According to aeromagnetic and gravitational data, the boundary and range of Ordos basin were determined based on an analysis of the characteristics of gravity and magnetic fields. And on the basis of compiling depth map of the metamorphic basement and structuring zoning map, research was conducted on the basin’s basement structure, characteristics and features of depth change, structure framework, and caprock thickness. The research indicates that the metamorphic basement is composed of Proterozoic metamorphic series, and the buried depth of crystalline basement can reach 5 000 to 20 000 meters. The caprock is the layers of Ediacaran, Paleozoic, and Mesozoic. The occurrence and development of the basin are restricted by nearly NE-and NWW-trending structures, forming a pattern of four depressions and three uplifts. All the new understanding and conclusions provide a reference for further oil and gas exploration in the basin.

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 airborne geophysical exploration flying vessel which performs operation in middle and high mountain areas needs plateau adaptability.Through a comparative study of the characteristics of AS350B3 helicopter in such aspects as its taking off condition,maximum flying altitude,maximum endurance and plateau flexibility,the authors put forward the type-choosing principle and flying method of the airborne geophysical exploration flying vessel for low altitude and large scale survey.The practical surveying flying in a certain surveying area of Gansu Province has proved the feasibility of the principle and method put forward by the authors.Analysis shows that AS350B3 helicopter can meet the requirement of airborne geophysical exploration in such areas.

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.

The shear wave velocity of subsurface can be estimated by analyzing the passive surface waves typically generated by cultural and natural sources. This article first introduces the passive surface waves and the processing procedure, and then utilizes the simulated passive waves to compare the FK and SPAC methods in deriving dispersion curves. It also discusses the general requirements of data acquisition and demonstrates some field examples.

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.

A soil gas radon survey was performed on a large scale to determine the distribution of radon in soil of Zhuhai City in Guangdong Province by means of a portable radon monitor of a semiconductor alpha spectroscopy. The survey sampled 469 sites covering an area of more than 100 km². The average of soil radon concentration in the soil depth of 0.6 m is 55.94 ± 58.54 kBq/m³ in Zhuhai urban area, whereas the concentration is 7.14±8.75, 37.64±25.92, and 151.25±196.23 kBq/m³ in the Quaternary sediments, the mixtures of sediments and weathered grain of granite, and the weathered granite in Doumen District, respectively. The high radon potential areas are located within biotitic granites and new industrial districts, as indicated by the strong correlation between the radioactivity level and geological lithology. The mean value of soil gas radon concentration in Zhuhai urban area (ZUA) is about ten times as high as that in Guangzhou, Quanzhou and Jinjing City. The results show that Zhuhai area has higher radon potential, and hence protective measures against radon should be taken into account.

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.

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 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.

With the rapid development of urban infrastructure,the demand for urban geological work is increasing,and urban geological surveys become particularly important.Urban geophysical exploration has different exploration purposes and working environments from conventional geophysical exploration.Accordingly,compared with conventional geophysical exploration methods,the geophysical exploration methods for urban geological surveys face the challenges of many interference factors,limited construction sites and time,and high requirements for exploration accuracy.The opposing-coils transient electromagnetic(OCTEM) method enjoys a strong anti-interference ability,convenient and efficient construction,and high resolution.Therefore,this study employed the OCTEM method to investigate the test profile in the urban geological survey and evaluation of Haidong City.This test profile was subjected to numerous interference sources since it crossed 11 highways and railways and passed through factories,schools,logistics parks,villages,living quarters,and rivers.Consequently,the OCTEM results agree well with the results of single-point resistivity sounding and drilling results.Therefore,the OCTEM method proposed in this study is effective for urban geological surveys.

