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.

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.

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.

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.

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 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.

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

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.

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.

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.

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 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 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.

Controlled source radio-magnetotellurics (CSRMT) measurements typically use artificial field sources transmitting at frequencies ranging from 1 to 1 000 kHz. Among the many transmitting sources of the artificial source electromagnetic method, the orthogonal horizontal electric dipole source and the orthogonal horizontal magnetic dipole source are preferred field sources for tensor resistivity measurements. Hence, using the analytical formulas for electromagnetic fields based on the horizontal electric dipole source and the horizontal magnetic dipole source, this study calculated the electromagnetic fields based on the orthogonal horizontal electric dipole source and the orthogonal horizontal magnetic dipole source in the homogeneous half-space model. The results show that: (1) The displacement current needs to be considered at transmitting frequencies above 100 kHz; (2) The effects of displacement current on the tensor apparent resistivity and the impedance phase can be ignored in the far zone; (3) With a constant model resistivity and varying distances between transmitter and receiver, model calculations indicate a larger measurement range in the far zone of the high-frequency electromagnetic field; (4) With a constant distance between transmitter and receiver and varying model resistivities, model calculations suggest that the far-zone range of the electromagnetic field is significantly influenced by resistivity, and that the high-resistivity model requires higher frequencies for achieving far-zone observation conditions.Compared with the electric dipole source, the magnetic dipole source exhibits smaller deviations on the tensor apparent resistivity and impedance phase with the actual value, which is more suitable for geological analysis.

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.

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.

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.

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.

This study aims to systematically assess the pollution risk of heavy metals in the soil-crop-human body system along the periphery of mining areas, thus providing a scientific basis for the classified management of ecological risks and safe crop production in mining areas. Hence, this study examined the soil and crops (rice, corn, and sweet potato) in arable land along the periphery of a typical mercury mining area in Chongqing City. The single-factor pollution index (P_i), Nemero composite index (P_综), and positive matrix factorization (PMF) model were employed to assess the pollution degree and ecological risk of soil heavy metals for source analysis. Moreover, the human health risk assessment model recommended by the United States Environmental Protection Agency (USEPA) was applied to assess the health risks of local staple crops for residents. The results are as follows: (1) The average contents of As, Cd, Cr, Cu, Hg, Ni, Pb, and Zn in the soil of the study area were all higher than the topsoil background values of Chongqing and China, suggesting that heavy metals are relatively enriched in topsoil; (2) The single-factor pollution index indicates that the over-limit ratios of Hg and Cd in the soil reached 96.29% and 92.59%, respectively, whereas rice, corn, and sweet potato samples with Cd content exceeding the value specified in the national food safety standard (GB 2762—2022) accounted for 16.67%, 18.75%, and 14.28%, respectively; (3) The Nemero composite index (P_综) was between 1.17 and 46.05, suggesting mild to heavy pollution in the study area, with heavy pollution primarily located around the mercury mining area and artisanal mercury smelters, as well as the lower reaches of the Rongxi River; (4) The PMF model analysis demonstrates that the heavy metals in the soil of the study area originate from three sources: natural source (47.21%), mining activities (16.00%), and a mixed source of mining and agricultural activities (36.79%). Specifically, Cd, Cr, and Ni are principally affected by the natural source, Hg by mining activities, As and Pb by the mixed source of mining and agricultural activities, and Cu and Zn are associated with the natural source and the mixed source of mining and agricultural activities; (5) The human health risk model reveals that the consumption of rice, corn, and sweet potato poses composite health risks for both adults and children. Rice consumption exhibits the highest risk index, especially in children, with the main risk factors being As and Cd.

Fine-scale characterization of reservoirs is critical for oil and gas exploration and production. Reservoirs in the Z gas field exhibit considerable burial depths and superposed sandstone and mudstone impedance characterized by dark spots, complicating their identification using conventional seismic methods. This study achieved the characterization of deep reservoirs in the Z gas field based on the dominant-channel stacking technique. First of all, this study analyzed the seismic response characteristics of deep reservoirs through forward modeling, positing that poor physical properties are the primary factor contributing to the formation of dark spots. Then, starting with the investigation of the near-well prestack gathers of the target layer, this study examined their amplitude variation with offset (AVO) characteristics and seismic phase stability at different angles, determining the dominant-angle seismic channels that can accurately reflect the phase stability of reservoirs. Finally, this study derived a lithology-sensitive 3D data volume through partial stacking of dominant-angle seismic channels, achieving the characterization of deep reservoirs. The near-trace superimposition (3°~15°) of phase-shift seismic data (-90°) allowed for effectively characterized the H3a reservoir in the Z gas field, providing a geophysical basis for subsequent well deployment. Therefore, the dominant-channel stacking technique can effectively characterize the spatial distribution of deep river-channel reservoirs, guiding the reservoir characterization of similar oil and gas fields.

