There is a lack of selection bases in the geochemical anomaly identification and the reconstruction of the geochemical background conforming to the metallogenic distribution using deep learning algorithms with different network structures. Given this, based on the 1∶200 000 stream sediment data of the copper-zinc-silver metallogenic area in southwestern Fujian Province, this study extracted the combined structural characteristics, spatial distribution characteristics, and mixed characteristics of multiple elements in the samples using three unsupervised deep learning models, i.e., AE, MCAE, and FCAE. Then, these characteristics were used to reconstruct the geochemical background and simulate the metallogenic distribution. The results show that the anomaly areas delineated by the FCAE model were the most consistent with the known copper ore occurrences, followed by the MCAE and AE models. The FCAE, MCAE, and AE models had an area under the curve (AUC) score of 0.80, 0.78, and 0.61, respectively. Moreover, the FCAE and AE models were not sensitive to the change in the convolution window size. These results indicate that when deep learning algorithms are constructed for geochemical anomaly identification, the algorithms based on the extraction of spatial distribution characteristics or mixed characteristics perform well, and those based on the extraction of combined structural characteristics or mixed characteristics have a strong anti-interference ability for the noise caused by the change or inconsistency of the spatial observation scale. This study provides some effective selection bases for constructing geochemical anomaly identification models based on deep learning algorithms.

The northeastern margin of the Linyi uplift is located at the eastern end of the Luxi Block and immediately adjacent to the Yishu fault in the east. The main structural framework of the study area is controlled by the NE-trending Tangwu-Gegou fault and the NW-trending Mengshan fault. Covered by the Cenozoic sediments, the boundaries of main tectonic units in the study area are almost all concealed, and it is necessary to further investigate the change in the strike of the eastern end of the Mengshan fault as well as the distribution of the angular unconformity along the northern boundary of the Linyi uplift. Using the latest 1:50,000 high-precision gravity data, this study mainly investigated the positions and intersection relationships of the boundaries of tectonic units based on the qualitative analysis of gravity field, the interpretation of multiple gravity potential field conversion, and the division scheme of geotectonic units in Shandong Province. The analysis results are as follows. The Mengshan fault at the junction of the Mengshan uplift and the Pingyi sag transitions from the NW trending to nearly-EW trending in the east of Bancheng Town, significantly cuts the NE-trending Tangwu-Gegou fault, and shows a NW-trending turn to the east again. The angular unconformity at the junction of the Linyi uplift and the Pingyi sag neither ends in the Mengshan fault in the north nor turns southward but extends to the Tangwu-Gegou fault in the east. This unconformity also controls the southern boundary of the Pingyi sag, making the NW-trending banded gravity anomalies of the sag turn eastward. Consequently, the boot-shaped low-value gravity anomalies were formed in the study area. Based on the high-precision gravity boundary identification, this study determined the fault system and tectonic division of the northeastern margin of the Linyi uplift, providing high-precision gravity data for the basic geological study in the study area and laying a good foundation for further mineral geological survey.

Karst is widely distributed in China. However, geological disasters frequently occur in karst zones due to the fragile geological environment, which seriously threatens the safety of people’s life and property and cause huge economic losses. In this study, the controlled source audio-frequency magnetotelluric (CSAMT) method and microgravity were used to extract residual gravity anomalies through the two-dimensional inversion of pseudosections and multi-scale wavelet analysis. As a result, rock-soil interfaces of karst zones and the development zones of strong karst were well divided; the locations, burial depths, scales, and spatial distribution of karst caves were delineated. As verified by drilling, the rock-soil interfaces and strong-karst development zones determined by CSAMT interpretation were roughly consistent with those revealed by boreholes, and the sizes and burial depths of collapsed karst caves that were delineated by microgravity roughly correspond to those revealed by boreholes of engineering exploration. These results show that the CSAMT combined with the microgravity method can achieve significant effects in the detection of concealed karst collapses and serves as a scientific detection method for the early warning of the prevention and treatment of potential karst collapses and similar geological disasters.

The edge depth of geological body plays a crucial role in the semi-quantitative interpretation of gravity and magnetic potential field exploration. At present, the main inversion methods of geological body edge depth mainly include Werner deconvolution method, analytical signal amplitude method, local wave number method, Tilt-depth method, Euler deconvolution method and curvature attribute inversion method. These methods all have problems of solution selection, stability and adaptability. This paper mainly studies the adaptability of different types of data and models. Through basic principle analysis and model test, the results show that Werner deconvolution method and Euler deconvolution method are applicable to the most types of data sources, followed by curvature attribute, and Tilt-depth is the least; Werner deconvolution method, Euler deconvolution method and curvature attribute methods can adapt to many models, the Tilt-depth is least. For gravity data, the analytical signal amplitude of the first vertical derivative as the data source is applicable to all methods. For magnetic data, the analytical signal amplitude as data source is applicable to all methods. At the same time, it is suggested that other scholars should follow the following principles when using these methods to invert the edge depth of the two-dimensional body: It is recommended that Werner deconvolution is preferred, followed by curvature attribute and Euler deconvolution. The gravity data source of Werner deconvolution method and Euler deconvolution method is recommended to use the horizontal derivative of the first vertical derivative, and the magnetic data source is recommended to use the horizontal derivative. The gravity data source of curvature attribute method is recommended to use the analytical signal amplitude of the first vertical derivative, and the magnetic data source is recommended to use the analytical signal amplitude. In addition, based on the above research conclusions, some suggestions on the future research directions of the solution screening, stability and adaptability of the edge depth inversion are given.

