武陵山褶皱-冲断带的地壳结构与形成机制

    • 摘要: 武陵山褶皱-冲断构造带位于扬子块体东缘,是华南地区最典型的由陆内挤压作用形成的线性构造带。针对该区的深部结构、构造样式和陆内变形机制,本文在集成近年来在该区开展的地球物理、构造地质和数值/物理模拟研究的基础上,以跨越该区线性褶皱带的一条NW-SE向构造廊带为切入点,系统分析了该区的地壳深部结构、变形过程及浅表构造响应。结果表明:(1)武陵山地区强重力梯度带的形成主要受控于地壳与岩石圈尺度的结构和物性差异;(2)新元古代扬子和华夏块体的拼合过程造成了该区Moho界面存在SE方向的俯冲痕迹;(3)晚中生代时期古太平洋板块俯冲作用的远程应力是造成该区褶皱-冲断变形的主要动力;(4)低速滑脱带的存在造成了上、下地壳的变形解耦,也和先存的齐岳山与华蓥山两个区域断裂一起控制了该区整个褶皱-冲断带的形成过程和变形方式。

       

      Abstract: The Wuling fold-and-thrust belt is a prominent tectonic feature situated on the eastern margin of the Yangtze block. It represents a prime example of a linear tectonic zone resulting from compressional forces within the South China region. In view of the deep structure, tectonic style and intra-continental deformation mechanism in this area, this paper systematically analyzes the deep crustal structure, deformation process and shallow tectonic response in this area, taking a NW-SE tectonic corridor spanning a linear fold belt as an entry point, based on the integration of geophysical, tectonic geological and numerical/physical modelling studies in recent years. The results show that: (1) the formation of the strong gravity gradient zone in Wuling Mountains region is mainly controlled by the difference of the structure and physical properties of the crust and lithosphere; (2) The merging process of the Yangtze and Cathaysian blocks in Neoproterozoic caused the Moho subduction trace in SE direction in this area; (3) The far-field stress of the Paleo-Pacific plate subduction during the late Mesozoic was the main driving force of the fold-and-thrust deformation in this area; (4) The existence of low-velocity décollements layer not only caused the deformation decoupling of the upper and lower crust, but also controlled the formation process and deformation style of the entire fold-and-thrust bel tin this area, together with the existing Qiyuefault and Huaying fault.

       

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