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.

Both the controlled source audio-frequency magnetotellurics (CSAMT) and the microtremor survey exhibit promising application prospectsunder strong urban interference. However,single geophysical inversion methods are challenged by a multiplicity of solutions. To achieve the complementary advantages of different geophysical methods, and address the lateral discontinuity of single-point inversion, this studyexplored the quasi-two-dimensional joint inversion of the CSAMTand microtremor survey data. It enabled the joint inversionby introducing a lateral constraint matrix into the objective function for joint inversion and employing the limited-memory Broyden-Fletcher-Goldfarb-Shanno (LBFGS) algorithm. The reliability and effectiveness of the joint inversion were verified using the inversion example of synthetic data from theoretical models. The results show that compared to single data inversion, the joint inversion can effectively improve the accuracy of inversion results, with the resistivity model more consistent with theshear-wave velocity structure. Moreover,lateral constraints can effectively reduce the discontinuity of the physical parameters of adjacentsurvey points. The quasi-two-dimensional joint inversion with lateral constraints enhances the inversion reliability by obtaining more reasonable profile results of physical parameters and structures with the efficiency of single-point inversion.

The Rongcheng uplift in North China boasts abundant geothermal resources. Research indicates that the Rongcheng uplift exhibits significantly different physical properties between the bedrock surface and the overlying Cenozoic strata. Moreover, the bedrock surface serves as the primary top boundary of the geothermal reservoir in the Wumishan Formation. Investigating the fine-scale structures, burial depths, and faults of the bedrock surface in the Rongcheng uplift holds critical significance for understanding the distribution and enrichment of geothermal resources in the area and guiding their exploration and production. Through elaborative processing of the north-south reflection seismic profile data of the Rongcheng uplift, collected by the Chinese Academy of Geological Sciences in 2018, this study obtained the high-precision geometric structure of the Rongcheng uplift within a depth of 4 km. The geometric structure was calibrated using geothermal borehole data before interpretation. Key findings are as follows: (1) The Cenozoic sedimentary strata overlying the bedrock surface of the Rongcheng uplift exhibit a nearly horizontal layered distribution, serving as cap rocks of the Rongcheng geothermal field; (2) The bedrock surface of the Rongcheng uplift manifests burial depths ranging from 700 to 3 000 m, with gentle changes in the central portion, and rapidly deepening to around 3 000 m towards the periphery; (3) The Niunan and Rongdong faults converge in the deep part, constituting a fault system along with other medium and small faults, thus facilitating the conduction of water and heat; (4) The geometric structure of the Rongcheng uplift on the bedrock surface contributes to the convergence of heat flow beneath the uplift.

Urban main water supply pipelines are mostly buried along roads. Large pipe diameters and deep burial depths make it hard to detect their leakage in the early stage. Their leakage will severely influence urban traffic and residents' daily life. Hence, the leakage monitoring of water supply pipelines is particularly important. However, factors such as dense traffic lines, hardened road surfaces, and electromagnetic interference limit the application of the ground resistivity method and geological radars in pipeline monitoring. To make up for the shortcomings of existing monitoring methods, this study explored the cross-hole resistivity method for pipeline leakage monitoring. First of all, pipelines with and without leakage were simulated using forward modeling and inversion methods, analyzing the detection characteristics of the cross-borehole resistivity method. Then, electrode materials and burial methods were examined through experiments, solving the problems of electrode corrosion and weak electric field signals. Finally, an experimental site was set up near a water supply pipeline in Beijing, obtaining multi-phase monitoring data using the cross-borehole resistivity method. Through comparative analysis of multi-phase resistivity sections, this study analyzed the changes in pipeline leakage, delineating the leakage influence scope, which was verified by the leakage data from the waterworks. The satisfactory monitoring results suggest that the method proposed in this study can be referenced for similar pipeline leakage monitoring in cities.