This study explored the geothermal resources in Yueliangwan, Binhai County, Jiangsu Province using the controlled source audio-frequency magnetotellurics (CSAMT) method and the wide-field electromagnetic method. Through the auxiliary correction of near-field and transition-field curves, as well as the inversion based on the CSAMT data, this study obtained the electrical structure information of underground geothermal resources in the Binhai port. Meanwhile, this study acquired the information on the underground geometric structure using the microtremor exploration method. By comprehensively analyzing the interpretation results of three kinds of geophysical data, this study obtained the geothermal model of the study area and determined the locations of the anomalies. A geothermal well with a depth of 2 919 m was drilled in the study area, obtaining water yield of 2 171 m³/d with a water temperature of 51 ℃. The high consistency between the results from the comprehensive geophysical exploration and the geological and geothermal well data indicates that the comprehensive geophysical exploration method can improve the reliability of geothermal exploration results.

As a fast and nondestructive geophysical exploration technique,the natural source surface wave technique performs well in exploration in a complex urban environment by extracting surface waves and other information using the natural earth vibration.This study applied this technique in an urban planning area to ascertain the distribution characteristics of the strata in the area through section interpretation,the extraction of site evaluation parameters including equivalent shear wave velocity and predominant period,and 3D visualized plotting.It can be concluded that the planning area has no concealed fault and thus has excellent site conditions.The results of this study can be utilized as an important reference for the site evaluation of similar areas.

To quickly and effectively detect the hidden hazards of dams,this study proposed the microtremor B-mode ultrasound technology based on linear arrays.Most of the (earth) dams also act as highways,and the vibration signals generated from running vehicles propagate along dams.Therefore,this study proposed deploying linear arrays along the dams,with the vibration propagation direction consistent with the signal receiving direction.In this way,abundant vibration sources can be provided for detecting hidden hazards of the dams.The results of this study show that the data on multiple exploration points can be simultaneously acquired using the multi-channel acquisition technique based on linear arrays,thus improving the efficiency of field data acquisition.Moreover,the influence of source differences can be avoided,and the lateral resolution and the accuracy of exploration results can be improved.The technology proposed in this study was applied to the pre-flood safety inspection of a dam in Jiujiang,Jiangxi Province.Three low-velocity hidden hazards were identified in this dam and were presumed to be the weak layers of the dam foundation and the loose media of the dam body.Practices have proved that this technology effectively counteracts the deficiencies (i.e.,low efficiency and lateral resolution) of the previous microtremor exploration.Moreover,this technology allows scanning at a spacing of 1 m or 0.5 m,thus improving the lateral resolution.This study will provide efficient and accurate guidance for dam safety management.

This study summarized the progress and major application performance of gravity and magnetic techniques for onshore hydrocarbon exploration in China in recent years.By combining the research results of the authors,this study elucidated the new progress made in the gravity and magnetic techniques for hydrocarbon exploration from the prospect of acquisition,processing,interpretation,and application and sorted the application performance of these techniques in key fields including deep targets,complex areas,and volcanic rocks.Moreover,this study future analyzed the demand for the gravity and magnetic techniques for hydrocarbon exploration.By combining the new trends of gravity and magnetic exploration techniques at home and abroad,this study proposed the development direction and application prospect of gravity and magnetic techniques for oil and gas in deep strata and igneous rocks in complex areas.The results of this study show that significant progress has been made in gravity and magnetic exploration techniques,which play an important role in supporting the current hydrocarbon exploration.It is expected to develop high-precision and high-density gravity and magnetic exploration techniques and gravity-gravity-electricity-seismic collaborative innovation techniques.

To explore in detail superficial paleochannels in Xiong'an New Area,this study investigated two profiles in the study area using the high-density resistivity method based on previous remote sensing.The interpretation results were verified through drilling.The distribution range of the paleochannels that was delineated using the high-density resistivity method was more accurate than that obtained from remote sensing.This study determined that the superficial paleochannels in the study area exhibit curved,tortuous,and braided planar distribution,achieving excellent application performance in the detailed exploration of superficial paleochannels.This study provided a new idea for future exploration and study of superficial paleochannels and can be used as a reference for the selection of methods used to investigate paleochannels in similar geological conditions.

As resource exploration deepens and becomes increasingly difficult,improving the imaging precision and the reservoir prediction accuracy under a complex tectonic setting has become a top priority of research.The full waveform inversion (FWI) method developed in recent years can be applied to complex geological structures.This method can reveal structural details in a complex geological setting using the dynamic and kinematic information in the pre-stack seismic wave field.However,this method involves many research elements such as model parameterization,building of inverse error function,data preprocessing,numerical simulation of wavelengths,and wavelet estimation.Thus,its development is bound to be a long-term gradual improvement process.The FWI method has been applied to actual observation data with the development of theory and computer technology.This study introduced the principle and processing flow of the FWI method and summarized its development history and its application status in marine and onshore seismic data,and deep seismic reflection data.Accordingly, this study presented the current application bottlenecks,data processing difficulties, and challenges of deep-crustal inversion imaging for subsequent research and application of the FWI method.

The Dashui gold deposit in Maqu County,Gansu Province is a typical mine of the western Qinling region.Owing to continuous mining,many mined-out areas have been formed at different depths below high and steep slopes No.5 and 9,causing local surface collapse and major safety hazards.According to the requirements for environmental protection and safety,there is an urgent need to determine the spatial distribution of concealed collapse to effectively prevent geological disasters.Using the opposing coils transient electromagnetic method (OCTEM),this study conducted the fine-scale interpretation of the anomalies on the typical sections of the exploration area.Based on this,as well as the comprehensive analysis of the hydrogeological data and basic geological data of the exploration area,this study determined the transparent and three-dimensional distribution of the concealed collapse of the Dashui gold deposit.The results of this study show that the subsurface investigation of mined-out areas using the OCTEM can effectively reveal the lithologic and electrical characteristics of concealed strata in mined-out areas.Moreover,the significantly different physical properties between mined-out areas and surrounding rocks can be used to effectively identify the locations and basic morphologies of subsurface mined-out areas.The data on the boundary characteristic points of the mined-out areas on geophysical profiles with multiple exploration lines and three-dimensional modeling allow for the three-dimensional visualization of the spatial morphology of the mined-out areas.The application performance of the OCTEM,along with three-dimensional modeling,provides a technical basis for mine restoration and safety evaluation,thus effectively serving the construction of digital mines.