In recent years,offshore OBC and OBN technology has achieved rapid development.Whether it is OBC acquisition or OBN acquisition,many new equipment and methods were developed.Based on the latest research results and published papers,this paper summarizes the development history and research status of offshore OBC and OBN technology,and summarizes the technology and equipment for offshore four-component seismic exploration and acquisition,as well as processing and interpretation techniques.It is considered that the seabed multi-component seismic is the development trend of marine seismic,because it has the advantages of multi-component data, wide azimuth and wide frequency compared with the marine tow streamer.But the processing of data and conversion wave need to be researched.Now offshore oil and gas exploration is in the stage of complex structures and lithologic reservoirs,as the cost of submarine seismic decreases and the processing technology advances, it will be get more applications.

Despite abundant geothermal reserves of the Tangyu geothermal field in Meixian County, Shaanxi Province, long-term exploitation has decreased the water temperatures and yields of its existing geothermal wells year by year. Hence, there is an urgent need to explore new potential geothermal resources in the geothermal field. Since the known geothermal wells in the geothermal field are significantly controlled by faults, investigating the deep fault propagation holds critical significance for exploring the geothermal field’s potential geothermal resources. Due to the method limitations and the topographic influence, identifying thermal control faults through conventional geological route investigation or large-scale engineering is not applicable to the geothermal field. Therefore, a new technical method combining the penetrating soil radon measurement and the controlled source audio magnetotelluric (CSAMT) method was employed in this study to find concealed faults and delineate potential geothermal areas. Based on the measured surface soil radon concentration anomaly data and the subsurface electrical structure model derived from the CSAMT data inversion, this study inferred six new concealed faults on the basis of corroborating the known faults, predicted two potential geothermal areas, and built a conceptual model for the Tangyu geothermal field. As revealed by the results, the soil radon concentrations at concealed faults are much higher than the regional background value, and the concealed faults are located in the low-resistivity fracture zones as indicated by the apparent resistivity results based on CSAMT data inversion. Besides, the two potential geothermal areas spread from 450~750 m and 850~1 150 m on the profile, respectively, at depths of approximately 250~300 m. This study concludes that the geothermal field resides in a low-resistivity region with soil radon anomalies three times the regional background value. The results of this study provide a reference for the subsequent sustainable production and utilization of potential geothermal resources in the region.

Geological and underground pipeline detection was carried out in several urban metro exit areas in the loess area by using ground penetrating radar (GPR). The distribution of soil layer in the loess area was emphatically studied. The GPR images of PVC pipelines and metal pipelines in the loess area under the conditions of holes, seepage and soil collapse were analyzed, and the respective GPR scans of underground pipelines in the loess area were summarized. By describing the characteristics of the images, the authors summarized the general analysis methods and rules of applying GPR to detecting urban geological stratification and pipeline radar images in the loess area, and used the image laws of "black-white-black" and "white-black-white" to analyze the GPR images, which provides a good guidance for subsequent engineering construction.

In this paper,a historical review of the gravity gradiometry is given, the application of this technique to oil exploration and some other fields is described,and its development in future is predicted.

The Fengtai ore concentration area is an important producing area of plumbum-zinc and gold ores in the middle of the Qinling orogenic belt. It hosts many large to super-large deposits, such as Qiandongshan-Dongtangzi, Bafangshan-Erlihe, Baguamiao, and Shuangwang deposits. With the exploitation proceeding, the reserves of these deposits have decreased significantly, and the ore prospecting in these deposits has shifted from the surface to the deep part. However, the geophysical fields in the deposits are yet to be ascertained, severely restricting research on the metallogenic regularity of the deposits and the ore prospecting and exploration in the peripheral zones. Based on the latest 1∶50,000 aeromagnetic and airborne radioactivity survey data, as well as gravity data, this study investigated the multi-source geophysical fields on the scales of the region, the ore concentration area, and deposits, aiming to summarize the distribution patterns of geophysical anomalies of different scales and provide evidence for research on metallogenic regularity and prospecting prediction. The results show that the Fengtai and the Xicheng ore concentration areas, with similar magnetic structures, are separated by the zone with strong magnetic anomalies caused by the crystalline basement of the Huicheng Basin. The first vertical derivative of gravity reveals that the Fengtai and Xicheng ore concentration areas have density structures similar to the Huicheng Basin. It can be inferred that the shallow part is a unified basin and that a large prospecting space exists between the two ore concentration areas. Many NW-trending linear magnetic anomaly zones occur in the Fengtai ore concentration area. Their locations are highly consistent with those of fault structures, and they were offset by NE-trending structures due to late transformation. The second vertical derivative of gravity reveals that many intermediate-acid intrusive stocks or veins have developed in the deep part of the Fengtai ore concentration area. Structural boundaries can be effectively identified based on the first vertical derivative, X-directional derivative, and wavelet transform of aeromagnetic data. Furthermore, ore bodies are mostly distributed in the NW direction along the tectonic belt. All these will play an important role in guiding ore prospecting and exploration in the Fengtai ore concentration area.

