南海北部深水区新生代岩浆岩分布规律及其与海底地质灾害的相关性

前人对南海北部新生代陆缘盆地结构、构造样式和期次等做了大量的研究工作,但对于具体体现内动力过程的岩浆活动关注较少,尤其是北部深水区的研究鲜有涉及。本文基于二维地震剖面的解译分析,将南海北部新生代岩浆岩划分为3个集中分布区:琼东南-西沙区、神狐区和东沙区。各区域岩浆岩的产出状态有所差异,其中琼东南-西沙区岩浆岩的平面展布规律性极强,主要受右行右阶的走滑断裂控制;神狐区岩浆岩位于NW向与NE向断裂的交汇处,侵位空间受先存断裂制约;东沙区岩浆岩的产生与东沙运动期间区域伸展过程有直接关系。作为内动力的表征,岩浆作用对于海底地形地貌具有重要的改造作用,与活动断裂、海底滑坡、浅层气等海底地质灾害也具有成因上的关联。

Distribution of Cenozoic igneous rocks and its relation to submarine geological hazards in the deepwater area of the northern South China Sea

The previous studies mainly focused on the structure of the basin,structural style and evolution in the northern margin of the South China Sea. Cenzoic magmatism in this region is less known,especially for the deepwater area. Based on the analysis and interpretation of many 2D seismic profiles,the igneous rocks can be divided into three regions,including the Qiongdongnan-Xisha Region,the Shenhu Region,the Dongsha Region. The occurrences in different regions have distinct differences. The igneous rocks of the Qiongdongnan-Xisha Region have an obvious rule of distribution controlled by the dextral Right-step pull-apart basin. The igneous rocks of the Shenhu Region are mainly located in the intersection of the NE and NW faults. There is a high correlation between the extensional stress field caused by the Dongsha Movement and the igneous rocks in the Dongsha Region. As a form of manifestation of internal geodynamics,the magmatism plays an important role in re-moulding the submarine surface topography. There is also an obvious relation among the magmatism,active faults,submarine landslides and shallow gas.