Laochang, Lancang, Yunnan is one of the most important polymetallic mining areas in the southern part of Sanjiang Tethys metallogenic belt. After years of mining, the shallow resources are nearly exhausted. In recent years, granite porphyry and porphyry polymetallic mineralization have been newly discovered in the deep part of the mining area, highlighting the prospecting potential of deep polymetallic deposits. In order to trace the occurrence of deep ore-controlling strata and structures in the study area and help to make a breakthrough in deep ore prospecting, high-power induced polarization method and audio magnetotelluric method were implemented to image the deep structure situated. Results obtained from the inversion of the measured induced polarization and electromagnetic data recuperated the distribution of induced polarization anomalies and the characteristics of deep electrical structure within the study area. Combined with the available regional geological settings, the main conclusions are as follows: The low resistance and high polarization anomalies in the northwest of the survey area are deeply related to the surface ferromanganese, silver manganese, and deep polymetallic mineralization, and the high resistance and high polarization anomalies in the middle and east of the survey area are in good agreement with the deep polymetallic mineralization. The upper Carboniferous limestone and dolomite strata are thick in the west and thin in the east, with the west strata dipping to SW and the east strata overlying the Yiliu Formation of the lower Carboniferous. The concealed granite porphyry dips in NE direction, and the coupling part between its deep 2 300~2 800 m horizontal section and deep fault is a favorable area for deep polymetallic mineralization. Notably, joint interpretation yielded from the high-power induced polarization method and the audio magnetotelluric method applied improved the reliability of deep polymetallic ore detection and provided more information of positioning the subsequent drilling layout.

The phase difference (i.e., time difference) and amplitude difference between the geomagnetic data of the offshore work area and the geomagnetic diurnal variation data of the remote stations are still challenges to the precision of the marine magnetic survey network. Based on the stations on both sides of the East China Sea and three stations in Europe at higher latitudes, this study analyzed and made statistics on the numerical differences in morphological characteristics, phase differences, and amplitude differences of the diurnal variation curves during the daytime, nighttime, and the periods of intense magnetic disturbance. The results are as follows. During the daytime, the phase difference between the stations is constantly changing, resulting in a large amplitude difference around noon. During the nighttime, the data of the stations have consistent phases, and the amplitude difference is mostly less than 4 nT. During strong magnetic disturbance activities such as magnetic storms, the phases of the stations are consistent, and the amplitude difference is even smaller than that during quiet days. According to the survey data of the ocean, the absolute value of the difference at intersections between the survey lines during magnetic storms and quiet days is less than 3.2 nT. The variation characteristics of the phase difference and amplitude difference of the geomagnetic diurnal data between stations facilitate the diurnal variation correction of the marine geomagnetic data.

To achieve the goals of peak carbon dioxide emissions and carbon neutrality, geothermal energy has great prospects for utilization as a type of widely distributed green and clean energy. The tectonic fissure-hosted geothermal water is regarded as an important type of hydrothermal energy for development and utilization because of its high water yield and easy reinjection. This study systematically analyzed the regional structures, formation lithology, water storage space, and water yield property of the urban area of Meixian County in the west of Guanzhong Plain through the regional integrated geophysical exploration, aiming to guide the target area prediction and well placement of geothermal wells. The results show that three concealed faults are present in the target area, of which two faults with favorable water yield property and large scale can be regarded as the faults of the target area. Based on this, geothermal wells were arranged near the fault prediction lines on the hanging wall of the faults, and the weathered zones of the bedrock surfaces were penetrated vertically along the dip angles of the faults. Given the actual geological conditions, such as the faults and the burial depth of the bedrock surface, the geothermal wells had an average drilling depth of 500 m from the bedrock surface. The drilling results show that there are dual-structure thermal reservoirs in the target area, including thermal reservoirs of pore water in the Neogene clastics and those of the bedrock fissure water. Among the eight geothermal wells, seven wells have a water yield of more than 100 m?/h, which mainly originates from the bedrock fissure water, and only one well has a relatively low water yield, which is mainly sourced from the pore water in the Neogene clastics.

This study introduced the development process, research status, and application effects of the tectono-geochemistry survey theory, and proposed the tectono-geochemistry weak information extraction method by summarizing the latest research results and understandings based on the prospecting practice in bedrock areas. Based on the contrastive analysis, this study pointed out the limitations of the conventional geochemical survey methods and the advantages of the tectono-geochemistry weak information extraction method, which was developed from the conventional tectono-geochemistry survey method. Moreover, this study systematically summarized the theoretical basis, operating conditions, deployment method, sampling principle, sampling media, anomaly interpretation, mapping, and application of the tectono-geochemistry weak information extraction method, highlighting the rationality of the deployment method, the representativeness of sampling points, the diversity of sampling media, and the validity (“yes” and “no”) of element anomalies and samples. Based on these, this study established the index system of this method. Finally, by combining the prospecting prediction of the eastern section of the Huijiabao anticline in the distribution area of Carlin-type gold deposits in southwestern Guizhou, this study concluded that the tectono-geochemistry weak information extraction method can extract the deep metallogenic weak information more effectively than the conventional tectono-geochemistry survey. It also inferred that this method has a good application prospect in the prospecting of concealed hydrothermal deposits and can be applied to the prospecting prediction of concealed hydrothermal deposits in all bedrock areas.

