The artificial source electromagnetic method is an important technique for deep resource exploration. The key challenge is to improve the depth and precision of detection through innovative technology. The detection mode of electromagnetic methods is evolving from far-field to near-field, and the study of near-source electromagnetic methods has become an international research frontier in recent years. Building on the recent advancements in wide-field electromagnetic methods and multi-channel transient electromagnetic methods, the short-offset transient electromagnetic method (SOTEM) has been further developed and proposed. The distinguishing features of SOTEM are its stronger signals and wider bandwidth, which are advantageous for achieving the detection requirements of greater depth and higher precision. This special issue presents eight articles covering the methods, techniques, software, and applications of SOTEM, providing strong support for the growing need for high-resolution subsurface detection.

Distributed acoustic sensing (DAS) technology, one of the most advanced sound field detection technologies, can achieve distributed, long-distance, and high-precision real-time detection of the ambient vibration and sound field information interacting with optical fiber. The optical fiber exploration system of the DAS technology solves the problems of high cost and deployment difficulty of conventional geophones in complex geological environments. In recent years, the DAS technology has experienced rapid development, especially in monitoring application scenarios that require long-term and large-scale deployment. However, its systematic understanding is insufficient due to divergent research results. To further understand the research advances of the DAS technology in geophysical exploration for more effective subsequent research, this study systematically classified and summarized the development history of the DAS technology and its recent research results in geophysical exploration based on the oil and gas, marine, and environmental engineering application scenarios through literature research. This study focused on the development process of the DAS technology in different directions, the research advances in data processing, and relevant literature with specific results. Finally, this study generalized the development trend and urgent problems of the DAS acquisition system, analyzing the DAS development prospect.

In geoscientific field, the essential object of all the research problems is the physical world which is derived from the crust-mantle interaction and has deeply influenced globally the environment and resources. The metallogenic geochemical theory believes that the metallogenic materials are the internal factors for the metallogenic system to influence the metallogenic process, and taking metallogenic materials as the main body to study the problems of metallogenic materials and metallogenic processes is the basic meaning of the metallogenic geochemical theory, and the core subject of the studies of metallogenic rules and theories. During the mineralization process of metallogenic system, metallogenic materials formed into metallogenic series of corresponding scale. This paper outlines several scientific topics of the metallogenic geochemical studies, among which, the topic of global metallogenic system mainly studies the metallogenic processes and relations of the series of metallogenic regions, provinces and belts formed by metallogenic materials in the context of global metallogenic process; the topic of regional metallogenic system mainly studies the metallogenic processes and relations of ore field series in the context of regional metallogenic process; the topic of ore field metallogenic system mainly studies the metallogenic processes and relations of mineral deposit series in the context of ore field metallogenic process; the topic of mineral deposit metallogenic system mainly studies the metallogenic processes and relations of ore-body series in the context of mineral deposit metallogenic process. The basic research ideas concerning above mentioned studies are discussed in this paper, including the metallogenic materials' geneses and sources, migration and evolution, differentiation and concentration, as well as the zoning relations of each level's metallogenic system and series of the world during the metallogenic processes. The purpose is to summary the metallogenic rules, explore the metallogenic mechanism and guide the mineral resources exploration. Supported by modern technologies and methods of IT(information technology), modeling and AI(artificial intelligence), the metallogenic geochemical theory uses the earth system scientific ideas to study the problems of metallogenic system and metallogenic series, construct the theoretical framework for metallogenic geochemical research, and provide a theoretical basis for the mineral resources exploration, evaluation and development technics and methods.

Airborne geophysical surveys, characteristic of being green, economical, efficient, and subjected to less influence by surface factors, serve as the one of most effective means of basic surveys and scientific research on the Qinghai-Tibet Plateau. This study reviewed the progress in the airborne geophysical surveys in the Qiangtang Basin of the Qinghai-Tibet Plateau in the past thirty years, systematically summarizing the progress and geological interpretation results of comprehensive airborne geophysical surveys in the basin. Furthermore, this study presented research progress and understanding of major basic geological issues of the basin, such as the basin's boundaries, central uplift zone, basement properties, deep structures, and cover characteristics, as well as the identification of favorable structural areas for oil and gas exploration. Finally, based on an analysis of the developmental trends of airborne geophysical surveys in the Qiangtang Basin, this study proposed opinions and suggestions for key research directions in the future.

China's complicated geological background and metallogenic environment have decided that the regional geochemical exploration can play an important role in the field of China's mineral resources prospecting. This is the strategic selection under special metallogenic conditions. The first round of regional geochemical exploration of China was carried out during mid-1950s. Since then, we carried out the second and third round of regional geochemical exploration. Until now, China's regional geochemical exploration has gone through a history of 70 years, and showed unique functions in fields of the exploration and development of nonferrous metals, precious metals as well as the rare minerals, rare earth and scattered minerals. According to incomplete statistics, during 36 years (1979~2015) of the second and third round of regional geochemical exploration, totally 182 different kinds of large to super-large scale deposits were discovered in China mainly by means of regional geochemical exploration. Of which, 61 deposits have nonferrous metals, 93 deposits have precious metals, 24 deposits have critical and scarce minerals, and 4 deposits have other kinds of minerals. On average, 5.06 large to super-large deposits were discovered each year, and one large to super-large deposit was discovered within every 37,000 square kilometers-Calculated on the basis that the second and third round of regional geochemical exploration covered 6.68 million square kilometers' area of China. Regional geochemical exploration has achieved outstanding results in the field of mineral prospecting, and made great contributions in terms of ensuring and promoting China's economic development. As our country's basic, public good and strategic geological work, regional geochemical exploration comes into the 21^st century marked by big data and earth system science. Based on high precision and good quality big data, guided by metallogenic geochemical theories, and supported by modern science and technology, the regional geochemical exploration will start a new period of development. In the future, we'll continue to carry out the high technical standard and high quality regional geochemical exploration, achieve our goal of complete covering the whole area of mainland China with regional geochemical exploration, and provide more strategic prospective areas for our country's mineral resources exploration. On the basis of high-precision big data, metallogenic theories and modern science and technology, we'll establish AI and IT application system, so as to push forward the exploration and utilization of deep minerals, buried deposits as well as the critical and scarce minerals which are difficult to identify, and achieve greater breakthroughs in the geological exploration of mineral resources. By using big data technics, China's regional geochemical exploration team will continuously solve the mineral resources exploration and evaluation problems, and in this process, our geochemical exploration system will be gradually integrated into our country's science and technology advancement.

