南海地球物理场特征与基底断裂体系研究

Researches on Geophysical Field Characteristics and Basement Fault System of South China Sea

南海海域主体可划分为南海北缘、中西沙、南沙、南海海盆四块 ,各块具有明显不同的重磁场特征 .反演得到的莫霍面总体趋势由陆向洋抬升 ,反映陆壳、拉伸陆壳、过渡壳、洋壳的分布 .东沙高磁异常含一定的高频成份 ,与新生代玄武岩及中生代岩浆岩有关 ,而其低频成份可能反映了发育的下地壳高速层 .南海海域断裂极为发育 ,可分为北东向断裂组、东西向断裂组、北西向断裂组和南北向断裂组 .南海北缘、南缘均以北东向张性断裂与北西向张剪性、剪性断裂为主要格架 ,形成了“南北分带、东西分块”构造格局 .

Geophysical features and basement faults system of South China Sea are studied. According to characteristics of geophysical fields, South China Sea can be divided to four blocks, which are north margin block, Zhongsha-Xisha block, Nansha block and central basin block with different features. Inversion shows Moho discontinuity depth increase from land to sea and the distribution of continental crust, extensional crust, transitional crust and oceanic crust. The high frequency part of Dongsha high-value magnetic anomaly may be related with Cenozoic basalt and Mesozoic magmatic rocks, and the low frequency part developing high-velocity lower crust. Fault systems develop well in South China Sea and can be divided to four groups, which are northeast-direction fault group, eastwest-direction fault group, northwest-direction fault group and northsouth-direction fault group. On north margin and south margin of South China Sea, northeast-direction extension faults and northwest extension/extension-shear faults characterize the main tectonic framework of separated stripes in north-west direction and blocks in west-east direction.