The detection of landslide deposits is frequently required in the infrastructure construction of the Western China Development. However, it is difficult to distinguish the landslide deposits using conventional electromagnetic methods because of the small differences in the resistivity between the sliding surface of the sliding bed and the Quaternary overburden. Therefore, this study proposed a scheme that detected the landslide deposits using opposing-coils transient electromagnetics (OCTEM) and then traced the mountain dislocation surface reversely. Accordingly, this study established a geoelectric structure model of the landslide deposits, investigated the transient electromagnetic response patterns of landslide deposits through forward calculation, and theoretically analyzed the transient electromagnetic response patterns of landslide deposits with different thicknesses and those of landslide deposits under different thicknesses of the Quaternary overburden. As verified by the detection results of known landslides, the method proposed in this study is correct and that OCTEM is valid in detecting landslide deposits in mountainous areas.

In recent years,surface karst collapse has frequently occurred in Beihuan New Village,Guigang City,Guangxi,severely threatening the life and property safety of local residents.This study analyzed the distribution of karst in the study area using electrical resistivity tomography (ERT) and delineated zones with strong groundwater runoff,aiming to guide the prevention and control of karst collapse.First,this study conducted numerical simulations to guide the preparation of the field exploration scheme and provide a reference for the analysis of the results measured in the field.Then,it explored the zones with shallow groundwater runoff in Beihuan New Village,delineating 11 zones with potential karst collapse and inferring one major runoff zone and three minor runoff zones.Finally,this study compared the exploration profiles with borehole logs.The comparison and verification results show that ERT has high precision and reliability and can play a significant role in the exploration of urban surface karst collapse.

Magmatic rock areas suffer poor water yield property and lack groundwater overall, encounter great difficulties with water exploration, and generally face the problem that available water resources fail to meet the demand. Targeting different types of water exploration targets and combining the geological and physical property characteristics, hydrogeological conditions, and field survey of the exploration target areas, this study comprehensively analyzed the electric structure characteristics, well completion modes, and water yield mechanisms of the strata around Xiaoshuicha and Wawu villages in Laiyang City through interpretation and analysis using comprehensive geophysical exploration method consisting of apparent resistivity profiles and apparent resistivity-based vertical sounding. After determining water exploration targets, conducting interpretation and analysis of geophysical prospecting, and locating wells through comprehensive analysis, this study successfully drilled two wells in the two villages, obtaining maximum water yield of 247.56 m³/d and 620.64 m³/d each. Finally, this study analyzed the water yield mechanisms in detail based on the intrusion-contact zone types and water-storage structural models with dykes conducting water. This study not only solves the difficulty with water use of local people but also provides a certain reference for future water exploration and well locating in similar areas.

Vanadium (V) is an essential trace element required by organisms for maintaining their normal life activities. It is also a harmful element listed as a priority environmental pollutant by the United Nations Environment Programme (UNEP). The study of the migration and enrichment patterns of V in the soil and plant system is of great practical significance for further understanding the ecological geochemical behavior of V and ensuring the safety of agricultural products and human health. This study systematically sampled the soil and plants in some ordinary farmland in Linyi City, Shandong Province and analyzed and tested the contents of V and its associated elements in the soil and plant samples. Moreover, this study conducted the source analysis and pollution assessment of V and investigated the migration and transformation patterns of V in the soil-plant system using statistical methods such as descriptive statistics, correlation analysis, and cluster analysis, as well as the single factor pollution index method, the potential ecological risk index method, and the biological enrichment coefficient method. The results are as follows: V is relatively concentrated in the study area, and its content increases with an increase in the Fe and Ti contents and decreases with an increase in the SiO₂, Na₂O, Sr, and CaO contents; The V in the study area mainly originates from the weathering of parent rocks, and the parts with a high V content is related to magnetite; As shown by the results of the single factor index method and the potential ecological risk index method, V is relatively clean in the soils of the study area, but attention should be paid to the pollution of the associated Cd; V is enriched primarily in the roots of plants, and plants' absorption capacity of V is generally negatively correlated with the contents of Cu, Pb, Zn, Ni, Co, Cd, and especially Cr in soils and is positively correlated with the As content in soils. This study enriches the ecological geochemical theory of V and provides a scientific basis for regional agricultural production, environmental quality assessment, and ecological pollution control.

The Luoning area is located at the junction of the Xiaoshan Uplift and the Luoning Basin and falls into the Quaternary shallow overburden area. Large-scale silver-lead-zinc deposits such as Laoliwan and Zhonghe have been discovered in this area, and their formation is closely related to the acidic plutons controlled by fault structures. This study investigated the distribution of fault structures and acidic plutons based on the processing of 1:50000 gravity and magnetic data using the minimum curvature potential field separation technique, the normalized vertical derivative of the total horizontal derivative (NVDR-THDR) technique, the correlation analysis method, and the three-dimensional physical property inversion. The study results are as follows: (1) The Luoning area is affected by the NW-, NE-, and EW-trending structures; (2) Centering on the Laoliwan area, multiple sets of faults present a ring-shaped distribution with a radius of 6.5 km; (3) Multiple concealed plutons were discovered, and the boundaries of Laoliwan and Zhonghe plutons were re-determined; (4) The distribution of granites is controlled by ring-shaped structures and have a burial depth of about 3 km; (4) The ring-shaped structures are well correlated with magnetic anomaly gradient zones, where ores were found in many boreholes. Therefore, it is of great significance to carry out prospecting studies in these zones.