Huize County of Yunnan Province is situated in the karst area in southwestern China, where karst groundwater is its primary water source. To conquer local difficulties in drinking water, this study constructed a conceptual model of groundwater occurrence by fully investigating the hydrogeological conditions of the Huize area. Moreover, this study evaluated the applicability and optimal combination of geophysical methods based on the measurement results of petrophysical properties. According to the actual local needs, this study deployed a comprehensive profile combining high-density electrical resistivity tomography (HDERT) and audio magnetotellurics (AMT) in Tuogu Village, Huize County. The groundwater enrichment site was delineated relying on resistivity anomalies, effectively guiding the layout of boreholes. The boreholes achieved the maximum single-borehole water yield of 20.76 m³/d, thus effectively alleviating the local drinking water problem. The HDERT-AMT combined exploration method proves to be optimal for prospecting for groundwater in carbonate rock areas. HDERT can accurately characterize weathered layer thicknesses, bedrock boundaries, fissure evolutionary degrees, and water-bearing properties of strata, constraining groundwater recharge channels, thus counteracting AMT's defects for identification of near-surface stratigraphic structures. AMT can accurately reflect the spatial structures of fracture zones and the macrostructures of strata, limiting the boundary conditions (aquicludes) of water-bearing structures, thus making up for the defects of insufficient detection depths of HDERT in high-resistivity stratigraphic regions. HDERT and AMT, which are complementary to each other in terms of accuracy and depth, can be applied to identify and constrain the spatial occurrence conditions of groundwater migration, storage, and enrichment.

To explore the critical factors influencing the results of microtremor-based exploration at a depth of thousands of meters,this study conducted experiments using triangular arrays based on spatial autocorrelation(SPAC) and extended SPAC(ESPAC).Focusing on factors such as array size,acquisition unit frequency,and acquisition duration,this study explored the frequency band ranges corresponding to different array sizes,the arrangement of arrays in kilometer-depth exploration for obtaining both deep and shallow data,and the improvement in deep resolution.Based on the analysis and discussion results,this study established a parameter-setting system to improve the accuracy of exploration at a depth of thousands of meters.

Southern China boasts great potential for normal-pressure shale gas resources,with distribution areas primarily including the peripheral complex structural areas and the extrabasinal fold belts of the Sichuan Basin.These areas exhibit intricate surface and subsurface geological conditions,leading to poor seismic acquisition quality,low imaging accuracy,and unclear varying patterns of sweet spot parameters.This study systematically summarized the research achievements and technical advances in the seismic acquisition,image processing,and reservoir prediction for normal-pressure shale gas in southeastern Chongqing,including:①The development of variable-density 3D observation system design technique and the seismic excitation and reception technique for complex mountains with limestone surfaces,ensuring sufficient sampling of the reflected wave field in complex subsurface structures and improving data quality and construction efficiency;②The optimization of prestack seismic preprocessing technique for complex mountains,imaging techniques for complex structures in basin-margin transition zones, and imaging techniques for synclinal structures in extrabasinal fold belts,achieving resulting profiles with high signal-to-noise ratios,wide effective frequency bands,and high structural imaging accuracy;③The quantitative prediction of the thickness,formation pressure coefficient,and brittleness of high-quality shales based on research on petrophysical characteristics;the quantitative prediction of the organic carbon content,gas content,and porosity of shales based on statistical petrophysics;the quantitative prediction of fractures formed due to the superimposed effect of multi-stage structural modifications based on the paleo-stress field evolution revealed using the finite element simulation technique;and the ascertainment of the distribution patterns of the current in-situ stress field using the current stress field prediction technique developed using the combined spring model.The above breakthroughs have effectively guided the sweet spot prediction,exploration,and production of normal-pressure shale gas,providing a basis for the discovery of the Nanchuan normal-pressure shale gas field.Subsequent research should focus on more scientific and reasonable seismic acquisition techniques based on seismic reception using 5G wireless nodes,high-precision automatic image processing technologies for high-steep structures in complex mountains,and integrated geology-engineering-economy seismic evaluation methods for sweet spots.

Significant aeromagnetic and gravity anomalies were found in the ultra-deep coverage zone of the Pandian area in the northwestern Shandong Province. Through systematic verification of gravity and magnetic anomalies, a breakthrough in prospecting for deep skarn iron deposits has been achieved through several boreholes around the Pandian gravity-magnetic anomaly zone. However, the gravity-magnetic anomaly zone spreads extensively and its characteristics cannot directly indicate the prospecting target, thus some boreholes failed to find ores or revealed poor ore-finding conditions. Hence, to accurately delineate the ore-forming location in the gravity-magnetic anomaly zone and achieve a further breakthrough in ore prospecting, this study conducted the wide-field electromagnetic (WFEM) sounding in the verified Pandian gravity-magnetic anomaly zone. Combining the drilling verification, this study delineated the deep ore-forming interval of skarn iron deposits in the deep coverage zone and the favorable structural plane for ore-forming, suggesting the deep fine-scale prospecting targets.

