摘要:
南海处于印度—澳大利亚、欧亚和太平洋三大板块汇聚中心,地理位置独特,地质作用复杂,是研究大陆裂解—海底扩张过程以及大陆边缘动力学的天然地质实验室。通过总结近年来对南海大陆边缘动力学研究的最新进展认为:①南海北部陆缘为非火山型被动陆缘,其东段虽有岩浆底侵活动,但其为海底扩张结束后的产物,南部陆缘未发现下地壳高速层,也为非火山型陆缘;②南海陆缘上下地壳的拉张因子存在差异,表明陆缘的张裂变形在纵向上并非是均一的,而具有随深度变化的特点;③南海海盆是通过2期扩张形成的,具有由NE向SW渐进式扩张的特点,其东侧表现为成熟的洋盆,而西侧保留了更多陆缘裂谷的特征;④南海海盆形成的动力学模型存在碰撞挤出模型和古南海拖曳模型2种争论,2种模型各有优缺点,需要今后进一步综合研究。
Abstract:
The South China Sea, as one of the largest marginal seas along the western Pacific, is located in the juncture of the Pacific, Eurasian and Indian-Australian plates. It is a right place for studying rift processes from the extension of the continental lithosphere up to the formation of the oceanic crust. We discussed in this paper the dynamics of the continental margin of the South China Sea and new progresses were summarized. Detailed data suggest that the northern continental margin of the South China Sea is a magma-poor passive margin. Magma underplating discovered in the east part was caused by the magmatism after the cessation of the sea-floor spreading. No high-velocity layer has been discovered under the southern continental margin, which indicates a magma-poor margin similar to the north. The stretching factors are different between the upper and lower crust of the continental margin, showing that the stretching is depth-dependent and not uniform vertically. Two sea-floor spreading events were observed in the Cenozoic. Spreading propagated from northeast to southwest and shows a transition from a steady sea-floor spreading in the east to an initially unsteady one with partly continental rifting in the west. Arguments remain about the opening mechanism of the South China Sea. Comprehensive study is required for future research.
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