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  20 February 2024, Volume 48 Issue 1 Previous Issue   
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Chronology and geochemical characteristics of trachytes in the Tiaojishan Formation, Xuanhua Basin, northwestern Hebei Province, and their geological implications
YANG Ji-Yuan, HU Xin-Zhuo, ZHOU Jing, QI Peng-Chao, LI Ze-Yang, MENG Jia-Bao, XU Fan, ZHANG Hui-Bin, QI Hui-Yun
Geophysical and Geochemical Exploration. 2024, 48 (1): 1-14.   DOI: 10.11720/wtyht.2024.2503
Abstract   HTML ( 8 )   PDF (8237KB)

The Tiaojishan Formation in northwestern Hebei Province is home to volcanic-sedimentary strata. Due to the lack of fossil organisms, insufficient isotopic dating data, and outdated dating methods, the formation epochs of these strata have been controversial. To accurately determine their formation epochs and examine their regional geotectonic setting, this study conducted a detailed field investigation of the lithologic assemblage of the Tiaojishan Formation in the Xuanhua Basin. Petrological, petrogeochemical, and high-precision isotopic dating studies were conducted on the trachytic volcanic rocks in the upper segment of the formation, obtaining the LA-ICP-MS-based zircon U-Pb isotopic ages, which were 161.1±1.2 Ma and 162.5±1.3Ma. As indicated by the petrological and petrogeochemical characteristics, these trachytic volcanic rocks belong to the shoshonite series, exhibiting enriched light rare earth elements, relatively enriched elements including Rb, K, Th, Ce, Zr, and Hf, and relatively depleted Ba, Nb, Sr, P, and Ti. According to the comparison of principal parameters and graphical discrimination, the magma originated primarily from the melting of continental crustal materials and formed in the tectonic setting of compressional continental margin volcanic arcs. The comprehensive research reveals that the Tiaojishan Formation formed primarily during the Middle Jurassic and continued to the Late Jurassic, and the trachytic volcanic rocks in its upper segment formed in the intraplate compressional tectonic setting. The results of this study provide new data for the division and correlation of Mesozoic volcanic-sedimentary strata and the analysis of their formation environment.

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Geological characteristics and origin of the Mogou fluorite deposit in Fangcheng County, Henan Province
ZHANG Qing-Song, XIA Ming-Zhe, WANG Chun-Lian, LI Ke-Kun, LIU Zeng-Zheng, JIANG Ji-Yong, JIANG Jian-Lang
Geophysical and Geochemical Exploration. 2024, 48 (1): 15-23.   DOI: 10.11720/wtyht.2024.2588
Abstract   HTML ( 2 )   PDF (6964KB)

The Mogou fluorite deposit of Fangcheng County, residing in the Neoproterozoic Meiyaogou Formation, is a crucial part of the fluorite metallogenic belt in southern Henan Province. Based on the analysis of the geological characteristics of the Mogou fluorite deposit, this study conducted petrographic and petrogeochemical studies to define the source of ore-forming materials and probe into the genetic mechanism of the fluorite deposit. The results show that the fluorite ore body is veined or lenticular, with mineralization-related alterations composed of silicification, fluorite and sericite alterations. Its ore structures are primarily massive, followed by banded, striped, and brecciated types. The chondrite-normalized rare earth element distribution pattern of the fluorite ore body is similar to that of the Meiyaogou Formation marbles and the Yanshanian porphyritic plagiogranites, suggesting a genetic relationship. The possible genetic mechanism is that the F-enriched ore-bearing hydrothermal liquids intruded along the interbedded fault and reacted with the surrounding rocks to form the fluorite ore /mineralized body. The deposit belongs to the epithermal filling type along the interbedded structure.

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Application of natural thermoluminescence measurement technique in natural gas hydrate exploration in permafrost areas
WANG Hui-Yan, TANG Rui-Ling, BI Jing
Geophysical and Geochemical Exploration. 2024, 48 (1): 24-30.   DOI: 10.11720/wtyht.2024.1037
Abstract   HTML ( 3 )   PDF (2704KB)

Since natural gas hydrates (NGHs) in permafrost areas feature complex formation mechanisms and multiple sources, there is an urgent need to develop multiple techniques for micro-leakage information capture in order to increase the exploration success rate. This study applied the natural thermoluminescence measurement technique to NGH exploration in a permafrost area for the first time. Specifically, it tested the thermoluminescence intensity in soil samples from the Muli permafrost area of the Qilian Mountains using an RGD-6 thermoluminescent dosimeter. Then, it summarized the heating procedure for NGH exploration in the area, as well as size fractions for sampling. The results show that the soil samples from the Muli permafrost area demonstrated optimal size fractions for sampling ranging from -60~100 meshes, an optimal heating rate of 5 ℃/s, and an optimal heating range of 50~400 ℃. Based on the anomaly characteristics of the natural thermoluminescence intensity in soil samples, this study determined the anomaly boundary of NGHs on the surface of the permafrost area. It revealed that the natural thermoluminescence intensity displayed anomalies on the top, which correspond well to the hydrocarbon anomaly mode. The natural thermoluminescence measurements of soil, unaffected by microorganisms and boasting high sensitivity, can be popularized as a promising method for NGH explorations in permafrost areas.

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Prospecting for concealed skarn iron deposits using the high-precision gravity-magnetic survey method
DONG Jian, LI Xiao-Peng, FU Chao, DANG Zhi-Cai, ZHAO Xiao-Bo, ZENG Qing-Bin, HU Xue-Ping, WANG Jin-Hui
Geophysical and Geochemical Exploration. 2024, 48 (1): 31-39.   DOI: 10.11720/wtyht.2024.1047
Abstract   HTML ( 3 )   PDF (7885KB)

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.

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Geophysical characteristics and deep prospecting prediction of the Dachaigou gold deposit in the eastern Kunlun area
YU Zhong-Hong, YAN Ling-Qin, ZHANG Zhan-Xiong, LI Peng, LI Feng-Ting, FU Jia
Geophysical and Geochemical Exploration. 2024, 48 (1): 40-47.   DOI: 10.11720/wtyht.2024.1126
Abstract   HTML ( 3 )   PDF (7232KB)

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.

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Airborne gravity-magnetic anomalies in the Baiyunhu sag,Qiangtang Basin:Characteristics and implications for oil and gas exploration
LIU Zhong-Rong, HU Yue, FAN Zhi-Wei, HE Hong-Bing, ZHOU Dao-Qing, GUO Zhi-Hong, CAO Bao-Bao, WEI Yan-Yan
Geophysical and Geochemical Exploration. 2024, 48 (1): 48-57.   DOI: 10.11720/wtyht.2024.1339
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Airborne gravity-magnetic data are effective in revealing the deep structures of a basin.Based on the latest airborne gravity-magnetic data,combined with field-measured physical property data,this study expounded the characteristics and geological origin of airborne gravity-magnetic anomalies present in the Baiyunhu sag.Using the airborne gravity-magnetic data,this study identified the distribution of faults and magmatic rocks in the Baiyunhu sag.Furthermore,it calculated the burial depth of the magnetic basement and the structural morphologies of the Mesozoic basement in the sag using the artificial tangent method, power spectrum analysis method,and Parker-Oldenburg iterative inversion algorithm.Additionally,this study verified the structural stratification results through the integrated interpretations of gravity and magnetism in target sections.The findings suggest that the undulations of the Mesozoic and Paleozoic sediments in the Baiyunhu sag are the primary cause of gravity anomalies,while the regional airborne magnetic anomaly primarily reflects the distribution features of the Precambrian basement.The deeply buried basement of the Baiyunhu sag,featuring continuously distributed,thick Mesozoic strata and the lack of regional faulting and magmatic activity,is scarcely affected by tectonic movements and possesses great potential for oil and gas exploration.

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Application of integrated geophysical exploration technology in the geothermal exploration of northern Jinan
ZHANG Yi, LIU Peng-Lei, WANG Yu-Min, ZHANG Peng-Peng, ZHANG Chao, ZHANG Ning
Geophysical and Geochemical Exploration. 2024, 48 (1): 58-66.   DOI: 10.11720/wtyht.2024.1141
Abstract   HTML ( 7 )   PDF (8896KB)

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.

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Two-dimensional joint inversion based on the marine controlled-source electromagnetic method and seismic full-waveform
KONG Fan-Xiang, TAN Han-Dong, LIU Jian-Xun
Geophysical and Geochemical Exploration. 2024, 48 (1): 67-76.   DOI: 10.11720/wtyht.2024.2583
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To reduce the limitations and the multiplicity of solutions of a single geophysical inversion method, this study investigated the two-dimensional joint inversion based on the marine controlled-source electromagnetic (MCSEM) method and seismic full-waveform inversion. The MCSEM method employs the data-space Occam’s algorithm, while the seismic full-waveform inversion utilizes the gradient algorithm. By incorporating a cross-gradient function for the mutual coupling of the two types of physical property parameters, this study developed a two-dimensional joint inversion method, whose accuracy was verified using three different models. As indicated by the results, compared to a single inversion method, the MCSEM-based joint inversion yielded significantly improved inversion results, predominantly in terms of the morphology characterization of anomalous bodies, as well as the reconstruction of their structure and textures and their physical property values. Therefore, the full-waveform inversion can enhance the reliability of the MCSEM inversion results.

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Bayesian prestack seismic stochastic inversion based on the exact Zoeppritz equation
NIU Li-Ping, HU Hua-Feng, ZHOU Dan, ZHENG Xiao-Dong, GENG Jian-Hua
Geophysical and Geochemical Exploration. 2024, 48 (1): 77-87.   DOI: 10.11720/wtyht.2024.2572
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The prestack seismic inversion method based on the exact Zoeppritz equation is challenged by seismic data with low signal-to-noise ratios(SNRs).The Markov chain Monte Carlo(MCMC) simulation is a heuristic global optimization algorithm that can achieve effective prestack nonlinear inversion of elastic parameters.The conventional MCMC-based prestack inversion method,which characterizes the statistical properties of elastic parameters via the Gaussian distribution,has significant limitations when applied to complex lithologic reservoirs.Besides,due to the influence of the huge parameter space of subsurface models and the noise in seismic data,the MCMC search process for the posterior probability distribution of elastic parameters is very sensitive to local extrema,making it difficult to obtain stable and accurate results from MCMC-based prestack inversion.This study proposed an improved MCMC-based elastic parameter inversion method to address the challenges faced by the prestack inversion based on the exact Zoeppritz equation under the conditions of actual complex reservoirs and seismic data with low SNRs.First,the method reduced the complexity of the posterior probability distribution by transforming the parameters to be inverted into the perturbations of the model parameters using a low-frequency model (LFM) constraint.Then,the seismic forward modeling process was constrained by taking the logarithm of the likelihood function and utilizing an LFM.Finally,a multi-chain algorithm based on random subspace sampling was employed to perform global optimization for the prestack nonlinear inversion problems,thus avoiding premature convergence of the sampling process to local extrema.As indicated by the tests on the simulated data with low SNRs and the actual data,the method proposed in this study can yield more accurate and stable inversion results while providing credible and quantitative uncertainty estimates for the inversion results.

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A key seismic processing technique for deep geothermal exploration in igneous province in southern China
ZHENG Hao, CUI Yue, XU Lu, QI Peng
Geophysical and Geochemical Exploration. 2024, 48 (1): 88-97.   DOI: 10.11720/wtyht.2024.1084
Abstract   HTML ( 1 )   PDF (15267KB)

Southern China's igneous province,as a significant geothermal resource area in China,possesses abundant geothermal resources owing to its favorable accumulation conditions for medium-to-high temperature geothermal resources.However,gravity-magnetic-magnetotelluric exploration methods fail to sufficiently characterize the formation structures,geothermal reservoir boundaries,and the spatial distribution of geothermal reservoirs within the concealed fault zones,posing challenges in exploring deep geothermal resources.Hence,this study delved into the key seismic processing techniques for deep geothermal exploration based on 3D seismic exploration data,establishing a targeted processing flow.First,the problem of low signal-to-noise ratios in deep layers was solved through fine-scale preprocessing for deep geothermal reservoirs,laying a solid data foundation.Then,a high-precision velocity model was built via fault-guided tomography velocity modeling.Finally,the high-precision imaging of deep geothermal reservoirs was achieved using the amplitude-preserving low-frequency reverse-time migration technology,thus improving the imaging quality and the characterization accuracy of geothermal reservoir spaces and high-steep boundaries.Field data-based testing verified the validity and practicability of the processing flow.

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A petrophysical model of shales considering soft-mineral aspect ratios and its application
YANG Qi-Yu, LI Jing-Ye, WU Fan, LI Wen-Jin, CUI Jin-Ming
Geophysical and Geochemical Exploration. 2024, 48 (1): 98-104.   DOI: 10.11720/wtyht.2024.2567
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Previous petrophysical modeling of shale reservoirs often ignored the influence of pore types and soft-mineral aspect ratios on the elastic modulus.This study built a petrophysical model for transversely isotropic shales considering pore types and shapes,and soft-mineral aspect ratios.In this study,solid minerals were divided into hard and soft minerals,and soft minerals'anisotropic characteristics and shape changes were considered.According to the actual conditions of reservoirs, pores were categorized into intragranular,organic,and intergranular pores,and they were classified into stiff and soft pores based on their shapes.Finally,the input parameters were inverted using the particle swarm optimization algorithm to further calculate compressional and shear wave velocities,anisotropy parameters,and rock mechanical parameters.Combined with the actual data application,the results of this study were compared with the known results of shear wave velocity and isotropic rock mechanical calculation,suggesting that the model in this study is effective.

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Prestack seismic inversion of fluid factors in fractured reservoirs based on the global adaptive MCMC algorithm
ZHANG Jing, WANG Yong, ZHAO Hui-Yan, HENG De, HUANG Jun, ZHANG Xiao-Dan, WANG Wen-Wen, HE Yan-Bing
Geophysical and Geochemical Exploration. 2024, 48 (1): 105-112.   DOI: 10.11720/wtyht.2024.2608
Abstract   HTML ( 0 )   PDF (3624KB)

Fractured reservoirs typically exhibit anisotropic characteristics,and their fractures show different seismic responses when filled with fluids.Accurate identification of fluids in fractured reservoirs plays a significant role in indicating the hydraulic fracturing process in the late hydrocarbon exploration and production stage.This study adopted the concepts of normal and tangential fracture quasi-weaknesses and constructed a new indicative factor for fluids in fractures.Combining the linear slip theory, this study derived the elastic stiffness matrix expression of the fracture-induced HTI medium.Based on the scattering theory and the Born approximation equation,this study derived the linearized P-wave incident anisotropic reflection coefficient equation for the weakly contrasted interface.Moreover,this study proposed an improved global adaptive MCMC algorithm by introducing the adaptation strategy into the MCMC algorithm.The results show that:(1)In the absence of noise,the model testing results were highly consistent with the log data,with a consistency degree of above 90%;(2)The inversion results of the actual data aligned closely with the log interpretation results,and hydrocarbons were discovered through drilling in the target interval.As indicated by the results of model testing and actual data application in a study area in Southwest China,the prestack seismic inversion of fluid factors in fractured reservoirs,yielding highly consistent results with log interpretation data,demonstrates certain reliability and applicability and thus can achieve accurate fluid identification and hydraulic fracturing indication.

