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Geophysics offers an important means to investigate the physical processes occurring inside the earth. In particular, since the 1960s, electromagnetic (EM) methods have played important roles in mineral exploration and engineering investigation. Such investigation requires extensive data acquisition and experimental analysis based on geophysical techniques. However, high-performance geophysical equipment, particularly EM exploration equipment, has been dominated by large geophysical companies from the United States, Canada, Germany, and other European countries for decades. This has limited the development of deep exploration technology in China. Recently, we have developed a high-resolution acquisition system with a wireless control unit and a high-power transmitting system for surface EM prospecting (SEP). The new system has been tested in the high-intensity, noisy environment in Jian-sanjiang area, Heilongjiang Province. We then conducted a field survey on the western edge of Qaidam Basin, Qinghai Province. A highly conductive anomaly was found in the upper mantle below the Qinmantage Mountains, which indicates a possible northward fluid channel that runs from below the Qinmantage Mountains to the bottom of the western crust of the Qaidam Basin. Identification of this significant feature was made possible by the new SEP for its better resolution than the previous systems. Also, geophysical analysis confirmed that the thick Cenozoic sediments of the Qaidam Basin are underlain by rigid Precambrian basement rocks and are characterized by a series of folds. The resistivity profile indicates that the Qaidam Basin was formed due to the folding structures in the northern part of the Qinghai-Tibet Plateau which provided an additional evidence for the uplifting of the Qinghai-Tibet Plateau. [ABSTRACT FROM AUTHOR]

The North China Craton is the oldest continental block, and has suffered from large-scale lithospheric thinning and destruction, which in turn led to gold deposits in northern China. The decratonic gold deposits in the North China Craton became the most important gold deposits in China, and geophysical methods are key means to detect and discover gold deposits there. In this paper, based on the geological and petrophysical characteristics of the North China Craton, the geological model of the decratonic gold deposits is transformed into a geophysical model. At present, two methods of geophysical exploration of decratonic gold deposits are in use: rapid and efficient exploration on the scale of the ore concentration area, and large depth exploration on the scale of the deposit area. In detail, the airborne electromagnetic, magnetic and gravity methods are used to detect the shallow (1,500 m) anomaly area on the scale of the ore concentration area. Through the ground-controlled source electromagnetic and ground magnetotelluric methods, explorations for targets at significant depth (5,000 m) are carried out in the mining area. Then, taking the Liaodong ore concentration area as an example, geophysical methods are used to discover two prospecting areas around the Jianshanzi Fault in the Qingchengzi ore concentration area, Baiyun-Xiaotongjiapuzi deep prospecting area, and Qingchengzi deep prospecting area. Next, three prospecting areas are delineated around the Jixingou Fault in the Wulong mining area, Wulong deep prospecting area, Weishagou deep prospecting area, and Chang'an deep prospecting area. The anomalies in the ore concentration area and mining area are revealed by means of three-dimensional exploration methods, thereby providing technical support for the exploration of metal minerals such as decratonic gold deposits. [ABSTRACT FROM AUTHOR]