The Laiwu area in central Shandong Province, situated in the eastern North China Craton, is a significant production area of skarn iron-rich ores. Its ore deposits occur primarily in the contact zone between the mining rock mass and the Middle Ordovician carbonate formation. Based on the latest areal gravity and magnetic survey results, this study thoroughly investigated the characteristics of gravity and magnetic anomalies along the Shijiaquan-Liujiamiao area in the western periphery of the mine rock mass. Then, this study delineated the deep prospecting target combining the characteristics of gravity and magnetic fields of the known iron deposits in the Laiwu area. Large-scale gravity and magnetic profiles were arranged in the favorable mineralization area. With the known boreholes as constraints, the gravity and magnetic anomalies were qualitatively and quantitatively interpreted using the 2.5D gravity-magnetic joint inversion technique. The interpretation results provide a basis for the location and depth of the borehole to be placed, which revealed a 15.8 m-thick iron-rich ore deposit, suggesting remarkable prospecting effects. This study holds critical indicative significance for further exploration of skarn iron ore deposits in this area.

This paper describes in brief some interference factors in the application of geological radar to engineering exploration, makes an analysis of image characteristics of interference factors and causes for their formation,suggests some measures for suppressing these interference factors, and provides some basic data for the interpretation of geological radar data in engineering exploration.

This article presents the plotting process of plane isoline map with hypsography, introduces the improtant effect of differential operator in geophysical exploration, at the same time , gives the real cases.

With the change of season, the physical parameters in the process of freezing and thawing in active layer of seasonal frozen soil region change significantly. Taking the seasonal frozen soil in Northeast China as an example, the authors used the Gaussian distribution rough surfaces to simulate the rough freezing and melting layers, established the random media model which can accurately described heterogeneity of the active layers, and carried out forward modeling. The results show that the depth of freezing and melting layers changes with the seasons, together with the change of permittivity and conductivity. The scattered waves in radar profile are very developed because of the heterogeneous active layer and the undulating freezing and melting layers. With the change of time, the greater the fluctuation of the melting layer, the stronger the scattered wave energy in the radar profile, the harder the reflection of the melting and the freezing layers. At the same time, it is proved that the application of GPR to monitor the seasonal variation, frozen depth and melting depth of seasonal frozen soil is a practical method.

The content of tin in geochemical water samples is generally low, and there is no standard method which can be used currently. In this investigation, the trace tin in water samples was detected by inductively coupled plasma mass spectrometry (ICP-MS) after separation and enrichment using mercapto containing dextran gel (SDG). The separation conditions of the SDG column were optimized. The separating effect of tin was the best when the acidity of the solution before filtering by the column was 1% (v/v) hydrochloric acid, the ion strength was 0.1mol/L counted by NaAc, the acidity of eluent was 6N hydrochloric acid and the volume of the eluent was 30 mL. When the proposed method was applied to analyzing actual water samples, the detection limit of tin was 0.37μg/L, the precision (RSD%) was less than 10%, and the recovery rate was in the range of 90%~110%, which could satisfy the determination requirement of trace tin in geochemical water samples.

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.