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3D correlation tomography inversion of gravity anomalies constrained by edge features and depth weighting
AN Guo-Qiang, LU Bao-Liang, GAO Xin-Yu, ZHU Wu, LI Bo-Sen
Geophysical and Geochemical Exploration. 2024, 48 (1): 113-124.   DOI: 10.11720/wtyht.2024.1053
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Correlation tomography is a fast tomography method using correlation coefficients to qualitatively interpret the spatial positions of geobodies. This method, featuring simple, stable, and fast calculations, can quickly and efficiently obtain the distribution of subsurface anomalies without solving large equations. However, the results of direct correlation tomography of gravity anomalies display deep divergence, excessive depth weighting function parameters, and low lateral and vertical resolution between anomalies. According to the fundamental principle of 3D correlation tomography inversion of gravity anomalies, this study introduced the balanced vertical derivative and balanced analytic signal amplitude of gravity anomalies as the edge features to horizontally weight the gravity anomaly correlation tomography, and proposed a more concise depth weighting function. As demonstrated by model tests, the lateral resolution of correlation tomography was improved under the constraint of gravity anomaly edge features, and the vertical resolution of correlation tomography was enhanced using the new depth weighting function. Finally, the method in this study was applied to the actual data of the Australian Olympic Dam polymetallic deposit, yielding consistent weighted tomography results with the actual geological data, thus proving the correctness and effectiveness of the method.

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Forward modeling of the seismic wave field of pure qP waves in TTI media based on the pseudo-analytical method
ZHANG Kui-Tao, LIAO Jia-Rong, GU Han-Ming, SUN Ying-Ying, CHEN Yi-Yang, WANG Kai
Geophysical and Geochemical Exploration. 2024, 48 (1): 125-133.   DOI: 10.11720/wtyht.2024.1090
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Forward modeling and reverse-time migration imaging techniques for pure quasi-P (qP) waves in anisotropic media have aroused extensive concern in recent years.However,conventional quasi-acoustic equations are subjected to the interference from quasi-shear waves,the limitation of model parameters (εδ),propagation instability,and low calculation accuracy,thus significantly restricting their application.Hence,this study shifted the quasi-differential equation of qP waves to the space-wavenumber domain and derived the second-order pure qP wave equation of TTI media in the time domain through coordinate transformation.To improve the calculation accuracy,this study conducted the forward modeling of the seismic wave field of pure qP waves in TTI media based on the pseudo-analytical method (PAM).The numerical simulation results show that:(1)The method proposed in this study was free from the limitations of quasi-acoustic equations,the interference from quasi-shear waves,and model parameters,enabling stable propagation of the seismic wave field;(2)Compared to other methods,the PAM can effectively improve the numerical simulation accuracy;(3)The testing of simple and complex models verified the correctness and applicability of the proposed method.

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Classification of carbonate reservoirs based on pore throat radius distributions
ZHAO Bing
Geophysical and Geochemical Exploration. 2024, 48 (1): 134-141.   DOI: 10.11720/wtyht.2024.2576
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Since carbonate reservoirs characterized by diverse reservoir spaces and high heterogeneity exhibit intricate internal pore structures,conventional petrophysical classification methods fail to accurately classify these reservoirs,especially the reservoirs with complex porous systems whose pore throat radii manifest a multimodal(e.g.,bimodal,and trimodal) distribution.By investigating the M Formation's carbonate reservoirs in an oil field in the Middle East,this study clarified that the internal pore structures of rocks determine the pore throat radius distribution,which in turn affects the classification of rocks.Hence,starting with the pore throat size distribution,and considering the contribution of pore components corresponding to each peak in the multimodal samples to the rock reservoir space and seepage capacity,this study proposed a pore throat radius parameter Rmax* combining pore throat sizes and their proportions to characterize the pore structures of rocks based on the cumulative permeability curve.Then,this study classified the selected 114 bimodal and 43 trimodal rock samples.Moreover,the characteristics of each type of reservoir were examined in depth by combining with physical properties,mercury injection data,thin-section observational data,and logs.The results of this study show that Rmax* can better characterize the pore structures of reservoirs and improve the reservoir classification effectiveness compared with the classification based on a single pore throat radius(R35,corresponding to mercury saturation of 35%).

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Log-based evaluation of intralayer heterogeneity of glutenite reservoirs in the Niudong area
ZHOU Jun, BIAN Hui-Yuan, CHEN Wen-An, ZHANG Di, LIU Guo-Liang, WANG Fei
Geophysical and Geochemical Exploration. 2024, 48 (1): 142-150.   DOI: 10.11720/wtyht.2024.1146
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Glutenite reservoirs in the Niudong area exhibit low porosity and permeability, intricate reservoir structures, and pronounced heterogeneity, making it difficult to classify the reservoirs using conventional logs and further impairing reservoir evaluation accuracy. As indicated by the data from core porosity and permeability tests, thin-section analysis, and X-ray diffraction tests, the glutenite reservoirs in the Niudong area feature high heterogeneity and can be classified into three types based on capillary pressure morphologies. This study evaluated the intralayer heterogeneity of the reservoirs using electrical imaging logs. First, reservoir porosity spectra were derived from the electrical imaging logs. Then, the averages, variances, Lorenz coefficients, and concentration functions of the porosity spectra of different depths were calculated by analyzing these depth-varying porosity spectra. Based on the integrated probability model, the weights of evaluation indices were determined through hierarchical analysis, obtaining the composite index of reservoir heterogeneity. Accordingly, the reservoirs were classified, and the evaluation criteria for reservoir heterogeneity were established. The results of this study were consistent with the results of mercury injection experiments. The method used in this study proves effective in reservoir heterogeneity evaluation, enriching current methods for reservoir heterogeneity evaluation and providing theoretical support for fine-scale reservoir evaluation.

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Numerical simulation of the field source for the CSAMT folded line source in a homogeneous half-space
DUAN Yue-Quan, LIU Yun, WANG Zi-Jun, LI Yu-Shan
Geophysical and Geochemical Exploration. 2024, 48 (1): 151-161.   DOI: 10.11720/wtyht.2024.1103
Abstract   HTML ( 2 )   PDF (5614KB)

For field surveys using the controlled source audio magnetotelluric (CSAMT) method, it is generally believed that the CSAMT line source is a simplified electric dipole source with a minimal length. However, CSAMT line sources are all arranged in a folded line pattern in field surveys. Based on the previous research results, this study derived the numerical calculation method for the electromagnetic field excited by the folded line source according to the linear superposition principle of electromagnetic fields. Through the calculation of different folded line source models, this study analyzed the influences of the folded line source on the apparent resistivity and impedance phase curves in the homogeneous half-space. Model calculations demonstrate that the folded line source significantly influenced the near and transition zones of the apparent resistivity and impedance phase curves but had no influence on their far zones. The influences on the near and transition zones were primarily caused by the azimuths of folded line segments, and higher azimuths were associated with more significant influences on the apparent resistivity and impedance phase of survey points. In the case of very low azimuth angles, the folded line source can be approximated as a straight line source for processing, improving the work efficiency while fully considering the morphology of the emission source. This study provides theoretical support for the near-field correction of subsequent CSAMT data processing and the CSAMT numerical simulation.

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Exploring electromagnetic noise suppression technologies for magnetotelluric sounding in high-interference ore districts
HAO She-Feng, TIAN Shao-Bing, MEI Rong, PENG Rong-Hua, LI Zhao-Ling
Geophysical and Geochemical Exploration. 2024, 48 (1): 162-174.   DOI: 10.11720/wtyht.2024.1140
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Magnetotelluric sounding (MT) has been extensively applied in mineral resource exploration. However, strong anthropogenic electromagnetic interference severely constrains the acquisition of high-quality original MT data. This study provided a detailed summary of the common types of electromagnetic noise sources in China and analyzed the characteristics of electromagnetic noise they produced. By comparing the methods for MT electromagnetic noise reduction at home and abroad, this study developed a rapid and effective construction and processing technology for MT data denoising in high-interference ore districts based on actual production demands. The results indicate that Robust processing, remote reference technique, and manual selection are effective and necessary in enhancing MT data quality. Besides, theoretical calculations suggest that the distance between the remote reference stations should be set at 3.56-fold skin depth or above, as verified by the MT experiments in the ore district of the Hongze salt basin, Jiangsu Province.

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Application of supervised descent method for 2D magnetotelluric inversion and its application
FU Xing, TAN Han-Dong, DONG Yan, WANG Mao
Geophysical and Geochemical Exploration. 2024, 48 (1): 175-184.   DOI: 10.11720/wtyht.2024.1417
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Traditional two-dimensional inversion methods of magnetotelluric are mature, but there are still some problems, such as reliance on the initial model, reliance on regularization parameter selection, and easy to fall into local minimum. In order to solve the above problems, this paper adopts the supervised descent method to improve the effect of two-dimensional inversion of magnetotelluric. The supervised descent method is a machine learning algorithm that learns the average descending direction to predict the residual of data. Based on the theory of supervised descent method, this paper develops the two-dimensional inversion algorithm of magnetotelluric, designs the theoretical model synthesis example to verify the correctness of the algorithm, and inverts the measured data on the Tibet Plateau to test the practicability of the supervised descent method. The inversion results of the theoretical model synthesis data and the measured data show that, compared with the traditional nonlinear conjugate gradient inversion, the inversion based on the supervised descent method has the characteristics of fast convergence speed, good inversion effect, and strong anti-noise ability.

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A prediction model of the industrial components and calorific values of coal seams based on multi-source log data
YU Yong-Peng, ZHANG Guang-Bing, HUANG Zi-Jun, YAN Jian-Bo, WANG Jia-Wen, YANG Yan-Cheng, MAO Xing-Jun
Geophysical and Geochemical Exploration. 2024, 48 (1): 185-193.   DOI: 10.11720/wtyht.2024.2553
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The industrial components and calorific values of coal seams serve as an important basis for the evaluation of coal quality, and the prediction of them based on log data allows for overcoming the deficiency in the experimental analysis of coal core samples. This study collected data from digital logs and coal quality analysis at different stages (e.g., detailed survey and exploration) of a coal field in Ningxia. Based on the investigation of the coal quality and log responses, as well as statistical analysis, this study developed the methods for extracting log response characteristics, establishing sample sets, and processing data and established a deep neural network-based prediction model. Then, it confirmed the validity of the prediction model by comparing the predicted results of testing data with the results from the experimental analysis.

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Design and implementation of key technologies for real-time three-dimensional ground-penetrating radar
YIN Da, XIN Guo-Liang, SUN Xue-Chao, ZHANG You-Yuan, ZHANG Qi-Dao
Geophysical and Geochemical Exploration. 2024, 48 (1): 194-200.   DOI: 10.11720/wtyht.2024.1030
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To improve the detection level of municipal roads for rapid and effective municipal road collapse warning and rapid search for municipal pipe network distribution, the 22nd Research Institute of China Electronics Technology Group Corporation designed and developed real-time three-dimensional ground-penetrating radar (3D GPR). With the real-time 3D GPR, which is based on the architecture of field programmable gate array and digital signal processor (FPGA&DSP), the institute achieved the design and implementation of several key technologies for the multi-channel high-speed acquisition system, enriching the road detection techniques and methods. The real-time 3D GPR enables high-speed acquisition of ten-channel radar data using the horizontally polarized antennae equipped with five transmitters and six receivers. The channels can be switched using high-speed switches, which operate in an interactive interpolation manner. The 3D GPR allows for up to 32 channels and detection speeds of above 60 km/h (channel interval: 2 cm). This is attributed to the switching of the antenna array using switches. The optimum antenna polarization design was verified by the comparison of experimental data from cavity- and metal-plate-based experimental sites. As a result, the optimal antenna scheme was determined. The measured results show that, compared to general LTD-2600 radar, the real-time 3D GPR boasts a higher acquisition speed and higher performance in terms of amplitude and phase, conducive to the improvement of road disaster detection technologies. Therefore, there is high market demand for the real-time 3D GPR.

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Design and implementation of a geochemical field sampling system based on mobile GIS
ZHOU Yi-Ning, GAO Yan-Fang, CHANG Chan, ZHANG Bi-Min
Geophysical and Geochemical Exploration. 2024, 48 (1): 201-209.   DOI: 10.11720/wtyht.2024.2410
Abstract   HTML ( 1 )   PDF (4751KB)

Cumbersome acquisition tools and laborious indoor data processing are bound to impair the quality and accuracy of conventional field geochemical surveys, especially in study areas with many samples and a harsh natural environment. The informatization and intelligence of field geochemical surveys are the requirements of the times and an inevitable trend for the advancement of methods and technologies. Based on the ArcGIS and Android platforms, this study developed a geochemical field sampling system, which comprises task planning, field data collecting, quality control, and other functions, to match the field geochemical survey process using mobile GIS and database technologies. This system enables the informatization and intelligence of the entire field geochemical survey process, simplifying the data collection procedure, reducing the time needed for fieldwork, and enhancing the data collection efficiency. Therefore, this system improves the quality and accuracy of field survey information, advancing the digitization of field geochemical surveys.

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Development of a digital γ spectral logging probe
CHEN Yuan-Qing, HUANG Qing-Bo, LIU Jin-Yao, WANG Xian-He, HUANG Liang, WU Wei-Jun
Geophysical and Geochemical Exploration. 2024, 48 (1): 210-215.   DOI: 10.11720/wtyht.2024.2455
Abstract   HTML ( 0 )   PDF (1689KB)

Given that it is difficult to accurately determine the uranium and thorium contents in the strata of uranium-thorium mixed deposits,this study developed a digital γ spectrum logging probe based on cerium tribromide (CeBr3) crystals.Using CeBr3 crystals with a diameter of 38 mm×38 mm,the logging probe improved the sensitivity to uranium and the detection efficiency of ore beds with low uranium and thorium contents.The logging probe operated as follows.First,the original signals from the CeBr3 detector were filtered and shaped using the C8051 single-chip microcomputer as the core processor.Then,the γ spectrum data were obtained using the energy spectrum collector.After the spectrum unfolding based on the inverse matrix is performed for the γ spectrum data,precise uranium and thorium contents in the ore beds were obtained.Finally,the γ spectrum data were transmitted to the host computer for logging through the RS-485 bus.The results show that the logging probe had high measurement accuracy in the standard uranium-thorium mixed model,with indication errors of less than 6%,stability of less than 1.5%,and repeatability of less than 1%.Moreover,the 2.62 MeV energy peak drift of thorium 208Tl did not exceed ±0.3 channels,and the relative errors of log anomalies were less than 4%.Therefore,the digital γ spectrum logging probe proposed in this study is applicable to the exploration and logging of uranium deposits.

