南海构造演化模式：综合作用下的被动扩张

南海处于欧亚板块、印度-澳大利亚板块和太平洋板块的交汇处,地质作用十分复杂,至今未能建立一个普遍适用的演化模式,成为南海研究中亟待解决的问题。通过总结南海构造演化的主要模式,分析各模式建立的依据和存在的问题,发现通过一个动力源来研究南海的形成演化是片面的。从南海构造特征分析,结合国外有关大陆岩石圈破裂的研究成果,认为南海海盆主体经历了被动大陆张裂到海底扩张的演化过程。动力源主要是古南海向南俯冲的拖曳力,辅助于南、南东向的地幔流作用。南海北部陆缘广泛存在的高速层,可能是地幔流沿拉张减薄面底侵的结果,因而不同于地幔柱作用引起南海的打开。印度板块碰撞、楔入产生的地幔流,经太平洋俯冲板块的阻挡,最终发生南、南东向流动。印支地块的挤出则对南海西部的拉张具有重要影响。

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.