As a kind of clean energy, geothermal energy has attracted the attention of scholars all over the world in recent years. Previous geochemical exploration methods for geothermal resources are limited to the analysis of individual geochemical indices. Moreover, previous studies of microorganisms in geothermal fields mostly focus on hot spring outcrops, lacking ecological studies of geothermal resources in complex terrains. This study investigated the soil geochemistry and microbial diversity of the Bantang Hot Spring geothermal field in Chaohu, Anhui Province. Geochemical indices such as head-space gas, soil gas, acid-hydrolyzed hydrocarbons, and altered carbonate were detected in this study. Combined with the microbial high-throughput sequencing technology, this study analyzed the composition and spatial-temporal distribution of the microbial population above the geothermal fields in uplifted mountains and the relationship between these bioinformatics characteristics and the geochemical indices. The results indicate that the acid-hydrolyzed hydrocarbons on the surface of the geothermal field showed a maximum methane concentration of 43.7 μL/kg in the area between faults F2 and F3, adequately reflecting the fault location of the geothermal field.Bacillaceae, Hydrogenophilaceae, and Thermodesulfovibrionaceae in the geothermal field and the background area showed large relative abundance differences, which were 0.178%, 0.108%, and 0.060%, respectively. This result indicates that they are sensitive to geothermal resources and correspond well to geochemical indices above the known geothermal field. This study preliminarily investigated the diversity of geothermal microorganisms in the geothermal field and analyzed the corresponding relationships between microbial distribution characteristics and geochemical indexes, providing technical support for the microbiological exploration of geothermal resources.

Previous studies have shown that CNN-GRU hybrid deep learning inversion EI has the advantages of strong applicability and strong generalization capability.However,there are many pre-stack inversion parameters based on deep learning,such as internal deep learning network learnable parameters and external hyperparameters.At present,there is still no systematic research on the impact of hyperparameter selection on network performance and computing speed,which will directly affect the further promotion and application of the method.Therefore,based on the hybrid deep learning inversion elastic impedance,this paper discusses the impact of five hyperparameters,i.e.,learning rate,Epoch,batch_size,regularization parameter,and the number of wells participating in network training on network performance and calculation speed,thus providing a basis for studying the selection of seismic inversion hyperparameters.The research results can provide a feasible quality control method for three-dimensional large-area deep learning inversion,which is of certain significance for promoting the wide application of deep learning methods in petroleum geophysical prospecting.

In this study, the authors built five kinds of pollution models and carried out numerical simulation with the finite-difference method to tackle different ways and different media of groundwater pollution, based on GPR forward modeling software (GPRMax). The simulation results show that GPR exhibits fairly good application effects in detecting groundwater pollution.

It is difficult to explore the overlapping double-layer waterlogged goafs using the transient electromagnetic method. The reason is that upper waterlogged goafs will hinder the propagation of the electromagnetic field, thus prolonging the observation of the lower waterlogged goafs and reducing the signal-to-noise ratio. Besides, the burial depths and layer spacings of double-layer waterlogged goafs affect the signal-to-noise ratio and the observation time of transient electromagnetic signals. By building a double-layer waterlogged goaf model based on the Majiayan coal mine in Shanxi, this study analyzed the electromagnetic field propagation under layer spacings of 25 m, 50 m, 75 m, and 100 m,and calculated the observation time of waterlogged goafs with different layer spacings. Furthermore, it quantitatively characterized the differences between induced voltages in the double-layer waterlogged goafs with different layer spacings using root mean square errors. Additionally, this study proposed the identification criteria for explorable lower waterlogged goafs based on the record errors and noise levels during the observation. The results of physical simulation experiments are as follows: The differences between the induced voltages of double-layered waterlogged goafs with different layer spacings occur mainly in the late stage; the differences between induced voltages gradually decrease as the layer spacing and the burial depth of upper waterlogged goafs increases; the difference between induced voltages is close to the noise level when the layer spacing is greater than 75 m. The actual detection of the double layer waterlogged goaf with a spacing of 75 meters was conducted in Majiayan Coal Mine, and the results showed that the lower waterlogged goaf was not effectively identified.Therefore, It is difficult to effectively explore the lower waterlogged goafs when the layer spacing is greater than 75 m.

