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.

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

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

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

Conventional seismic facies analysis based on seismic sedimentology principle mainly uses seismic slicing technology to extract RMS amplitude attributes along the target layer.When the signal-to-noise ratio of seismic signals is low and the target layer is thin,the accuracy and reliability of seismic facies analysis will be easily affected.In this study,on the basis of the principle of seismic sedimentology,the feature vectors of seismic waveforms were extracted along stratigraphic slices,and then the Agglomerative Hierarchical Clustering (AHC) method was introduced to classify seismic facies.Waveform AHC is an unsupervised machine learning algorithm.Compared with the traditional method of seismic facies analysis for stratum slices,the method based on waveform clustering considers the amplitude, phase and frequency attributes of seismic signals synthetically through the change of waveform characteristics.It has better anti-noise capability and higher horizontal resolution.The stability and applicability of this method have been proved by physical model data testing and practical data application.It has been proved that this method has a good capability of distinguishing sedimentary facies characteristics,and hence it is a new kind of reservoir facies analysis tool and has a good application prospect.

This paper describes the automated Burris metal zero-length spring gravity meter produced by the Zero-Length Spring Corporation,USA,which is an upgrade of LaCoste & Romberg land meters. The new land gravity meter features the UltraGravTM control system, worldwide range with micro-Gal precision, and a fully integrated meter design. This paper also deals with the concept of the zero-length spring and the history of LaCoste & Romberg land meters.

Due to the specific surface conditions as well as the complex and varied surface structure of the beach and shallow sea area, the exploration work in such an area is different from both continental exploration and sea exploration. In the amphibian zone, in particular, there exist two working means (sea and continental means). Based on a systematic study of such field collection links in the field as the excitation seismic source, the detector and the observational system, the authors put forward the method for solving the difficult problem of collecting high-quality seismic data. On the basis of a thorough investigation into the interference wave suppression and the difference correction, a complete set of high-precision and practical special techniques for oil and gas exploration in the beach and shallow sea area was developed, and the results show that its geological effect is satisfactory.

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.

This paper deals with methods and properties of Tilt-Euler deconvolution by analyzing the theoretical model and the measured gravity data. The results show that the Tilt-Euler deconvolution method can rapidly provide automatic estimation of the source location and source type from gridded gravity or magnetic data on condition that no structural index is required, and can also automatically estimate the structural index. With simple calculation and high practical use, this method is of great significance in large-area aeromagnetic and airborne gravity data processing and interpretation.

borehole acoustic testing is an important in situ geotechnical engineering geophysical testing project. But during the test and test methods and equipment layout parameters selection, elastic wave identification, integrity coefficient calculation, and test results of engineering applications, such as wave column contains geological information and the application of the wave velocity and integrity of the relationship, testers not easy control and very questionable. Therefore, it is necessary, the above problems are discussed, with wants to improve investigation technology level.

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.

Usually, city road consists of the surface layer and the subbase layer, and each layer contains several layers of different media with different relative dielectric constants. So using one relative dielectric constant to analyze the GPR data of all depths in city road detection is not accurate. This paper deduced the calculation formula of the equivalent dielectric constant of multi-layer underground media. Then the authors took two-layer media model and three-layer media model as examples to calculate the equivalent dielectric constant and the relation between the depth and the travel time. At last, theoretical modeling data of two-layer media were used to check the formula, and the results prove that the calculation formula of equivalent dielectric constant of multi-layer underground media is much better for practical GPR data analysis when there are multi-layer underground media.

On the basis of the electric, radioactive and magnetic differences of soil, rock and water body and through investigating physical character variations of these three bodies, the authors conducted structural mapping and studied and evaluated water resource environment. It is concluded that three major factors have affected the water environment of coastal areas, i.e., the influence of marine transgression caused by geological movement, the surface subsidence resulting from the falling of the underground water level caused by human activities, and the water quality pollution and living environmental pollution from the natural and humancaused nuclear radiation.

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

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

Carbonate reservoirs have various pores and complex pore structures.However,the microstructure of rocks cannot be characterized using conventional saturation evaluation models,making it extremely difficult to perform the saturation evaluation of carbonate reservoirs.Given this,this study proposed a Thomeer saturation model combined with the nuclear magnetic resonance (NMR) logging based on the data of capillary pressure curves and NMR logging.Specifically,information about the structure of the pore system in the mercury injection data was analyzed,and then the capillary pressure curves of multiple pore types were obtained through fitting using the Thomeer function.Finally,the complex pore structure was characterized using multiple Thomeer curves.The NMR logging is the only logging method that can continuously and quantitatively characterize the pore structure of reservoirs.The Thomeer parameters B_v,P_d,and G and the modal element Porositon of the maximum pore throat diameter were calculated using the logarithmic mean of T2 transverse relaxation time for NMR (T2LM) and the NMR total porosity (MPHS),as well as the classification of pore throat R35.Accordingly,the saturation evaluation model for carbonates reservoirs with complex pore structures was constructed.This model allows for the continuous evaluation of formation pore structure that cannot be achieved using experimental methods.This model was applied to the saturation evaluation of the carbonate reservoirs with complex pore structures in oilfield X in the Middle East.By comparison with the J function model and Archie's formula,this model decreased the relative error from 0.496 and 0.442,respectively to 0.272,better characterized the variation trend,and achieved encouraging application effects regardless of the saturation of reservoirs.Therefore,this model can minimize the impacts of carbonate reservoirs with complex pore structures and improve the precision of the reservoir saturation evaluation.

