlike the Alps, the Himalaya is relatively simple with profiles across the range from India in the west to Bhutan in the east all remarkably similar. The deepest levels of the crust are exposed in the Greater Himalayan Sequence (GHS) where metamorphism is attributed to a regional Barrovian type event in response to crustal shortening and thickening following continental collision (e.g. Searle 2015). A series of greenschist, staurolite- kyanite- and sillimanite-grade gneisses with a central core of migmatite and crustal melt leucogranites are exposed along the highest peaks. Mapping of metamorphic isograds has characterised the base of the GHS as a zone of inverted metamorphism along the Main Central Thrust zone (Stephenson et al. 2000, 2001) and the top of the slab along the Zanskar Shear zone as a zone of right way up isograds (Honegger 1983; Searle et al. 1999; Walker et al. 1999, 2001). The Suru Valley transect in western Zanskar (NW India) cuts through the entire top section of the GHS - providing a complete profile of regional metamorphism and is almost 75-80% exposed, unlike everywhere in the central and eastern Himalaya where there is far more forest cover). This valley section provides an ideal field transect in which to map out in detail the structures and collect samples over at least 20 km structural profile through the thickened crust of the Himalaya for thermobarometry and geochronology.

喜马拉雅山是了解大陆碰撞造山过程的最佳造山带之一，因为它是地球上最年轻、仍在持续、暴露最充分、研究最深入的山地带。与阿尔卑斯山不同，喜马拉雅山脉相对简单，从西部的印度到东部的不丹，其轮廓都非常相似。地壳最深处暴露在大喜马拉雅层序（GHS）中，其中变质作用归因于区域性巴罗夫型事件，响应大陆碰撞后地壳缩短和增厚（例如 Searle 2015）。一系列绿片岩、十字石-蓝晶石和硅线石级片麻岩，中心为混合岩和地壳熔融淡色花岗岩，沿着最高峰暴露出来。变质等梯度测绘将 GHS 的底部描述为沿主中央冲断带的倒转变质作用区（Stephenson 等，2000，2001），沿 Zanskar 剪切带的板块顶部为等梯度正上方的区域（Honegger，1983；Searle 等，1999；Walker 等，1999， 2001）。赞斯卡西部（印度西北部）的苏鲁山谷横断面穿过 GHS 的整个顶部，提供了区域变质作用的完整剖面，几乎 75-80% 暴露在外，这与喜马拉雅山中部和东部的任何地方（那里的森林覆盖率要高得多）不同。该山谷部分提供了理想的野外横断面，可在其中详细绘制结构图并通过喜马拉雅山增厚的地壳收集至少 20 公里结构剖面的样本，以进行温压测量和地质年代学。