| 青藏高原P波速度层析成像与岩石圈结构 |
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| 引用本文： | 瞿辰,胥颐,杨文采,汪晟,刘晓宇.青藏高原P波速度层析成像与岩石圈结构[J].地球物理学报,2020,63(3):847-859. |
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| 作者姓名： | 瞿辰 胥颐 杨文采 汪晟 刘晓宇 |
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| 作者单位： | 1. 中国地质科学院地质研究所, 北京 100037;2. 中国科学院地质与地球物理研究所, 北京 100029;3. 浙江大学地球科学学院, 杭州 310027;4. 澳大利亚国立大学地球科学学院, 堪培拉 1026 |
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| 基金项目： | 国家自然科学基金项目（41374066）资助. |
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| 摘 要： | 利用中国西部地震台网的数据,通过体波层析成像反演了青藏高原及邻域的三维P波速度结构.根据地壳和上地幔的速度变化和构造特征,重点讨论了下地壳流动、地幔上涌、岩石圈减薄以及与藏北新生代火山岩和藏南裂谷系的关系等问题.分析表明,青藏高原中、下地壳平均速度偏低,低速区主要分布在拉萨和羌塘块体内部,随着深度的增加逐渐扩大到松潘—甘孜块体.上述低速区之间多被高速带分隔,暗示地壳中、下部的韧性变形被限制在特定的区域,不太适于产生贯穿整个青藏高原的大规模横向流动.此外,地幔上涌也并非普遍发生于整个青藏高原,而是集中在羌塘、松潘—甘孜以及喜马拉雅东构造结附近,导致上述区域的岩石圈地幔较薄,并且伴生火山活动和岩浆作用.此外,由于印度大陆岩石圈在向北俯冲,板片下沉过程中引起地幔上涌,热流物质有可能上升进入地壳,这一作用对藏北新生代火山岩和藏南裂谷系的形成以及中、下地壳的韧性变形产生了明显的影响.
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| 关 键 词： | 青藏高原 P波速度 岩石圈结构 层析成像 |
| 收稿时间： | 2019-03-22 |
P-wave velocity imaging and lithosphere structure of the Tibetan plateau |
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| QU Chen,XU Yi,YANG WenCai,WANG Sheng,LIU XiaoYu.P-wave velocity imaging and lithosphere structure of the Tibetan plateau[J].Chinese Journal of Geophysics,2020,63(3):847-859. |
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| Authors: | QU Chen XU Yi YANG WenCai WANG Sheng LIU XiaoYu |
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| Institution: | 1. Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100037, China;2. Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China;3. School of Earth Sciences, Zhejiang University, Hangzhou 310027, China;4. Research School of Earth Sciences, Australian National University, Canberra 1026, Australia |
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| Abstract: | Using arrival data from seismic networks in western China, we inverted three-dimensional P-wave velocity structures of the Tibetan plateau and surrounding areas by the body-wave tomography technique. Based on the velocity variation and tectonic features in the crust and lithospheric mantle, our analysis focuses on the lower crust flow, mantle upwelling and lithospheric thinning, and their relations with Cenozoic volcanic activity and the rift system in southern Tibet. The results indicate that the Tibetan plateau is underlain by the low-velocity zones in middle and lower crust, which are distributed in the Lasa and Qiangtang blocks, enlarged to the Songpan-Garzê block at the lower crust depth. These low-velocity zones are not interconnected, instead separated by high-velocity zones. This implies that ductile deformation in the mid-lower crust is restricted in tectonically special regions and a large-scale crusal flow could not happen throughout the plateau. Likewise, the mantle upwelling seems not to occur widespread in the Tibetan plateau, only confined to the Qiangtang, Songpan-Garzê and eastern Himalayas, which had lead to the thinning of the lithospheric thickness and strong volcanic and magma activities there. Due to the mantle upwelling, which is caused by the subduction of the Indian continental lithosphere, heat flows probably intruded up into the crust. This effect has a significant impact on the formation of Cenozoic volcanic rocks in northern Tibet, the rift system in southern Tibet and the ductile deformation of the middle and lower crust. |
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| Keywords: | Tibetan Plateau P-wave velocity Lithosphere structure Seismic tomography |
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