Since individual geophysical exploration methods suffer the multiplicity of solutions, comprehensive geophysical prospecting has been extensively applied in deep ore prospecting presently. This study conducted the geological exploration of the Duhu porphyry copper deposit in Xinxing County using multiple geophysical methods such as high-precision magnetic survey and controlled source audio-frequency magnetotellurics (CSAMT). It was inferred that the CSAMT-derived medium-low resistivity anomalies and the low-gentle anomalies derived from the high-precision magnetic survey serve as significant prospecting indicators. Satisfactory results were achieved in follow-up verification of the anomalies. Specifically, copper, molybdenum, silver, and gold mineralized bodies with a cumulative thickness of 178.2 m were identified in a 1 000 m deep borehole, with the highest copper grade of 1.45%. The application of comprehensive geophysical prospecting holds great significance in guiding the exploration of porphyry copper deposits in western Guangdong.

Underground cavities with shallow burial and small scale are difficult to detect. With the development of gravity sensing technology, the accurate and rapid acquisition of micro-gravity variations brings new opportunities for detecting underground cavities, and it has wide research and practical value for the detection of small-scale underground cavities. This paper systematically analyzes and studies underground cavities from three aspects: gravity basic theory, gravity detection technology, and gravity data processing and inversion. Under given body size and gravity data accuracy, the maximum burial depth of gravity detection is calculated using the bisection method. High-density acquisition and high-precision gravity detection methods are applied to the actual detection of an underground pedestrian tunnel in a certain area of a passenger station. A set of high-precision gravity grid data is obtained. The theoretical research and measurement results indicate that existing gravity instruments have the ability to detect underground cavities. By using the minimum curvature potential field separation method, 2.5D interactive inversion and the target area recognition three-dimensional physical property fast inversion method, the approximate SN distribution and burial depth of the underground pedestrian tunnel are obtained, which is approximately 2.5~5 m, consistent with the actual situation. This study has developed a complete gravity exploration process for detecting underground cavities, and it has certain reference value.

The extended spatial autocorrelation (ESPAC)-based microtremor exploration(natural-source surface wave exploration) technology has been extensively used in shallow formation exploration owing to its simplicity,efficiency,and accuracy.However,the imaging effect of dispersion energy extracted based on the ESPAC method is unsatisfactory in practical applications.In particular,different observation array arrangements influence the extraction of dispersion curves from collected data.By investigating the imaging principle of the ESPAC method,this study conducted the simulation experiment of natural-source microtremor recording through ambient noise simulation.It compared the differences in dispersion energy under various dominant frequency distributions of wavelets.Moreover,it quantitatively analyzed the influence of different station arrangements and acquisition durations on the imaging quality of dispersion energy.The comparative study reveals the imaging patterns of the ESPAC method in shallow surface exploration.The ESPAC method can maximize the imaging quality of dispersion energy in the fundamental mode while considering both efficiency and exploration costs.The results of this study were applied to engineering application cases to further verify the simulation results.

As mature oilfields are in their middle to late exploitation stage, the Gaotaizi oil layer exhibits significantly increased water saturation, elusive longitudinal stratification, and unknown distribution patterns of regional residual oil. These complicate the potential exploitation, energy conservation, and emission reduction. To ascertain the distribution of residual oil in the Gaotaizi oil layer in order to guide production operations and clarify potential targets, this study identified the longitudinal distribution of residual oil in the study area using the pulsed neutron-neutron (PNN) logging technique. The comparison between the monitoring results and production data of 10 wells revealed a coincidence rate of measures of 80%. The results of this study show that the PNN logging technique can be used to effectively identify the longitudinal distribution of residual oil in reservoirs and yields encouraging application performance in guiding the hole filling and water plugging for single wells in high-water-cut layers, thus increasing oil production. This technique has increased the evaluation accuracy of residual oil saturation in the Gaotaizi oil layer in the mature oilfield. It can provide technical support for formulating and adjusting subsequent oilfield exploitation schemes and offer a scientific basis for further guiding efficient reservoir exploitation, energy conservation, and emission reduction.

China has accumulated massive data on total gamma radiation (γ) from the prolonged extensive surveys of uranium deposits. However, there is a marked lack of studies on radioactive environment assessment using these data. Based on the measurement principles of total gamma radiation and the absorbed dose rate in air, this study ascertained the relationships of the absorbed dose rate in air with the total natural gamma radiation and nuclide content and, accordingly, established the relationship between total gamma radiation and the absorbed dose rate in air. Furthermore, it analyzed the effects of instrument parameters on the measurement error, concluding that there existed a strictly linear relationship between the measured total gamma radiation and the absorbed dose rate in the air when b_K/b_U = 2.287 and b_Th/b_U = 0.430. Therefore, the b_K/b_U and b_Th/b_U ratios closer to both values correspond to more accurate absorbed dose rates in air converted from the measured total gamma radiation. Using the model of the Hunan Ionizing Radiation Measuring Station, this study calculated the coefficient for converting total gamma radiation into the absorbed dose rate in air, analyzed the error, and deduced the approximate uranium equivalent ranges of potassium and thorium in the instrument parameters. Furthermore, for the rock mass in Panjia Village, Guiyang County, Chenzhou City and the limestone area of Tuqiao Village in Yongxing County of the city, this study measured the total gamma radiation, gamma spectra, and absorbed dose rates in the air at the same stations. The results show that when the average nuclide content ratio C_K/C_U was less than 1 and C_Th/C_U ratio was less than 3, the absorbed dose rates in air estimated based on the total gamma radiation (measured using the FD3013 instrument) shared roughly the same error levels with those estimated based on energy spectra using the Beck formula, both yielding root mean square errors below 15%. As inferred from the average C_K/C_U and C_Th/C_U ratios of nuclides in China, the absorbed dose rate in air in most areas of China can be estimated using the total gamma radiation measured using an FD3013 instrument (or an instrument with similar performance). Overall, converting the total gamma radiation data from available extensive surveys of uranium deposits into effective absorbed dose rates in the air provides a methodological reference for rapid, large-area assessment of the external exposure level of natural radioactivity in the environment.

