南海海盆中南—礼乐断裂带研究进展*

文章首先论述了中南—礼乐断裂带的研究现状, 然后基于重力、磁力、地震剖面和地形等地球物理资料, 综合分析了中南—礼乐断裂带在南海海盆中的空间展布和内部构造形变特征。研究表明: 该断裂带在海盆中由北至南具有明显的分段性。北段(西北次海盆与东部次海盆北部之间)断裂带宽15km, 由(18°00'N, 115°30'E)向(17°30'N, 116°00'E)呈NNW向分布。南段(西南次海盆与东部次海盆之间)断裂带宽约60~80km, 由中沙海台东侧向礼乐地块西侧呈NNW向展布。中南—礼乐断裂带的主控断裂沿中南海岭呈NNW向分布。断裂带在南北两段的过渡区总体呈NNE向展布。断裂带两侧海盆的沉积厚度和洋壳厚度存在差异, 推断该断裂带对其东西两侧海盆的地质构造具有控制作用。根据地壳结构变化, 推测该断裂带至少是一条地壳级断裂。

Research progress on the Zhongnan-Liyue Fault Zone in the South China Sea Basin*

In this paper, we review latest research on the Zhongnan-Liyue Fault Zone (ZLFZ), and then analyze the spatial distribution and tectonic deformation feature of the ZLFZ based on the geophysical data including topographic, seismic, gravity, and magnetic data. The results show that the ZLFZ in the South China Sea Basin has obvious north-south segmentation characteristics. The north section, which is between northwest sub-basin and east sub-basin, is a NNW trend narrow zone with a width of ~16 km from (18°00'N, 115°30'E) to (17°30'N, 116°30'E). The south section, which is between southwest sub-basin and east sub-basin, is a NNW trend wide zone with a width of 60~80 km from the east of the Zhongsha Bank to the west of the Liyue Bank. The main fault of the ZLFZ is NNW trend along the seamounts’ ridge of Zhongnan. The ZLFZ of transition region is NNE trend from the north section to the south section. On the eastern and western sides of the ZLFZ, the sub-basin’s sedimentary thickness and oceanic crust thickness are obviously different. We speculate that the ZLFZ plays an important role in the geological structure of sub-basin. According to the change of crustal structure, we suspect that the ZLFZ is at least a crustal fracture zone.