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Delineation of areas with high geological background values of heavy metals in soils in Yunnan Province, China based on geological big data technology
XIAO Gao-Qiang, ZHAO Juan, CHEN Zi-Wan, SONG Xu-Feng, ZHU Neng-Gang
Geophysical and Geochemical Exploration. 2024, 48 (1): 216-227.   DOI: 10.11720/wtyht.2024.1129
Abstract   HTML ( 2 )   PDF (4168KB)

This study aims to systematically investigate the distribution and over-limit elements of areas with high geological background values of heavy metals in soils in Yunnan Province. GIS spatial analysis was conducted based on the heavy metal content data from a province-wide 1∶200,000 stream sediment survey and the regional geological map. The analysis results were validated using the data of heavy metals in soils in Kunming, Yuxi, Zhaotong, and other regions. A total of 61 geological units were identified, with heavy metal content in soils exceeding the screening values of agricultural land, accounting for 21.09% of the total land area of Yunnan. The cultivated land in high geological background areas covers an area of approximately 2.844 1 million hectares, accounting for 7.22% of the total land area of Yunnan. The lithologies that cause over-limit heavy metals in soils primarily comprise carbonate rocks, mafic-ultramafic volcanic rocks, intermediate mafic intrusive rocks, coal-bearing clastic rocks, and clastic rocks with mafic components. The over-limit heavy metal elements in high geological background areas are dominated by Cu, Cr, Ni, and Cd. In contrast, As manifests an over-limit risk mainly in carbonate rock formations, Pb and Zn only exhibit an over-limit risk in individual strata, and Hg almost shows no over-limit risk.

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Cumulative effects of atmospheric dust fall on major environmental elements in soils and their evaluation: A case study of Gaomi City, Shandong Province, China
JIANG Bing, ZHANG De-Ming, LIU Yang
Geophysical and Geochemical Exploration. 2024, 48 (1): 228-236.   DOI: 10.11720/wtyht.2024.1136
Abstract   HTML ( 1 )   PDF (5160KB)

This study aims to investigate the pollution distribution of major environmental elements of atmospheric dust fall in Gaomi City, Shandong Province, as well as its effects on soils in a supergene environment. Hence, this study systematically collected and tested the atmospheric dust fall from Gaomi City, obtaining the testing data of nine environmental elements, including Cu, Pb, Zn, Ni, Cr, Cd, As, Hg, and Se. Furthermore, this study calculated the annual sediment fluxes and annual increments of these elements, simulated the minimum annual sediment fluxes for them to reach limit values, and evaluated their pollution levels. The results show that the average contents of various elements in atmospheric dust fall all exceeded their soil background values, exhibiting different degrees of enrichment. In terms of annual sediment fluxes, Cu was significantly positively correlated with Pb, while Zn, Ni, Cr, Cd, As, and Hg were mostly positively correlated in pairs, and Se showed a non-significant correlation with other elements. A higher correlation suggests a higher homology. Atmospheric dust fall, serving as an input end member of major environmental elements in soils, resulted in annual growth rates of various elements in topsoils ranging from 0.03%~0.52%. Cd would be the closest to its soil limit value over a few years. As revealed by geoaccumulation index-based evaluation, Ni, As, and Cr exhibited non-pollution to slight pollution, Se primarily manifested heavy pollution, Cd and Zn displayed moderate to heavy pollution, and Hg, Cu, and Pb mainly showed slight to moderate pollution, corresponding to a pollution order of Se>Cd>Zn>Hg>Cu>Pb>Ni>As>Cr.

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Distribution characteristics and source analysis of heavy metals from dry and wet atmospheric deposition in northern Xiushan County, Chongqing
CAI Ke-Ke, ZHAO Zhi-Qiang, MENG Li, WANG Xiao-Meng, LIU Jian, LUO Ren-Feng
Geophysical and Geochemical Exploration. 2024, 48 (1): 237-244.   DOI: 10.11720/wtyht.2024.2432
Abstract   HTML ( 0 )   PDF (3776KB)

This study aims to determine the contents of heavy metals from dry and wet atmospheric deposition in northern Xiushan County for targeted environmental pollution prevention and control and safe farmland soil utilization. Based on the dry and wet atmospheric deposition samples continuously received from 18 sampling sites in northern Xiushan County from November 2019 to November 2020, this study tested the contents of seven heavy metal elements, including Cd, Cr, Cu, Ni, Pb, Zn, and Hg. Considering the topographic features, this study analyzed the distribution patterns and sources of heavy metals from dry and wet atmospheric deposition in northern Xiushan County. Moreover, this study assessed the soil pollution caused by heavy metals from dry and wet atmospheric deposition using the geoaccumulation index method. The results show that except Hg, the other six heavy metal elements exhibited significant zoning, with their high-value deposition areas distributed primarily in the flanks and eastern segment of Chuanhegai, where their contents were much higher than the national and Chongqing's averages. In contrast, their depositional fluxes in other general deposition areas were less than the national averages by 25%. The high dry and wet atmospheric deposition in the flanks of Chuanhegai was subjected to both the mining of the lead-zinc deposit in Huayuan County in the east and the special topography. The abrupt topography increased the fluxes of the seven heavy metals in the dry and wet atmospheric deposition by 49 times. Therefore, the monitoring and assessment of environmental safety in this type of landform area should be strengthened. According to the assessment results of the geoaccumulation index method, the flanks of Chuanhegai were moderately-severely to extremely polluted by Cd, slightly-moderately polluted by Pb, and slightly-moderately to severely polluted by Zn.

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Speciation of selenium in typical meadow soils in Tumed Left Banner, Inner Mongolia, China
LIU Jin-Bao, XU Hong-Guo, YUAN Hong-Wei, ZHANG Xiao-Feng
Geophysical and Geochemical Exploration. 2024, 48 (1): 245-254.   DOI: 10.11720/wtyht.2024.2403
Abstract   HTML ( 0 )   PDF (2134KB)

This study determined the speciation, available content, and physicochemical properties of selenium in soils using samples of topsoil and soil column profiles from Tabusai Township, Tumed Left Banner, Inner Mongolia, China. Accordingly, this study investigated the compositions of the speciation and available content of soil selenium, as well as their influencing factors. The results indicate that: (1) the major forms of selenium in topsoil include humic acid bound, strong organic bound, and residue forms; (2) the concentration of in the humic acid bound selenium correlates positively with the cation exchange capacity (CEC) and the concentrations of organic matter, phosphorus, and potassium; the total selenium concentration correlates positively with the concentrations of humic acid bound selenium, Fe-Mn oxide bound selenium, strong organic bound selenium, and residue selenium, all of which exhibit promotion effects; (3) the sulfur concentration correlates negatively with the concentration of water-soluble selenium, demonstrating an inhibitory effect; (4) the concentrations of selenium in various forms tend to decrease from the surface layer to the deep layer; (5) the concentration of bioavailable selenium correlates positively with the total selenium concentration, organic-bound selenium, and water-soluble selenium and correlates negatively with the sulfur concentration. The soils in the study area, featuring a high concentration of water-soluble selenium and fairly high bioavailability, are suitable for planting selenium-rich agricultural products.

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Enrichment characteristics, source identification, and health risk assessment of soil heavy metals in typical cultivated land in the mountainous area of southern Anhui Province
YANG Yan, LIU Bin, XIA Fei-Qiang, CHEN Ping-Feng, ZHANG Xiang
Geophysical and Geochemical Exploration. 2024, 48 (1): 255-263.   DOI: 10.11720/wtyht.2024.2595
Abstract   HTML ( 2 )   PDF (4743KB)

This study aims to explore the enrichment characteristics and origin of soil heavy metals in typical cultivated land in the mountainous area of southern Anhui province. With Ningguo City in southeastern Anhui Province as the research object, this study collected 1399 topsoil samples in the cultivated land for determining the concentrations of As, Cd, Hg, Pb, Cr, Ni, Cu, and Zn. Furthermore, this study conducted a health risk assessment and source identification of heavy metals using the correlation analysis, the soil environmental quality - risk control standard for soil contamination of agricultural land, the geoaccumulation index, the health risk index, and the positive matrix factorization (PMF) model. The results are as follows: (1) The average concentrations of As, Cr, Hg, Pb, Cr, Ni, Cu, and Zn were 15.8×10-6, 0.41×10-6, 0.106×10-6, 31×10-6, 67×10-6, 29×10-6, 29×10-6, and 94×10-6, respectively, which were all higher than their background values in Anhui Province, except Ni. (2) The soil heavy metals generally exhibited low pollution risks, with the heavy metal concentrations of 866 soil samples lower than their risk screening values. (3) The cultivated soil was primarily polluted by Hg, Cd, and As, as indicated by the geoaccumulation index results. (4) Both non-carcinogenic and carcinogenic risk levels in adults in the study area were within the acceptable ranges, as revealed by the health risk assessment results. (5) Four sources of heavy metals in the study area were identified based on the PMF model: industrial and agricultural emissions associated with human activities, atmospheric deposition, soil parent materials related to soil types, and the geological background source.

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Improvement in active-source surface wave acquisition device and its application in subway construction exploration
QIN Chang-Chun, WANG Guo-Shun, LI Jing
Geophysical and Geochemical Exploration. 2024, 48 (1): 264-271.   DOI: 10.11720/wtyht.2024.1132
Abstract   HTML ( 0 )   PDF (8905KB)

With the rapid development of cities and the accelerated construction of subway tunnels,there is an urgent demand for the detection of unfavorable geological bodies ahead of tunnel excavation.It is difficult for traditional electromagnetic methods to yield excellent detection results in an urban environment with high electromagnetic interference.Active-source surface wave exploration has gained increasing popularity in shallow superficial exploration and engineering geophysical prospecting in cities due to its strong anti-interference,convenient acquisition devices,and low construction cost.However,the traditional active-source reflection seismic method uses only a heavy hammer with limited excitation energy as a seismic source,and the collected signals are prone to be disturbed by urban activities.Meanwhile,the asphalt or cement pavement in urban areas is unfavorable for the placement of geophones and the excitation of seismic signals from a hammer.Given these,this study improved the geophones and seismic source devices at low costs,obtaining a more efficient and user-friendly surface wave acquisition device.As confirmed by practical engineering exploration,the improved device can collect surface-wave signals with strong energy and high signal-to-noise ratios,resulting in high-quality data,desirable inversion and imaging results,and high consistency between the geological defects and actual geological conditions.The improved acquisition device can be extensively promoted and referenced in active-source surface wave exploration in cities.

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Application of logging-resistivity joint exploration to 3D geological modeling for environmental investigation of a certain landfill site
SONG Tao, BAO Yi, ZHAO Song, WU Jian-Feng, XU Yuan-Shun, TU Hai-Feng
Geophysical and Geochemical Exploration. 2024, 48 (1): 272-280.   DOI: 10.11720/wtyht.2024.1100
Abstract   HTML ( 1 )   PDF (5420KB)

Geological exploration accuracy is a significant factor in the reliability of the comprehensive environmental survey outcomes of informal landfill sites.This study conducted drilling-high-density resistivity joint exploration of an informal landfill site using 754 high-density resistivity measurement points,12 parameter wells,and aerial surveys.Based on the binary analysis method of landfill layers and base,as well as the fuzzy mathematics theory,this study analyzed and interpreted the distribution characteristics of four layers of landfills,base,and leachate.Furthermore,this study established a 3D geological model of the landfill site and analyzed the spatial distribution of environmental geological elements.The drilling-derived verification results and the applicability evaluation demonstrate that the drilling-high-density resistivity joint exploration can be used to investigate informal landfill sites to obtain reliable geological results consistent with site characteristics.

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Exploring geological conditions for tunnel construction in hydropower engineering using a 3D resistivity method
HUANG Yao
Geophysical and Geochemical Exploration. 2024, 48 (1): 281-286.   DOI: 10.11720/wtyht.2024.2602
Abstract   HTML ( 0 )   PDF (2923KB)

To explore the geological conditions for the tunnel construction in hydropower engineering, this study built a calculation model for tunnel geological conditions using a 3D resistivity method. Through numerical simulations, this study determined the 3D resistivity distribution of the tunnel model. Then, the model was applied to the field exploration of a water resource allocation project in Yunnan, yielding satisfactory exploration results, as verified through drilling. The findings suggest that the 3D resistivity method can be effectively applied to the exploration of geological conditions for tunnel construction in hydropower engineering by accurately determining formation thicknesses, as well as the sizes, locations, and filling characteristics of karst cavities. The quantitative and qualitative data obtained from exploration in this study lay a reliable foundation for the management, informatization, and disaster prevention of tunnel construction.

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AN ANALYSIS OF THE SPECIAL WAVE IMPACT ON THE INTERPRETATIONOF THE COALFIELD COLLAPSE COLUMN
YANG Xiao-Dong, YANG De-Xi
Geophysical and Geochemical Exploration    2010, 34 (5): 627-631.  
Abstract2621)      PDF (4180KB)(4899)      


In the light of typical coneshaped columns in the Lu'an mine of Shanxi Province, the authors

established a mathematical model for the collapse column, and used the wave equation model for

seismic ray tracing and wavefield simulation of collapse columns. The simulation results show that,

due to the special nature of the collapse columns, such waves as the normal reflected wave, the fault

point diffraction wave, the delay diffraction wave, the delay reflected wave and  the "diffraction

wave" consisting of Pwave field are formed around the collapse columns. On such a basis, the field

shot was simulated, and then a single shot record for routine processing  was generated to produce

stacking sections and migrated sections. The forward section and the actual data analysis reveal that

the fallen columns of the special wave constitute an important feature for recognizing collapse

columns; nevertheless, the resultant scale of the actual seismic data interpretation is often smaller

than the scale of actual collapse column. Some suggestions are also put forward for reference.

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The application of integrated geological, geochemical and geophysical techniques to the exploration of the Bogutu gold deposit
YAO Tie, ZHOU Yong, DU Zhan-Jun, ZHAO Zhen-Ming
Geophysical and Geochemical Exploration    2015, 39 (5): 877-884.   DOI: 10.11720/wtyht.2015.5.01
Abstract1331)   HTML151)    PDF (12833KB)(4297)      

Low density geochemical survey in Yishenjilike mountain area led to the discovery of a huge gold geochemical block, and the verification and evaluation of gold anomalies led to the discovery of the Bogutu gold deposit. In combination with the geological characteristics of the prospecting area, the authors carried out a series of geological-geophysical-geochemical exploration work, delineated quite a few geochemical and IP anomalies, and detected the characteristics of ore-bearing structural belt. Through trenching and drilling verification, the authors found more than 40 gold orebodies, thus achieving good ore-prospecting results.

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The application of integrated geophysical prospecting methods to the exploration of urban buried fault
LIU Wei, HUANG Tao, WANG Ting-Yong, LIU Yi, ZHANG Ji, LIU Wen-Tao, ZHANG Qi-Bin, LI Qiang
Geophysical and Geochemical Exploration    2021, 45 (4): 1077-1087.   DOI: 10.11720/wtyht.2021.1525
Abstract737)   HTML408)    PDF (4078KB)(3777)      

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.

