Preliminary lithospheric electrical structure of Southern Greater Khingan Range, North China

The central–southern Greater Khingan Range (GKAR) is a key polymetallic metallogenic region in China, hosting major deposits such as the Baiyinchagan and Weilasituo deposits (Fig. 1). Tectonically, it lies in the eastern Central Asian Orogenic Belt and has been shaped by the closure of the Paleo-Asian Ocean and Paleo-Pacific Ocean and the ongoing subduction of the Pacific Plate. The region is transected by major deep faults, including the northern boundary of the North China Craton, and the Solonker–Xar Moron fault.

In July 2025, a joint team from the Inner Mongolia Geologic Survey and Research Institute and Zhejiang University acquired 77 broadband magnetotelluric (MT) sites, Each site observed for more than 40 hours, yielding high-quality responses with periods up to 5000 s. A 3D inversion using ModEM produced a preliminary lithospheric resistivity model.

The model reveals high-resistivity bodies beneath the GKAR axial fault down to ~60 km, likely reflecting intense east–west compressional metamorphism. Two dominant low-resistivity anomalies are identified: C1 is situated in the southeastern part of the study area and at depths exceeding 80 km, whereas C2 is located in the northwestern part at a shallower depth but exhibits good connectivity with C1 (shown in Figs. 2 and 3). These features are spatially consistent with localized low-velocity upwellings and regions of moderate-to-high heat flow. We infer that mantle-derived melts and fluids, possibly sourced from Pacific Plate subduction, underlie the region’s metallogeny. The spatial linkage between deep fluid migration and shallow ore systems requires further investigation.

This study was supported by the National Science and Technology Major Project for Deep Earth Exploration and Mineral Resources Exploration(2024ZD1000200) and the National Natural Science Foundation of China (42474103).

Figure 1: Overview map of the study area. White inverted triangles denote MT sites, large orange circles represent major mineral deposits, labeled with numbers as follows, 1: Weilasituo Polymetallic Deposit (WLST), 2: Hegerao La (HGL), 3: Hegen Shan (HGS), 4: Baiyinchagan Pb-Zn-Ag Deposit (BYCG), 5: Zhalageamu Cu Deposit (ZLGM), 6: Daolundaba Cu-W-Sn Deposit (DLDB), 7: Shuangjianzi Shan Ag-Pb-Zn Deposit (SJZ), 8: Baiyinnuo Pb-Zn Deposit (BYN), 9: Haobugao Polymetallic Deposit (HBG), 10: Maodeng-Xiaogushan North Sn-Cu-Zn Deposit (MD-XGSN), 11: Baiyinchagan Dongshan Ag-Sn Polymetallic Deposit (BYCG-DS). Small yellow circles indicate minor mineral occurrences. Black dashed lines show the locations of resistivity profiles, with endpoints of profiles P1 to P4 marked accordingly. Red solid lines represent faults. GKAR: Greater Khingan Range, XMF: Xar-Moron Fault.

Figure 2: Resistivity profiles, red inverted triangles denote MT sites near profiles.

Figure 3: 3D Resistivity model, green surface is 70 Ωm isosurface.