Deep electrical structure and dynamic mechanism of the Helanshan tectonic belt

Helanshan tectonic belt is a typical intracontinental contractional deformation area of the western North China Craton since the Mesozoic. Based on the analysis and inversion of magnetotelluric data collected in the field, the deep electrical structure of the Helanshan tectonic belt was obtained. The results reveal that the Helanshan tectonic belt develops the thrust−nappe structure in the upper crust, and there are intact and thick crustal roots in the middle and lower crust. The magnetotelluric sounding profile shows that there is a low resistivity channel upwelling to the NW of the Helanshan tectonic belt, and there are mantle material upwelling characteristics in the Yinchuan Garben and Ordos Bain in the southeast. The Helanshan tectonic belt of the Late Jurassic WNW—ESE compressive fold−thrust belt and the Cretaceous tectonic uplift process are related to the subduction of the Western Pacific Plate, which records the early upwelling of deep mantle material in the NW direction. Controlling by the Cenozoic Western Pacific Plate subduction and rollback and the Tibetan Plateau growth northward, the adjacent area of the Helanshan tectonic belt deep mantle material upwelling into the crust. Then, the Ordos Basin deep lithosphere thinned, forming the present basin and mountain tectonic pattern.