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 Xihuang vanadium deposit is located in the black rock series of the lower Cambrian Shuigoukou Formation in southern Qinling Mountain. The orebody is large, and the ore-bearing horizon and grade are relatively stable. The ore types are mainly carbonaceous mudstone and siliceous mudstone. The analysis of petro-geochemical elements and REE indicates that the vanadium deposit was formed in the hypoxic reductive environment from the continental margin to the deep sea, and the rock material source came from sea water, hydrothermal jet and terrigenous debris, with the biological activity playing an important role in the aggregation and precipitation of the vanadium deposit. Based on the comprehensive geological and geochemical characteristics, it is concluded that the vanadium deposit belongs to the biogenesis of hot water deposition, and that the vanadium deposit should be of biological and hydrothermal sedimentary origin.

Full waveform inversion (FWI) is one of the most accurate velocity inversion tools.It can be used to obtain high-precision subsurface structures through iterative inversion and provide a more accurate velocity field for prestack imaging technology,thus satisfying the increasingly complex demand for petroleum exploration and development.However,FWI requires accurately estimated source wavelets,which are very difficult to extract from the seismic data collected in the field.Furthermore,in the inversion process,there is a strong nonlinear relationship between model parameters and observed data,which is liable to induce cycle skipping.To overcome the cycle skipping and the difficulty in extracting seismic wavelets in the inversion process of medium-low wavenumber,this paper developed a multi-scale waveform inversion method using combined source encoding.Specifically,the wavelets and seismic data were combined by applying time-shift stacking,and gradients can be determined through only one calculation of reverse time migration.According to the calculation results using a model,the FWI method using combined source encoding can be used to achieve multi-scale inversion and obtain more stable inversion results.Meanwhile,relatively accurate inversion results can be obtained by combining this method with a source-independent method.

After the major breakthrough in oil and gas was obtained from the Well Anye 1, the Ministry of Natural Resources increased the residual shale gas and oil and gas exploration and development of 7,800 square kilometers in the Wuling Mountain. The Wulong Mountain area has complex geological structures, undulating terrain and large areas of carbonate rock, which has led to great challenges to traditional oil and gas exploration methods based on seismic exploration. Wide field electromagnetic method has the characteristics of green, high efficiency and low cost, and hence has become one of the powerful methods for oil and gas exploration and is now being widely used in shale gas exploration in southern China. It is a favorable method for shale gas exploration in southern China. The strata in Tongzi Guizhou are relatively stable, and the organic carbon content in the upper Ordovician Wufeng-Lower Silurian Longmaxi Formation is high. Through surface sample collection and well logging data analysis, the organic shale in this formation shows obvious low resistivity characteristics, which has the physical conditions of electromagnetic exploration. The wide field electromagnetic method was used to carry out shale gas exploration in Tongzi area of northern Guizhou, which overcame the complex influence of topography, carbonate rocks and structure. It is found that the structure pattern of Tongzi area is characterized by "depression and uplift" from northeast to southwest. The spatial distribution characteristics of the Wufeng-Longmaxi Formation in the target layer were detected, and four favorable areas for shale gas exploration were delineated. The prediction of shale gas exploration target area by wide area electromagnetic method is expected to help realize the breakthrough of shale gas exploration and development from point to surface in Wuling Mountain area and promote the development of clean energy industry along the river.

With the domestic borehole magnetometer, the authors calculated magnetic azimuth in the nonmagnetic interference hole and introduced the concept of Δβ, which is called magnetic azimuth anomaly. The relationship between the symbol of Δβ and the direction of ΔH was clarified, and the relationship between the figure of Δβ and the magnetic body position was obtained. It is thus held that we can use Δβ as an auxiliary parameter in the calculation of magnetic source position.

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.

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.

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

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.