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A NEW DEVELOPMENT PERIOD OF THE GRAVITY AND MAGNETIC EXPLORATION
ZHANG Chang-Da, DONG Hao-Bin
Geophysical and Geochemical Exploration    2010, 34 (1): 1-7.  
Abstract3363)      PDF (431KB)(3506)      

A review on the airborne gravity survey and airborne magnetic survey are given in this paper. The

authors hold that these techniques have entered into a new development period, as evidenced by the

emergence of such technologic indicators as airborne vector magnetometry, magnetic fulltensor LTSSQUID

and HTSSQUID gradiometry, airborne gravimetry, gravity gradiometry and geophysical survey by UAV.

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THE ADVANCES IN THE STUDY OF THE AIRBORNE GRAVIMETRY SYSTEM
WANG Jing-Bo, XIONG Sheng-Qing, ZHOU Xi-Hua, GUO Zhi-Hong
Geophysical and Geochemical Exploration    2009, 33 (4): 368-373.  
Abstract2948)      PDF (1014KB)(3373)      

This paper gives a brief review of the history of the airborne gravimetry. Based on the principle of the airborne gravimetry, the paper deals emphatically with the history, the present  research situation and the developments of the airborne scalar gravity survey system. Further development trends are also indicated.

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3D DISPLAY FOR GROUND PENETRATING RADAR BASED ON Matlab
WU Bao-Jie, JI Mei-Xiu, YANG Hua
Geophysical and Geochemical Exploration    2009, 33 (3): 342-344.  
Abstract6740)      PDF (532KB)(3142)      

 With powerful Matlab image processing functions, this paper has realized the 3D display of ground penetrating radar data, whose procedures are simple to prepare and easy to learn. A detailed description of the code is given, and the three-dimensional test data show that, by setting transparency, the target can be displayed in an intuitive and visual way.

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CALCULATION OF THE ANOMALY AREA
Zhao Rongjun
Geophysical and Geochemical Exploration    2000, 24 (2): 154-156.  
Abstract1566)      PDF (346KB)(2656)      

This paper puts forward a new method for calculating anomaly area—the polygonous approximation method,and gives corresponding algorithm and precision controlling technique.With this method,one can calculate anomaly area rapidly and precisely,thus yielding relatively satisfactory results.

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THE UTILIZATION OF EXCEL TO THE PERFORMANCE OF R-MODE CLUSTER ANALYSIS
CHUN Nei-ya
Geophysical and Geochemical Exploration    2007, 31 (4): 374-376.  
Abstract4606)      PDF (659KB)(2602)      

The R-mode cluster analysis is a mathematic statistical method for obtaining the quantitative similarity of several elements. Its procedure includes: the conversion of the original data; the solution of the relevant coefficient ; the clustering of the result. The above operation can be realized by using the data analysis tool of Excel. This method is quite suitable for field utilization.

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THE CHOICE OF GRIDDING METHODS FOR GEOPHYSICAL DATA
LIU Zhao-Ping, YANG Jin, WU Wei
Geophysical and Geochemical Exploration    2010, 34 (1): 93-97.  
Abstract3151)      PDF (1939KB)(2599)      

In drawing the contour map of geophysical data, suitable gridding methods should be chosen according to objective

environment characteristics and characteristics of data themselves. With practical examples, this paper deals with some common

gridding methods such as inverse distance to a power, Kriging, Minimum Curvatrue, Nearest Neighbor, Polynomial Regression, Radial

Basis Function, and Triangulation/Liner Interpolation, probing into their choosing means, applicable fields and parameter

installment.

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THE APPLICATION OF THE GRADIENT SOUNDING PROFILE METHOD TO THE GOLD PROSPECTING IN THE YINAN GOLD MINE
DU Li-ming, WU Jun-jie, YANG Jin-duo, WANG Peng, YU Bao-xian
Geophysical and Geochemical Exploration    2013, 37 (2): 225-228.   DOI: 10.11720/j.issn.1000-8918.2013.2.07
Abstract2334)      PDF (964KB)(2530)      
IP is an important method for mineral resources exploration, but it can only be applied in a few pivotal places because its difficult performance, and hence the information obtained from the survey area is very limited. The aim of this study is to find a simple and effective IP method with which we can get much valuable information form the survey area so as to improve the exploration effect. In the Yinan gold ore district, the authors applied the gradient sounding profile method, calculated 2D resistivity and obtained the IP model. The results show that the gradient sounding profile method is simple and effective.
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THE APPLICATION OF ATOM INTERFEROMETER TO THE MEASUREMENT OF GRAVITATIONAL ACCELERATION
ZHANG Chang-da
Geophysical and Geochemical Exploration    2000, 24 (5): 321-326.  
Abstract1731)      PDF (673KB)(2501)      

This paper has described and reviewed the pinciples,expermental set up and observational results of applying atom interferometer to measuring the earth's gravitational acceleration.This method was developed by Nobelist Steven Chu,M.Kaservich,A.Peters et al.,who demonstrated a resolution of 10-10.The application of this technique to geophysics and the related problems are also discussed.

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CHEMICAL COMPOSITIONS OF CONTINENTAL CRUST AND ROCKS IN EASTERN CHINA
Yan Mingcai, Chi Qinghua, Gu Tiexin, Wang Chunshu
Geophysical and Geochemical Exploration    1997, 21 (6): 451-459.  
Abstract3014)      PDF (2969KB)(2384)      

Element abundances of the continental crust and rocks cited in the past and recent literature have been based on compilations of data from various studies. This leads to uncertainties in sample representativeness and data quality. The present study is based on systematic collection of 28 253 individual rock samples over an area of 3.3 million km2 in eastern China, east of eastern longitude of 105°.The sampling involves more than 800 igneous intrusive bodies and metamorphic complexes as well as more than 500 type stratigraphic sections. From the individual rock samples, 2 718 composite samples were made and analyzed for 77 elements by 15 specific methods, dominantly XRF and INAA. Analytical quality was controlled by international and national preliminary geochemical reference materials of GSR, GAu and GPt series. Synthetic results from geological, geochemical and geophysical studies were used to construct crustal constitution model, from which element abundances of the continental crust in the North China platform, the upper crust and exposed crust in eastern China, chemical composition of igneous rock in China and of sedimentary rock and metamorphic rock in eastern China were derived.

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THE APPLICATION OF NEW GEOCHEMICAL EXPLORATION METHODSTO MINERAL EXPLORATION AND ITS GEOLOGICAL EFFECT
JIANG Yong-Jian, WEI Jun-Hao, ZHOU Jing-Ren, WANG Zhong-Ming, JI Zhao-Jia, WANG Fa-Yan
Geophysical and Geochemical Exploration    2010, 34 (2): 134-138.  
Abstract4294)      PDF (403KB)(2359)      

As an important prospecting technique and an effective means for obtaining mineralization data,

geochemical exploration has been proved to be very successful in mineral exploration. This paper focuses on

commenting the present research situation and application effect of some new methods such as structural

superimposed halos method, heat released mercury method, separatory electrogeochemistry method, enzyme leach, and

geogas and selective leaching of mobile metals method. It is emphasized that any one of these methods has its

unique applicability and that, in the practical application, we should pay attention to the cooperation of

geochemical exploration, geologicalgeophysical exploration and remote sensing and depend on the study of

geological background so as to demonstrate the usefulness and effectiveness of geochemical exploration.

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RECENT ADVANCES IN THE RESEARCH AND DEVELOPMENT OF QUANTUM MAGNETOMETERS
ZHANG Chang-da
Geophysical and Geochemical Exploration    2005, 29 (4): 283-287.  
Abstract1727)      PDF (376KB)(2335)      

In this paper, recent advances in the research and development of quantum magnetometers have been described together with some suggestions on further research work.

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THE EXTRACTION METHOD AND PROGRAM DESIGN FOR DISPERSION CURVE IN F-K DOMAIN
LI Jie, CHEN Xuan-hua, ZHANG Jiao-dong, ZHOU Qi, LIU Gang, LIU Zhi-qiang, XU Yan, LI Bing, YANG Jing
Geophysical and Geochemical Exploration    2011, 35 (5): 684-688.  
Abstract3721)      PDF (534KB)(2259)      

Based on two-dimensional Fourier transform and half-wave theory, this paper has studied the seismic Rayleigh wave dispersion curve extraction in f-k domain and made this theory fit in with a program by means of Delphi7.0. It is concluded that the f-k method overcomes the shortcomings of the one-dimensional digital processing technology and makes full use of multi-channel Rayleigh wave data record.

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THE PRESENT SITUATION AND RESEARCH ADVANCES OF EXPLORATION GEOCHEMISTRY FOR PORPHYRY COPPER DEPOSITS
HU Shu-qi, MA Sheng-ming, LIU Chong-min
Geophysical and Geochemical Exploration    2011, 35 (4): 431-437.  
Abstract3732)      PDF (643KB)(2243)      

Porphyry copper deposit is the most important copper deposit type in China. With the deepening of mineral exploitation, exploration geochemistry in mineral exploration has become increasingly important. Based on related literature, this paper sums up the exploration geochemical research results of porphyry copper deposits, which include such aspects as geochemical characteristics, exploration methods, anomaly evaluation and prospecting indicators. Exemplified by the Fujiawu copper deposit, this paper reports the latest advances in the study of porphyry copper deposits.

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FEATURES OF GEOPHYSICAL COMPOSITE ANOMALIES AND ORE RESOURCES IN YIHUANG AREA, JIANGXI PROVINCE
WANG Wei-Beng, FANG Ying-Yao, TUN Cheng-Beng
Geophysical and Geochemical Exploration    2010, 34 (5): 573-578.  
Abstract3061)      PDF (2717KB)(2226)      

According to the data obtained from air-borne electromagnetic and magnetic survey and

ground two-frequency IP and magnetic survey, this paper discusses the relationship between the

features of air-borne and ground geophysical composite anomalies and the ore resource distribution.

On the basis of an integrated analysis, geophysical composite anomaly criteria in search for iron, zinc

and lead deposits were established, and 12 important ore-prospecting targets were delineated, which

provides very important clues for finding iron, zinc, lead and some other ore resources.

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RESEARCH AND APPLICATION ON NUMERICAL INTEGRATIONOF HANKEL TRANSFORMS BY DIGITAL FILTERING
ZHANG Wei, WANG Xu-Ben, QIN Qing-Yan
Geophysical and Geochemical Exploration    2010, 34 (6): 753-755.  
Abstract3715)      PDF (363KB)(2190)      

 Numerical integration of Hankel transforms is effective tools for EM Sounding 's forward numerical simulation, this paper made out formula derivation of numerical integration of Hankel transforms by digital filtering, and use digital coefficients to do numerical compute which was put forward by Guptasama and Singh,finally contrasted to theoretical resolve expression and analyzed this algorithm's error distribution. The results show that the calculation of this algorithm continuously approximate its theoretical solution, it has no oscillation, high precision and great practical value in the numerical simulation study.

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PARAMETER SELECTION IN VIBROSEIS SEISMIC EXPLORATION
XUE Hai-Fei, DONG Shou-Hua, TAO Wen-Peng
Geophysical and Geochemical Exploration    2010, 34 (2): 185-190.  
Abstract3491)      PDF (3477KB)(2178)      

 Vibroseis exploration, as an important method of seismic exploration, has become increasingly valued by geologists. During the field work, different geological conditions need different parameters, and the choice of suitable excitation parameters has become a very important problem. This paper mainly introduces six kinds of parameters, namely numbers of controlled seismic source, scanning bandwidth, vibration period, scanning length, scanning slopes, and vibration rate. The influence of these parameters on the quality of seismic records was studied in detail, and the simulation of the proper parameters was performed in Jiulishan area to enhance the resolution of vibroseis exploration and improve the signaltonoise ratio of seismic records.

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Characteristics of gravity and magnetic fields in Ordos Basin and their geological significance
Bing LI, Yan-Bing SONG, Lei SHI, Qi WANG, Jiu-Ming JIANG, Jiu-Qiang JIN, De-Wen ZHOU, Ming XU, Gang-Yi XIAO, Min-Ying XIE
Geophysical and Geochemical Exploration    2019, 43 (4): 767-777.   DOI: 10.11720/wtyht.2019.1391
Abstract596)   HTML3)    PDF (3147KB)(2164)      

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.

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THE UTILIZATION OF SURFER TO CONDUCT THE DRAWING OF PROFILE-PLAN
SUN Zhong-ren, ZHAO Dong-liang
Geophysical and Geochemical Exploration    2006, 30 (2): 172-174.  
Abstract3541)      PDF (572KB)(2129)      

This paper has put forward the idea of utilizing Surfer to draw the initial data profile-plan. The programme compiled can realize the construction of Bln file. The profile-plans for regular net and irregular net have been constructed, and the results are satisfactory.

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MIGRATION VELOCITY ANALYSIS AND MIGRATION IMAGING RESEARCH
YE Jing-Yan, YAO YA-Lin, WANG Yan-Qun, LI Qing
Geophysical and Geochemical Exploration    2009, 33 (6): 674-677.  
Abstract2813)      PDF (1927KB)(2119)      

Migration velocity analysis and migration imaging constitute two important parts in seismic data processing. At

present, time migration has become mature, and depth migration is getting more and more perfect. The common method for time

domain migration imaging is pre-stack time migration. By adopting stacking velocity analysis along the layer, exact layer

stacking velocity can be obtained. Through dip correction, pre-stack time migration and CRP de-migration velocity analysis, the

velocity is optimized step by step, and then a desired RMS velocity field that is up to the geological rule is acquired. In

addition, the method for building the accurate migration velocity field is summed up through the study of the depth migration

method. A new seismic data processing flow in combination of Kirchhoff arithmetic based on ray tracing and wave equation

arithmetic based on wave field extrapolation is presented. As a result, migration velocity analysis and migration imaging are

considerably improved.

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THE AUTOMATIC FORMATION OF THE SUFFER SOFTWARECONTOUR LEVEL FILE BASED ON AREA STATISTICS
REN Lei, CHEN Hua-Gen
Geophysical and Geochemical Exploration    2009, 33 (5): 595-598.  
Abstract3639)      PDF (830KB)(2114)      

The implied contour level and color scheme in Surfer software fail to express the subtle difference of DEM and the effect

of color solid. In addition, the artificial setting of the levels and color values are timeconsuming and laborious, and the

results are sometimes not perfect. With the consideration of contour level and color scheme and on the basis of Surfer platform

automation technology, this paper presents a program that can automatically generate a level file with different intervals and

different colors, thus resulting in satisfactory effect and efficiency.

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ABUNDANCE OF CHEMICAL ELEMENTS OF SOILS IN CHINA AND SUPERGENESIS GEOCHEMISTRY CHARACTERISTICS
Yan Mingcai, Gu Tiexin, Chi Qinghua, Wang Chunshu
Geophysical and Geochemical Exploration    1997, 21 (3): 161-167.  
Abstract2600)      PDF (2180KB)(2096)      

On the basis of accurate analysis of 154 composite soil samples collected from various landscape in China and other reference information, abundance of 79 elements and composition of soils in China have been given, chemical composition of soils under the influence of matrix rock and supergenesis geochemistry condition have been studied preliminarily.

