A crustal structure profile across the northern continental margin of the South China Sea
A crustal structure profile across the northern continental margin of the South China Sea
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DOI：
10.1016/s0040-1951(01)00062-2
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发表时间：
2001-08
期刊：
影响因子：
2.9
通讯作者：
Y. Pin;Z. Di;Zhao-shu Liu
中科院分区：
文献类型：
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作者：
Y. Pin;Z. Di;Zhao-shu Liu
在南海北部大陆边缘进行了海底地震仪（OBS）地球物理实验。采用二维运动射线追踪法构建合成记录，并沿OBS剖面确定地质模型。根据折射p波相位的计算和解释，地壳厚度从沿海地区的22km （OBS-1）减少到深海的8km （OBS-15）。火山作用构造的下斜坡在莫霍深度22 ~ 9km范围内变化剧烈。下斜坡上的火山是海陆过渡带的标志。在陆架和斜坡上的下地壳底部发现了平均厚度为4km的高速层（HVL）。南海是由华南大陆被动裂谷和海底扩张形成的。然而，在南海北缘收集的地质和地球物理数据表明，在拉裂和破裂过程中，有少量岩浆侵入或喷发到地壳上。进一步分析表明，大陆薄壳基底的HVZ与南海海底扩张停止后发生的岩浆活动有关。地壳伸展和破裂过程中的岩浆作用非常弱。因此，将南海北部大陆边缘划分为非火山被动边缘。南海南缘地壳厚度稳定在18-24km，与南海北缘地壳逐渐变薄不同。它们构成了一对非对称共轭的被动边缘。
An ocean bottom seismometer (OBS) geophysical experiment was carried out across the northern continental margin of the South China Sea. Two-dimension kinematic ray tracing was used to construct synthetic records and to define the geological model along the OBS profile. According to the calculation and interpretation of refracted P-wave phases, the crustal thickness decreases from 22km (OBS-1) in littoral area to 8km (OBS-15) in deep sea. The lower slope structured by volcanism changes sharply in Moho depth from 22 to 9km. The volcanoes over the lower slope were markers of ocean–continental transition zone. A high velocity layer (HVL) with an average thickness of 4km was found in the base of the lower crust over the shelf and slope. The South China Sea was originated by the passive rifting of South China continent and seafloor spreading. However, geological and geophysical data collected in the northern margin of the South China Sea show a small amount of magma intruded into or erupted onto the crust during pull-apart and breakup. Further analysis shows that the HVZ in the base of the thinned continental crust was related to magmatism that occurred after the cessation of seafloor spreading of the South China Sea. Magmatism during the crustal extension and breakup is very weak. Therefore, the northern continental margin of the SCS is classified as non-volcanic passive margin. The southern margin of the South China Sea has a crust with a steady thickness of 18–24km, which is different from the northern margin of the South China Sea with a gradually thinned crust. They constitute an asymmetrically conjugated pair of passive margins.