| 喜马拉雅西部雅鲁藏布江缝合带地壳尺度的构造叠置 |
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| 引用本文： | 卢占武,高锐,Simon KLEMPERER,王海燕,董树文,李文辉,李洪强.喜马拉雅西部雅鲁藏布江缝合带地壳尺度的构造叠置[J].地学前缘,2022,29(2):210-217. |
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| 作者姓名： | 卢占武 高锐 Simon KLEMPERER 王海燕 董树文 李文辉 李洪强 |
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| 作者单位： | 1.中国地质科学院 地质研究所 自然资源部深地动力学重点实验室, 北京 1000372.中山大学 地球科学与工程学院, 广东 广州 5102753.斯坦福大学 地球物理系, 美国 加利福尼亚州 斯坦福 94305-22154.中国地质科学院 深部探测中心, 北京 1000375.南京大学, 江苏 南京 210093 |
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| 基金项目： | 次青藏高原综合科学考察研究项目;国家自然科学基金;自然资源部深地动力学重点实验室项目;国家重点研发计划;国土资源部深部探测项目 |
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| 摘 要： | 陆陆碰撞过程是板块构造缺失的链条。印度板块与亚洲板块的碰撞造就了喜马拉雅造山带和青藏高原的主体。然而,人们对印度板块在大陆碰撞过程中的行为尚不了解。如大陆碰撞及其碰撞后的大陆俯冲是如何进行的、印度板块是俯冲在青藏高原之下还是回转至板块上部(喜马拉雅造山带内)以及两者比例如何,这些仍是亟待解决的问题。印度板块低角度沿喜马拉雅主逆冲断裂(MHT)俯冲在低喜马拉雅和高喜马拉雅之下已经被反射地震图像很好地揭示。然而,关于MHT如何向北延伸,前人的研究仅获得了分辨率较低的接收函数图像。因而,MHT和雅鲁藏布江缝合带之间印度板块的俯冲行为仍是一个谜。喜马拉雅造山楔增生机制,也就是印度地壳前缘的变形机制,反映出物质被临界锥形逆冲断层作用转移到板块上部,或是以韧性管道流的样式向南溢出。在本次研究中,我们给出在喜马拉雅造山带西部地区横过雅鲁藏布江缝合带的沿东经81.5°展布的高分辨率深地震反射剖面,精细揭示了地壳尺度结构构造。剖面显示,MHT以大约20°的倾斜角度延伸至大约60 km深度,接近埋深为70~75 km的Moho面。越过雅鲁藏布江缝合带运移到北面的印度地壳厚度已经不足15 km。深地震反射剖面还显示中地壳逆冲构造反射发育。我们认为,伴随着印度板块俯冲,地壳尺度的多重构造叠置作用使物质自MHT下部的板块向其上部板块转移,这一过程使印度地壳厚度减薄了,同时加厚了喜马拉雅地壳。
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| 关 键 词： | 构造叠置 地壳结构 深地震反射剖面 雅鲁藏布江缝合带 青藏高原 |
| 收稿时间： | 2021-06-19 |
Crustal-scale duplexing beneath the Yarlung Zangbo suture in the western Himalaya |
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| LU Zhanwu,GAO Rui,Simon KLEMPERER,WANG Haiyan,DONG Shuwen,LI Wenhui,LI Hongqiang.Crustal-scale duplexing beneath the Yarlung Zangbo suture in the western Himalaya[J].Earth Science Frontiers,2022,29(2):210-217. |
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| Authors: | LU Zhanwu GAO Rui Simon KLEMPERER WANG Haiyan DONG Shuwen LI Wenhui LI Hongqiang |
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| Institution: | 1. Key Laboratory of Deep-Earth Dynamics of Ministry of Natural Resources, Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100037, China2. School of Earth Sciences and Engineering, Sun Yat-sen University, Guangzhou 510275, China3. Department of Geophysics, Stanford University, Stanford 94305-2215, USA4. Deep Exploration Center, Chinese Academy of Geological Sciences, Beijing 100037, China5. Nanjing University, Nanjing 210093, China |
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| Abstract: | The fate of the Indian plate during continental collision with Asian terranes, and the proportion of the Indian crust that is underthrust or subducted beneath Tibet as opposed to transferred to the upper (Himalayan) plate, are much debated. The active geometry of low-angle underthrusting or subduction of the Indian plate beneath the Lesser and Greater Himalayan thrust sheets is well known from seismic imaging. Previously, only images with lower resolution have been obtained in the Main Himalayan Thrust beneath the Yarlung Zangbo suture that separates Indian and Asian rocks at the surface. It remains controversial whether the orogenic wedge between the Main Himalayan Thrust and the Yarlung Zangbo suture, formed of Indian crust transferred to the upper plate, is evolving by thrust-faulting in a critical-taper wedge or by southward extrusion of a ductile channel flow. Here we present a seismic reflection profile across the western Himalaya at 81.5°E, and show that the Main Himalayan Thrust dips 20 to 60 km depth beneath the Yarlung Zangbo suture, approaching a continuous Moho reflection at 70-75 km depth. The Indian crust being transported northwards beyond the Yarlung Zangbo suture is no more than 15 km thick, reduced from its original 40 km thickness by transfer of material from the lower plate to the upper plate through crustal-scale duplexing. |
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| Keywords: | duplexing crustal structure deep seismic reflection profile Yarlung Zangbo suture the Tibetan Plateau |
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