南海南部海域主要沉积盆地构造演化特征

Tectonic evolution of the main sedimentary basins in southern area of the South China Sea

南海南部海域主要沉积盆地沿南沙块体南部、西部两条不同的边界分布,其成盆时代、盆地类型、盆地演化历史以及油气资源效应都有较大的差异,它们的发生发展均与南海的两次海底扩张有关；构造演化具有明显的阶段性,早期均与区域拉张作用有关,都经历了中中新世末期的变形、改造和随后的区域沉降过程,并受到礼乐运动、西卫运动和南沙运动的影响。万安、曾母和北康盆地是南海南部海域具有代表性的新生代沉积盆地,分属于不同的盆地类型。万安盆地是叠置在较薄地壳和高热流值背景之上的一个新生代走滑拉张盆地,经历了三个构造演化阶段。曾母盆地是南沙块体向南俯冲与婆罗洲块体发生软碰撞而形成的一个周缘前陆盆地,经历了四个不同的构造演化阶段。北康盆地是在南沙块体上于白垩纪末—第三纪早期由于地壳拉伸、裂陷而形成的一个陆缘张裂盆地,经历了三个构造演化阶段。

The main sedimentary basins in southern areas of the South China Sea located at eastern, southern, and western boundarys around the Nansha Block, whose formation time, basins＇ type, evolution process, and contribution to oil and gas resources are quite different, of which the formation and development were related to the twice sea-floor spreading of the South China sea. The tectonic evolution of the basins possesses distinct stages, from the stage related to territorial extension in the early period, to the stages of distortion and reconstruct in the end of middle Miocene and the succedent territorial subsidence, and to the stages under the influence of Lile movement, Xiwei movement, and Nansha movement. Wan＇ an Basin, Zengmu Basin, and Beikang Basin are the representative Cenozoic basins in the southern areas of the South China Sea, belonging to different basin types. Wan＇an Basin is a Cenozoic slip-extension basin, superposing on the thin crust with the setting of high heat flux, and experienced three stages of tectonic evolution. Zengmu Basin is a peripheral foreland basin, formed from southern subduction of Nansha Block and gentle collision with Borneo Block, and experienced four stages of tectonic evolution. Beikang Basin is a peripheral extension-rift basin, formed from crust extension and rift of Nansha Block in the end of Cretaceous to early Tertiary, and experienced three stages of tectonic evolution.