中国大陆东、南缘构造带沉积盆地类型及其成因机制探讨

SOUTHEASTERN CHINA CONTINENTAL MARGIN PETROLEUM BASINS AND CONTINENTAL MARGIN TECTONIC-STRUCTURAL ZONES

中国大陆东、南边缘经历了欧亚板块与太平洋板块和特提斯板块会聚作用的复杂过程。大陆东缘,受太平洋板块对欧亚板块的俯冲作用,受区域引张应力作用,地壳发生破裂、扩张和沉陷,形成一系列弧间盆地、边缘海盆地和弧后裂谷盆地;晚期受吕宋和台湾碰撞产生挤压应力的影响,东海盆地形成前陆盆地。大陆南缘,于早第三纪早期,由活动的转换为不活动的大陆边缘,具有典型的不活动边缘的重力效应特征——沿大陆架转折部位出现正负配对伴生的自由空间重力异常带;大陆边缘的张裂活动与海底扩张轴系相关的两个对称磁异常带;以及沿原南中国大陆边缘的火山弧活动在大约85百万年前停息。根据构造演化分析,南缘的陆缘盆地属于不活动边缘拉裂盆地,南海中央海盆则属于边缘海盆地。本文着重阐述了环绕亚洲大陆东南缘的主要转换断层系统,同时对这些断层系统所反映的太平洋—特提斯板块和欧亚板块之间板块边界的应力机制和活动方式进行了讨论。认为在环西太平洋域,它们是左旋剪切带,而在特提斯—印度洋域,从西向东延伸,分别属于右旋和左旋滑移。这些转换断层系统对中国大陆东、南缘含油气盆地和边缘构造带的形成和地质演化起着重要的作用。

Southeastern China continental margin has undergone a complicated convergence process of the Eurasian plate with the Pacific plate and Tethys plate. With the subduction of the Pacific plate under the Eurasian plate, the Eastern China continental margin crust was subject to aregional tension stresses that caused the breakdown, spreading and subsidence of the back-arc basement and formed a series of intra-arc basins, margin sea basins. and rift basins. The East China Sea basin grew up under the influence of compressional stresses caused. by the collision between Luzon and Taiwan in the later stage and a fore-continental basin was formed. The Southern China continental margin has transformed from active into passive continental margin no later than early Eocene. It is characterized by typical passive continental gravity effect—a couple plus-minus special free gravity anomaly zones, along the continental shelf break-line, The rifting of the proto-Southern China continental margin and the two axes of seafloor spreading, correlated with two symmetric sequences of megnetic anomalies in the South China Sea central basin, and then the are volcanism along the proto-Southern China continental margin ceased to be active about 85 m. y. According to an analysis of tectonic evolution the Southern China continental margin basins belong to passive margin pull-apart basins and the South China Sea central basin belongs to margin sea basin. The paper illustrates the main transform fault series around the Southeastern Asia continental margin. The stress regime and the activity form of boundaries between the Pacific-Tethys plate and the Eurasiav plate as reflected by the presence of such a fault series are discussed,In the circum-Western Pacific region they are left-lateral shear zones. In the Tethys-Indian Ocean region they belong separately to dextral slip and sinistral slip, extending from the west to the east. These transform fault series play an important role in the formation and the geological evolution of the Southeastern China continental margin basins and the tectonic-structural zones.