Miocene to Holocene exhumation of metamorphic crustal wedges in the NW Himalaya: Evidence for tectonic extrusion coupled to fluvial erosion
Miocene to Holocene exhumation of metamorphic crustal wedges in the NW Himalaya: Evidence for tectonic extrusion coupled to fluvial erosion
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DOI：
10.1029/2002tc001429
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发表时间：
2004-02
期刊：
影响因子：
4.2
通讯作者：
J. Vannay;B. Grasemann;M. Rahn;W. Frank;A. Carter;Vincent Baudraz;M. Cosca
中科院分区：
文献类型：
--
作者：
J. Vannay;B. Grasemann;M. Rahn;W. Frank;A. Carter;Vincent Baudraz;M. Cosca
沿着Sutlej山谷（印度）出露的喜马拉雅结晶核区由两个高级变质片麻岩片组成，这两个片由于印度板块边缘地壳变形的前陆定向传播而相继被下冲和构造挤压。高喜马拉雅结晶层序（HHCS）由角闪岩相到混合岩副片麻岩组成，在始新世和早中新世之间，在30 km深处的温度高达750°C时变质。早中新世，主中央冲断带（MCT）的沿着逆冲推覆作用和桑拉拆离带的沿着伸展作用的联合作用导致了HHCS的快速折返和冷却，而中中新世以来的折返主要受侵蚀控制。小喜马拉雅结晶层序（LHCS）由角闪岩相的帕拉片麻岩和正片麻岩组成，在MCT下方30 km深处的俯冲过程中，在高达700°C的温度下变质。晚中新世以来，由于受沿着Munsiari逆冲断层的逆冲作用和MCT上盘的延伸控制的折返作用，LHCS冷却非常迅速。喜马拉雅前缘的构造挤压的更新阶段仍然活跃，正如当今区域地震活动以及与LHCS近地表地热梯度升高有关的热液循环所表明的那样。正如最近在喜马拉雅构造结中所证明的那样，沿着Sutlej山谷沿着的深部地壳岩石的活跃剥露在空间上与这条主要的跨喜马拉雅河流的高侵蚀潜力相关。这种相关性支持了大陆碰撞期间地壳尺度构造热改造与沿着主要河流系统的有效侵蚀之间正反馈的新观点。
The Himalayan crystalline core zone exposed along the Sutlej Valley (India) is composed of two high‐grade metamorphic gneiss sheets that were successively underthrusted and tectonically extruded, as a consequence of the foreland‐directed propagation of crustal deformation in the Indian plate margin. The High Himalayan Crystalline Sequence (HHCS) is composed of amphibolite facies to migmatitic paragneisses, metamorphosed at temperatures up to 750°C at 30 km depth between Eocene and early Miocene. During early Miocene, combined thrusting along the Main Central Thrust (MCT) and extension along the Sangla Detachment induced the rapid exhumation and cooling of the HHCS, whereas exhumation was mainly controlled by erosion since middle Miocene. The Lesser Himalayan Crystalline Sequence (LHCS) is composed of amphibolite facies para‐ and orthogneisses, metamorphosed at temperatures up to 700°C during underthrusting down to 30 km depth beneath the MCT. The LHCS cooled very rapidly since late Miocene, as a consequence of exhumation controlled by thrusting along the Munsiari Thrust and extension in the MCT hanging wall. This renewed phase of tectonic extrusion at the Himalayan front is still active, as indicated by the present‐day regional seismicity, and by hydrothermal circulation linked to elevated near‐surface geothermal gradients in the LHCS. As recently evidenced in the Himalayan syntaxes, active exhumation of deep crustal rocks along the Sutlej Valley is spatially correlated with the high erosional potential of this major trans‐Himalayan river. This correlation supports the emerging view of a positive feedback during continental collision between crustal‐scale tectono‐thermal reworking and efficient erosion along major river systems.