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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]

As an important branch of geophysical exploration method, the electromagnetic method with artificial source has advanced rapidly in the past decade. These methods are classified as airborne electromagnetic method, ground-air electromagnetic method, ground electromagnetic method, and marine electromagnetic method. Over the years, researchers in China have made significant improvement to the fundamental theory, forward modeling and inverse for series of electromagnetic detection methods. Conversely, significant progress was made in the development of corresponding equipment. The researched techniques and their developed equipment have been successfully utilized to detect underground targets as deep as 10 km. However, there is increasing need for deep resources exploration, urban subsurface study, and prediction, monitoring and detection of geological hazards. To meet the increasing need and catch up with the advanced international level of exploration technologies and developed equipment, there is urgent necessity and requirement to continue developing geophysical methods and the corresponding equipment. [ABSTRACT FROM AUTHOR]

The Tianshan-Xingmeng Orogenic Belt (TXOB) is located in China's northern region, and is one of the country's most important Au-Pb-Zn-Ag-Mo-Cu metallogenic belts. This metallogenic belt is known to have good minerogenetic conditions and exploration potential. However, the engineering detection depths of the majority of the metal deposits are generally less than 300 m. Therefore, high precision geophysical detection techniques are necessary to achieve the required accurate detection results. Among the commonly used techniques, the Stratagem EH4 system has been found to be the better choice for the deep prospecting of the metal deposits in the TXOB. Furthermore, a good understanding of the physical characteristics of the different rock formations in the region is essential for effective and efficient geophysical prospecting. This study revealed that the resistivity values of the ore and rock formation walls were different. In previous related research, the EH4 Conductivity Image System, which is a system combining MT and CSAMT, has been successfully used for ore explorations in China. The results of the geophysical prospecting processes indicated that there was good exploration potential of the aforementioned system in the TXOB. In the current study, the hidden gold ore bodies of disseminated (altered rock-type) gold deposits within the study area were defined by resistivity values of less than 150–1000 Ωm. The concealed gold orebodies in the quartz-type gold deposits were confirmed by resistivity values of 300 Ωm. The mineralization anomalies of the epigenetic lead-zinc deposits were defined by the smaller resistivity values, which were lower than the 100–1000 Ωm range. [ABSTRACT FROM AUTHOR]