The Huailai area is rich in geothermal resources, but the formation mechanism of its deep heat source is still unclear. In this paper, based on 16 broadband magnetotelluric sounding points, the two-dimensional electrical structure of the crust and mantle in the Huailai area was obtained. Combined with deep seismic reflection and P-wave seismic tomography, the geophysical characteristics of deep heat sources and reservoirs in the Huailai area are described. The Huailai area is characterized by low resistivity and layered reflection above 2 km in depth, which shows the distribution of the Cenozoic sedimentary cover layer. The upper crust is characterized by high resistivity without an obvious reflector, corresponding to the crystalline basement of the basin, whose main lithology is Archean gneiss. There is a highly conductive and bright-spot-reflective structure under the basement, which extends to 100 km, indicating the upwelling of mantle-derived material. Combined with the results of helium isotope tracing, a magma-type geothermal model in the Huailai area is proposed. The upwelling mantle-derived magma material is enriched under the basement to form a heat source. The heat is transferred to the upper crust through heat conduction along the crystalline basement. Then, groundwater circulation brings deep heat to the surface, forming hydrothermal resources.

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The middle part of the Da hinggan mountains is an important mineral resource base in China. Since the Mesozoic, due to the uplift of the mantle, the extension of the crust, the strong intraplate volcanic eruption and magmatic intrusion, the Mesozoic magmatic tectonic belt has attracted worldwide attention. For further exploring the deep structure of this area, the final geoelectricity structure was established based on a 50-kilometer magnetotelluric sounding profile in this area. Through data acquisition, phase tensor decomposition processing, and nonlinear conjugate gradient inversion, the model reveals the main electrical structural characteristics of this area: 1. The whole has a characteristic of “longitudinal layering and horizontal block”, and the shallow electrical structure is consistent with known geological conditions; 2. There is a distribution inferred that a low-resistance anomaly appears due to the fragmentation of the surface rock layer caused by the uplift of deep intrusive rocks on the surface; 3. There are three more obvious electrical gradient zones or low-resistance anomalies in the deep part, which are presumed to be fault zones or structural erosion variable zone; 4. Three electrical gradient zones in the section divide the deep structure into four large-scale and high-resistance bodies, which reflects the spatial distribution of deep concealed granite, thereby restoring the complex anticline, secondary grade anticline, oblique uplift and depression. In addition, given the electrical structural characteristics and known the mine locations and the field exploration conditions, we conclude that the location of the prospecting target should be on a belt with Shuangjianzishan Pb-Zn-Ag mine, Nailinba Cu-Ag mine, Nailinba Fe mine, and Baiyinnuoer Pb-Zn mine. Moreover, this target is further divided into the middle area of Nailinba Cu-Ag mine and Baiyinnuoer Pb-Zn mine in combination with field surveys.