Due to various strong electromagnetic mechanical interference and traffic barriers, many geophysical exploration techniques are ineffective in urban geophysical exploration.Based on transient surface waves,microtremor arrays,and microtremor spectral ratios,this study synthetically extracted two kinds of characteristic curves for joint inversion from the multi-source frequency-domain seismic data obtained by multi-point three-component low-frequency sensors.Consequently,this study achieved multi-source frequency-domain seismic exploration that integrated three techniques and developed the two-source synthetic dispersive spectrum extraction technique,the two-source characteristic curve joint inversion technique,and the equivalent homogeneous medium forward modeling technique based on inhomogeneous media.Engineering practice results demonstrate the improvements in the exploration accuracy and efficiency.

This study aims to investigate the characteristics and influencing factors of selenium (Se) content in the tea leaf-rhizosphere soil system of the Liubao tea in Wuzhou, Guangxi. With the main tea gardens in Liubao and Shizhai towns, the core production areas of the Liubao tea, as study areas, this study conducted statistical analysis of the Se content in the tea leaves, rhizosphere soils, and tea leachate samples of the Liubao tea. The results show that: ① The Se content in soils of the study areas ranged from (0.40~1.98)×10^-6, averaging 1.08×10^-6; ② The Se content in Liubao tea leaves was between (0.03~0.25)×10^-6, averaging 0.07×10^-6, with a Se enrichment rate of 68%; ③ The leaching rates of Se in tea leachate ranged from 0~23.95%; ④ The Se content in the rhizosphere soils of tea gardens principally depended on soil parent materials and silica-sesquioxide ratios; ⑤ The P and N elements in soils can facilitate the absorption of soil Se by tea leaves, while the iron and aluminum oxides in acidified soils hinder the full utilization of soil Se by the Liubao tea. Hence, appropriate biochemical and agronomic measures are recommended for acidified soil amelioration to enhance the Se enrichment ability of the Liubao tea.

Investigating the spatial distribution of permafrost is critical for cryosphere research. At present, China's investigation concerning the spatial distribution of permafrost generally employs the detection method of ground geophysical exploration combined with logs to obtain local point or line data. Alternatively, different remote sensing models can be used to simulate and estimate the thickness of regional permafrost. This study inferred the spatial distribution of permafrost based on airborne time-domain electromagnetic (TDAEM) data and resistivity calculation results. The comparative analysis of the inference results and the known drilling data reveals an average error of 18.5% between the permafrost thickness inferred from the inversion results of TDAEM data and the result determined by borehole temperature measurements. This suggests that the TDAEM method exhibits high effectiveness and accuracy in permafrost thickness investigation. With technical advantages like high efficiency and minor topographic influence, the TDAEM method can be applied to the large-scale, rapid, and quantitative permafrost investigation in the Qinghai-Tibet Plateau and the Greater Khingan Range in northeast China. Therefore, this study provides a new and effective technical solution for a comprehensive investigation of the spatial distribution of permafrost and its influence on ecological environment changes.

Birimian rocks, the most significant Au ore-forming rocks in western Africa, are widespread in Harper, southeastern Liberia. As indicated by the geochemical parameters from the 1∶250 000 stream sediment survey of this region, elements Au and Hg exhibit high enrichment and high differentiation while element As manifests enrichment and high differentiation. These findings suggest considerable potential for Au prospecting. Based on the correlation analysis of elements, this study selected factors F1 (for the Au-Hg-Pb-Sn association) and F2 (for the As-Sb-W association) to effectively guide the exploration of gold deposits. Thirteen composite anomalies were delineated by extracting the anomaly information of Au, Hg, As, and Sb from the two principal factors, effectively reflecting the anomaly distributions of different gold deposits or ore occurrences. The geological and mineral surveys in anomaly areas reveal that areas HS1-HS3 and HS12-HS13 with composite anomalies characterized by directional distribution and high intensities show distinct Au mineralization information. Based on this, two major Au prospects, i.e., Seethum New and Behwan, have been identified for further detailed exploration.

The Galinge iron deposit in Qinghai is overlain by deposits measuring greater than 150 m in thickness. The great burial depths of ore bodies lead to gentle magnetic anomaly morphology, making it difficult to characterize the spatial distribution of ore bodies. Therefore, this study employed three-dimensional magnetic anomaly inversion to determine the three-dimensional distribution characteristics of subsurface magnetic intensity in the study area. Given the prior information of non-magnetic surrounding rocks, the three-dimensional magnetic intensity model clearly presented the spatial distribution of the ore bodies and reflected the presence of intense magnetic bodies at depths of less than 500 m in existing boreholes. Accordingly, it can be inferred that there exist concealed ore bodies at depths exceeding 500 m in the study area. The results of this study suggest that three-dimensional magnetic anomaly inversion can effectively improve target identification, providing clear information on the horizontal positions, depths, and scales of magnetic ore bodies. The proposed inversion method can offer strong support for drilling design and reserve estimation, warranting promotion in detailed exploration of solid minerals.

