论文部分内容阅读
南沙海域处于已俯冲消亡的古南海和海底扩张形成的新南海洋盆之间,其研究对于了解中生代末期以来南海北部陆缘张裂、新南海海底扩张和古南海向南俯冲消亡等构造过程具有重要意义.通过利用平衡剖面反演对该区新生代以来的构造活动和盆地演化进行研究.结果发现,该区新生代以来的构造活动具有显著的分区性特征,表现为以区内深大断裂为界,所分隔的3个块体其构造活动的主导因素和活动阶段性存在差异.南沙块体构造活动的主导因素为NW向应力,构造活动以中-晚中新世为界前张后压,具有明显的阶段性;万安盆地构造活动受万安断裂控制,构造活动阶段性不明显;曾母块体构造活动特征与南沙块体类似,具有明显的阶段性,但具体表现不同.在此基础上,将该区主要盆地的演化划分为4个阶段,即裂陷阶段、同沉积阶段、挤压阶段和区域沉降阶段.其表现又因盆地成因类型而有所不同:北康盆地裂陷和挤压阶段突出,沉降阶段缺失;南薇西盆地裂陷阶段南弱北强;万安盆地缺少挤压阶段;曾母盆地则4个阶段均非常明显.
The Nansha sea area is between the subducted paleo-Nanhai submarine and the new South China Sea basin formed by the seafloor expansion. The study of this area is of great significance in understanding the tectonic processes of the northern margin of the South China Sea, the seabed expansion of the New South China Sea and the southward subduction of the South China Sea since the late Mesozoic It is found that the tectonic activities since Cenozoic in this area have significant regional characteristics and are characterized by deep faults in the area , The dominant factor and the active phase of the tectonic activities of the three separated blocks are different.The dominant factor of the Nansha block tectonic activity is the NW stress and the tectonic activity is dominated by the Middle-Late Miocene The tectonic activity of Wan’an basin is controlled by Wanan fault and the tectonic activity is not obvious. The structural activity of Zengmu block is similar to that of Nansha block, and it has obvious stage but different concrete manifestation. On this basis, the evolution of the main basins in the area is divided into four stages, that is, the rifting stage, the synsedimentary stage, the compression stage and the regional subsidence stage. In the Northern Kang basin, the rifting and extrusion stages are prominent, and the subsidence stage is absent. The southern Weisi basin is weak in the south and north strong in the rifting stage, while the Wan’an basin lacks the extrusion stage. The Zengmu basin has four stages Are very obvious.