Study of deep electrical structure along a profile from northern Ordos block to Yinshan orogenic belt

Under the support of the SinoProbe-01 program in China, a magnetotelluric (MT) profile up to 440 km was deployed across the northern Ordos block, Hetao rift basin and Yinshan orogenic belt, which consists of 24 broadband MT sites among which 4 sites acquired simultaneously long period data. After inverting TM and TE data with NLCG algorithm, typical 2D electrical features of this profile are outlined. The results show that the electrical structure of northern Ordos block is relatively simple from top to bottom and are generally layered,which can be roughly distinguished into three layers as sedimentary cover of low resistivity, upper crust of high resistivity and lower curst and upper mantle of low resistivity; the electrical structure of Hetao rift basin and Yinshan orogenic belt are relatively complex, where the resistors and the conductors alternate with each other. Large scale bodies of high-conductivity in crust-mantle beneath the Ordos block probably represent high-conductivity minerals. However, the high conductivity bodies in crust-mantle beneath the north margin of Ordos block, Hetao rift basin and Yinshan orogenic belt may be caused by sulphides and partial melting. The sedimentation of Hetao rift basin,uplifting of Yinshan orogenic belt and the rise of Dongsheng and Hanjin Banner area which lie in the north margin of Ordos block must be closely related with each other. Their formation may be highly relevant to the upwelling of asthenosphere material under the extensional tectonic background.