The progress in seismic acquisition techniques characterized by wide azimuths,wide frequency bands,and high densities has greatly promoted the application of the prestack P-wave fracture inversion technique based on the azimuthal anisotropy theory.Azimuthal anisotropy-based inversion can yield the azimuths and intensities of fractures.However,different inversion techniques yield different parameters for fracture intensity characterization,resulting in inconsistent inversion results.Consequently,the azimuthal anisotropy-based inversion results of fractures are non-unique,leading to confusion about accurate results.Based on the Thomsen anisotropy theory,as well as the interrelationships between fracture models(the Hudson coin model and the Schoenberg linear sliding model),this study established the connections of anisotropic parameters between different fracture inversion techniques(VVAZ,Ruger's approximation,and Fourier series),presenting the real meanings and mathematical expressions of results from different azimuthal anisotropy-based fracture inversion techniques.Additionally,this study summarized the relationships of parameters between different inversion techniques and fracture models,further deepening the research on azimuthal anisotropy-based fracture inversion.This study lays solid theoretical and technical foundations for large-scale fracture detection based on the seismic data obtained using the seismic acquisition techniques featuring wide azimuths,wide frequency bands, and high densities.

Magnetotelluric (MT) sounding is a vital exploration method in tunnel engineering. Inversion methods can assist geologists in interpreting geological data by converting MT data into geoelectric parameters. However, conventional inversion methods exhibit inferior timeliness and reliance on initial model settings. In this study, deep learning was applied to the one-dimensional inversion of magnetotelluric data. First, an improved DenseNet model was constructed and trained to invert geological models of various resistivity-variable strata, yielding a fast computational speed and high accuracy. Then, the robustness of the improved DenseNet model was tested, suggesting that its network structure can achieve satisfactory inversion results for noisy data. Finally, this artificial intelligence technique was applied to the MT data inversion of the Hongjiaqian tunnel in the Huangshan area, obtaining geophysical exploration results that match the geological research results. Additionally, relevant construction recommendations were given based on the inversion results.

Specific computational tools assist geologists in identifying and classifying the lithology of rocks in oil well exploration,reducing costs,and enhancing operational efficiency. Machine learning methods integrate a vast amount of information,enabling efficient pattern recognition and accurate decision-making. This article categorizes the lithology of five oil wells in the Norwegian Sea,randomly dividing the data into a training set (70%) and a test set (30%). Using multivariate well log parameter data for training and validation,the application effectiveness of models such as Multilayer Perceptron (MLP),Decision Tree,Random Forest,and XGBoost is compared. The research results indicate that the XGBoost model outperforms others in terms of data generalization,achieving an accuracy of 95%. The Random Forest model follows with an accuracy of 94%. Meanwhile,Multilayer Perceptron (MLP) and Decision Tree models exhibit good robustness,with accuracies of 92% and 90%,respectively.

In the context of the goals of both peak carbon dioxide emissions and carbon neutrality, scientific and efficient exploration and exploitation of geothermal resources are criticalfor the geothermal industry. To address the commonly concernedtechnical challenges in the exploration of moderately deep geothermal resources, this study investigated the effectiveness of comprehensive geophysical prospecting in the exploration of geothermal resources inthe Linjiadi area, Aohan Banner, Inner Mongolia. Based on the analysis ofthe geological and hydrogeological conditions, this studypreliminarilyascertainedthe geothermal field characteristicsand the hydrochemicalcharacteristics of groundwater in the Linjiadi area. By comprehensively employingcontrolled source audio-frequency magnetotellurics (CSAMT), CSAMT; microtremor survey; radioactive radon survey; this study roughly determined the distribution of strata, magmatic rocks, and fault structures in the study area, inferring the factors controllinggeothermal anomaly areas and hot-water migration.Accordingly, exploration boreholes were arranged, allowing for drilling verificationwith a total length of 960 m. The results show that the comprehensiveapplication of CSAMT and microtremor survey, combined with radioactive radon survey for auxiliary verification, is effective in exploringmoderately deep geothermal resources. This study will provide a methodological reference for geothermal resource exploration in other areas.

The grounded-source short-offset transient electromagnetic (SOTEM) method involves many parameters in field data acquisition. The selection of these parameters is closely associated with the signal quality and detection sensitivity of measured data. Based on the relevant provisions in the organization standard, Technical specification for grounded-source short-offset transient electromagnetic method (T/CGS 002—2021), issued by the Chinese Geophysical Society, numerical emulations, and practical cases, this study analyzed and expounded the selection criteria of critical parameters like transmitting source length, transmitting fundamental frequency, offset, device type, and observation component. The insights obtained in this study are significant for guiding the field construction of the SOTEM device and leveraging its detection performance.

There exists a continued debate concerning the spatial distribution and deep structural characteristics of the Yagan fault zone in northeastern Ejina Banner, Inner Mongolia. Adhering to the known-to-unknown research approach, this study completed five magnetotelluric sounding (MT) profiles. First, it delved into the relationship between the electrical structure characteristics of a MT profile (MT01) on the west side of the study area and the geological structure information of the Yagan fault zone within the profile. In terms of electrical characteristics, the Yagan fault zone was determined as a resistivity gradient zone characterized by northward dip, high dip angles, and deep depths. Based on these characteristics, and combined with the inversion interpretation results of four MT profiles (MT02~MT05) on the east side, this study identified the deep positions and structural characteristics of the Yagan fault zone within all the MT profiles. Moreover, it determined the major electrical directions of all the MT profiles using the impedance tensor decomposition technique, and the spatial trend of the Yagan fault zone based on the two-dimensional inversion interpretation results. As revealed by the results, the Yagan fault zone within the study area exhibits an overall nearly EW strike at the shallow surface and a strike of NE45° in the deep part, with an average width of approximately 6.8 km. It is a reverse fault with a gradual arc deflection to the north from west to east, manifesting a generally northward dip direction, dip angles ranging from 60° to 67°, and a fault depth of about 20 km. The obtained deep electrical structure model effectively reveals the deep structural characteristics of the study area. providing certain reference significance for the study of regional tectonic evolution