The dam failure and leakage risk of tailings dam are directly related to the safe operation of tailings pond, which is an important environmental safety problem. In this paper, the authors used the high density resistivity method to detect the two-dimensional fine section of tailings dam, and found four weak areas of tailings dam structure. Since the leakage is mainly caused by the movement of groundwater, monitoring studies were carried out for three times on the tailings dam before and after the rainy season and, as a result, the dynamic response of the electrical structure of the dam body was obtained, with a suspected dew point determined. The feasibility of application of high density resistivity method to the tailings dam monitoring was verified, and the result provides a new technical means for tailings dam stability study.

This paper has summed up the progress of the ERI method over the past decade of years as well as its future development trend in the following aspects: ① A comparison of the performances of the main ERI instruments used at present shows that the ERI instruments tend to develop in the multi-channel, multi-parameter, multi-functional, high-power direction; ② ERI measurement environment has changed from surface measurement to water surface, underwater and cross-hole measurements, with the last three kinds of measurements analyzed in this paper; ③ On the basis of analyzing ERI data processing method and inverse development status, this paper describes three-dimensional and four-dimensional inversion theory of ERI with practical examples; ④ ERT applications are summed up, and several new applications are introduced. It is concluded that, with the improvement of the probing depth and observation precision as well as the diversification of the observation models, the application field of ERI will become broader and broader, and this technique will surely have wide development prospect.

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.

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.

The existing geological data show that there are several buried faults in the main urban area of Chengdu. However, the specific location and distribution of these faults are still unclear, which poses great security risks to the comprehensive and scientific exploitation and utilization of underground space resources and the optimization of urban construction planning and layout in Chengdu. In view of such a situation, four geophysical methods, namely, micromotion survey, high-density electrical method, transient electromagnetic method and soil radon measurement, were used in this paper to comprehensively explore the buried Baojiangqiao fault in the work area. The integrated geophysical prospecting methods not only identified the stratigraphic structure along the survey line, but also obtained the location, property, attitude and scale of the buried Baojiangqiao fault. This work indicates that the integrated geophysical prospecting methods can achieve better results in the exploration of urban buried fault.

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.

The development of Se-rich land has been carried out in many regions of China, achieving remarkable results. However, no Se-rich land or crop has been reported in Tibet. This study analyzed the characteristics and influencing factors of the Se content in the soils and crops of the key arable land areas in Bailang County, Tibet, aiming to lend support to the development and utilization of Se-rich land in the Qinghai-Tibet Plateau. The results are as follows: The soils in the study area have a Se content of (0.05~0.76)×10^-6, which is higher than the background value of soils in Tibet (0.15 ×10^-6); 76.83% of the land in the study area has sufficient Se, and land in the study area with a Se content of greater than 0.3 ×10^-6 covers an area of 45.43 km², as determined according to the standard threshold of Se content in alkaline soils (w(Se)≥0.3 ×10^-6). Further investigation shows that highland barley seeds have a Se content of (0.017~0.17)×10^-6 (average: 0.063 ×10^-6) and rapeseeds have a Se content of (0.043~0.14)×10^-6 (average: 0.078 ×10^-6) in the distribution area of Se-rich soils. As indicated by the root soil results of the zones with Se-rich soils, the Nieru Group controls the source of Se in soils, and Se and effective Se content in the soils are significantly positively correlated with N, P, alkali-hydrolyzable nitrogen, and rapid available phosphorus but is significantly negatively correlated with pH. These results indicate that the behavior of Se is significantly affected by a large number of nutrient elements in the soils and pH. Overall, the distribution areas of Se-rich soils in Bailang County have high soil environmental quality, crops with a high Se content, and great potential for the development of Se-rich plateau characteristic agricultural products.