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THE INVERSED PROBLEM IN GRAVITY AND MAGNETICEXPLORATION: A REVIEW
Zeng Hualin
Geophysical and Geochemical Exploration    1990, 14 (3): 182-190.  
Abstract2029)      PDF (737KB)(2071)      

On the basis of mote than230 English and Russian papers or monographsissued in the last 30 years as well as nearly 50 Chinese articles published overthe past 10 years on the inversed problem in g avity and magnetic explora-tion, combined with his practice in the study of the inversed problem, the all-thor expounds the inversed methods in gravity and magnetic exploration cur-rently used both at home and abroad, briefs the readers about the researchsituation in China and foreign countries, and makes a detailed review on achi-evements gained in China in comparison with the research levels abroad.Final-ly, suggestions are put forward concerning some subjects which are worthnoticing in future research work.

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WAVE FIELD SEPARATION NUMERICAL MODELING OF SECOND ORDER ELASTIC WAVE EQUATION BY HIGH-PRECISIONSTAGGEREDGRID FINITE DIFFERENCE SCHEME
CHEN Ke-Yang, YANG Wei, LIU Hong-Lin, WU Qing-Ling
Geophysical and Geochemical Exploration    2009, 33 (6): 700-703.  
Abstract3162)      PDF (1060KB)(2051)      

This paper proposes an equivalent second order elastic wave equation to solve the problem of being unable to completely

separate the coupled P and S wave by full elastic wave equation. Through solving this equivalent wave equation by high-order

staggeredgrid finite difference scheme together with Flux Correction Technology (FCT) and separating wave fields of the

isotropic model and layered model, the authors accurately obtained the hybrid wave field and completely separated fields of pure

P wave and pure S wave fields. An analysis of the numerical results shows that the method is effective and reliable in isotropic

media, and there exists abundant energy transform information in separated pure P and pure S wave field. The result of the study

is of significance in understanding the propagating law and the elastic wave theory in the complex wave field.

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PML ABSORBING BOUNDARY CONDITION FORNUMERICAL MODELING OF RAYLEIGH WAVE
XIONG Zhang-Qiang, TANG Sheng-Song, ZHANG Da-Zhou
Geophysical and Geochemical Exploration    2009, 33 (4): 453-457.  
Abstract3435)      PDF (2025KB)(1990)      

The algorithm of the finite difference oforder velocitystress staggered grids has been built, which is

suitable for the perfectly matched layer (PML) absorbing boundary for elastic media. Meanwhile, the construction of the

PML absorbing boundary condition and the realization of the finitedifference algorithm are discussed in detail. Wave

field modeling calculations show that, compared with the conventional decaying exponential absorbing boundary and non

absorbing boundary, the PML absorbing boundary can perform absorption much more clearly and absorb the boundary

reflection from various angles, whose absorptivity (the ratio of absorption energy to unabsorbable energy) can reach

99.99%. The PML absorbing boundary can well eliminate the periodic folding effects, which makes the calculation of the

wave field characteristics very distinct, and the Rayleigh wave can be clearly shown in the waveform record.

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PRESENT RESEARCH SITUTATION AND DEVELOPMENT TREND OF AIRBORNE GRAVITY GRADIOMETER
SHU Qing, ZHOU Jian-xin, YIN Hang
Geophysical and Geochemical Exploration    2007, 31 (6): 485-488.  
Abstract2192)      PDF (690KB)(1990)      

The development of the gravity gradiometer is described simply in this paper, and the measuring principle and development experience of the rotating accelerometer gravity gradiometer are emphatically discussed. On the basis of researches on the existing airborne gravity gradiometer, the prospects of the airborne gravity gradiometer are also presented.

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YANG Li-De
Geophysical and Geochemical Exploration    2009, 33 (6): 741-742.  
Abstract2194)      PDF (240KB)(1983)      
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SOME PROBLEMS CONCERNING THE CONVERSIONOF MAPS BETWEEN SURFER AND MAPGIS
QIN Lin-Jiang
Geophysical and Geochemical Exploration    2010, 34 (5): 677-680.  
Abstract5464)      PDF (865KB)(1982)      

With the extensive adoption of computer technology in geology and geophysics, computer graphics becomes more and more important. For the purpose of improving quality and efficiency, several software should be combined in practical work. In this paper, some basic characteristics of Surfer and MapGIS are discussed, and their application in geological field is described from the angle of geological mapping, thus drawing forth the necessity of the conversion between Surfer and MapGIS. The general method and steps for the conversion of maps between Surfer and MapGIS are presented in detail, and several problems concerning the conversion and corresponding solutions are emphatically discussed.

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THE PROGRESS AND PROSPECT OF THE ELECTRICAL RESISTIVITY IMAGING SURVEY
YAN Jia-yong, MENG Gui-xiang, LV Qing-tian, ZHANG Kun, CHEN Xiang-bin
Geophysical and Geochemical Exploration    2012, 36 (4): 576-584.   DOI: 10.11720/wtyht.2012.4.13
Abstract4913)      PDF (1427KB)(1978)      
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.
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Geophysical and Geochemical Exploration    1982, 6 (3): 154-156.  
Abstract1153)      PDF (190KB)(1972)      
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THE COMPARATIVE STUDY AND APPLICATION OF SEVERALTIMEFREQUENCY ANALYSIS METHODS IN THE COAL FIELD
HU Ming-Shun, PAN Dong-Ming, XU Hong-Li, ZHAO Li-Gui
Geophysical and Geochemical Exploration    2009, 33 (6): 691-695.  
Abstract2499)      PDF (2110KB)(1944)      

In the light of the characteristic time-frequency properties of different time-frequency analysis methods, it is

important to select an optimal time-frequency analysis method for high precision seismic exploration in the coal field on the

basis of comparing and studying these methods. Aimed at probing into STFT, Wavelet Transform, S-Transform, Choi-Williams

Distribution, Wigner-Ville Distribution and its improved methods, this paper studied advantages and disadvantages of every method

through numerical simulation in time resolution, frequency resolution and interference. The First Break Picking and Separate

Frequency Display for Collapse Column interpretation were realized by SPWVD and S-Transform, with a good result obtained.

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THE APPLICATION OF SEISMIC REFRACTION WAVE METHOD ANDHIGHDENSITY RESISTIVITY METHOD TO TUNNEL INVESTIGATION
ZENG Guo, CUI De-Hai, LIU Jie, LI Kai
Geophysical and Geochemical Exploration    2009, 33 (5): 608-612.  
Abstract3219)      PDF (1351KB)(1943)      

 Basic principles and techniques for the shallow seismic refraction wave method and the highdensity resistivity method

are described in this paper in combination with engineering practice to explain the results of the refraction wave method and the

high-density resistivity method in railroad and highway tunnel exploration. The application effects of the combination of these two

methods in detecting positions, sizes, natures and characteristics of such harmful geological bodies as concealed faults and shatter

zones are also discussed. Some measures for improving the investigation accuracy of these two methods are put forward.

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The application of the integrated geophysical-geochemical method to the Yiliu polymetallic ore district in northern Guangdong Province
WU Wei-Guo
Geophysical and Geochemical Exploration    2015, 39 (6): 1097-1103.   DOI: 10.11720/wtyht.2015.6.01
Abstract1134)   HTML152)    PDF (11771KB)(1918)      

The main minerals in the Yiliu polymetallic ore district are mainly As, Sb, Pb, Zn, Ag, W, Sn, Nb and Ta, the deposit types and the ore-controlling factors are complex and diverse. Recently, by using 1:50000 geochemical stream sediment survey, geochemical soil survey and CSAMT method in this ore district, supergene distribution of elements were found, and many integrated anomalies were delineated. A comprehensive evaluation of all kinds of anomalies shows that the F3 fault has features of ore-passage structure and ore-storage structure, and the area sandwiched between F2 and F3 fault are favorable ore-forming place, whereas the depression parts of biotite granite which have high resistance and multiple sets of fracture intersections are most favorable places for mineralization.

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THE EXPLORATION EFFICIENCY OF THE TERRATEM ELECTROMAGNETIC SYSTEM,IN THE CONCEAL IRON DEPOSIT,HENAN PROVINCE
LI Shui-Peng, ZHANG Tong-Zhong, JING Jin-Ming
Geophysical and Geochemical Exploration    2009, 33 (4): 424-426.  
Abstract2773)      PDF (608KB)(1894)      

This thesis supply a profile about performance of TerraTEM system and the  distinguishing feature of TEM. By exploring

work on two conceal iron deposit in HeNan province and analyzing. the abnormal value of the TEM system.combining with drill

drawing,The writer prove that the TEM can take a obvious effect on exploring iron mineral.

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THE APPLICATION OF THE RAYLEIGH SURFACE WAVE TECHNIQUE TO RAILWAYS
LI Hai
Geophysical and Geochemical Exploration    2002, 26 (2): 160-162.  
Abstract1903)      PDF (480KB)(1865)      

With practical examples, this paper deals with the basic principle and technique of the Rayleigh surface wave exploration, the technology for its application to railways, the data acquisition, processing and interpretation, and the calculation method for converting the velocity of the Rayleigh surface wave to the bearing capacity. The reliability of applying this technique to railways is also pointed out.

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A COMPARISON OF SEVERAL THRESHOLD DETERMINATION METHODS IN GEOCHEMICAL DATA PROCESSING: A CASE STUDY OF STREAM SEDIMENTS IN CHABAQI AREA OF INNER MONGOLIA
DAI Hui-Min, GONG Chuan-Dong, BAO Qing-Zhong, SUN Zhong-Ren, YOU Hong-Liang, JIN Xin, GAO Fei
Geophysical and Geochemical Exploration    2010, 34 (6): 782-786.  
Abstract3878)      PDF (1006KB)(1854)      

The authors made statistic calculation of stream sediment data using such means as traditional statistics, robust estimation,cumulative percentage of 85% and multifractal statistical method in Chabaqi area and compared the thresholds obtained by the four methods. The thresholds of the same elements obtained by the four methods are obviously different from each other. The thresholds calculated by the cumulative percentage statistics are lowest except for lead, and the thresholds calculated by the other three methods fail to show obvious regularity.The results are closely related to the distribution characteristics of the geochemical data and the statistical methods used. Comparing the anomaly characteristics with the geological characteristics, the authors have found that, although weak and gentle geochemical anomalies will be mostly detected by cumulative percentage of 85%, the larger anomaly areas will bring difficulties to anomaly inspection in the field. It is therefore thought that the thresholds obtained by multifractal statistical method are suitable for the study area. A comparative study of the thresholds has led the authors to believe that the reasonable method must be combined with the actual geological conditions and based on a thorough study of the geological background of the study area.

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CHAMP, GRACE AND GOCE: THREE SATELLITES FOR SENSING AND/OR MEASURING THE EARTH'S GRAVITY FIELD
ZHANG Chang-da
Geophysical and Geochemical Exploration    2005, 29 (5): 377-382.  
Abstract2109)      PDF (749KB)(1853)      

In this paper, the working principle of three satellites (CHAMP, GRACE and GOCE) has been described, and the important geopotential models and the newest geopotential models (EIGEN-CG01C, GGM02) have been introduced.

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A TENTATIVE DISCUSSION ON THE RESOLUTION OF THE GROUND-PENETRATING RADAR
YUAN Ming-de
Geophysical and Geochemical Exploration    2003, 27 (1): 28-32.  
Abstract2517)      PDF (512KB)(1847)      

In the light of the pulse width of the radar wave, this paper deals with the difference and the relationship between the vertical resolution and the transverse resolution of the ground-penetrating radar, indicates the influence of the noise upon the resolution and, with practical examples, points out that the digital handling of the signal can greatly improve the resolution of the radar.

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Gravity field characteristics and boundaries of geotectonic units on the northeastern margin of the Linyi uplift, Shandong Province
WANG Run-Sheng, WU Bin, ZHANG Hai-Rui, YU Jia-Bin, DONG Yan-Long, GUO Guo-Qiang, KANG Yi-Ming
Geophysical and Geochemical Exploration    2023, 47 (2): 279-289.   DOI: 10.11720/wtyht.2023.1144
Abstract835)   HTML25)    PDF (9602KB)(536)      

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.

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Progress and prospect of gravity and magnetic techniques for hydrocarbon exploration in China
LIU Yun-Xiang, SI Hua-Lu, QIAO Hai-Yan, LIU Bai-Chuan
Geophysical and Geochemical Exploration    2023, 47 (3): 563-574.   DOI: 10.11720/wtyht.2023.1484
Abstract523)   HTML344)    PDF (3583KB)(379)      

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.

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Application of a comprehensive geophysical exploration methods in the exploration of geothermal resources in Yueliangwan, Binhai County
WANG Jun-Cheng, ZHAO Zhen-Guo, GAO Shi-Yin, LUO Chuan-Gen, LI Lin, XU Ming-Zuan, LI Yong, YUAN Guo-Jing
Geophysical and Geochemical Exploration    2023, 47 (2): 321-330.   DOI: 10.11720/wtyht.2023.1205
Abstract311)   HTML10)    PDF (6825KB)(397)      

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.

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Seismic characteristics of the paleo-underground river system in Ordovician carbonate paleo-buried hills in the western Lungu area
DAN Guang-Jian, ZHOU Cheng-Gang, LIU Yun-Hong, LI Xiang-Wen, ZHANG Liang-Liang, ZHANG Ming, WANG Chun-Yang
Geophysical and Geochemical Exploration    2023, 47 (2): 290-299.   DOI: 10.11720/wtyht.2023.1052
Abstract306)   HTML16)    PDF (8684KB)(245)      

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

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Research on edge depth inversion of 2D geological body based on gravity and magnetic field
WANG Wan-Yin, LUO Xin-Gang
Geophysical and Geochemical Exploration    2023, 47 (3): 547-562.   DOI: 10.11720/wtyht.2023.1464
Abstract291)   HTML383)    PDF (8058KB)(444)      

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.

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Application of shallow drilling geochemical survey to shallow overburden area at the peripheral of Nanjinshan gold mine in Beishan, Gansu Province
WEI Zhen-Hong, ZHAO Ji-Chang, QU Zheng-Gang, FAN Xin-Xiang, LI Sheng-Ye, CHEN Hai-Yun, LIU Yong-Biao, YANG Zhen-Xi
Geophysical and Geochemical Exploration    2023, 47 (2): 331-342.   DOI: 10.11720/wtyht.2023.1192
Abstract258)   HTML3)    PDF (8368KB)(243)      

The Nanjinshan gold deposit is a typical epithermal deposit in Beishan metallogenic belt, which extends in a N-E direction to the peripheral shallow cover zone. In order to further achieve the breakthrough of prospecting in the peripheral shallow overburden area, the pilot work of motorized shallow drilling geochemical survey carried out. Based on the nature and thickness of the overburden, 126 motorized shallow drilling geochemical exploration samples are taken in the shallow overburden area using the vehicle mounted air positive circulation and three wing alloy scraper drilling or pneumatic DTH hammer drilling technology, with a sampling density of 16.8 points per square kilometer. The shallow drilling geochemical exploration methods and technologies in the shallow overburden area are further discussed, including the selection of drilling technology, sampling network, sampling materials, sample collection, etc. Soil survey was carried out in sporadic bedrock areas, and 278 samples were collected, and the sampling density was 48.77 points per square kilometer. Fifteen elements including Au, Ag, as, Sb, Hg, Cu, Pb, Zn, W, Sn, Mo, Bi, Cr, Co and Ni were analyzed. Through the above work, seven comprehensive geochemical anomalies were delineated. After anomaly investigation, six gold deposit bodies and one silver deposit body were found in the new circle in the bedrock area, and two concealed gold deposits and one silver deposit body were found in the shallow overburden area. The results show that shallow drilling geochemical survey is effective and feasible in the shallow overburden area of arid Gobi landscape in Beishan.

