西沙海域盆地构造格局及其差异演化过程分析

Tectonic Framework in the Xisha Area and Its Differential Evolution

西沙海域夹持于南海西北次海盆和西南次海盆之间,构造演化过程与南海的扩张和南海西部的走滑作用关系密切.基于覆盖西沙海域的区域地震资料开展了构造‒地层解释、盆地结构特征分析和区域构造演化制图,整体上将西沙海域划分出3种类型盆地,即高角度断层控制的盆地、低角度拆离断层控制的盆地和走滑盆地.结合地壳厚度变化和伸展薄化程度,突出断层的构造样式,将西沙海域划分为北部拆离断层构造发育区、东南部拆离断层构造发育区、西部走滑断层发育区和中部高角度断层发育区,进而明确了西沙海域盆地的基本构造格局.同时,以关键构造界面为主线,强调了不同类型断层在岩石圈地壳减薄过程中的作用,阐明了西沙海域盆地的差异构造演化过程.

Xisha area is located between the Northwest subbasin and the southwest Subbasin of the South China Sea,whose tectonic evolution is closely related to the oceanic spreading of the South China Sea and the strike-slip movement along the west part of the South China Sea.Together with regional seismic data,we carried out tectono-stratigraphic analysis in the Xisha area.Our study mapped three types of basins,i.e.subbasins controlled by high-angle faults,low-angle detachment faults and strike-slip faults,respectively.The lithospheric crust thickness varied a lot here indicating the different crust thinning across the region.We divided the Xisha area into four tectonic domains,i.e.the northern domain with detachment fault system,the southeastern domain with detachment fault system,the western domain with strike-slip fault system,and central domain with high angle fault system.Our results will improve our understanding on the tectonic evolution in Xisha area,with implications for petroleum exploration there.