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

The spatiotemporal changes in soil organic matter (SOM) hold great significance forthe elevation of both regional soilquality and the potential of soil carbon sequestration. Based on two periods of soil data from the second soil reconnaissance surveyof Heilongjiang Province in 1980 and thesoil geochemical survey of Heilongjiang Province in 2020, this study analyzed the spatiotemporal changes in SOM content in surface soil (0~20 cm) in the Songnen and Sanjiang plains in Heilongjiang Province over 40 years through spatial analysis in GIS. Furthermore, this study summarized the distribution patterns of SOM lossof different soil types in various cities and counties. The results indicate that the average SOM content in the surface soil in the major two plains decreased by 5.68×10^-3over 40 years, generallyexhibiting a downward trend. Areas with decreased SOM are primarily distributed in Qiqihar, Daqing, western Suihua of the Songnen Plain, along with Hegang and western Jiamusi of the Sanjiang Plain, with the largest decreased amplitudeobserved in the Qiqihar Zhaoyuan area along the Nenjiang River basin. Regarding soil types, swampsoils exhibited the highestSOM loss rate (-44.68%), while grassland soilsexhibited a contribution rate for SOM of 44.14%, which established these soilsas the soil type making the most significant contribution to SOM in both plains. The SOM loss area in Wangkui County, Zhaoyuan County, and Daqing City accounted for over 72.11% of the total. This study determines the spatiotemporal changes in SOM in the major two basins in Heilongjiang Province on a scale of 40 years, providing a theoretical basis for the primary prevention and control targets of regional black soil degradation.

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

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

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.

For the underground construction of coastal cities in China, there is an urgent need to accurately position unfavorable geobodies such as faults and boulders. Based on the geological characteristics of coastal cities, this study conducted 3D numerical simulations using a high-density resistivity method, determining the effects of the electrical properties and thickness of the overburden on the survey results, as well as the DC electric field characteristics varying with the sizes and burial depths of detection targets. The results show that the resistivity difference between the overburden and the targets serves as a critical factor in determining the influence of the overburden. For low-resistivity fracture zones, a higher resistivity of the overburden signifies more prominent responses from the fracture zone. Under middle- to high-resistivity overburden conditions, shallowly buried boulders can be easily found, and larger boulders exhibit more significant high-resistivity characteristics. In the exploration along the Qingdao metro line 5, the high-density resistivity method played a vital role in exploring fracture zones and boulders, verifying the effective application effects of the method. The results of this study provide a basis for selecting engineering exploration methods and determining operating parameters in coastal cities.

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.

To study the quality of the arable soil in peri-urban area of Huangshi City, the present research focused on analyzing heavy metals distribution characteristics, assessed its risk to environment, and subsequently identified its sources by multivariate statistical analysis based on high-density topsoil and subsoil sampling. The results show that the content of heavy metals in the soil isas follows: As (5.2×10^-6~155.9×10^-6), Pb (19.2×10^-6~426.1×10^-6), Hg (0.012×10^-6~1.823×10^-6), Cd (0.03×10^-6~4.59×10^-6), Zn (34.8×10^-6~529.6×10^-6), Ni (8.5×10^-6~86.2×10^-6), Cu (16.52×10^-6~104.39×10^-6) and Cr (51.2×10^-6~145.5×10^-6). The average content of Cd exceeds the regional soil environmental background value, and Cd even exceeds the soil risk screening value of agricultural land. Heavy metal pollutants are mainly concentrated in the topsoil above 40 cm. Among the land use types, paddy lands and dry lands are heavily polluted, and Cd, As and Pb are the main pollutants. In paddy lands, As, Pb, Cu and Zn exhibit slight pollution, Cd and Hg exhibit moderate pollution, whereas Cr and Ni do not exhibit pollution. In dry lands and forest lands, As, Pb and Hg exhibit slight pollution, Cd exhibits moderate pollution and Cr, Cu, Ni and Zn do not exhibit pollution. The multivariate statistical analysis indicates that Cr and Ni in the soil of the study area are of natural origin and related to the parent material of the soil. Cd, Pb, As and Hg are mainly of anthropogenic pollutants, which is related to high-intensity industrial and mining production and sulfide mineral acidification release in Huangshi City.However Cu and Zn constitute mixed sources, partly from soil environmental background, and partly from human activities and industrial production emissions.

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.

In recent years, with the improvement of the radiometric tecbnique, rema-rkable advances have been made in the application of radiometric method to the prospecting for oil and gas fields. Portable microcomputerized instruments and equipments have been developed. In field work, high-precision and multi-parameter radiometric survey has been carried out; in indoor work, radiome tric stations have been utilized to undertake data processing and interpretation. Through integrated investigation of some oil and gas fields and model experi mentation on migration regularity of radioactive elements, new understanding has been gained concerning the relationship between radioactive anomalies and oil-gas accumulations and the formation mechanism of anomalies. Lots of case studies demonstrate that radiometric method is a simple, convenient, rapid, economical, practical and safe method in search for oil and gas fields and will surely yield good economic benefits in petroleum exploration.

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.