For the high-density resistivity method, favorable grounding conditions are required to ensure the establishment and measurement of the geoelectric field. Otherwise, unfavorable grounding conditions, like rigid pavement, will prevent some electrodes from being inserted into the ground, leading to the loss of valid data from standard observation devices and reducing the imaging quality. Therefore, this study proposed a method for the fast observation device design. This method supplemented data using an asymmetric quadrupole electrode array according to the spatial positions of missing data's recording points. Numerical simulations show that the method proposed in this study significantly improved the imaging effects of Wenner, Schlumberger, and dipole-dipole arrays, with a second-scale design time. In this study, an observation device based on asymmetric design for high-density resistivity imaging was successfully applied to the embankment detection in Ningbo, reducing the influence of motor lanes on data quality and accurately locating the embankment position.

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.

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).

Data integration based on MapGIS includes data conversion, data normalization, data fusion, and related research. A synthesis of existing research suggests that data conversion has been intensively studied, while there is a lack in studies of data normalization and data fusion. This study improved the data normalization method based on the complex and extensively applied geological maps, achieving the normalized annotation and color filling for thousands of geobodies at one time. A technical process for data fusion was established by analyzing the applicable conditions of various commonly used methods for data fusion and making some supplementation. Besides, ASCII code files were prepared for mapping small coal pillars in batches. The results of this study show that improving the data normalization method, establishing the technical process for data fusion, and making full use of ASCII code files can significantly enhance the efficiency of data integration and broaden the mind for problem solving.

Due to the multiplicity of solutions and the multiple extrema of the inversion objection functions,conventional nonlinear optimization algorithms are susceptible to unstable convergence and local optimum in the inversion of Rayleigh wave dispersion curves.This study improved the standard butterfly optimization algorithm by incorporating dynamic switch probability and nonlinear self-adaptive weight factors,yielding an elevated global exploration capacity in the early stage and a high local research ability in the latter stage.Furthermore,the dimension-by-dimension Cauchy mutation,along with a greedy algorithm,was employed to update the current best position during each iteration,ultimately directing the whole swarm population toward the global optimum.Tests of four commonly used benchmark functions demonstrate that the improved butterfly optimization algorithm(IBOA) outperformed other nonlinear algorithms,including the genetic algorithm and particle swarm optimization algorithm,in terms of the global research capacity of both unimodal and multimodal functions.Different algorithms were adopted for the inversion of the dispersion curves of three theoretical geological models.The results show that IBOA yielded inversion results that were closer to the models even when the dispersion curves contained 10% random noise.Finally,the IBOA was applied to actual Rayleigh wave data,and the inversion results were highly consistent with the strata revealed by drilling.Compared with the genetic algorithm and the particle swarm optimization algorithm,the IBOA significantly improved the convergence speed,as well as solution accuracy and stability.Therefore,the IBOA has a certain practical value and application prospects.

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.

Given the low resolution and poor wavelet coherence of seismic data for the loess tableland area of the Ordos Basin, this study proposed a method for calculating the near-surface Q-value model for near-surface Q-absorption compensation of seismic data. Investigations reveal that micrologs have been used to obtain the Q field of a whole survey area by calculating the Q value and subsequent interpolation. Based on previous research results, this study calculated the Q values of well sites and near-surface velocity values using dual-well micrologs. Then, the regional relationship function between near-surface velocity and Q was determined through fitting using the least squares method. Furthermore, the near-surface Q field of the study area was obtained using the near-surface velocity field derived from the tomographic inversion of the first arrival wave post basic static correction. Consequently, the near-surface Q field of the whole survey area were calculated from the Q values of microlog positions, and the near-surface Q absorption compensation of prestack gathers was achieved. As indicated by the application of the study area’s seismic data, which are characterized by complex surface and subsurface conditions, the inversion of the Q field for near-surface Q absorption compensation using the method proposed in this study can effectively enhance the wavelet coherence of seismic data, broaden the frequency band, improve the log-seismic matching relationship, and eliminate the influence of near surface on seismic wavelets.

