SEGMENTATION OF SUBDUCTION SYSTEM IN THE EASTERN SOUTH CHINA SEA AND DYNAMICS OF RELATED BASIN GROUPS: SEGMENTATION OF SUBDUCTION SYSTEM IN THE EASTERN SOUTH CHINA SEA AND DYNAMICS OF RELATED BASIN GROUPS

The east part of the South China Sea is located at the convergence zone between the Eurasian Plate and the Pacific Plate(the Philippine Sea Plate).To the east of the South China Sea,there are the Manila Subduction Zone,the Luzon Arc and the East Luzon Philippine Subduction Zone,consisting of a opposite-dipping trench-arc-basin system which is called subduction system in this paper.The system can be subdivided into three segments from north to south by the Babuyan Strike-slipping Fault and the Sibuyan Strike-slipping Fault respectively,based on the differences in geomorphology,earthquakes,volcanism,faulting,basins and geophysical characteristics.The north segment is affected by the collision of the Taiwan Orogen,and the NWW-directed indentation of the Philippine Sea Plate and the stopping of the Beikang Uplift to the west of the Taiwan Orogen,resulted in the extrusion of the continental blocks of northeastern South China Sea,and the formation of the Taixinan Basin and the Taixi Basin,which are a series of collision-wedge-extrusion related basins.The middle segment is controlled by "Slab Window" during the subduction of fossil mid-oceanic ridge of the South China Sea,the earthquakes,magmatism,geomorphology and stress fields are different from north to south,and the formation of the basin group is controlled by arc strike-slip faults.The south segment is dominated by west-dipping subduction of the Philippine Sea Plate.The intensive earthquakes and volcanism are near the Philippine Trench.However,the stopping of the Sunda Block and the Palawan Block to the west of the Manila trench and the adjustment of the Great Philippine Fault in the central Philippine islands result in curvature of the Manila Trench in plane and decrease in earthquakes and volcanism in the west of the segment.The basin group is located in the segment developed on the basement resulting from collisions of different block fragments.The adjustment and pull-apart faulting of strike-slip faults caused the present-day basin pattern and distribution.The subduction system in the east of the South China Sea is affected by the NNW-directed indentation in the north segment and west-directed subduction in the south segment of the Philippine Plate,while the tectonic evolution of the middle segment of the subduction system is dominated by the east-directed subduction of the Manila Trench.