Application of surface and borehole TEM joint exploration in 2 000 m deep mineral exploration

Deep mineral exploration is a challenge. The borehole Transient Electromagnetic Method (TEM) goes deep underground through the sensor along the borehole, and gets closer to the deep target, so as to improve the ore discovery rate and prospecting effect. TEM is widely used in deep prospecting and exploration in foreign countries, and has achieved many important results. However, in China, due to the slow development of instruments, theoretical research and interpretation technology, it is less used in practical deep prospecting. This paper introduces a typical case about the 2 000 m deep prospecting in Baiyun Gold Deposit in Qingchengzi, Liaoning Province. The borehole and surface TEM exploration is carried out, and the TEM data are tried to be comprehensively interpreted in order to explain the favorable metallogenic sites around the borehole more reasonably. The measured results show that the original TEM profile curve in the borehole has typical negative anomaly characteristics at the depth range of 1 400-1 650 m, indicating the existence of local conductive anomalies outside the borehole. In addition, polarization in the middle and late stages is caused by the mineralization of gold-related pyrite concentrated in fracture zones. The inversion results of surface TEM clearly show the typical distribution under the survey line, and the large extension of deep concealed faults, showing good metallogenic conditions. Through comprehensive analysis and interpretation, there are still good conditions for gold concentration in the deep part of the concealed fault speculated by TEM L52. The drilling data show that the comprehensive interpretation results of surface and borehole TEM are correct and reliable. The research results show that the surface and borehole TEM joint detection has a good application prospect in deep mineral exploration.