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The Yangbajain Geothermal Field in Tibet is located in the fault subsidence basin of the central Yadong-Gulu Rift Valley. The spatial distribution of the field is controlled by mountain-front fault zones on the northwestern and southeastern sides of the basin. Geothermal power has been generated in Yangbajain for more than 40 years. However, owing to the lack of three-dimensional (3D) geophysical exploration data, key geological issues related to the partial melt body of the Yangbajain Geothermal Field, such as its location, burial depth, and geometric form, as well as the ascending channel of the geothermal fluid, have for a long time been controversial. In this study, 3D inversion was performed using measured geo-electromagnetic total impedance tensor data from 47 survey points. The extracted horizontal sections at different depths and profiles, and at different lines, reflect the 3D electrical structure model of the geothermal field in the study area. Subsequently, three findings were obtained. First, the partial melt body, located below the China-Nepal Highway extending along the northeast direction, is the heat source of the Yangbajain Geothermal Field. The burial depth range of the molten body was determined to range between approximately 6.2 and 14 km. Moreover, the geothermal fluid ascended a horn-shaped circulation channel with an up-facing opening, located in the northern section of the sulfur ditch area. The study results revealed that deep rock fissures (>2 km) were not well developed and had poor permeability. In addition, no layered heat reservoirs with high water richness were observed in the northern part of the study area. However, the application of enhanced geothermal system (EGS) technology in the northern region would be essential to improving the power generation capacity of the Yangbajain Geothermal Field. In addition, the study found no deep high-temperature heat storage areas in the southern region of the study area. [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]

The Fengtai Pb–Zn metallogenic deposits located in China's western region have good minerogenetic conditions and exploration potential. However, the Fengtai mining area passed through complex orogenic process zones, such as subduction, collision, and integration between the Yangtze Plate and the North China Plate. Existing geological research and drilling results showed that the ore bodies of large‐scale Pb–Zn deposits in the ore‐gathering area were steeply inclined, and the detection depths of the majority of the metal deposits were generally less than 300 m. Deep ore‐controlling structures at approximately 500–1,000 m are not well understood. Therefore, high‐precision and large‐depth geophysical detection techniques are necessary to achieve the required accurate detection results. This study revealed that the resistivity values of the ore and host rocks were quite different, which is essential for effective and efficient geophysical prospecting. Based on the petrophysical result, the grounded‐wire transient electromagnetic method system has been found to be one of the better choices for the deep prospecting of the metal deposits and was applied to detect Pb–Zn deposits in the Bafangshan‐Erlihe area. First, the grounded‐wire transient electromagnetic method's effectiveness was verified using results from survey line 1 at a known ore deposit verified by the drilling result. Then, the technique was used to identify deposits in an unexplored area. A deep anticline and ore body were successfully imaged. Most lead‐zinc ore bodies are controlled by the hinge and two wings of the tight anticline, and distributed in the contact zone between limestone and phyllite. The results provide a critical basis for deep prospecting and drilling design. [ABSTRACT FROM AUTHOR]

Xiaoshan gold–polymetallic concentrated area is located in Henan Province, central China. The area is principally underlain by typical metamorphic core complexes (MCCs), along with essential components of the basins and ranges of western Henan. Mineralization occurs in the regions where the geochemical anomalies of Au and related elements are widely distributed and consist predominantly of mineralized altered rocks and auriferous quartz veins, both of which are hosted within shear zones or fractures of varying sizes and orientations. Several small‐ to medium‐sized gold–polymetallic ore deposits, along with numerous clustered occurrences, have been found in the area in recent years. However, despite the fact that the Xiaoshan District has traditionally been deemed as an excellent geological endowment area with enormous potential for large‐sized deposits, no significant discoveries have been made to date. It is suggested that the main reason responsible for the present exploration situation could be the scarcity of applications of deep‐penetration geophysical prospecting in the area. It is anticipated that integrating geological and geophysical data would be crucial to enhance the successful mineral explorations. In this contribution, a conceptual geological model for the study area was initially reviewed so that the corresponding electromagnetic responses could then be modelled, which would simulate a geophysical type of survey, with appropriate uncertainties added into the analyses. Then, based on such an integrated approach, the required precision of detecting deep‐buried deposits could then be evaluated. In addition, by employing supplementary geophysical data acquired over known deposits, it is possible to gain more instructive insights into the practical geological model. The viabilities of this approach were demonstrated through a case study in which a hidden gold deposit in the studied area was successfully detected. Geophysical surveys were carried out by employing a grounded‐wire short‐offset TEM (SOTEM) technique and revealed two new anomalies (one of which was subsequently tested by drilling). The drilling then confirmed that this anomaly was caused by an ore body 30 m in thickness occurring at about 550 m below surface. [ABSTRACT FROM AUTHOR]