南海晚新生代构造运动与天然气水合物资源

TECTONIC MOVEMENTS IN THE LATE CENOZOIC AND GAS HYDRATE RESOURCES IN THE SOUTH CHINA SEA

南海在新生代经历过两次海底扩张产生了南海洋盆。南海北部和南部原来都是被动大陆边缘,但北部在晚新生代由于菲律宾海板块与欧亚板块在台湾地区发生了碰撞,使陆缘遭受到北西向挤压,在陆缘上产生了北西向左旋走滑活动,我们命名此次构造活动为东沙运动;南部陆缘在早中新世末由于南移的南沙地块与婆罗洲地块发生了碰撞,加上此时北移的菲律宾海板块在明都洛岛地区与欧亚板块发生碰撞,以及南部的东南苏拉威西地块与西北苏拉威西地块发生碰撞,在南海南部产生了挤压构造,我们命名此次构造运动为南沙运动。这两次新生代的构造运动改变了南北陆缘的性质,北部陆缘有人因此称之为准被动陆缘,而南部陆缘的南部则变成了挤压边缘。南海南北陆缘在晚新生代受到的挤压活动,对油气成藏和天然气水合物的形成有重要的推动作用,因为挤压活动有利于流体的流动,进而在适当的地方形成油气藏和天然气水合物。

There in the South China Sea area occurred two seafloor spreadings in Cenozoic that produced the South China Sea Basin. The north and south margins were passive originally in Cenozoic, but in the late Cenozoic the Philippine Sea Plate collided with Asian Plate, which compressed the north and south margins partly. In these two margins there were left lateral and strike slip faults in late Cenozoic. We named this phenomenon Dongsha movement in the north margin and Nansha movement in the south. Therefore, we call the two margins similar-passive margins. As the left-lateral and strike-slip faults were active in the margins in late Cenozoic, fluids flowed along the faults. Oil and gas （including the methane） flowed into some favorable positions （anticline, faulting anticline and stratigraphic trap etc. ）, then petroliferous structures were formed. Gas hydrate resources are abundant in the gas hydrate stability zone （GHSZ） because of the NW bearing left-lateral and strike-slip faults. Therefore, we believe that the NW bearing left-lateral and strike-slip faults are very good tectonic conditions for the formation of gas hydrate resources in the north and south margins of the South China Sea area.