南海北部区域构造和陆壳向洋壳的转化

1.海底扩张和陆壳大洋化,均能形成洋壳。陆壳转化为过渡壳是大洋化的必经阶段。 2.航磁测区内的中央海盆,具有类似于大洋中海底扩张形成的对称磁异常条带。 3.在西沙北裂谷、莺歌海裂谷型拗陷,以及属于断陷盆地性质的珠一、珠二拗陷等地,有沿着断裂上升的类似于洋壳成分的地幔物质喷溢或在地壳上层侵位,那里的地壳都有不同程度的减薄,属于过渡型地壳。西沙北裂谷的“莫霍面”,比相邻的南北两侧高出约10公里。 4.在南海北部发生多中心微型扩张和大洋化。

ON THE STRUCTURAL FEATURE AND THE OCEANIZATION IN THE NORTH PART OF SOUTH CHINA SEA

1. Both sea-floor spreading and oceanization may lead to the formation of oceanic crust. The transformation of continental crust to transitional crust is necessarily effected through the process of oceanization.2. In the deep basins within the surveyed area, the aeromagnetie anomaly zones are very similar to the symmetric linear magnetic anomaly stripes formed by sea-floor spreading.3. In the rift valley north of the Xisha Islands and in the Yingge Sea as well as zhu-1 and zhu-2 downwarps rift-type fault basins, upper mantle materials similar to oceanic crust in composition usually formed eruptions through deep fractures or were emplaced in the upper part of some extent and thus belongs to transitional type of crust. The Mohorovicic boundary surface under the submarine rift to north of Xisha Islands is about 10 km higher than that of its surrounding areas to the north and south.4. In the northern part of South China Sea, some polycentered micro-spreading and oceanization of crust have occurred.