Magnetotelluric (MT) data collected from offshore areas are generally distorted due to coastal effects, posing challenges in obtaining true subterranean electrical structures. Based on the model of half-space with seawater, 2D electrical isotropy and anisotropy models, and 3D electrical isotropy model, this study analyzed the distortion patterns of MT responses under coastal effects through forward modeling. Moreover, it conducted 2D and 3D inversions of MT data with or without seawater constraints. Key findings are as follows: (1) The initial frequency points of distortion in MT apparent resistivity curves are closely correlated to the distances from survey points to seawater; (2) Compared to MT responses free from coastal effects, the high-frequency sections exhibit increased amplitudes in real induction vectors only at survey points in offshore areas and higher phase tensor ellipticity, whereas the low-frequency sections display expanded influence areas subjected to coastal effects; (3) Excluding seawater constraints, the inversion results show false anomalies in offshore areas and poor reconstruction effects on subsurface anomalies. Considering seawater constraints, the constrained inversion can effectively suppress the distortion caused by coastal effects. Overall, this study will provide a significant reference for the collection, processing, and interpretation of MT data from offshore areas.

Heavy metal pollution in soils has become increasingly prominent. To explore the distributions of heavy metals in soils in Fangshan District, Beijing, China, this study collected 152 topsoil samples and 240 deep soil samples from this district. Based on these samples, this study statistically analyzed the distributions and enrichment factors (EF) of seven heavy metal elements, namely As, Cd, Cr, Cu, Hg, Ni, and Pb. Furthermore, this study investigated the correlations, sources, and contribution rates of these elements through principal component analysis (PCA) and positive matrix factorization (PMF). The results show that: ① Elements As, Cd, Cu, Ni, and Pb exhibit high contents in the topsoil of the Shidu, Shijiaying, Xiayunling, and Puwa areas. Besides, elements Cr, Ni, and As manifest high contents locally in Zhoukoudian, Nanjiao, and Hebei Town. Element Hg displays high content in the eastern plain areas including Doudian, Yancun, and Changyang; ② Elements Hg and Cd are highly enriched, and there exist strong corrections among elements As, Cr, and Ni; ③ These elements primarily originate from natural sources (soil parent materials), which contribute to 73.6% to 78.6% of the elements. Element Cd is mostly sourced from an anthropogenic mixed source, which contributes 83.3% of Cd. The mixed source predominantly consists of industrial and mining activities, agricultural production, and traffic emissions. Elements Cu and Pb showed similar contribution rates of natural and mixed sources, both about 50%. Element Hg in soils primarily stems from dry and wet atmospheric deposition, which yields a contribution rate of 72.4%.

The Xilin fault zone,intimately associated with gold and polymetallic mineralization,exhibits high potential for gold resources.In deep exploration,identifying the deep structural characteristics of ore-controlling faults plays a critical role in achieving breakthroughs in gold exploration.Through the analysis of gold metallization regularity and the reflection seismic methods,this study clarified the seismic response to the changes in the attitude of the dominant ore-controlling fault zone in the Jiaodong area.It posited that the changes in energy intensity of the seismic event on the seismic time profile,as well as large continuity deterioration zones,can indicate the changes in the fault attitude,demonstrating high mineralization potential.Moreover,this study predicted and verified the metallization targets in the area.

Water and soil erosion affects the distribution and partitioning of elements in soils. The distribution and partitioning patterns and bioavailability of trace beneficial elements such as selenium (Se) and zinc (Zn) in water and soil erosion areas serve as significant factors for measuring the ecological effects of water and soil erosion. Through the geochemical survey of soil and crops, this study investigated the geochemical characteristics and bioavailability of Se and Zn in the water and soil erosion area of Changting County, Fujian Province, obtaining the critical geochemical parameters of Se and Zn in soil and crops in the study area. The results are as follows: (1) The soil Se and Zn contents in the study area show median values of 0.43×10^-6 and 46×10^-6, respectively; (2) Se is enriched in the soil developed from metamorphic rocks, whereas Zn is enriched in the soil developed from metamorphic rocks and granites; (3) The soil Se and Zn contents are higher in bamboo forests compared to other land-use types; (4) The soil Se content shows a decreasing trend as the water and soil erosion intensifies; (5) The bio-concentration factors of Se and Zn are significantly positively correlated with w(Si)/w(Al) ratios, and negatively correlated with Se, Zn, and organic matter. As indicated by the results above, the distribution and partitioning of soil trace beneficial elements like Se and Zn in the study area are primarily subjected to metamorphic rocks and granites. The water and soil erosion is accompanied by a significant soil Se loss. The bioavailability of soil Se and Zn is reduced by the adsorption of clay minerals and organic matter. Additionally, there may be a large proportion of inactive Se and Zn in the soil of the water and soil erosion area.