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Application of integrated geophysical methods in deep ore prospecting of Laochang polymetallic mining area in Lancang, Yunnan
YOU Yue-Xin, DENG Ju-Zhi, CHEN Hui, YU Hui, GAO Ke-Ning
Geophysical and Geochemical Exploration    2023, 47 (3): 638-647.   DOI: 10.11720/wtyht.2023.1578
Abstract249)   HTML20)    PDF (6931KB)(368)      

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

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Distribution of microorganisms in the typical geothermal field environment and its significance for geothermal exploration
ZHENG Xu-Ying, XU Ke-Wei, GU Lei, WANG Guo-Jian, LI Guang-Zhi, GUO Jia-Qi, ZOU Yu, BORJIGIN Tenger
Geophysical and Geochemical Exploration    2023, 47 (5): 1127-1136.   DOI: 10.11720/wtyht.2023.1151
Abstract238)   HTML17)    PDF (4903KB)(187)      

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.

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Application of the opposing coils transient electromagnetic method in investigation of mined-out areas of a gold deposit
REN Xi-Rong, LI Xin, ZHOU Zhi-Jie
Geophysical and Geochemical Exploration    2023, 47 (2): 540-546.   DOI: 10.11720/wtyht.2023.1225
Abstract235)   HTML6)    PDF (5274KB)(354)      

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.

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Fluid inclusions and formation mechanisms of the Dongjianian silver deposit in Lingbao City, Henan Province, China
LIU Chang, ZHANG Can-Hui, ZHANG Xin, ZONG Rui
Geophysical and Geochemical Exploration    2023, 47 (2): 343-352.   DOI: 10.11720/wtyht.2023.1095
Abstract226)   HTML3)    PDF (7090KB)(157)      

The Dongjianian silver deposit, located on the southern margin of the Xiaoqinling Mountains, is controlled by the secondary structures of the Xiaohe fault and is the first large precious metal deposit discovered in the southern belt of the Xiaoqinling Mountains. This deposit has three hydrothermal metallogenic stages, namely the quartz-pyrite metallogenic stage (Ⅰ), the dominant quartz-polymetallic sulfide metallogenic stage (Ⅱ), and the quartz-carbonate metallogenic stage (Ⅲ). Three types of inclusions have primarily developed in the ore bodies, namely gas-liquid two-phase inclusions (W-type), CO2-bearing inclusions (C-type), and pure CO2 inclusions (PC-type). Stage I primarily witnessed the development of C- and W-type inclusions and a small quantity of PC-type inclusions, and stage II mainly saw the development of W-type inclusions and a small amount of C-type inclusions. The quartz fluid inclusions formed in stages I and II have homogenization temperature ranges of 151~270 ℃ and 126~240 ℃, respectively, which exhibits a downward trend. Their salinity varies slightly in the ranges of 3.8%~22.42% NaCleqv and 4.16%~20.48% NaCleqv, respectively, indicating a low-salinity environment. Their CO2 content transformed from enrichment into deficiency. The metallogenic pressure and depth were estimated to be 22.08~76.6 MPa and 3.77~7.13 km, respectively. Therefore, the Dongjianian silver deposit is a low-salinity medium- to low-temperature meso-epithermal silver deposit.

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A review of the research progress and application status of seismic full waveform inversion
CHEN Zi-Long, WANG Hai-Yan, GUO Hua, WANG Guang-Wen, ZHAO Yu-Lian
Geophysical and Geochemical Exploration    2023, 47 (3): 628-637.   DOI: 10.11720/wtyht.2023.1469
Abstract215)   HTML14)    PDF (3181KB)(255)      

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.

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Surface geochemical anomalies of concealed volcanic hydrothermal uranium deposit in northern Hebei
ZHANG Yang-Yang, CHEN Yue-Long, LI Da-Peng, KANG Huan, FANG Ming-Liang, XU Yun-Liang
Geophysical and Geochemical Exploration    2023, 47 (2): 300-308.   DOI: 10.11720/wtyht.2023.2695
Abstract212)   HTML7)    PDF (2883KB)(237)      

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

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Karst exploration in urban complex environments based on electrical resistivity tomography: A case study of Beihuan New Village in Guigang City
QIN Jian-Wen, JIANG Xiao-Teng, XIE Gui-Cheng, SUN Han-Wu, HE Liu, SUN Huai-Feng
Geophysical and Geochemical Exploration    2023, 47 (2): 530-539.   DOI: 10.11720/wtyht.2023.1253
Abstract211)   HTML6)    PDF (10783KB)(316)      

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

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Aerogeophysical anomalies and prospecting direction in the Fengtai ore concentration area
XU Xue-Yi, XIONG Sheng-Qing, YANG Xue, GAO Wei-Hong, FAN Zheng-Guo, JIA Zhi-Ye
Geophysical and Geochemical Exploration    2023, 47 (5): 1157-1168.   DOI: 10.11720/wtyht.2023.0068
Abstract194)   HTML9)    PDF (14675KB)(186)      

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.

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A real-time correction method based on time-varying zero offset for the equivalent sampling of ground penetrating radars
FENG Wen-Ya, CHENG Dan-Dan, WANG Cheng-Hao, CHENG Xing
Geophysical and Geochemical Exploration    2023, 47 (2): 372-376.   DOI: 10.11720/wtyht.2023.2657
Abstract182)   HTML3)    PDF (1781KB)(190)      

Echoes can be distorted due to the temperature drift of the ground penetrating radar (GPR) system,the low-pass effect of lossy media,and the decline in the coupling between the antenna and the ground.The mixing of effective radar echoes and zero-offset components makes it difficult to detect weak signals.The conventional front-end correction and post-processing methods,which aim to improve the transmission efficiency and remove the clutter noise,fail to improve the signal-to-noise ratio (SNR) and sensitivity of the system.To overcome these obstacles,this study improved the equivalent sampling circuit using a real-time correction method based on time-varying zero offset.Specifically,the zero-offset coefficient of each sampling was controlled separately and was updated in real time on each sampling.No DC and low-frequency components were sent into the subsequent programmable amplifier along with effective signals,ensuring the correct acquisition of weak signals and the dynamic range of the system.Experiments have proved the validity and feasibility of this method,which has been applied to a new type of digital GPR product.

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The anomalies determined using a soil geochemical survey and prospecting model of the Matou gold deposit in Sichuan Province
LI Jun-Jun, WEI Yu, ZHANG Qing-Song, WANG Wei-Hua, LIU Wei, XIANG Liang
Geophysical and Geochemical Exploration    2023, 47 (2): 309-320.   DOI: 10.11720/wtyht.2023.2456
Abstract181)   HTML7)    PDF (4740KB)(275)      

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

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Application of a comprehensive geophysical exploration methods to water exploration in magmatic rock mountainous areas with water shortage in Jiaodong Peninsula
LIU Chun-Wei, WANG Chong, HU Cai-Ping, SHI Yan-Fang, YANG Xiao-Hui, LIU Xiao-Tian, HAN Yu-Ying, LI Bo
Geophysical and Geochemical Exploration    2023, 47 (2): 512-522.   DOI: 10.11720/wtyht.2023.1319
Abstract172)   HTML3)    PDF (11619KB)(299)      

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

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An application study of the comprehensive geophysical prospecting method in the exploration of mineral water: A case study of the Langqiao area, Jing County
ZHANG Zhi, XU Hong-Miao, QIAN Jia-Zhong, XIE Jie, CHEN Hao-Long, ZHU Zi-Xang
Geophysical and Geochemical Exploration    2023, 47 (3): 690-699.   DOI: 10.11720/wtyht.2023.1443
Abstract168)   HTML15)    PDF (7344KB)(276)      

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

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Gravity survey and audio magnetotellurics-based insights into the deep structures and geothermal resource potential of the Rucheng Basin
ZHAO Bao-Feng, WANG Qi-Nian, GUO Xin, GUAN Da-Wei, CHEN Tong-Gang, FANG Wen
Geophysical and Geochemical Exploration    2023, 47 (5): 1147-1156.   DOI: 10.11720/wtyht.2023.1449
Abstract168)   HTML8)    PDF (8018KB)(227)      

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.

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Application of opposing-coils transient electromagnetics in the detection of landslide deposits
LUO Shu, CHEN Zheng-Yu, LAN Yu-Cheng, LIU Yang-Fei, DUAN Ming-Jie
Geophysical and Geochemical Exploration    2023, 47 (2): 523-529.   DOI: 10.11720/wtyht.2023.1152
Abstract166)   HTML6)    PDF (5088KB)(324)      

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

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Identification of footwalls and roofs of coal seams in underground coal mines using borehole radar
LIU Si-Xin, SHI Wei, SONG Zi-Hao, CHEN Chun-Lin, DAI Zheng
Geophysical and Geochemical Exploration    2023, 47 (2): 365-371.   DOI: 10.11720/wtyht.2023.1392
Abstract161)   HTML16)    PDF (3287KB)(171)      

In coal mining, the accurate determination of the locations of the footwalls and roofs of coal seams and the identification of the geological structures that threaten the safety of excavation are important measures to ensure safe coal mining. This study proposed a technique for detecting the footwalls and roofs of coal seams, which consisted of a mining face-based borehole radar detection method for underground coal mines and a data processing process. Then, this study applied this technique to the Xinyuan coal mine. Specifically, radar profiles were denoised and enhanced through the correction of zero-moment point, DC elimination, band-pass filtering, direct wave removal, and gain processing of measured borehole radar data of boreholes along a mining face of the Xinyuan coal mine. Then, the locations of the roofs and footwalls of coal seams in the underground coal mines were identified and presented through a series of processing and interpretation, including velocity pickup, reflective surface extraction, and diffraction stack migration, as well as time-depth conversion, flipping, splicing, and the correction of borehole trajectories. The technique proposed in this study serves as an effective means for the safe operation of coal mines and thus is of value for promotion.

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Rapid determination of soil cation exchange capacity using a cation exchange capacity pretreatment system and a Kjeldahl apparatus
HU Meng-Ying, ZHANG Peng-Peng, XU Jin-Li, LIU Bin, ZHANG Ling-Huo, DU Xue-Miao, BAI Jin-Feng
Geophysical and Geochemical Exploration    2023, 47 (2): 458-463.   DOI: 10.11720/wtyht.2023.1133
Abstract159)   HTML2)    PDF (636KB)(137)      

The soil cation exchange capacity (CEC) refers to the total amount of various cations that can be absorbed by soil colloids. It is an important measure of the buffering capacity and fertilizer retention capacity of soil and is also an indicator that must be analyzed in soil environment assessment. The conventional ammonium acetate exchange method described in Chinese forestry standard LY/T 1243—1999 has been widely used in soil and agrochemical laboratories in China due to its high stability, buffering capacity, and repeatability. However, when applied to the batch analysis of soil, this conventional method is time-consuming and has other shortcomings such as cumbersome steps and low efficiency. Based on previous studies, this study optimized the conventional ammonium acetate exchange method in three steps, namely centrifugation, distillation, and titration. Specifically, samples were treated with displacement using mixed EDTA and ammonium acetate solution and cleaning with ethanol using the CEC pretreatment system. Then, the ammonium ions displaced were determined using an automatic Kjeldahl apparatus, followed by the calculation of the CEC. This study discussed the effects of the stirring time of ammonium acetate, ethanol dosage, and distillation time in the Kjeldahl apparatus on CEC determined. On this basis, this study comprehensively established and optimized the method for determining the CEC in soil using the CEC pretreatment system and the Kjeldahl apparatus. As shown by the experimental results, under the optimal conditions of displacement time, ethanol dosage, and distillation time, the optimized method determined the CEC of a batch of samples (100) in only 8 h, which was shortened by nearly 85% compared with the conventional method, thus greatly improving the efficiency. As verified using the certified reference material for the chemical composition of first-grade soil, the determined CEC values agreed with the certified values, with relative standard deviations (n = 6) of all less than 2%. The optimized method is characterized by high efficiency and simple operation and can greatly reduce possible errors caused by manual operation and improve the accuracy of results. Therefore, it is applicable to the bulk determination of soil CEC.

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Application of the opposing-coils transient electromagnetic method in urban geological surveys
HE Sheng, WANG Wan-Ping, DONG Gao-Feng, NAN Xiu-Jia, WEI Feng-Feng, BAI Yong-Yong
Geophysical and Geochemical Exploration    2023, 47 (5): 1379-1386.   DOI: 10.11720/wtyht.2023.1554
Abstract158)   HTML4)    PDF (5856KB)(261)      

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.

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Geochemical characteristics and Cr metallogenic potential evaluation of the middle section of the northern margin of the Qaidam Basin
CHEN Xi, AN Zhao, ZHANG Wen-Quan, XU Yun-Fu, MA Ying, SHI Lian-Chang, TAO Zhi-Hua
Geophysical and Geochemical Exploration    2023, 47 (2): 353-364.   DOI: 10.11720/wtyht.2023.2540
Abstract157)   HTML3)    PDF (8534KB)(172)      

This study extracted 59238 pieces of original data on different scales (1:50000 stream sediment surveys and 1:25000 geochemical surveys) of the middle section of the northern margin of the Qaidam Basin. Based on these data, this study conducted the superposition analysis of mathematical index statistics and multivariate statistics, aiming to discover the element association relationship and determine the major metallogenic elements in the region and provide basic support for subsequent mineral work. According to the statistics, the mathematical indexes of Au, W, and Cr in the study area show great metallogenic potential. Combined with the multivariate statistical analysis and existent metallogenic facts, the authors of this study believed that the study area has the great potential for the prospecting of chromium deposits associated with ultramafic rocks besides tectonic altered rock-type and hydrothermal gold deposits. Owing to the relatively high overall background value of local chromium (Cr) element, the traditional method using X+2σ (129×10-6) or the cumulative frequency 85% (142.9×10-6) used to delineate the anomaly threshold cannot meet the requirement for delineating local anomalies in the study area. Therefore, this study improved the anomaly threshold using the 1/4 concentration grading value (234×10-6). As a result, many anomalies exhibiting significant zonal distribution in the concentration center were delineated, and most weak anomalies were eliminated. Based on the geological, geophysical, and geochemical results, this study inferred zones favorable for the further exploration of chromium deposits and determined four favorable metallogenic zones and five prospecting areas.