Deep metal deposits tend to be associated with heterogeneous geological bodies on different scales.Moreover,their orefields mostly lie in areas with complex geological structures,developed faults,and intense lithological changes and have complex surface conditions and structures.As a result,the seismic data of metal deposits frequently originate from complex and variable seismic wave fields suffering the mutual inference of multiple types of waves.Therefore,the seismic data have extremely low signal-to-noise ratios,which severely restricts the seismic interpretation of metal deposits and the prediction of concealed orebodies. With the 2D seismic data of the Chaganhua molybdenum orefield in Inner Mongolia as a case study,this study explored the key techniques for the seismic data processing of deep metal deposits.Specifically,this study analyzed the characteristic of seismic data of the Chaganhua molybdenum deposit and summarized the difficulties with seismic data processing of the metal deposit.Based on these,this study developed a set of processes for the data processing of the Chaganhua molybdenum orefield.The actual processing results agree well with the known orebody distribution in the geological borehole section.To be specific,zones with thick ore bodies generated strong reflected energy,while thinner ore bodies exhibited low-amplitude reflected waves.The results of this study can provide strong support for inferring geological structures and delineating concealed orebodies in the study area.

The area around Maduqiao Village, Langqiao Town, Jing County has great potential for the development of high-quality mineral water. However, due to the geological conditions and the inhomogeneity of water-bearing media, the investigation of the distribution range of the mineral water in the area and the quantitative evaluation of the water quantity and quality have always been challenges to the development and utilization of mineral water in the area. With the Langqiao area of Jing County as the target area, an application study on the comprehensive geophysical prospecting method that comprehensive ground geophysical prospecting with hydrogeological logs was conducted, achieving important progress. The major results are as follows: (1) The fault structures in granodiorites were precisely located through comprehensive ground geophysical prospecting, and the horizon of tectonic fissure water was precisely identified based on hydrogeological logs; (2) The metasilicate natural mineral water for drinking with a single well water yield of 50~80 m³/d was identified; (3) The water-rich fault structures in the study area have a medium to shallow burial depths of about 75~140 m and primarily have a NW strike. These results reveal the spatial distribution characteristics of the mineral water-bearing structures in the study area and are of great significance to the subsequent investigation of the mineral water range. Moreover, the systematic research philosophy and technical methods used for the Langqiao area of Jing County in this study can guide the mineral water exploration in similar areas.

As a karst reservoir with the highest altitude in Wenshan City,the Xiaohewei reservoir has been suffering from severe water seepage since its completion.Despite several seepage control treatments,the seepage of the reservoir is still not effectively controlled.To determine the locations of underground karst seepage pathways of the reservoir and guide the later seepage control project,this study detected the seepage pathways in the project area combining the high-density resistivity method and the audio magnetotelluric method.The 2D inversion trial calculation of geophysical testing data indicates the feasibility of combining the two methods.The methods show highly consistent geophysical anomaly positions and can accurately reflect the geological conditions at different burial depths.Thus,their detection results can be referenced for later design and construction.Based on the inversion of measured data,the surface geological data,and the drilling verification means,it is speculated that the reservoir mainly has two NNE-directed karst water-bearing seepage pathways with an elevation of more than 1 800 m.These two karst seepage pathways (No.1 and No.2) are located near the contact zone between limestones and siliceous rocks,and in the karst fissures inside limestones,respectively.Based on the geophysical exploration results,this study also puts forward some suggestions on the deployment of the curtain grouting project for later seepage control of the Xiaohewei reservoir.

Many karst fracture-vug reservoirs have been found in the Ordovician carbonate paleo-buried hills in the Lungu area,Tarim Basin.Hydrocarbons are mainly enriched in these fracture-vug reservoirs,which are mainly related to the paleo-underground river system in carbonate paleo-buried hills.The paleo-underground river system is well developed,especially in the western Lungu area.The fracture-vug reservoirs related to the paleo-underground river system have strong longitudinal and lateral heterogeneity,and ascertaining the seismic and geological characteristics of the paleo-underground river system in this area is the key to the efficient development of fracture-vug reservoirs in this area.Based on the characteristics of modern karst underground rivers and the log and drilling data of this area,this study established a geological model of underground rivers for forward modeling.The study results are as follows.The underground river system developing under the tight limestone setting showed continuously linear strong reflections on the seismic profile.The seismic amplitude decreased as the height and width of underground rivers decreased,and higher seismic amplitude corresponded to larger underground river caves and lower filling velocity.The amplitude can accurately characterize the horizontal range of the underground river on the seismic profile.Meanwhile,the frequency and phase can describe the outline of the underground river on the seismic profile,but the outline described was larger than that of the real underground river.The main channels of the underground river system were prone to be filled with mud.By contrast,the branch channels had a low filling probability and thus serve as the main areas for both the occurrence of underground river reservoirs and the hydrocarbon accumulation.

