TECTONIC EVOLUTION MODES OF SOUTH CHINA SEA: PASSIVE SPREADING UNDER COMPLEX ACTIONS

Because of the location in the convergent hinge of Eurasian plate, India-Australian plate and Pacific plate, the geological processes of South China Sea are very complicated and have so far failed to establish a universally applicable model of tectonic evolution and thus become urgent issue of the South China Sea research to be resolved.In this paper, by summarizing the main modes of South China Sea tectonic evolution and analyzing the proofs and problems of these models,we found it's one-sided to study the formation and evolution of the South China Sea by one power source.Based on the analysis of structural characteristics of South China Sea,combined with foreign research achievements of continental lithosphere rifting,we consider that the main South China Sea basin has experienced a process from passive continental rifting to seafloor spreading.The process might be caused by slab pull of the proto South China Sea subduction,assistant with the southward and southeastward mantle flow.High-speed layer widely found in the northern South China Sea continental margin may be the result of mantle flow underplating along the thinning regions,which differs from the opening of the South China Sea caused by the mantle upwelling.Because of the obstruction from subduction of Pacific plate,the mantle flow generated by Indian plate moved towards south and southeast finally.The extrusion of Indo-China block has an important influence on the rifting of the western South China Sea.