This study conducted magnetotelluric profiling in the Bengbu-Huaibei area of Anhui Province. Combined with gravity and magnetic anomalies, it obtained the deep electrical structure, the distribution of primary strata, and the properties of faults in the area, particularly the morphology of the Xuzhou-Suzhouarcuate nappe structure and the development of deep coal-measure strata. The results indicate that: (1) The Upper Paleozoic strataare primarily distributed under the high-resistivity nappe on the surface of the Xuzhou-Suzhouarcuate nappe structure. Theymanifest low-resistivity and low-densityphysical properties and high continuity, suggesting high exploration potential for coal beneath the nappe structure;(2)On the profile, early-stage faulting was dominated by reverse faults, resulting in local Lower Paleozoic and Proterozoicstrata overlying the Upper Paleozoic strata. In the later stage, normal faults predominated, controlling the Cenozoic deposition;(3) The Xuzhou-Suzhouarcuate nappe structure exhibits a 'high-low' double-layer electrical structure at burial depths shallower than 4 km, withthe dominant thrust fault plane composed of F5 and F6 faults. The leading edge of the high-resistivity nappe on the surface extends northwestward to Xiaoxian County and southward to northern Guzhen County, experiencing significant denudation in the Zhahe area. The above results provide critical geophysical information for the basic geological research and mineral exploration in the study area.

The extensively applied audio magnetotellurics (AMT) has become a primary method for deep geophysical exploration of solid mineral resources. However, its data processing and interpretation often only consider electromagnetic effects but ignore induced polarization (IP) effects, which is inconsistent with actual geological conditions. Based on the two-dimensional AMT finite-element forward modeling with IP effects, this study simulated the magnitude and regularity of the influence of various parameters of IP effects on the two-dimensional forward response. Moreover, this study conducted a numerical simulation on the geoelectric model of sandstone uranium deposits in the Erlian Basin. The results show that: (1) With an increase in the values of polarizability, frequency correlation coefficient, and time constant, the two-dimensional AMT forward modeling with IP effects based on the Cole-Cole model primarily reduced the abnormal response value of two-dimensional forward modeling apparent resistivity and increased the abnormal response value of impedance phase. This is beneficial for detecting low-resistivity targets rather than high-resistivity targets; (2) The zero-frequency resistivity and polarizability in IP effects exhibit a significant influence on the two-dimensional forward response. The influence of both frequency correlation coefficient and time constant on the forward response primarily depends on the polarizability. High polarizability suggests their significant influence on the forward response; (3) In the case of disseminated and sulfide-bearing lithologies in the sand bodies of sandstone uranium deposits, greater IP effects will significantly influence the detection of target sand bodies using frequency-domain AMT. Therefore, forward modeling is necessary before detection to determine the magnitude of IP effects.

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.

This study conducted SKS shear-wave splitting measurements of 39 distant earthquakes with magnitudes above 5.8 and epicentral distances between 88° and 120° recorded by the monitoring stations of China Earthquake Networks Center in the Qinghai-Tibet region in the past five years. Based on these measurements, this study investigated the anisotropic and deformation characteristics of Tibetan Plateau and its surrounding areas. Within the Qinghai-Tibet region, the fast axis of SKS shear-wave splitting measurements from west to east gradually shifted from NE-SW to E-W and then to NNW, roughly aligning with the direction of the GPS velocity field and changing in a clockwise direction. The reason for the measurement results in this region lies in that the westward retreating of the Burma plate during the eastward subduction may have caused circular deformation in the local lithosphere. The GPS data of the southern Sichuan-Yunnan region reveal nearly ES-directed surface deformation and NW-SE-trending strike-slip faults, with the fast-axis direction of the Pms wave for crustal anisotropy being S-N or NNE-SSW. The SKS splitting measurement results of this study reveal the E-W-directed anisotropy of the upper mantle, which intersects at a high angle with or is perpendicular to the fast-axis direction of the Pms wave. This suggests that the mantle flow field of the deep asthenosphere in Yunnan is inconsistent with the deformation characteristics of the crust and surface, and the mantle and crust show distinct deformation mechanisms and anisotropy sources, resulting in decoupling deformation.