| 南海北部珠江口—琼东南盆地地壳速度结构与几何分层 |
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| 引用本文： | 张中杰,刘一峰,张素芳,张功成,范蔚茗.南海北部珠江口—琼东南盆地地壳速度结构与几何分层[J].地球物理学报,2009,52(10):2461-2471. |
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| 作者姓名： | 张中杰 刘一峰 张素芳 张功成 范蔚茗 |
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| 作者单位： | 1.岩石圈演化国家重点实验室，中国科学院地质与地球物理研究所，北京 100029;2.中国科学院研究生院，北京 100049;3.中海石油（中国）有限公司北京研究中心，北京 100027;4.中国科学院广州地球化学研究所，广州 510640 |
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| 基金项目： | 中国科学院知识创新工程重大项目，国家自然科学基金项目 |
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| 摘 要： | 基于南海北部大陆边缘珠江口—琼东南盆地深水区实施的14条近垂直深反射地震探测叠加速度谱，利用Dix公式将叠加速度剖面转换为地壳层速度剖面，并利用时深转换方法构建了深度域地壳层速度模型，综合各地壳速度剖面分析了南海北部大陆边缘珠江口与琼东南盆地不同深度层次的P波速度变化趋势以及地壳几何分层特征.结果表明，琼东南盆地区可分为4～8 km沉积层（VP为1.7～4.7 km/s）、4～10 km厚的上地壳层（VP为5.2～6.3 km/s）、5 km〗左右的下地壳层（VP为6.4～7.0 km/s）以及2～6 km厚的高速下地壳底层（VP＞7.0 km/s）.VP＞7.0 km/s下地壳高速层的存在被认为是岩石圈伸展、下地壳底部底辟构造或者是残存的原始华夏下地壳基性层的地震学指示；综合研究区地球物理探测成果构建了跨越华南大陆与南海北部陆坡区剖面莫霍和岩石圈底界图像，揭示出岩石圈上地幔在华南大陆与南海北部大陆边缘的减薄特征.
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| 关 键 词： | 南海 珠江口与琼东南盆地 地壳结构 底辟构造 残余下地壳基性层 岩石圈减薄 |
| 收稿时间： | 2009-7-7 |
| 修稿时间： | 2009-9-21 |
Crustal P-wave velocity structure and layering beneath Zhujiangkou-Qiongdongnan basins, the northern continental margin of South China Sea |
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| ZHANG Zhong-Jie,LIU Yi-Feng,ZHANG Su-Fang,ZHANG Gong-Cheng,FAN Wei-Ming.Crustal P-wave velocity structure and layering beneath Zhujiangkou-Qiongdongnan basins, the northern continental margin of South China Sea[J].Chinese Journal of Geophysics,2009,52(10):2461-2471. |
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| Authors: | ZHANG Zhong-Jie LIU Yi-Feng ZHANG Su-Fang ZHANG Gong-Cheng FAN Wei-Ming |
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| Institution: | 1.State Key Laboratory of Lithospheric Evolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029,China;2.Graduate University of the Chinese Academy of Sciences, Beijing 100049, China;3.Beijing Research Center of CNOOC, Beijing 100027,China;4.Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640,China |
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| Abstract: | Base on stack velocity spectrum dataset of 14 near-vertical deep reflection profiles in the Zhujiang River estuary-Qiongdongnan basin in the continental margin of northern South China Sea, we use Dix formula to transform the corresponding stack velocities into the crustal-layer-velocities (in TWT domain) and convert the layer velocities into the depth domain by time-depth transformation scheme. Integrating all the crustal velocity models, we analyze the spatial variation of P wave velocity in different depths and the stratified geometry of crust in the Yinggehai and Qiongdongnan basin area in the continent margin of northern South China Sea. The results demonstrate that the kinematic structure of Qiongdongnan basin can be divided into 4~8km thick sediment layer (Vp is 1.7~4.7 km/s), 4~10 km thick upper crust (Vp is 5.2~6.3 km/s), about 5 km thick normal lower crust (Vp is 6.4~7.0 km/s) and about 2~6 km thick anomalous lower crust with high velocity (>7.0 km/s). The existence of anomalous lower crust layer with high velocities >7.0 km/s can be considered as seismic signature of the underplating at the lower crust bottom induced by lithosphere extension in South China and its continental margin, or the residual mafic layer of the extended Cathaysia lower crust. Integrating the related geophysical sounding results, we construct the depth images of Moho and the lithosphere bottom across the continent of South China and the continental slope of South China Sea, which reveals the lithosphere thinning across continental South China and the continental margin of the South China sea. |
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| Keywords: | South China Sea Zhujiankou and Qiongdongnan basins Crustal structure Underplating Residual lower crustal mafic layer Lithosphere thinning |
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