The copper mineralized bodies and orebodies of the Pulang copper deposit in Yunnan Province are mainly distributed in the Pulang complex porphyry body and were formed through complex multi-stage development. This study aims to detail the geophysical response and fractures of copper reservoirs and provide detailed orebody characteristics, fractures, and horizon burial depth to be referenced in the exploration and exploitation of the Pulang copper deposit. First, the borehole-log data in the Pulang copper deposit were sampled for comprehensive evaluation. Then, in combination with the drilling reports and data on partial core samples, this study analyzed the log response characteristics and fractures and identified the lithology of the Pulang copper deposit using mathematical statistics, three-dimensional cross plots, convolutional neural networks (CNNs), and fracture parameter calculation. The log response characteristics of the three major strata of quartz monzonite porphyries, quartz diorite porphyrites, and hornstones in the study area are as follows. The hornstone strata have relatively high resistivity, followed by the quartz diorite porphyrite strata and the quartz monzonite porphyry strata in sequence. The resistivity decreases significantly at the intervals with fractures occurring or at the relatively fractured intervals. The quartz monzonite porphyry strata have a relatively high charge rate (polarization rate) of up to about 10%. The hornstone strata have relatively high radioactive intensity than the quartz diorite porphyrite strata and the quartz monzonite porphyry strata. CNNs were used to identify and analyze the lithology of the three major types of strata based on log data, with an accuracy rate of 97.94%. Finally, this study identified fractures in these strata using dual laterolog data. The resistivity significantly decreases at intervals with fractures occurring and differs greatly between deep and shallow lateral resistivity. The quartz monzonite porphyry strata with a high copper grade have relatively low resistivity and relatively well-developed high-angle fractures. The results of this study are of significance for the identification of ore body characteristics and the exploitation of ore bodies in the Pulang copper deposit.

The heavy metal element contents in soil affect the quality of soil environment. Their prediction using different models based on survey data is an important means to study the changing trends of soil element contents and soil environmental quality. Based on the data from 1∶250 000 multi-purpose regional geochemical surveys and 1∶50 000 land quality geochemical assessments, this study predicted the contents of five heavy metal elements in the soil of the study area in 2027 using the single-period incremental model and the input-output flux model individually. The results are as follows. The two models yielded different prediction results but consistent trends that the contents of five heavy metal elements increased to different degrees. Moreover, the single-period incremental model yielded larger increments than the input-output flux model. Among the various input channels of the flux model, Cd and Pb entered the soil mainly through dry and wet atmospheric subsidence, As and Cr entered the soil mainly through fertilization, and Hg entered the soil mainly through irrigation water. Based on the survey and prediction data of soil monitoring sites, the soil environmental quality grade was classified for these sites. The proportion of the sites for priority protection showed a downward trend, indicating that the soil environmental quality decreased year by year.

To investigate and assess the characteristics of cadmium, lead, and zinc in the soil and crops in the farmland around the old industrial area in the south of Baotou City, this study analyzed and tested the heavy metal content in soil, crop root soil, and seeds, assess the pollution according to relevant standards, and conducted the risk assessment and source analysis of heavy metals using the pollution index, the bioconcentration factor, and human health risk index. The results are as follows:Regarding the soil environmental quality, the soils in the study area are dominated by clean soils, with the polluted soils distributed primarily on both sides of the old sewage canals.The sites of over-limit root soils are also primarily distributed around the old sewage canals.Among the heavy metal morphologies, carbonate-bound, Fe-Mn-bound, and residue heavy metals account for relatively high proportions, while exchangeable heavy metals (water-soluble and ion-exchange) account for relatively low proportions. Most of the seed samples exhibited normal and low enrichment of heavy metals. Compared with other crops, sunflower seeds showed super adsorptivity of cadmium, lead, and zinc, posing significant non-carcinogenic and carcinogenic health risks to children and adults.

Ji'nan possesses highly abundant geothermal resources, which are hosted by Ordovician-Cambrian karst-fissured geothermal reservoirs and Neogene-Paleogene clastic pore-fissure geothermal reservoirs. The geothermal exploration in this study focuses on the Ordovician-Cambrian karst fissured geothermal reservoirs in Daqiao Town in northern Ji'nan. Through geophysical profile measurements, this study aims to identify the distributions of strata and fault structures and the burial depths of geothermal reservoirs, infer the attitudes and spatial morphologies of fault structures associated with heat control and conduction, delineate the target area for geothermal well construction, and conduct drilling verification in the favorable underground water-rich position. Building on the collected data, this study interpreted and inferred the fault structures in the study area and comparatively analyzed the water-bearing properties by employing direct-current sounding, controlled source audio magnetotellurics, and magnetotelluric survey. A geothermal exploration and production combined well was constructed in a favorable position of the geothermal target area, manifesting a completion depth of 1 532.06 m, a static-water burial depth of 13.03 m, a wellhead water temperature of 50.1 ℃, a water yield of 132.998 m³/h, and a dropdown depth of 18.27 m.

Based on the characteristics of the physical geography,topography,and hydroclimatology of Morocco and years of experience in the geochemical survey in Morocco, this study divided the geochemical landscapes in Morocco and plotted the geochemical landscape zoning map of Morocco. As a result, Morocco was divided into six first-order geochemical landscape areas, namely a forest coverage area, a semi-arid high mountain area, a humid-semi-humid middle-low mountain and hill area, an arid-semi-arid middle-low mountain and hill area, an arid desert and gobi area, and a desert coverage area. According to the elevation and surface cutting intensity, the humid-semi-humid and arid-semi-arid middle-low mountain and hill areas were subdivided into four second-level landscape areas each, namely a hill area, a low mountain area,a shallow-cutting middle mountain area,and a medium-deep-cutting middle-mountain area. Based on this division scheme, this study proposed several suggestions for geochemical surveys in Morocco.

The Matou gold deposit is located in the Mianning-Yanyuan strike-slip orogenic belt and is part of the deeply cut Quaternary coverage area and, thus, has limited surface prospecting clues. In this prospecting stage, a comprehensive anomaly area was delineated through the 1:10 000 soil geochemical survey. Then, gold ore bodies were discovered through trenching engineering, indicating excellent prospecting performance. Moreover, this study established a geological-geochemical prospecting model dominated by the HT³ anomaly area by combining the geological and geochemical anomalies in the work area. Finally, the next prospecting direction was proposed.