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Spatial distribution patterns of concealed plutons in the western Zhen’an area based on gravity anomalies
ZHANG Jin-Ai, YANG Yuan, ZHANG Lin
Geophysical and Geochemical Exploration    2023, 47 (3): 618-627.   DOI: 10.11720/wtyht.2023.1465
Abstract157)   HTML11)    PDF (8220KB)(240)      

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

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An experimental investigation of the CO2 and SO2 gas geochemical survey method for mineral exploration in forested areas
WAN Wei, WANG Ming-Qi, CHENG Zhi-Zhong, FAN Hui-Hu, ZUO Li-Bo, LI Jun-Hui
Geophysical and Geochemical Exploration    2023, 47 (5): 1137-1146.   DOI: 10.11720/wtyht.2023.1615
Abstract155)   HTML7)    PDF (4627KB)(110)      

This study aims to explore the feasibility of the carbon dioxide (CO2) and sulfur dioxide (SO2) gas geochemical survey method for mineral exploration in forested areas. Based on the newly designed gas rapid analysis instrument, this study conducted an experimental investigation of the method in the forested Jiapigou gold concentration area, Jilin Province. The results show that significant CO2 and SO2 anomalies were observed above the concealed ore bodies and structures. In the forested area, the CO2 and SO2 gas geochemical survey method reflected the fault structures and effectively indicated the deep concealed gold deposit. This method holds critical significance for the breakthrough of prospecting technology in China's covered areas.

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Application of seismic frequency-divided iterative inversion in the prediction of thinly laminated channel sand bodies
REN Xian-Jun, LI Zhong, MA Ying-Long, DONG Ping, TIAN Xing-Da
Geophysical and Geochemical Exploration    2023, 47 (2): 420-428.   DOI: 10.11720/wtyht.2023.1175
Abstract152)   HTML2)    PDF (6781KB)(171)      

The channel sand reservoirs in the Longfengshan area have the characteristics of typical lithologic reservoirs.This area has thin sand bodies,narrow channels,and strong vertical and horizontal lithologic heterogeneity.It is difficult to predict the reservoirs at a depth of 5 m or greater.The frequency-divided iterative inversion can fully utilize the full-frequency band seismic data and transmit the seismic information of different frequency bands and scales step by step,thus optimizing the inversion results.In this study,the seismic signal frequency bands were divided using the matching pursuit algorithm to obtain seismic data volumes of different scales.Under the constraints of log data,the low-frequency,large-scale inversion results were used as the initial model for the next-order frequency band inversion,and the inversion results.During the inversion,wavelets were adaptively selected using the correlation algorithm to enhance the inversion accuracy.Regularization parameters were adaptively selected based on the Bayesian theory to adjust the relationship between resolution and stability to achieve the optimal balance and avoid chaos in inversion.In 2019,gas reservoirs in subzones 1-2-6 and 1-2-8 of the Yingcheng Formation were encountered in the drilling of four wells in the Longfengshan area.This result is consistent with the inversion prediction results.Therefore,compared with conventional frequency division inversion,the method proposed in this study has the advantages of high inversion accuracy,coincidence with seismic information,and full application of frequency bands.This method can effectively improve the identification performance of thinly laminated channel sand bodies and guide the exploration and development of related lithologic reservoirs.

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The comprehensive evaluation of farmland soil environmental quality and suggestions on the development of agriculture with distinctive local features in Tumed Left Banner, Inner Mongolia
BAO Feng-Qin, CHENG Hang-Xin, YONG Sheng, YANG Yu-Liang, MA Zhi-Chao, ZHAO Li-Juan
Geophysical and Geochemical Exploration    2023, 47 (2): 487-495.   DOI: 10.11720/wtyht.2023.1044
Abstract150)   HTML1)    PDF (3162KB)(177)      

Land is an important basic resource for human survival and stable social and economic development, and cultivated land is an integral part of land resources. Ascertaining the quality of cultivated land is of great significance for the scientific and rational utilization of cultivated land and the sustainable development of green ecological agriculture. Using the methods for 1:50,000 geochemical survey and evaluation, this study conducted the quality evaluation and the classification of land in the study area based on the contents of beneficial nutrient elements and toxic and harmful elements in soils and analyzed the distribution and controlling factors of elements in soils. The results of this study are as follows. The soils in the study area consist mainly of alluvial-proluvial deposits from the Yellow River and are primarily used for agriculture and animal husbandry. The soils are not contaminated by heavy metals and are rich in nutrients, with the first- and second-grade excellent soils collectively accounting for 88.85%. Moreover, most soils in the study area have moderate selenium content. Therefore, it is recommended that selenium-rich land resources should be incorporated into the government land planning to develop agriculture with distinctive local features.

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Geochemical characteristics and prospecting potential of Jianchi Town, Shaanxi Province, China based on 1∶25,000 stream sediment survey
ZHANG Jia-Sheng, ZHOU Wei, LI Wei-Liang, QI Xiao-Peng, YANG Jie, WANG Lu
Geophysical and Geochemical Exploration    2023, 47 (3): 659-669.   DOI: 10.11720/wtyht.2023.1122
Abstract141)   HTML216)    PDF (6805KB)(221)      

Jianchi Town of Shaanxi Province is located in the Nanjiang foreland-superimposed basin on the northern margin of the Yangtze Plate. To determine the prospecting potential, this study conducted a 1∶25,000 stream sediment survey in the study area. Based on the testing results of 12 elements and compounds closely related to mineralization, namely K2O, Na2O, CaO, MgO, Cl, S, B, Rb, Cs, Li, Br, and I, this study analyzed the geochemical characteristics of these elements and compounds and determined that Li is the major metallogenic element, Li-B-Rb-Cs-K2O is the indicator element association for the prospecting of lithium deposits, and the spatial morphology of Li agrees with that of various geological bodies. By combining the metallogenic geological setting, this study delineated 18 integrated anomalies. Through the follow-up examination of the anomalies, multiple lithium ore bodies (mineralized points) were discovered, indicating that the study area has favorable metallogenic geological and geochemical conditions and great prospecting potential.

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Advancements in research on geochemical exploration methods and technologies for mineral resources in overburden areas
SUN Yue, ZHANG Zhen-Yu, FENG Bin, YANG Shao-Ping, WANG Zhi-Feng
Geophysical and Geochemical Exploration    2023, 47 (6): 1387-1399.   DOI: 10.11720/wtyht.2023.0109
Abstract139)   HTML8)    PDF (2899KB)(148)      

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.

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Speciation of selenium in the selenium-rich cultivated land in Linhe District, Bayannur City, Inner Mongolia and its influencing factors
LI Shi-Bao, YANG Li-Guo, XIONG Wan-Li, MA Zhi-Chao, YUAN Hong-Wei, DUAN Ji-Xue
Geophysical and Geochemical Exploration    2023, 47 (2): 477-486.   DOI: 10.11720/wtyht.2023.1010
Abstract137)   HTML1)    PDF (3596KB)(163)      

This study investigated the speciation of selenium in 51 surface soil samples from the selenium-rich cultivated land in Linhe District, Bayannur City, Inner Mongolia and explored the content and speciation of selenium and their influencing factors. The results showed that the surface soil in the study area had total selenium content of (0.19~0.48)×10-6, averaging 0.33×10-6, indicating a soil environment with moderate-high selenium content. Among the seven forms of selenium speciation, major forms include the residue, humic acid bound, and strong organic bound forms. The remaining forms, namely water-soluble, ion exchange, iron-manganese oxide bound, and carbonate bound forms accounted for only 13.67%. Water-soluble selenium consisted mainly of moderate-high water-soluble selenium (92.16%), with the absence of water-soluble selenium deficiency. The selenium content in each form was highly correlated with the total selenium content in the soil. The organic matter content, pH, Eh, and CEC had different effects on the distribution characteristics of selenium speciation.

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Predicting the geothermal resources of the Tangyu geothermal field in Meixian County, Shaanxi Province, based on soil radon measurement and the controlled source audio magnetotelluric method
XUE Dong-Xu, LIU Cheng, GUO Fa, WANG Jun, XU Duo-Xun, YANG Sheng-Fei, ZHANG Pei
Geophysical and Geochemical Exploration    2023, 47 (5): 1169-1178.   DOI: 10.11720/wtyht.2023.0010
Abstract137)   HTML9)    PDF (4345KB)(223)      

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.

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Post-stack P-wave impedance inversion based on spectral inversion
XING Wen-Jun, CAO Si-Yuan, CHEN Si-Yuan, SUN Yao-Guang
Geophysical and Geochemical Exploration    2023, 47 (2): 429-437.   DOI: 10.11720/wtyht.2023.1222
Abstract134)   HTML2)    PDF (7004KB)(201)      

Based on spectral inversion,this study proposed a p-wave impedance inversion algorithm for post-stack seismic data to improve inversion accuracy.Spectral inversion is widely used in high-resolution seismic inversion and the reflection coefficient inversion.Based on the odd-even decomposition of reflection coefficients,spectral inversion can reduce the tuning effect between thin layers and enhance the resolution of inverted data volumes.However,the calculation of p-wave impedance using reflection coefficients is ill-posed, and the step-by-step inversion of p-wave impedance tends to introduce a large cumulative error.Therefore,this study proposed a post-stack p-wave impedance inversion method based on spectral inversion.This method introduced the objective equation constrained by TV regularization and calculated the relative p-wave impedance using the iterative method.Then,the absolute p-wave impedance was determined through the frequency-domain fusion of the relative p-wave impedance and the pre-built low-frequency model.As demonstrated by the model and actual data,the method proposed in this study has a higher inversion resolution than the impedance inversion based on sparse-spike deconvolution and is more conducive to subsequent research such as reservoir prediction.

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Geological and geochemical characteristics and prospecting potential of rare element and rare earth element deposits in Saima alkaline complex
NAN Zhe, WANG Lin-Shi, HOU Xu, ZHAI Zheng-Bo, WANG Yang, LIU Yang
Geophysical and Geochemical Exploration    2023, 47 (3): 670-680.   DOI: 10.11720/wtyht.2023.2185
Abstract129)   HTML10)    PDF (5011KB)(193)      

The Saima alkaline complex is a unique and complex geologic body. It is well known for its diverse rock types and mineral types and high contents of uranium, thorium, and rare and rare earth elements. This study analyzed and summarized the geological exploration results of the Saima alkaline complex area in recent years, discovering that the rocks in the second intrusive stage of the Saima alkaline complex show the wide mineralization of rare and rare earth elements, with a moderate- to low- mineralization temperature. There are mainly two types of deposits in Saima alkaline complex area, namely the residual magmatic metasomatism type and the skarn type. Furthermore, the prospecting potential of the whole alkaline complex was analyzed by combining the 1∶200,000 stream sediment survey data and the 1∶10,000 primary halo survey data. Three predicted metallogenic zones of rare earth and radioactive elements were delineated in the Saima alkaline complex and its surrounding area, namely Saima-Gujia, Aiyang, and Shuangshanzi. This study is of great significance for the prospecting of rare and rare earth polymetals in the Saima alkaline complex area.

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A study of tectonic framework of the Qinnan sag in Bohai Basin and its adjacent areas based on satellite gravity anomalies
YANG Rong-Xiang, WANG Wan-Yin, CAI Meng-Ke, WANG Ding-Ding, LUO Xin-Gang
Geophysical and Geochemical Exploration    2023, 47 (3): 584-596.   DOI: 10.11720/wtyht.2023.1463
Abstract128)   HTML174)    PDF (15824KB)(206)      

The Bohai Basin has the most offshore oil and gas fields discovered in China. As a potential hydrocarbon-rich sag in the Bohai Basin, the Qinnan Sag is of high value in exploration. Therefore, the study of the tectonic framework of the sag and its adjacent areas is of great significance and application value. Based on satellite gravity anomalies, this study determined the Bouguer gravity anomalies by correcting the influences of land topography and seawater and obtained the planar distribution and apparent depths of faults, the thickness of Cenozoic strata, and the boundaries of tectonic units using methods such as the normalized vertical derivative of the total horizontal derivative (NVDR-THDR), the Euler deconvolution, the minimum curvature potential field separation, and the fast for the gravity field based in a dual interface model. Based on the geological and geophysical data, this study analyzed the distribution and geophysical characteristics of major faults and tectonic units in the study area. The results of this study are as follows: The faults in the Qinnan Sag and its adjacent areas mainly have NE, NEE, and NW strikes and an apparent depth of primarily 1~10 km, which is up to 15~25 km at some positions of the sag-controlling faults and the intersections of the faults; The Cenozoic strata have a thickness of 0~11 km. The Cenozoic tectonic units are distributed in alternating NE and NEE directions, and their boundaries are mostly controlled by faults; Through further investigation, this study classified the sub-sag on the west side of the Qinnan sag as the Laoting sag and adjusted the boundaries of other tectonic units. The results of this study on the distribution of the faults and tectonic units can provide geophysical data for hydrocarbon exploration in the Qinnan Sag.

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Regional geochemical characteristics and metallogenic prospect area prediction of strategic mineral antimony in the Eerguna block, Heilongjiang Province, China
WAN Tai-Ping, ZHANG Li, LIU Han-Liang
Geophysical and Geochemical Exploration    2023, 47 (5): 1179-1188.   DOI: 10.11720/wtyht.2023.1439
Abstract127)   HTML3)    PDF (4012KB)(126)      

The Eerguna block with metallogenic geological conditions is an important metallogenic area in Heilongjiang Province. Globally, China boasts the richest resource of antimony. However, the high mining intensity in recent years imposes huge challenges to this resource advantage of China. In this context, it is necessary to ascertain the geochemical characteristics of antimony in the Eerguna block. Based on the data of the 1∶250 000 stream sediment survey in the Eerguna block, this study explored the geochemical parameters of antimony in different tectonic units and the regional geochemical anomalies of this block. The results show that the study area has median and average concentrations of antimony of 0.33×10-6 and 0.55×10-6, respectively. The Mohe foreland basin is rich in antimony, with median and average concentrations of antimony higher than those of the study area. Furthermore, zones with high and extremely high antimony concentrations in the study area are distributed primarily in the Mohe foreland basin. Based on the 85% cumulative percentage, this study determined 66 geochemical anomalies of antimony, among which two reach the scale of geochemical provinces. Furthermore, this study identified significant geochemical anomalies of antimony in the discovered gold, antimony, and plumbum deposits or ore occurrences (mineralization points). Based on the spatial distributions of geochemical anomalies and metallogenic geological conditions of antimony, arsenic, and gold, this study delineated three metallogenic prospect areas of antimony: the Beijicun-Sanlianshan metallogenic prospect area, the Wangsushan-Daling metallogenic prospect area, and the Baikalushan-Huzhong metallogenic prospect area. In addition, the geochemical anomalies and metallogenic prospect areas for antimony, arsenic, and gold provide important areas for searching for sulfide deposits such as gold, antimony, and plumbum ones in the study area.

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Application of the wide-field electromagnetic method in hydrogeological exploration under the extremely-thick low-resistivity layer: A case study of a coal mine in the Huainan area, Anhui Province
Qi Zhao-Hua
Geophysical and Geochemical Exploration    2023, 47 (3): 700-706.   DOI: 10.11720/wtyht.2023.1178
Abstract123)   HTML14)    PDF (4532KB)(224)      

To investigate the water yield properties of the aquifers in the hanging and foot walls of coal seams under the extremely-thick low-resistivity layer, this study conducted the hydrogeological exploration using the wide-field electromagnetic method (WFEM) targeting a coal mine in the Huainan area, Anhui Province. The geological results obtained through multiple means, such as test analysis and data acquisition and interpretation, agree well with the downhole conditions. As indicated by the successful WFEM application in the hydrogeological exploration of the coal mine, the WFEM features strong penetrability, large investigation depth, and high accuracy. Therefore, the WFEM can be used as a new geophysical exploration method for the hydrological survey of large-depth coal fields.

