Abstract:The available shallow mineral resources in China are increasingly depleted, and how to improve the effectiveness of deep mineral exploration is an important issue urgently to be solved. However, for the exploration of deep resources, limited by the detection accuracy, depth, and anti-interference ability of surface geophysical exploration technology, traditional electromagnetic methods are difficult to accurately detect useful information of deep hidden mines on the surface. In order to improve the resolution of controllable source electromagnetic method, this work used a borehole as the measuring point location for receiving the total electromagnetic field response, collected vertical magnetic field data in the borehole, and obtained three-dimensional spatial distribution information of underground electrical conductors. The finite difference method was used to study the forward response of different borehole locations to abnormal bodies. The results show that the closer the borehole is to the boundary of the underground abnormal body, the greater the response is. The fast 3D inversion based on the limited-memory-Broyden-Fletcher-Goldfarb-Shanno (LBFGS) method further proves that the borehole magnetic field data can effectively improve the recognition of deep spatial information. Finally, the joint inversion of borehole magnetic field data and surface magnetic field data has achieved high-precision imaging from shallow to deep, providing theoretical support for practical deep mineral exploration.