The eastern Kunlun metallogenic belt, as a significant metal metallogenic belt in China, hosts extensive orogenic gold deposits and large-scale Kunlunhe, Gouli, and Wulonggou gold concentration areas. The Dachaigou gold deposit is a large-scale gold deposit newly discovered in the Wulonggou gold field in recent years. Despite its high metallogenic potential, the western extension of its ore belt has not been defined. Hence, this study conducted induced polarization (IP) sounding and wide-field electromagnetic sounding in the deposit. The results show that the known ore belt is situated in the regional gravity anomaly gradient zone, the transition zone of positive and negative weak magnetic anomalies, the edge of IP anomalies, or the electrical gradient zone. The development zone of the regional tectonic belt resides in the large-scale IP anomaly section. The regional tectonic belt is characterized by a wide range of low-resistivity anomaly zones. The IV and III alteration zones of the known ore belt are located in the opening position of the low-resistivity anomaly zone and the shallow electrical anomaly gradient zone, respectively. Based on the above understanding and the electromagnetic anomaly change patterns of several parallel profiles in the western extension segment, it was inferred that the regional ore-controlling structure extends steadily in the W-NWW direction, forming a favorable prospecting space in the western extension segment of the deposit. The results of deep geophysical exploration in the Dachaigou deposit indicate that geophysical methods manifest significant advantages in deep geological prospecting research, providing successful experience for deep prospecting in the eastern Kunlun gold deposit area.

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.

An application test of the broadband magnetotelluric method (BMT) was carried out in the Mandulatu area based on the construction needs of a large-scale sandstone-type uranium deposit base in the Erlian Basin. The purpose is to study the detection ability and effect of this method at a depth of 2,000 m and above, provide effective technical support for the evaluation of uranium resources in the area, and improve the effects and benefits of uranium prospecting. In this study, the data acquisition time and the lowest frequency were tested by the test area method. Given the work efficiency and benefit, it is determined that the lowest detection frequency is 0.10 Hz and the observation time is 60 min so that the prospecting depth of Erlian Basin can reach the requirement of 1,500~2,000 m. The comparative analysis of the test results with borehole and shallow seismic data shows that BMT is feasible in solving geological problems such as caprock structure, basement structure, sand body development characteristics of the target layer, and fault structure in the basin.

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.

The gamma spectrometry logging is widely used in survey of radioactive, metallic and non-metallic deposits and stratigraphic correlation. In order to obtain a wider energy range of gamma spectra, the authors designed the wide-energy spectra logging system with the combination of LaBr₃ and BGO detectors. To determine the optimal selection principle of the wide-energy range gamma spectra logging system, the authors built a model of wide-energy spectra logging system on MCNP to simulate the measured gamma spectrum. The simulation shows that the best effect is achieved when the shield is made of tungsten-iron-nickel alloy. When the shield thickness reaches 14 cm, simulation shows better shielding effect for the distal detector. The effect for the proximal detector is close to the distal one when its relative position is 35 cm or more. The effect of changing the position of the neutron source on the thermal neutron shielding is limited. As a thermal neutron shield, boron could achieve obvious shielding effect with 0.2cm layer. The effect of fast neutron can be reduced by increasing shield thickness and the distance between the proximal detector and the shield.

The understanding of the Paleogene Dongying formation and the Jixianian Wumishan formation have been gradually deepened with the exploration and development of deep thermal reservoirs in the Binhai New Area.This paper analyzes the hydrochemical characteristics, reservoir temperature, and hydrogeochemical effects of the geothermal fluid of the Dongying and Wumishan formations, thus providing bases for the further development and utilization of deep geothermal resources. The Wumishan formation in the Ninghe salient is adequately recharged. In contrast,the Dongying formation occursin a relatively closed environment, and the geothermal fluid in it is at a state of chemical equilibrium. The average temperature of the geothermal reservoirs in the Wumishan and Dongying formation scalculated using geothermometers is about 126 ℃ and 100 ℃, respectively. The geothermal fluid in both formations originates from atmospheric precipitation. Compared to the Wumishan formation, the geothermal fluidin the Dongying formation exchanges heat with rocks for a longer time and has a weaker cycling capacity. The runoff direction of the geothermal fluid in the formations is from northeast to southwest, with leaching, cation exchange, precipitation,and mixing mainly occurring during the fluid runoff.

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.