从陆缘伸展探讨新生代南海构造演化

Discussion on the Cenozoic tectonic evolution of the South China Sea from continental margin extension

南海的形成和演化是地学界长期争论的问题,前人给出了多种成因模式,目前较流行的模式是海底扩张,但它难以合理解释南海海底扩张中的洋中脊跳跃现象及南海大洋中的大陆残片。基于欧亚东缘的陆缘伸展,从地幔上涌和陆壳沿莫霍面的重力滑移的新大陆漂移模型出发,通过横跨南海的几条地震勘探剖面的地质新解释,研究了南海的形成和演化过程。结果说明,南海的形成是一种“构造被动挤出+微陆块主动漂移”模式。构造被动挤出是指印度-欧亚碰撞造成的欧亚大陆东南缘的微陆块被大规模挤出,而由陆缘伸展形成的微陆块在被挤出后发生了主动裂解漂移,南海的海底扩张现象是诸多微陆块主动漂移的结果。这个新的模式能够合理地解释南海形成过程中的洋中脊跳跃现象及南海中大陆残片的成因机制。进一步恢复了南海演化过程中周边陆块的运动演化历史,说明欧亚东缘在中生代晚期发生的大规模伸展构造运动是南海形成的基础,新生代印度-欧亚碰撞是南海形成的直接动力,微陆块的裂解漂移是南海形成的主要参与者。

The formation and evolution of the South China Sea has been a long-standing debate in the field of geology.Many genetic models have been proposed by predecessors.The most popular model is seafloor spreading model,but it is difficult to reasonably explain the phenomenon of mid-ocean ridge jumping and continental debris in the South China Sea.We based on the stretch of the continental margin of northeast Eurasia,from the new continent drift model driven by mantle upwelling and gravitational slip along the Moho surface,using new geological explanation for several seismic profiles across the South China Sea,to study the process of the formation and evolution of the South China Sea,the result shows that the formation of the South China Sea is a kind of"passive tectonic extrusion+active microcontinents drift"mode.Passive tectonic extrusion was caused by the Indo-Eurasia collision,and the microcontinents formed by the extension of the continental margin drifted actively after extrusion.The seafloor spreading phenomenon in the South China Sea is the result of the active drift of many microcontinents.This new model can reasonably explain the mid-ocean ridge jumping phenomenon during the formation of the South China Sea and the genetic mechanism of the continental debris in the South China Sea.We have further recovered the movement and evolution history of the surrounding continents during the evolution of the South China Sea.It is concluded that the large scale extensional tectonic movement in the eastern margin of Eurasia in the Late Mesozoic was the foundation for the formation of the South China Sea,the India-Eurasia collision in Cenozoic was the direct driving force for the formation of the South China Sea,and the microcontinents drift was the main participant in the formation of the South China Sea.The proposed new continent drift model provides a new dynamic model for plate motion.