Industrial oil flows have been successively obtained from the basal conglomerates of the Cretaceous Qingshuihe Formation in the Shinan area, Junggar Basin. However, this set of reservoirs exhibits multi-layer three-dimensional oil-bearing properties and significant vertical and horizontal variations. Therefore, there is an urgent need to overcome the challenge of the identification and fine-scale characterization of reservoirs. Based on the accurate calibration of seismic and geological horizons, this study reconstructed the paleogeomorphology of the first member of the Cretaceous Qingshuihe Formation using based on the seismic flattening and residual thickness methods in three steps. By combining the reservoir prediction through natural gamma-ray pseudo-acoustic wave inversion, this study roughly identified the predominant factors controlling sedimentation and the spatial distributions of sand bodies. The results of this study provide an effective method combination for predicting Cretaceous reservoirs in the Shinan area. Furthermore, these results offer a sufficient scientific basis for oil and gas exploration in the glutenite reservoirs of the Cretaceous Qingshuihe Formation, thus effectively reducing the exploration risk.

Unfavorable geobodies such as Karsts, weak soil, and water-rich areas are extensively distributed in China. Under heavy rainfall, they are prone to geologic hazards like collapse. A severe geological collapse occurred in Xiacun Town, Yushui District, Xinyu City, near the Shanghai-Kunming high-speed railway. The space around the collapsed foundation pit was limited, with many interference sources like underground pipelines. With early signals subjected to the mutual inductance effects of receiver and transmitter coils, the conventional transient electromagnetic method exhibited low detection accuracy and anti-interference ability, encountering significant shallow blind zones. To locate unfavorable geobodies in the study area and provide suggestions for the prevention and control of geologic hazards, this study innovatively applied the opposing-coils transient electromagnetic method (OCTEM), supplemented by borehole-based verification. The results show that: (1) The OCTEM exhibited high accuracy, as demonstrated by the high consistency between the geophysical exploration results and the drilling results of the study area; (2) The low-resistivity zone spread across the study area, and the low-resistivity anomalies revealed by geophysical exploration were caused by groundwater according to borehole-based verification; (3) The strata from top to bottom were composed of soft plastic silty clay, hard plastic silty clay, soft plastic silty clay, and moderately weathered limestones; (4) The subsurface micro-confined water in the collapse area surged upward, gradually eroding the soft plastic silty clay layer around the area. The static water level in the collapsed foundation pit manifested an elevation of 55.60 m, located approximately 1.4 m below the surface; (5) A groundwater channel existed under the collapse area, with soil caves formed in the limestone layer under the prolonged erosion effect of water flow; (6) Long-term groundwater extraction may expand the underground seepage zone; (7) The administrative department in charge must promptly contain groundwater in the collapse area to prevent it from further eroding the surrounding unconsolidated soil layer.

Based on the combination ofdata- and model-driven approaches, this study expanded the labels of the training set through model inversion results, and added the model inversion objective function to the deep learning algorithm. By constructing a new loss function, this study proposed a seismic impedance optimization inversion method combining model inversion with deep learning inversion. The semi-supervised deep learning network inversion under a pseudo-label was achieved using the RNN network structure. The network inversion results were used as the initial model to participate in the model inversion. The final optimization inversion was completed by continuous iterative optimization of both network and model inversion. The method proposed in this study proves to possess high inversion accuracy and practicability, as demonstrated by the synthesis of the Marmousi model and the actual data.

In the Prospecting Breakthrough Strategy (2011~2020), China has made significant progress in the exploration of gold deposits, demonstrating considerable prospecting potential. Element sulfur, a mineralizer, is closely associated with the formation of gold deposits, proved to be the most significant element in gold deposit formation by scholars at home and abroad. Sulfur isotopes have been extensively used to trace the sources of minerals in gold deposits. Different gold deposits reside in distinct geological settings. Since sulfur isotopic compositions are governed by various sulfur sources, sulfur isotopes in gold deposits can reflect the geological settings of mineralization. The ore-district-scale spatio-temporal distribution of sulfur isotopes has theoretical implications, playing a significant role in guiding ore prospecting. The gold resources in China are distributed in 42 gold ore districts, typified by Jiaodong, Xiaoqinling, and Yunnan-Guizhou-Guangxi. This study comparatively analyzed and summarized the characteristics of sulfur isotopes in the three typical gold ore districts, providing theoretical and methodological support for future gold prospecting.

The gold ore zone in the Daduhe area of Shimian County, Sichuan Province, is located in the rare metal-precious metal-nonferrous polymetal metallogenic belt in the southern segment of the Songpan-Ganzi orogenic belt. It exhibits complex structures and steep terrains, severely restricting prospecting and exploration. Based on the geological settings, conditions, and geophysical characteristics for regional mineralization, this study investigated the typical Luoluoping gold deposit in Shimian by conducting deep geophysical exploration centered on audio-frequency magnetotellurics (AMT). Three low-resistivity anomalies (M1, M2, and M3) were identified, corresponding to the mineralized alteration zone I, the gold mineralization zone III, and the gold-copper ore body, respectively, demonstrating the effectiveness and applicability of geophysical methods for deep prospecting. Combined with geological understanding and engineering verification, this study summarized geological and geophysical prospecting markers for the typical gold deposit, establishing the geological-geophysical prospecting model for the gold ore zone in the study area. Therefore, this study provides technical support for deep prospecting in the study area.

