南海热幔柱构造与油气分布

南海处于欧亚、印度—澳大利亚和太平洋—菲律宾海三大板块的夹持地带,区内以NE向深海区-海盆为中心,周围有众多的含油气盆地。南海区具有"北断(裂)、南褶(皱)、东(俯)冲、西(碰)撞"的构造特征。南海及其周缘新生代玄武岩和花岗岩广为分布,故有潜在的大火成岩省之称。其中,火山岩以碱性玄武岩为主,多为OIB型成因,其成岩年龄自南海中心至外围呈由新逐渐变老的趋势。深部地幔流动呈现出涡旋式上涌的特点,上地幔明显具环带状结构,中心部位为上升流,外围为下降流,表现出热幔柱和冷幔柱活动"双模式"对流。从区域S波速度扰动异常来看,在670km间断面,对热流体上涌确有阻挡作用。通过层析成像研究,证实本区存在巨型复蘑菇云状地幔低速体,演化过程和相邻板块活动构成相辅相成关系。由于地幔热流体上涌,促使地壳-岩石圈上隆、熔融、减薄和断陷,形成南海从边缘向中心(海盆)热流温度逐步升高的轨迹,基本控制油气田"外油内气"环形有序分布的格局。

The mantle plume structure and oil-gas distribution in the South China Sea

The South China Sea is held the Eurasia, India and Australian and Pacific-Philippines plates with NE abyssal zone-basin in the center and numerous petroliferous basins at periphery. The South China Sea region is characterized by "Faulting in North, Folding in South, subduction in East, and collision in west ". In the South China Sea region and adjacent areas Cenozoic basalt and granite are widely distributed thus it is known as a potential large igneous province. The volcanic rock is dominated by alkaline basalt in OIB origin. Outward from the center age of the rocks gets older. Deep mantle flows in scroll during upwelling with ring have structure in the upper mantle. At central part fluid flow up, at periphery flow down, showing heat and cool "dual-mode" convection mantle plume activity. From the regional velocity of S wave disturbance abnormal the hot fluid upwelling was hindered by discontinuity surface at the 670km level. By tomography studies the presence of composite huge mushroom cloud of mantle low velocity body is confirmed and the evolution process and the adjacent plate activities constitute a complementary relationship. As a result of mantle heat fluid upwelling uplifting, melting, thinning and faulting of the lithosphere was prompted and from edge to center (basin) heat flow temperature gradually elevated Such regime basically controls the ring distribution pattern of "external oil and inner gas" in the South China Sea region.