Application of wide-field electromagnetic method for skarn-type polymetallic deposits’ exploration in the Yemaquan, Qinghai Province, China

Abstract The Qimantag region in the East Kunlun Mountains is a significant skarn-type polymetallic metallogenic belt in China. With the exhaustion of shallow deposits due to extensive geological and exploration work, there is a pressing need to explore deeper buried ore bodies. The desert soil cover limits the effectiveness of geological and geochemical surveys. Traditional magnetic and gravity surveys have been the primary methods for early exploration but are inadequate for deep exploration. This study applies the Wide-field Electromagnetic Method (WFEM) to mineral exploration in the Yemaquan area of Qimantag region. Developed from the Controlled Source Audio-frequency Magnetotellurics (CSAMT), WFEM uses a vertical or horizontal dipole source to generate electromagnetic responses. It calculates apparent resistivity from a single observed parameter, significantly reducing data acquisition costs. The method is especially effective for identifying deep metal deposits under thick cover. WFEM data were recorded and then processed using the Gauss–Newton method for 2D inversion, followed by 3D kriging interpolation to generate a resistivity model at a depth of 1000 meters in the study area. The results revealed the distribution and contact relationships of sedimentary strata and rock bodies, correlating well with existing geological and geophysical data. Drilling verified the presence of iron, copper, and other polymetallic ore bodies, demonstrating the potential of WFEM for mineral exploration in areas with weak magnetic anomalies. This study validates the effectiveness of WFEM in detecting deep polymetallic deposits in the Qimantag area and provides valuable reference for future exploration in similar geological environments.