中国近海海域新生代成盆动力机制分析

中国近海海域发育了渤海湾、东海和南海等10多个新生代富油气沉积盆地，其发育演化过程及动力学背景的异同需要在统一的研究思路和方法下进行系统的总结.以海域盆地油气勘探开发中积累的丰富的地质地球物理资料为基础，详细解释和分析了渤海、东海和南海三大海域新生代盆地的构造地层格架，进一步明确了渤海湾盆地斜向拉分盆地的演化阶段，证实了区域走滑断裂体系对盆地发育的重要控制作用；在东海陆架盆地划分出弧后前陆盆地的演化阶段，认识到区域挤压作用对该盆地的演化过程的重要性；在南海北部深水区发现了大型拆离断层及其所控制的拆离盆地，提出大型拆离断层作用是地壳薄化、地幔剥露和陆缘深水盆地形成演化的主要机制.研究揭示出中国近海海域盆地新生代期间在经历了古新世-中始新世期间分布全区的均一断陷作用之后，从晚始新世开始进入到区域构造的差异性演化阶段，其中渤海湾盆地进入斜向走滑拉分阶段，并持续到渐新世末期，随后是中新世的热沉降和上新世以来的加速沉降过程；东海陆架盆地则进入长期的弧后前陆盆地演化阶段，直到上新世开始才进入区域性的沉降过程；而南海则持续伸展形成深水拆离盆地，并最终在渐新世初期（32 Ma）发生岩石圈裂解，南海洋盆开始扩张，陆缘则进入被动大陆边缘演化阶段.区域板块运动学分析表明，晚始新世发生的全球板块运动重组事件导致了中国近海海域盆地构造的差异性演化.该事件发生之前，中国东部处于欧亚板块和太平洋板块相互作用构建的"双板块"动力体制之下，太平洋板块的俯冲后退作用导致了陆缘弧后伸展，形成了广布中国东部大陆边缘的盆岭式断陷盆地系.该事件之后，中国大陆处于印度板块、欧亚板块、太平洋板块和菲律宾海板块等构建的"多板块体制"之下，印度-欧亚大陆的碰撞、太平洋板块俯冲方向的转变、古南海的俯冲碰撞、菲律宾海板块的楔入及其与太平洋板块向西运移俯冲等产生了更为复杂的板块运动过程和多期次的运动重组事件导致了中国海域盆地成因类型的多样性和构造演化过程的差异性.海域盆地是我国重要的油气生产基地，本文的研究不仅进一步深化了中国海域盆地的形成演化过程和动力机制的认识，而且对于该区的油气勘探和开发也具有重要的实际应用价值. 

Genetic Dynamics of China Offshore Cenozoic Basins

More than 10 Cenozoic oil-rich sedimentary basins have been developed in the offshore area of China. The differences and similarities in their evolution process and dynamic background need to be systematically summarized with unified research ideas and methods. Based on abundant geological and geophysical data in petroleum exploration and production in the offshore basins, this paper analyzes the tectono-stratigraphic framework of the Cenozoic basins located in the Bohai Sea, the East China Sea and the South China Sea. First, we further clarify the obliquely pull-apart evolution stage of the Bohai Bay Basin by demonstrating the regional strike-slip fault system dominated the basin development. After presenting the importance of regional compression on the evolution of the East China Sea Basin, we sub-divide an evolution stage of the retroarc foreland basin. As for the northern South China Sea, we discover large detachment faults and their controlling detachment basins in the deepwater areas; and thus propose that the large-scale detachment faulting is the main mechanism for the crustal thinning, mantle exhumation and the formation of deepwater marginal basins. Our study reveals offshore basins in China had experienced an early-stage extension covering the whole region; then they entered into a differential tectonic evolution stage since Late Eocene. To be specific, the Bohai Sea experiences an evolution process of early rifting through an oblique strike-slip deformation, a thermal subsidence and finally a rapid subsidence. The East China Sea evolved from a rift basin to a retroarc foreland basin, then became a regional subsidence basin. While the South China Sea had a continuing extension evolution process of an early-rift basin, detachment basin, seafloor spreading with continental lithospheric breakup, and the present-day passive continental margin. The kinematics analysis of the regional plate tectonics suggests the global plate reorganization in Late Eocene resulted in the differential evolution of the offshore basins, before which the East China had mainly been under a "double-plate" dynamic system constructed by the interaction between the Eurasian plate and the Pacific plate. The subduction and retreat of the Pacific plate led to the back-arc extension on the continental margin and the formation of a massive Basin-Range type basin system in the eastern margin. After the reorganization, mainland China has been under the "multi-plate system" constructed by the Indian plate, the Eurasian plate, the Pacific plate and the Philippine sea plate. The India-Eurasia collision, the direction change of the Pacific plate subduction, and subduction and collision of the paleo South China Sea, the subduction of the wedge-shaped Philippine Sea plate and its westward migration and subduction with Pacific plate led to more complex plate motion processes and a multi-stage kinematical reorganization. These plate tectonic events caused the diversity of the offshore basin genesis and the differences of their tectonic evolution processes.