We have conducted magnetotelluric (MT) sounding on a 200km-long profile across the northern section of the western margin of the Ordos basin. This profile runs in east-west direction along Chaganchi-Yinchuan-Wuhudong and has 67 measurement stations. We have used the remote reference track and Robust methods to process the acquired MT data and obtained a series of parameters at each station, including apparent resistivity, impedance phase, 2D skewness, azimuths of primary electric axes, and real magnetic induction vectors. We have also made 2D inversion with the data of TE and TM modes using the NLCG technique to determine 2D electric structure beneath the study area. The result shows that the Chahan fault, the east-edge fault of the Helanshan Mountains, and the Yellow River fault on the profile are major boundaries of electricity, which extend downward through the entire crust, while the Sanguankou fault has a small extension downward in the crust. Along the profile, the Alax block, Helanshan fold zone, Yinchuan basin and Ordos block exhibit different characters of deep electric structure, respectively. The Alashan block is largely of high resistivity down to depth 50km except the shallow subsurface of low resistivity. The Helanshan fold zone is featured by alternating high and low resistivity values. In the Yinchuan basin, there exists a low-resistivity body with a broad upper portion and a narrow lower portion at depth 8km, exhibiting a character of fault-bounded depression basin. And the deep electric structure of the Ordos block is characterized by a low-high-low resistivity pattern with conspicuous layering in the crust.
