于洋^1,,
徐啸^1,,,
高锐^1,2,
郭晓玉¹
1. 中山大学地球科学与工程学院, 广州 510275
2. 中国地质科学院地质研究所, 国土资源部深部探测与地球动力学重点实验室, 北京 100037

基金项目: 国家自然科学基金（41874102，41674087，41590863）资助


详细信息

作者简介: 于洋, 女, 1995年生, 硕士, 主要从事构造地质学研究.E-mail:yuyang59@mail2.sysu.edu.cn

通讯作者: 徐啸, 男, 1980年生, 副教授, 主要从事地球物理数据的处理、解释及相关构造建模研究.E-mail:xuxiao8@mail.sysu.edu.cn

中图分类号: P315

收稿日期:2019-06-03
修回日期:2019-12-15
上线日期:2020-03-05

Seismic evidence for tectonic affinity of the Yungbwa ophiolitic complex, Western Tibet

YU Yang^1,,
XU Xiao^1,,,
GAO Rui^1,2,
GUO XiaoYu¹
1. School of Earth Sciences and Engineering, Sun Yat-Sen University, Guangzhou 510275, China
2. Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100037, China


More Information

Corresponding author: XU Xiao,E-mail:xuxiao8@mail.sysu.edu.cn

MSC: P315

--> Received Date: 03 June 2019
Revised Date: 15 December 2019
Available Online: 05 March 2020


摘要
摘要:前人研究表明喜马拉雅造山带西部出露的拉昂错蛇绿混杂岩为新特提斯洋壳岩石圈的一部分，代表了新特提斯洋的关闭及其随后大洋岩石圈物质的仰冲.鉴于拉昂错蛇绿岩的构造演化历史尚不明确，前期对于拉昂错蛇绿岩带构造归属的研究主要基于岩石学研究和地表地质调查等，缺少精细的深部地壳结构进行运动学指示，因此证明拉昂错蛇绿混杂岩体的构造归属并非易事.本次研究中，我们对前期获得的一条南北向延伸穿过雅鲁藏布江缝合带和喜马拉雅造山带西部拉昂错蛇绿岩体的112 km长的深反射地震剖面进行了构造解释.高分辨率的深反射地震剖面清晰地显示了喜马拉雅山脉西部造山带内发育良好的地壳双冲构造几何结构，该地壳尺度双冲构造将印度俯冲地壳物质从底部运移到上部.同时，地震剖面还显示拉昂错蛇绿岩体和雅鲁藏布江蛇绿岩体在上地壳深处呈倾向相反但底部相通的结构构造.结合前人的岩石学/地球化学/地表地质研究成果，我们认为拉昂错蛇绿岩体为雅鲁藏布江缝合带蛇绿岩体的一部分.印度俯冲前缘的双冲构造折返将深部物质带到地表过程的同时，还将部分雅鲁藏布江蛇绿混杂岩携带至南侧距主缝合带位置大约20 km的拉昂错蛇绿岩区域.
关键词: 喜马拉雅造山带/
拉昂错蛇绿岩/
地壳深部结构/
构造归属

Abstract:The Yungbwa ophiolitic complex in the western Himalayas represents segment of the Neo-Tethyan oceanic lithosphere and its subsequent obduction onto the continental margin. Given the unclear stages of evolution, elucidating the affinity of this complex is not a simple task. To address this issue, models were proposed mainly from conventional observations, such as petrological studies and surficial geology investigations. In this case, additional constraints on crustal-scale geometry derived from deep seismic reflection imaging were required. In this study, we presented a 112 km long deep seismic reflection profile that cuts through both the Yarlung-Zangbo suture zone and the Yungbwa ophiolite in the western Tibetan Plateau. A high-resolution seismic image clearly shows the well-developed, duplexing crustal geometry up to the surface within the western Himalayan orogen. The seismic image also shows the opposite dipping but connected structures at depths between the Yungbwa ophiolite and the Yarlung-Zangbo ophiolites at a upper-crustal scale. Coupled with previous studies, we suggest that the Yungbwa ophiolites were emplaced from a deep segment of the original Yarlung-Zangbo suture zone to the surface allochthonous ophiolites. This process occurred as an accommodation to the top-to-the-south crustal-scale duplexing of the subducted Indian crust from the lower plate to the upper plate during subduction reorganization.
Key words:Western Tibet/
Yungbwa ophiolitic complex/
Seismic evidence/
Tectonic affinity



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