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Research on structural characteristics and mineral prediction of the Luoning area based on the characteristics of gravitational and magnetic fields
ZHANG Lei, WANG Wan-Yin, WANG Xiao-Bo, LI Wen, ZHANG Xue-Li, SONG Hao, YANG Min, AN Li-ming
Geophysical and Geochemical Exploration    2023, 47 (3): 608-617.   DOI: 10.11720/wtyht.2023.1462
Abstract123)   HTML178)    PDF (10842KB)(286)      

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

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Simulated detection experiments of underground water supply pipeline leakage based on ground penetrating radar
WANG Yu-Cheng, WANG Hong-Hua, SU Peng-Jin, GONG Jun-Bo, XI Yu-He
Geophysical and Geochemical Exploration    2023, 47 (3): 794-803.   DOI: 10.11720/wtyht.2023.1199
Abstract122)   HTML10)    PDF (7153KB)(207)      

As an important part of urban infrastructure, underground water supply pipelines frequently leak or break due to disrepair,corrosion,and poor construction quality.It is of great significance to identify the leakage locations and affected areas of underground water supply pipelines using a non-destructive testing method for the purpose of early warning and follow-up treatment.This study conducted simulated detection experiments and analysis of underground water supply pipeline leakage using the ground penetrating radar (GPR) method.Firstly,this study established the leakage model of water supply pipelines in sandy soil using the SEEP/W module in the GeoStudio software and calculated the volumetric water content of different leakage locations and leakage times.Then,it established the relative dielectric constant and conductivity model for water supply pipeline leakage using the Topp equation and the empirical equations of electrical conductivity and water content.On this basis,this study conducted the GPR simulated detection of the water supply pipeline leakage model with different leakage locations and different leakage times using the finite difference time domain (FDTD) method and analyzed the simulation results.Finally,this study conducted the GPR-based physical simulated detection tests of water supply pipeline leakage and compared the test results with the numerical simulation results.The study results are as follows.Compared with the hyperbolic diffracted wave of the water supply pipelines without leakage,that of the water supply pipelines with leakage at different locations are stated as follows.For the leakage on the upper side,a longer leakage area and a larger leakage area were associated with an earlier present hyperbolic diffracted wave with weaker energy,while the horizontal position of the hyperbolic diffracted wave's vertex remained unchanged.For the leakage on the lower side,two hyperbolic diffracted waves appeared,which moved up and down individually.Moreover,a longer leakage time corresponded to two weaker and more separated hyperbolic diffracted waves.The horizontal positions of the hyperbolic diffracted waves' vertexes remained unchanged.For the leakage on the left (right) side,a longer leakage time was associated with a weaker hyperbolic diffracted wave,whose vertex deviated farther toward the upper left (right).The simulated detection results of this study can provide a reliable basis for early warning and follow-up treatment of water supply pipeline leakage.

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One-dimensional focusing inversion of the semi-airborne transient electromagnetic method and its application
WANG Shi-Xing, HE Ke, YIN Xiao-Kang, WEI Dong-Hua, ZHAO Si-Wei, GUO Ming
Geophysical and Geochemical Exploration    2023, 47 (2): 410-419.   DOI: 10.11720/wtyht.2023.1337
Abstract122)   HTML2)    PDF (3837KB)(192)      

The semi-airborne transient electromagnetic method (SATEM) is an emerging flexible and efficient geophysical exploration method using ground launch and air reception. The present inversion methods applied to the SATEM produce very smooth inversion results since they apply the maximum smoothing criterion, thus failing to effectively identify the information of specific layer interfaces. This study introduced the focusing inversion theory to the one-dimensional inversion of the SATEM. First, a focusing inversion stabilizer was determined by selecting appropriate focusing and regularization factors. Then, the inversion objective function including the focusing inversion stabilizer was solved to allow the inversion results to effectively identify the abrupt interfaces of layered strata. Furthermore, multiple layered geoelectric models were built to verify the reliability of the focusing inversion. Moreover, the focusing inversion results were compared with the Occam inversion results to highlight the advantages of the focusing inversion in interface identification. This study conducted the focusing inversion calculation of actual data on groundwater detection of a certain area. The calculation results were then combined with the hydrogeological and logging data for comprehensive analysis. Finally, this study determined the locations and spatial distribution of underground aquifers in the area, verifying the feasibility of the SATEM for groundwater detection.

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Application of the geochemical block method to the assessment of copper resources in Ethiopia
XIANG Wen-Shuai, BAI Yang, JIANG Jun-Sheng, LEI Yi-Jun, HUNDIE Melka, SISAY Degu, ZHANG Yuan-Pei, WU Ying, ZHENG Xiong-Wei
Geophysical and Geochemical Exploration    2023, 47 (4): 845-855.   DOI: 10.11720/wtyht.2023.1198
Abstract122)   HTML5)    PDF (6040KB)(127)      

Low-density geochemical mapping is characterized by high order streams to be sampled and a large coverage area and can be used to effectively trace geochemical blocks with high metal contents. Based on the 1:1,000,000 low-density geochemical mapping data of Ethiopia and the processing of the testing data of Cu in the original stream sediments, this study calculated the anomaly threshold of Cu at 37×10-6 through iterative deletion. Then, this study delineated three geochemical blocks and two regional anomalies with 37×10-6, 42×10-6, 47×10-6, 52×10-6, 59×10-6, and 66×10-6 as grading intervals. It calculated the mineralization coefficient of Cu ore bodies in the study area at 0.055% by referencing the known reserves of Cu deposits in geochemical blocks with a high level of copper exploration in the same metallogenic belt. Moreover, this study estimated the Cu resources in the study area at 2,600,000 t based on a rock mass thickness of 1,000 m. By combining the analysis of metallogenic geological conditions, this study determined that the zones where geochemical blocks nos. 2, 3, and 4 are located can be considered key metallogenic prospect areas for further detailed exploration.

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Environmental quality characteristics of soil and health risk assessment of crops of farmlands in the southern suburb of Baotou
Bao Feng-Qin, Cheng Hang-Xin, Yong Sheng, Zhou Li-Jun, Yang Yu-Liang
Geophysical and Geochemical Exploration    2023, 47 (3): 816-825.   DOI: 10.11720/wtyht.2023.1159
Abstract121)   HTML739)    PDF (2468KB)(189)      

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

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Application of wide field electromagnetic method in the fracturing monitoring of well Anye-2
HU Zhi-Fang, LUO Wei-Feng, WANG Sheng-Jian, KANG Hai-Xia, ZHOU Hui, ZHANG Yun-Xiao, ZHAN Shao-Quan
Geophysical and Geochemical Exploration    2023, 47 (3): 718-725.   DOI: 10.11720/wtyht.2023.1089
Abstract118)   HTML742)    PDF (3531KB)(189)      

To evaluate the fracturing performance of two horizontal wells of well Anye-2,this study explored the layout of the fracturing monitoring network and data acquisition and processing using the fracturing monitoring technique combined with the wide field electromagnetic method.Through the qualitative and semi-quantitative difference analysis of the pre-,in-,and post-fracturing monitoring data,this study preliminarily determined the propagation direction of induced fractures and semi-quantitatively calculated the parameters such as fracture length and height.For each fracturing interval,the parameters such as fracture height and length were quantitatively determined through fine-scale inversion with depth as constraints and difference calculation.The fracturing monitoring results show that the fractures at two horizontal wells had lengths of 100~125 m and heights of 20~25 m.The fracturing production was guided by evaluating the fracturing performance of each fracturing interval.The fracturing results of the previous interval were used to guide the fracturing of the subsequent interval.Finally,the fracturing performance of all fracturing intervals was evaluated.The application results show that the wide field electromagnetic method can effectively predict the spread direction and range(e.g.,fracture length) of fracturing fluids,achieving encouraging performance.

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Influence of DEM grid spacing and correction radius on terrain correction in gravity exploration
ZHANG Fei-Fei, WANG Wan-Yin, LI Qian, WANG Lin, MA Jing
Geophysical and Geochemical Exploration    2023, 47 (3): 597-607.   DOI: 10.11720/wtyht.2023.1472
Abstract117)   HTML174)    PDF (7804KB)(258)      

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

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Migration and enrichment patterns of vanadium in the soil and plant system of farmland
ZHAO Yu-Yan, JIANG Tao, YANG Bing-Han, ZHANG Ze-Yu, LI Zheng-He, LI Bing, TANG Xiao-Dan
Geophysical and Geochemical Exploration    2023, 47 (3): 835-844.   DOI: 10.11720/wtyht.2023.1206
Abstract116)   HTML10)    PDF (1991KB)(341)      

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

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Regularized joint inversion of magnetotelluric and gravity data based on inequality and Gramian constraints
CHEN Xiao, ZENG Zhi-Wen, DENG Ju-Zhi, ZHANG Zhi-Yong, CHEN Hui, YU Hui, WANG Yan-Guo
Geophysical and Geochemical Exploration    2023, 47 (3): 575-583.   DOI: 10.11720/wtyht.2023.1474
Abstract115)   HTML502)    PDF (4544KB)(244)      

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

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Application of the DC resistivity method in the study of saline groundwater distribution in the lower reaches of the Yellow River
XU Yan, ZHANG Tai-Ping, XIE Wei, ZHANG Hong-Jun, WANG Qiang, WANG Wei, GUO Peng, WANG Kui-Feng, YIN Ji-Guang, ZHANG Rui-Hua
Geophysical and Geochemical Exploration    2023, 47 (2): 496-503.   DOI: 10.11720/wtyht.2023.1034
Abstract115)   HTML1)    PDF (6413KB)(251)      

This study investigated the distribution characteristics of saline groundwater in the Huimin area of the lower reaches of the Yellow River using the DC resistivity method. Specifically, this study determined the distribution range of the apparent resistivity of the saline water and the variation in the saline-fresh groundwater interface in the area based on resistivity logs, aiming to constrain the resistivity sounding data analysis and improve the interpretation accuracy of the distribution of the saline groundwater. The results are as follows. The top boundary of the saline water in the area mainly had a burial depth of 20~50 m and developed to the shallow surface locally. It was inferred that the bottom boundary of the saline water had a burial of mainly 160~300 m and gradually became shallow in a nearly NW direction. As verified by the later investigation of water samples and drilling, the inferred saline groundwater characteristics agreed roughly with the actual situation. This result indicates that the DC resistivity method has a good application performance in the study of the distribution of saline groundwater.

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Frequency-domain 2D seismic forward modeling method based on the LSCG method and the wavenumber compensation
ZHANG Ru-Hua, ZHANG Dong-Jun, HUANG Jian-Ping, GOU Qi-Yong, ZHOU Jia-Ni
Geophysical and Geochemical Exploration    2023, 47 (2): 384-390.   DOI: 10.11720/wtyht.2023.2633
Abstract115)   HTML0)    PDF (3675KB)(144)      

The seismic forward modeling technique is critical to seismic exploration.Moreover,it shows a faster rate and higher calculation efficiency in the frequency domain than in the time domain.Presently,there is a need to complete the forward calculation in the frequency domain efficiently and accurately.The specific problems include the numerical dispersion and the high memory consumption for calculating and decomposing impedance,which should be reduced by improving the calculation efficiency.Different from the conventional direct method,this study adopted the least-squares conjugate gradient (LSCG) method used to determine the impedance matrix for the frequency-domain forward modeling and proposed an expression for wavenumber compensation to suppress the numerical dispersion.The numerical tests of simple and complex models show that the LSCG method can effectively reduce the calculation time and that the frequency-domain forward modeling method based on wavenumber compensation can effectively suppress the numerical dispersion and thus improve the precision of wave field simulation.

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Formation mechanisms and significance of saline-lacustrine Se-rich soils in the Xining Basin
ZHANG Ya-Feng, JI Bing-Yan, SHEN Xiao, YAO Zhen, MA Qiang, WANG Shuai, HE Lian-Zhen, HAN Wei-Ming
Geophysical and Geochemical Exploration    2023, 47 (2): 470-476.   DOI: 10.11720/wtyht.2023.1325
Abstract113)   HTML1)    PDF (2079KB)(203)      

As shown by the investigation and analysis of the Se content in soils and rocks of the Xining Basin, the rocks and soils in the Paleogene Xining Formation and the Cretaceous Minhe Formation have the highest Se content, which makes them the major Se-rich parent materials of soils in the basin. By combining the paleogeographic data on the retreating process of the basin, it can be concluded that the Paleogene Xining Formation and the Neogene Guide Group were deposited from the arid and hot saline lacustrine facies to the humid and cool saline-freshwater lacustrine facies. The combined action of the saline lake boundary and the arid and hot saline-lacustrine environment, as well as the following transformation by landforms and water systems, contributed to the formation of the existing framework of saline-lacustrine sedimentary Se-rich soils in the Xining Basin. Such Se-rich soils enjoy the advantages of a low heavy metal content, a moderate Se content, and a high available Se content and thus are of great value in development and utilization.

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Migration of heavy metals in the soil-tea plant system and health risks of drinking tea: A case study of Qiongzhong County, Hainan Province
GONG Qiu-Li, YANG Jian-Zhou, WANG Zhen-Liang, YAN Hui
Geophysical and Geochemical Exploration    2023, 47 (3): 826-834.   DOI: 10.11720/wtyht.2023.1321
Abstract111)   HTML13)    PDF (2497KB)(151)      

This study sampled the soil and the corresponding roots, stems, and leaves (including large leaves, new leaves, and sprouts) of tea plants from three ecological tea plantations in Qiongzhong County, Hainan Province. Based on these samples, this study investigated the migration of heavy metals in the soil-tea plant system and analyzed the migration patterns of heavy metals and the health risks caused by heavy metals in tea. As indicated by the results, the Pb, Cr, Cd, As, and Hg concentrations in the soil are slightly higher than the background values of corresponding soil elements in Hainan, showing non-significant accumulation. The enrichment of heavy metals varies significantly in different organs of tea plants. Specifically, Cr, Zn, Pb, Hg, and Cd are enriched in roots, while Cu and Ni are enriched in leaves; Pb, Cd, and Hg have higher concentrations in large leaves than in new leaves and sprouts, indicating that these elements are enriched with the growth of leaves; Cu, Ni, and Zn have higher concentrations in sprouts than in leaves, showing that these elements are enriched in the growing parts of leaves. Bio-concentration factors (BCF) indicate that soil physicochemical composition, heavy metal species, and leaf age have effects on the absorption of heavy metals by tea leaves. The results of the risk assessment show that the target hazard quotients (HQ) and hazard indices (HI) of all samples are less than 1, indicating acceptable health risks caused by heavy metals in tea. This study can provide a scientific basis for the prevention and control of heavy metals in tea plantations and has a positive guiding significance for managing tea plantations and ensuring the health of tea consumers.

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