Orogen-parallel extension and exhumation enhanced by denudation in the trans-Himalayan Arun River gorge, Ama Drime Massif, Tibet-Nepal
Orogen-parallel extension and exhumation enhanced by denudation in the trans-Himalayan Arun River gorge, Ama Drime Massif, Tibet-Nepal
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DOI：
10.1130/g24722a.1
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发表时间：
2008-07
期刊：
影响因子：
5.8
通讯作者：
M. J. Jessup;D. Newell;J. Cottle;Aaron Berger;J. Spotila
中科院分区：
文献类型：
--
作者：
M. J. Jessup;D. Newell;J. Cottle;Aaron Berger;J. Spotila
在许多活跃的构造环境中，集中剥蚀和中地壳流动是耦合的，包括喜马拉雅山脉，在地壳缩短期间，由逆冲断层和低角度拆离系统调节的中地壳岩石的挖掘得到了很好的记录。珠穆朗玛峰地区的新构造和(U-Th)/He磷灰石资料表明，在造山带平行伸展过程中，在1.5 ~ 3.0 Ma之间，跨喜马拉雅阿玛原始岩以1 mm/年的最小速率被掘出。以往的研究将阿马堆西侧北北东—南西向剪切带解释为主要的中央逆冲带；然而，我们的数据显示，阿玛原岩的两侧被100 - 300米厚的正常意义上的剪切带和拆离系统所束缚，这些剪切带和拆离系统在运动学上与年轻的脆性断裂相联系，这些断裂与第四纪沉积相抵消，记录了活跃的造山带平行伸展。结合现有资料，这些结果表明，阿玛原岩是在造山带平行伸展期间被挖掘出来的，这种伸展是由横跨喜马拉雅的阿伦河峡谷的剥蚀作用增强的，或者可能与剥蚀作用相结合。
Focused denudation and mid-crustal flow are coupled in many active tectonic settings, including the Himalaya, where exhumation of mid-crustal rocks accommodated by thrust faults and low-angle detachment systems during crustal shortening is well documented. New structural and (U-Th)/He apatite data from the Mount Everest region demonstrate that the trans-Himalayan Ama Drime Massif has been exhumed at a minimum rate of ~1 mm/yr between 1.5 and 3.0 Ma during orogen-parallel extension. The Ama Drime Massif offsets the South Tibetan detachment system, and therefore the South Tibetan detachment system is no longer capable of accommodating south-directed mid-crustal flow or coupling it with focused denudation. Previous investigations interpreted the NNE-SSW–striking shear zone on the west side of the Ama Drime Massif as the Main Central thrust zone; however, our data show that the Ama Drime Massif is bounded on either side by 100–300-m-thick normal-sense shear zone and detachment systems that are kinematically linked to young brittle faults that offset Quaternary deposits and record active orogen-parallel extension. When combined with existing data, these results suggest that the Ama Drime Massif was exhumed during orogen-parallel extension that was enhanced by, or potentially coupled with, denudation in the trans-Himalayan Arun River gorge. This model provides important insights into the mechanisms that exhumed trans-Himalayan antiformal structures during orogen-parallel extension along the southern margin of the Tibetan Plateau.