张八岭隆起及邻区深部电性结构研究

Study on deep electrical structure of Zhangbaling uplift and its adjacent area

研究区位于华北陆块近东西向构造与扬子陆块北东向构造的交接部位,对其深部的电性结构研究可以为两大陆块的拼接与构造演化提供证据.通过对一条从安徽凤阳到全椒一条130 km长的长周期大地电磁测深剖面的处理与二维反演,获得了100 km以浅的电阻率剖面模型.该电阻率剖面模型在纵向上可分为中上地壳高阻层、下地壳低阻层和上地幔高阻层,电性莫霍面深度30~35 km.合肥盆地之下存在巨厚的高阻体,或为南北向挤压应力下缩短的中上地壳的反映;扬子陆块上下地壳发生解耦,中上地壳产生紧闭褶皱、冲断,下地壳则为宽缓的塑性变形.张八岭隆起之下的下地壳受到华北陆块的阻挡,分别向上和向下塑性变形.向上的变形推挤张八岭的进一步隆起,向下则产生向上地幔的俯冲,造成壳幔物质交换.电性模型支持华北陆块和扬子陆块的斜向汇聚模式.

The study area is located at the junction of the nearly EWtrending structure of the North China block and the NEtrending structure of the Yangtze block.The study of its deep electrical structure can provide evidence for the splicing and tectonic evolution of the two continents.Through processing and two-dimensional inversion of a long-period magnetotelluric sounding profile crossing Zhangbaling uplift,the resistivity profile model of Zhangbaling uplift and its adjacent area is obtained.The resistivity profile model can be divided into middle and upper crust high resistance layer,lower crust low resistance layer and upper mantle high resistance layer in vertical direction,and the depth of electrical Moho surface is 30~30 km.There is a thick highresistance body under Hefei basin,or it is a reflection of the shortened middle and upper crust under the northsouth compressive stress;The upper and lower crust of Yangtze block is decoupled,the middle and upper crust is tightly folded and thrust,and the lower crust is wide and gentle plastic deformation.The lower crust under the Zhangbaling uplift is blocked by the North China landmass and plastically deformed upward and downward respectively.The upward deformation pushes the further uplift of Zhangbaling,while the downward subduction of the upper mantle leads to the exchange of crust and mantle materials.The electrical model supports the oblique convergence model of the North China and Yangtze landmasses.