The accurate identification of fluid properties is critical for reservoir evaluation.However,for the Paleogene low-porosity and low-permeability reservoirs in the Lufeng area,Pearl River Mouth Basin,the low contrast between oil and water layers in conventional logs due to the presence of high-resistivity water layers complicates the identification of oil and water layers.This study first ascertained the reservoir characteristics and genetic analysis of low-contrast oil layers.Then,it developed the Flair gas logging response equation and the Flair logging response correction method,aiming to overcome the challenge that gas logging response values of low-porosity and low-permeability reservoirs are significantly influenced by factors such as drilling rate and porosity.Given the differences in the properties and components of various fluids,this study constructed new oil-bearing and water-content indices using Flair gas logging curves.Moreover,this study characterized the geochemical chromatogram using a gamma probability distribution function and extracted the shape and scale factors to describe the chromatogram characteristics.Based on sensitivity parameters,this study plotted the characteristic parameter-based fluid property identification chart.The practical application shows that the log-based comprehensive fluid property identification method can yield satisfactory effects,achieving a compliance rate of 91.3%.Therefore,this method can be popularized.

The Ximeng-Lancang area in southwestern Yunnan resides in the southern section of the Nujiang-Lancangjiang-Jinshajiang orogenic belt in Southwest China. The 1∶50,000 geochemical soil survey revealed 24 rare-earth-element (REE) geochemical anomalies, which are primarily distributed in the Carboniferous Pingzhang Formation mafic volcanic rocks and the Carboniferous-Permian Yutangzhai Formation sedimentary carbonate rocks within and near the Changning-Menglian deep fault zone. Furthermore, the AP00 REE geochemical anomalies ranking high in the evaluation were analyzed in detail through a 1∶10,000 geochemical soil survey, a 1∶10,000 special geological survey, and light-duty prospecting engineering in mountainous areas. A new type of REE ores in weathering crusts has been first discovered in sedimentary carbonate strata, with preliminarily estimated REE resources reaching a medium scale, suggesting a prospecting breakthrough. This finding shows a new prospecting approach, which can be referenced for similar research. As revealed by a comprehensive analysis of the regional geological and geochemical settings and the data of AP00 REE anomalies, the AP00 REE ores in weathering crusts have undergone a gradual enrichment and mineralization process involving four different geological processes, suggesting polygenetic compound REE ores. Considering the low leaching efficiency of AP00 REE ores and significant structural (magmatic) superimposed mineralization of the heavy REE yttrium, it is inferred that yttrium-dominated primary REE ores might exist in the deep part, implying high potential for heavy-REE ores.

The development of gold deposits in the Liaodong region is considered to be controlled by the superimposed detachment fault zone of the metamorphic core complex system. The traditional view holds that the thickness of the cap rocks of the Yongning Formation in the Yongning Basin can exceed thousands of meters, thus hindering the migration of ore-bearing fluids and the formation of large-scale metal deposits. The exploration of deposits in the Liaodong region has remained within a depth of 1 km due to limited exploration efforts and insufficient research. This study obtained the resistivity distribution characteristics within a depth of 3 km in the Zhengtun area using the wide-field electromagnetic method (WFEM), ascertaining that the thickness of the cap rocks in the Liaodong region is around 1 km, in sharp contrast to the extremely thick cap rocks in the Yongning Formation. As verified by the 2 km deep drilling, an unconformable contact between the Yongning Formation and the underlying Archean basement was observed at a hole depth of 1 345 m, without significant structural detachment near the boundary. This study demonstrates that the thickness of the cap rocks in the Yongning Basin is merely around 1 km. Considering multistage active fault structures and densely distributed hypabyssal rock vein swarms in the area, it is preliminarily determined that the geological setting for mineralization in the Yongning Basin is akin to that of the Jiaodong gold ore concentration area. The ore-bearing metamorphic fluids or magmatic-hydrothermal fluids might have migrated to the upper part of the boundary for mineralization during the destruction of the North China craton. Overall, the Liaodong region has the potential to achieve breakthroughs in polymetallic prospecting, and the WFEM pinpoints the deep mineralization prediction.

The telecontrol electrode array is a new type of electrode array for power supply and observations that utilizes the carrier waves of the power-supply and measurement wires used in conventional electrical prospecting to transmit signals. By remotely controlling a series of coded electrode switches between various wires and their connections, this array allows for orderly power supply and measurements. This array enables flexible spacings between electrodes and the gradual expansion of the distances between power supply electrodes via remote control, thus achieving a gradient-based sounding array. The borrowing-line remote controller can be used combined with single-channel, multi-channel, and high-density resistivity instruments, and the combined arrays can perform 2D/3D electrical prospecting more effectively. Followed by the brief introduction of the principle of the borrowed-line telecontrol electrode array, this study discusses the applications and examples of this array and several combined arrays in the resistivity method and induced polarization (IP).

The goaf and subsidence areas formed ue to the mining of subsurface coal seams can cause damage to surrounding ecological environments.At present, the detection effects of double-layer goafs in coal mines, especially the second-layer goafs, are unsatisfactory. In response to this challenge, this study delineated goafs using apparent resistivity and impedance phase derived from the data acquired by an efficient controllable source audio-frequency magnetotelluric instrument. In the case of a shallow water-bearing goaf with low resistivity, the apparent resistivity displays shadow effects, leading to an extended abnormal range of the upper target, which is unfavorable to the identification of the lower high-resistivity goaf. In contrast, the impedance phase, exhibiting minor shadow and static effects, shows a significant response to the lower goaf. As indicated by the theoretical model testing results, the combination of apparent resistivity and impedance phase can effectively determine shallow water-bearing goafs and deep unfilled high-resistivity goafs. This combination method was employed to interpret the double-layer goaf in the Shenfu mining area of the Jurassic coal field in northern Shaanxi, achieving satisfactory results through the mutual verification of the two parameters. Engineering verification results indicate that this method demonstrates reliable inference and expected exploration effects. Overall, this method provides a new approach for CSAMT-based inference and interpretation in the exploration of double-layer goafs in coal mines, thus holding critical technical promotion and reference significance.

