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Kinematic, Metamorphic and Age Constraints on the Miyar Thrust Zone: Implications for the Eohimalayan History of the High Himalayan Crystalline of NW India
Tectonics ( IF 3.3 ) Pub Date : 2020-11-01 , DOI: 10.1029/2020tc006379
Martin Robyr 1, 2 , Pierre Lanari 2
Affiliation  

NE‐vergent folds and thrust faults are an enigmatic feature of the High Himalayan Crystalline in the NW Indian Himalaya, as these structures are in marked contrast to the SW‐directed thrusts and fold vergences that predominate in the rest of the Himalaya since the continental collision between India and Asia. However, it is controversial whether these unusual NE‐vergent structures reflect local heterogeneities in strain during the main SW‐vergent deformation or whether they are associated with a postulated NE‐directed early Eocene deformation phase. In this study, microstructural analysis and monazite geochronology across the SW‐dipping Miyar Shear Zone (Miyar Valley, NW India) reveal that these NE‐verging structures result from a NE‐directed propagation of crustal deformation that was initiated before 40 Ma, likely slightly after continental collision at ca. 55 Ma. The new data presented in this study identify that the kinematic evolution of the High Himalayan Crystalline in NW India was initially controlled by an early Eocene NE‐directed crustal thickening phase. Consequently, the SW‐verging kinematic evolution widely accepted for the High Himalayan Crystalline in the central and eastern Himalayan sections should be reconsidered for the western part of the Indian Himalaya. In a broader sense, these results reveal that crustal shortening during the initial stage of continental subduction is not exclusively accommodated by foreland‐directed folding and thrusting but may also be adapted by deformation involving opposite‐directed vergence.

中文翻译:

Miyar 冲断带的运动学、变质和年龄限制:对印度西北部高喜马拉雅结晶的始喜马拉雅历史的影响

NE-vergent 褶皱和逆冲断层是西北印度喜马拉雅高喜马拉雅结晶的一个神秘特征,因为这些结构与自大陆碰撞以来在喜马拉雅其余部分占主导地位的 SW 向逆冲和褶皱辐合形成鲜明对比印度和亚洲之间。然而,这些不寻常的NE-vergent结构是否反映了主要SW-vergent变形期间应变的局部异质性,或者它们是否与假设的NE导向的早期始新世变形阶段有关,这是有争议的。在这项研究中,西南倾斜的 Miyar 剪切带(Miyar Valley,NW India)的显微结构分析和独居石年代学表明,这些 NE 接近的结构是由 40 Ma 之前开始的地壳变形的 NE 定向传播引起的,大约在大陆碰撞后不久。55 马。本研究中提供的新数据表明,印度西北部高喜马拉雅结晶的运动演化最初是由始新世 NE 导向的地壳增厚相控制的。因此,印度喜马拉雅西部应重新考虑喜马拉雅中部和东部高喜马拉雅结晶体的近西南运动演化。从更广泛的意义上讲,这些结果表明,大陆俯冲初期的地壳缩短不仅受前陆定向折叠和逆冲作用的影响,也可能受反向辐合变形的影响。本研究中提供的新数据表明,印度西北部高喜马拉雅结晶的运动演化最初是由始新世 NE 导向的地壳增厚相控制的。因此,印度喜马拉雅西部应重新考虑喜马拉雅中部和东部高喜马拉雅结晶体的近西南运动演化。从更广泛的意义上讲,这些结果表明,大陆俯冲初期的地壳缩短不仅受前陆定向折叠和逆冲作用的影响,还可能受反向辐合变形的影响。本研究中提供的新数据表明,印度西北部高喜马拉雅结晶的运动演化最初是由始新世 NE 导向的地壳增厚相控制的。因此,印度喜马拉雅西部应重新考虑喜马拉雅中部和东部高喜马拉雅结晶体的近西南运动演化。从更广泛的意义上讲,这些结果表明,大陆俯冲初期的地壳缩短不仅受前陆定向折叠和逆冲作用的影响,还可能受反向辐合变形的影响。印度喜马拉雅西部应重新考虑喜马拉雅中部和东部高喜马拉雅结晶体广泛接受的近西南运动学演化。从更广泛的意义上讲,这些结果表明,大陆俯冲初期的地壳缩短不仅受前陆定向折叠和逆冲作用的影响,还可能受反向辐合变形的影响。印度喜马拉雅西部应重新考虑喜马拉雅中部和东部高喜马拉雅结晶体广泛接受的近西南运动学演化。从更广泛的意义上讲,这些结果表明,大陆俯冲初期的地壳缩短不仅受前陆定向折叠和逆冲作用的影响,还可能受反向辐合变形的影响。
更新日期:2020-11-01
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