To remove the effect of terrain mass on observed gravity values, it is necessary to conduct terrain correction in gravity exploration. Terrains have the greatest impact on gravity values because they are the closest to observation points. However, the complex topographic relief makes it difficult to precisely determine the variation of topographic relief. Therefore, terrain correction is the most critical factor in the improvement of the precision of gravity exploration. The grid size of terrain data and the terrain correction radius are the key factors affecting the calculation precision of terrain correction. This study collected the DEM data with resolutions of 5 m, 10 m, 25 m, 50 m, and 100 m for plains, hills, and mountains. Based on these data, this study calculated conventional and generalized terrain correction values under different grid spacings and correction ranges and analyzed the influence of different grid spacings and correction radii on terrain correction in gravity exploration. The results are as follows: the gravity effect of the terrain mass above the geoid on the observation points was mainly concentrated in the range of 0~5 000 m and accounted for about 90% of the influence value of the total terrain mass. Attention should be paid to the correction of the middle and far areas during the terrain correction of hills and mountains, and it is necessary to appropriately increase the correction range of the middle areas; Different types of terrains had different requirements for grid spacings, and greater variations in topographic relief imposed higher requirements for the resolution DEM data. Based on the results of the comparative analysis, this study proposed some suggestions on the selection of DEM grid spacings and correction radii for different types of terrains. This study provides an important reference for the theoretical study and specification refinement of gravity terrain correction and has a great prospect for applications.

This study designed a group of 2D peak-valley comprehensive terrain models with different widths and slopes and investigated the influence of differently undulating terrains in mountainous areas on the audiomagnetotelluric (AMT) data and corresponding distortion characteristics from seven aspects, namely polarization modes, frequency, positions of measurement points, the width of a mountain top, the elevation difference and slope of terrain, and phase curves. The results are as follows. The transverse magnetic mode (TM mode) is more susceptible to terrain than the transverse electric mode (TE mode). The undulating terrain has little influence on the high-frequency parts of AMT data but has a great influence on their low-frequency parts. The apparent resistivity and phase of different frequency points at a measurement point reflect the comprehensive influence of all terrains within the skin depth level rather than just the influence of a single mountain peak or valley near the measurement point. Measurement points located at the mountain peaks are more easily affected by terrains than those in the valleys. Moreover, narrower mountain tops correspond to greater elevation differences of terrain, and steeper terrain exerts greater influence. In addition, the comparison of the 2D_TE results of the inversion considering and not considering terrains show that the 2D inversion considering terrains can effectively eliminate the influence of terrain. The 2D inversion considering terrains was carried out for measured AMT data. As indicated by the inversion results, the 2D inversion considering terrains can effectively eliminate the false high and low resistance anomalies and relieve the "hanging surface" phenomenon of signals, and the results corresponded well with the horizons with encountered manganese of three boreholes.

Following China's planning for ore prospecting in overburden areas, China's geochemical exploration researchers have conducted extensive research on the fundamental theories, methods, and technologies of geochemical exploration for overburden areas in the past decade. They achieved significant advances mainly in two aspects: (1) the research on the migration mechanism, occurrence state, and anomaly formation mechanism of elements in overburden areas; (2) advances in methods and technologies, including geoelectrochemistry, active state of elements, geogas, separation of micro-fine-sized soil particles, soil thermomagnetic composition, and integrated gas survey, as well as numerous experimental demonstrations. These advances represent continuous progress in the research on the fundamental theories, methods, and technologies of geochemical exploration for overburden areas, providing new geochemical methods and technologies for ore prospecting breakthroughs in overburden areas.

The high-precision magnetic field measurement module is mainly used in the scientific fields such as geology, geophysics, and national defense. However, the existing three-component magnetic field measurement module suffers poor portability (requiring a PC for data acquisition), large background noise, and short operating time. Therefore, this study developed a portable three-component magnetic field measurement module:a high-precision data measurement module and an Android control program. The test results show that the measurement module supports the interactive control using Android mobile phones and enjoys the advantages of low background noise (dynamic range>121dB@fs=1,000Hz), high clock synchronization precision (time drift±0.87 ms/day), long operating time (for one-week continuous work), and high scalability (supporting multiple fluxgate sensors).Portable three-component magnetic field mesurement module is portable,simpk and easy to use,suitable for field testing.

The western Zhen'an area enjoys superior ore-forming conditions of tungsten-molybdenum polymetallic deposits. A batch of large and medium-scale tungsten-molybdenum deposits such as Dongyang, Qipangou, Guilingou, Yueheping, and Hetaoping, have been discovered in this area, and they are related to intrusions. To explore tungsten-molybdenum ore bodies, it is necessary to carry out studies on intrusions related to mineralization, especially concealed intrusions. Based on high-precision gravity anomalies, this study extracted the gravity anomaly data of concealed plutons using the minimum curvature potential field separation method. Moreover, it investigated the plane positions of the concealed plutons in the western Zhen'an area by combining the geophysical characteristics of the exposed plutons, identifying five concealed plutons, namely Lanbandeng, Shapingcun, Yuehetai, Dongchuanjie, and Huangjinmei, through investigation. Moreover, this study conducted the 3D gravity anomaly inversion for typical concealed plutons, determining the spatial distribution characteristics of the concealed plutons. The Yuehetai and eastern Lanbandeng concealed plutons have been verified through boreholes, with high-grade wolframite being discovered. The method proposed in this study can provide technical support for the study of concealed plutons in the Zhen'an area and other areas, as well as important data for the study of the tectonic-magmatic-metallogenic evolution of the southern Qinling metallogenic belt.