The Fuling rock mass in southern Anhui Province, located in the eastern section of the Jiangnan uplift zone, is a complex granitic rock mass that has experienced multi-stage evolution. It primarily comprises two lithologies: Monzogranite and K-feldspar granite. By investigating the geological, petrographic, and petrogeochemical characteristics of the Fuling rock mass, this study delved into its evolutionary characteristics, genetic types, and tectonic environment, aiming to clarify its indication significance for rubidium enrichment. The results of this study are as follows: ① The geochemical characteristics of the Fuling rock mass demonstrate high SiO₂, Na₂O, K₂O, and Al₂O₃ contents, high w(K₂O)/w(Na₂O) ratios, and aluminum saturation indices (A/CNK) ranging from 0.95~1.08 (average: 0.99), suggesting high-K calc-alkaline quasi-aluminous to peraluminous granites; ② In terms of trace elements, the Fuling rock mass possesses high Li, Rb, Nd, and Ta contents and significantly low Sr and Ba contents, which may be associated with the fractional crystallization of feldspar; ③ The w(Nb)/w(Ta) ratios ranging from 5.71~10.94 (average: 8.41) and Mg^# values ranging from 0.02~0.31 (average: 0.13) indicate that the Fuling rock mass was primarily derived from the partial melting of lower crust rocks, suggesting A-type granites in a non-orogenic extensional environment; ④ The Rb content in the Fuling rock mass increases with the magmatic evolution degree. Compared to monzogranites, K-feldspar granites with a higher evolution degree display higher Rb content, implying that the Rb content in the Fuling rock mass is generally controlled by magmatic evolution. Overall, this study holds some reference significance for understanding the Yanshanian diagenesis and mineralization of southern Anhui Province.

Surface water resources are scarce in Ritu County of the Ali area due to the absence of large rivers. The strata in the area are primarily composed of Jurassic and Cretaceous sedimentary rocks, exhibiting significantly varying spatial water abundance, thus posing challenges in water exploration through drilling. Based on hydrogeological survey data, this study summarized the occurrence patterns of pore water in Quaternary unconsolidated rocks and fissure water in fault structures and the electrical characteristics of aquifers in the area. It explored the structural fissure water with high water abundance in the area using the high-density resistivity method and the audio magnetotelluric method. Based on the geophysical exploration results, it delineated favorable aquifers. Furthermore, it verified the exploration accuracy through drilling, obtaining high-yield water wells, and ensuring the supply of drinking water. Therefore, the combination of multiple geophysical exploration methods is effective in groundwater resource surveys, improving the exploration accuracy of groundwater resources and providing effective technical support for well deployment.

The stability assessment of strip mine slopes is a fundamental means to prevent slope accidents. To investigate the influence of step topographies on the exploration using the high-density resistivity method on strip mine steps, this study conducted flume experiments for simulation using similar materials to explore the current field distribution in the profile to be surveyed. The experimental results show that: (1) The shallow positions near the upper and lower slope lines and the breadth line of the cleaning berm exhibited high current densities and even current distributions; (2) The middle positions manifested sharply changed current densities, with their contours akin to the step topography; (3) The deep positions displayed low current densities and tardy current changes; (4) A significant current gathering effect was observed near the slope bottom line on the profile; (5) Compared to flat topographies, step topographies exhibited high current densities and uneven current distributions. This suggests that in the exploration using the high-density resistivity method, step topographies in strip mines can cause abnormal inversion results for the middle positions and positions near the slope bottom line.

For deep coalbed methane (CBM) exploration and production, accurate in situ stress prediction holds critical significance for safe and efficient drilling and completion of wells. Deep CBM reservoirs, once considered restricted areas for exploration and exploitation, have been highly anticipated owing to their high yields in recent years. However, their in situ stress prediction model has not been investigated effectively. Hence, this study systematically analyzed six in situ stress prediction models commonly used for conventional oil and gas reservoirs and unconventional gas (like CBM) reservoirs. Based on these prediction models, this study calculated the in situ stress, and found that the combined spring model and the Newberry model yielded relatively high accuracy through comparative analysis of closure pressures. To improve the accuracy of in-situ stress prediction models, the effective stress coefficient of coal rocks was employed to optimize the two models. The optimized in-situ stress models yielded prediction accuracy errors reduced by 4%, roughly meeting the requirements of in-situ stress prediction accuracy for deep CBM exploration and production in the Daji block.

Thenorthern Laojunmiao gold deposit is located in the southern zone of the Beishan area, Gansu Province, and on the northeastern margin of the Tarim block. It resides in a tectonic environment of the Yaodongliang-Xiaoxigong Paleoproterozoic rift basin. This study delineated five comprehensive anomaly zones in the area through a 1∶10,000 geochemical soil survey. As verified by trenching exploration, three gold ore bodies, one gold-silver ore body, and two low-grade gold ore bodies were identified in the comprehensive anomaly zones, suggesting satisfactory prospecting results. Based on the comprehensive geological and geochemical anomaly characteristics of the deposit, this study established an integrated geological-geochemical prospecting model centering on the HT1 comprehensive anomaly zone. Moreover, it proposed the subsequent prospecting direction, providing a significant reference for the deep and peripheral prospecting in the area.