The phase-shift method is commonly used to extract the Rayleigh wave dispersion curves.However,in the case of a complex wave field,the dispersion spectra calculated using the phase-shift method have a low resolution of Rayleigh wave dispersion energy,reducing the accuracy of the dispersion curves.This study improved the phase-shift method by obtaining the power exponent of the amplitude of each point on the dispersion spectra to improve the convergence and focusing properties of the dispersion energy.The improved phase-shift method was used to process the simulated data of the theoretical stratigraphic model and the actual seismic data of a coalfield in a certain study area.The processing results were compared with the dispersion spectra generated using the conventional phase-shift method.Moreover,the inversion based on dispersion curves of the actual data was conducted to generate a two-dimensional (2D) S-wave velocity section of the study area.As revealed by the study results,the improved phase-shift method can enhance the signal-to-noise ratio of the Rayleigh wave signals in the frequency-velocity domain and improve the resolution of the dispersion energy spectra and the accuracy of the dispersion curves.

Geothermal resources are significant clean energy and tourism mineral resources. The Rucheng Basin, a carbonate basin in the southeastern mountainous area of Hunan Province, possesses favorable conditions for the formation of convective geothermal energy. However, the basin is enclosed on three sides by the giant Zhuguangshan rock mass, and its basement is subjected to the intrusion and destruction by the rock mass, resulting in severely deformed formations, crisscrossing faults, and significantly different eastern and western structures. The understanding of the basin's water- and heat-conducting pathways and deep reservoir structures remains elusive, thus restricting the investigation of the basin's geothermal potential. Hence, this study probed the basin's deep structures through gravity survey and audio magnetotellurics (AMT), obtaining the following insights: (1) The Rucheng Basin has developed into a bidirectional ramp structure due to east-west differentiation. The synclinorium in the east experienced compression and clockwise rotation due to the emplacement of the Yanshanian rock mass, rocks were fragmented in the core zone, and strike-slip fracture zones were found at the boundary. The faults have vertical cutting depths exceeding 4 km, widths ranging from 300~600 m, and dip angles between 80°~90°. (2) The basin's basement anticlinal axis hosts several NWW-directed concealed rock masses, with diameters from 3~4 km and buried depths from 0.5~1.5 km. Hot springs reside in the fracture zones crossing the boundaries of the concealed rock masses. (3) The basin boasts favorable conditions for the formation of convective geothermal energy. Folds, fault zones, and concealed rock masses match each other to form a unified spatial combination of heat-controlling elements, manifesting heat accumulation characterized by east-west recharge and intermediate discharge. With more thriving deep geothermal reservoirs in the east, the basin has high potential for geothermal resources.

The Daguanchang uranium deposit, a typical concealed volcanic hydrothermal uranium deposit, was selected to investigate the relationship between surface geochemical characteristics and deep uranium ore bodies of volcanic hydrothermal uranium deposits in North China. The samples for soil survey were collected in the Daguanchang mining area. They were taken from the soil in the upper part of boreholes revealing deposits and mineralization for the analyses of the instantaneous radon (Rn) concentration, mobile-state uranium, and ²¹⁰Po of soil. Then, this study explored the relationships between these geochemical characteristics and deep uranium ore bodies. The results are as follows. The soil in the upper part of boreholes revealing high-grade deposits (also referred to as high-grade boreholes) had significantly higher instantaneous Rn concentration than that in the upper part of boreholes revealing mineralization (also referred to as mineralization boreholes). The high instantaneous Rn concentration in the soil samples collected from a large area corresponded well to the deep uranium ore bodies. The high-grade boreholes had slightly high ²¹⁰Po. However, the ²¹⁰Po in the surface soil samples showed small dispersion and relatively uniform distribution and did not exhibit differences between the barren and mining areas. Mobile-state uranium in high-grade boreholes did not exhibit significant anomalies. The maximum anomaly value of mobile-state uranium in soil samples collected from a large area occurred in the known barren areas. Therefore, it can be preliminarily concluded that, for the exploration of deeply buried uranium ore bodies on a large scale, the anomalies of instantaneous Rn concentration in the soil can indicate the anomalies of deeply buried uranium ore bodies, while the mobile-state uranium and ²¹⁰Po in soil are less sensitive than instantaneous Rn.

Regularized joint inversion based on Gramian constraints is a hot research topic in the field of geophysical joint inversion. Given the difficulty in selecting weighted factors of the regularization and constraint items, it is necessary to introduce inequality constraints into the regularized joint inversion. To investigate the regularized joint inversion of magnetotelluric (MT) and gravity data based on Gramian constraints, this study compared the application effects of the penalty function method and the transform function method in the joint inversion and processed the measured data of a survey line in Xiangshan, Jiangxi Province. According to the results from model experiments, both methods can effectively constrain petrophysical parameters, and the penalty function method has higher flexibility but requires the artificial setting of the weighted factors. Moreover, the processing of the measured data shows that the joint inversion based on inequality and Gramian constraints is highly practical and can improve the precision of geophysical interpretation.

Spectral induced polarization (SIP) response testers for rock and ore specimens determine the SIP response differences between ore bodies and host rocks by measuring the SIP characteristics of rock and ore specimens, thus providing a basis for ore prospecting. They are widely used in geophysical exploration. However, the existing SIP response testers have shortcomings in terms of bandwidth, intelligence, portability, and power consumption. Given this, this study developed a piece of measurement and control software for SIP response testers based on the Internet of Things (IoT) techniques including NB-IoT, Bluetooth, and Wifi, realizing the functions such as near-field communication, cloud communication, data visualization, and data processing. The test results verify that the software can achieve the desired effect owing to its easy operation, stable running, and friendly man-machine interaction.