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  20 February 2023, Volume 47 Issue 1 Previous Issue   
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Prediction of the soil element accumulation trends based on 1∶250 000 and 1∶50 000 geochemical surveys and assessments of land quality:A case study of Xixiangtang District, Nanning City, Guangxi zhuang Autonomous Region
WANG Lei, ZHUO Xiao-Xiong, WU Tian-Sheng, LING Sheng-Hua, ZHONG Xiao-Yu, ZHAO Xiao-Meng
Geophysical and Geochemical Exploration. 2023, 47 (1): 1-13.   DOI: 10.11720/wtyht.2023.2613
Abstract   HTML ( 9 )   PDF (3192KB)

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

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Comprehensive application of borehole log data of the Pulang copper deposit, Yunnan Province
YANG Chao-Yi, ZHU Qian-Kun, JIE Shao-Peng, KONG Chui-Ai, SHA You-Cai, ZHONG Zhi-Yong, SHEN Qi-Wu, CHEN Zhi-Jun, MA Huo-Lin
Geophysical and Geochemical Exploration. 2023, 47 (1): 14-21.   DOI: 10.11720/wtyht.2023.1128
Abstract   HTML ( 4 )   PDF (6134KB)

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

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Iterative inversion method for ultradeep fault-controlled fracture-vug reservoirs:A case study of the Fuman oilfield,Tarim Basin
ZHANG Ming, LI Xiang-Wen, JIN Meng, ZHENG Wei, ZHANG Lei, MA Wen-Gao
Geophysical and Geochemical Exploration. 2023, 47 (1): 22-30.   DOI: 10.11720/wtyht.2023.1049
Abstract   HTML ( 3 )   PDF (6873KB)

The ultradeep Ordovician limestone fracture-vug reservoirs in the Fuman oilfield on the south bank of the Tahe River in the Tarim Basin is the core target area for the production capacity construction of the oilfield.These reservoirs in the study area contain massive dissolution vugs formed by the formation fracturing due to the strike-slip faulting and thus are highly heterogeneous.The low-frequency models based on conventional wave impedance inversion are built using data on horizons,faults,and logs,and thus they cannot characterize the fault-controlled heterogeneity of the reservoirs.For this reason,this study proposed an iterative inversion method constrained by fault fractured zone facies to predict reservoirs.The technical process of this method is as follows.First,the original seismic data were interpreted to obtain the attribute volumes that can reflect the characteristics of the fault fractured zones of the reservoirs.Then,the attribute volumes were proportionally fused with the initial low-frequency model and the spatial profile data of high-quality reservoirs obtained from the conventional inversion based on wave impedance.As a result,a new heterogeneous low-frequency model was formed.Using this model,multiple rounds of iterative inversions were conducted.The inversion results can truly describe the characteristics of the fault fractured zones in the heterogeneous reservoirs.The prediction results of 10 wells had coincidence rates of up to 92.86%.As indicated by the application,the method proposed in this study can improve the reservoir prediction performance and the prediction precision of fault-controlled reservoirs,thus effectively supporting the work in the study area.

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The feasibility of applying hydrocarbon-mercury gas measurement method in the prospecting of sedimentary copper deposits in Central Africa
HUANG Xue-Qiang, CHEN Yuan-Rong, WU Er, LIU Feng, LU An-Ning
Geophysical and Geochemical Exploration. 2023, 47 (1): 31-38.   DOI: 10.11720/wtyht.2023.2565
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Sedimentary copper deposits are the predominant type of copper (cobalt) mineralization in the Central African copper-cobalt metallogenic belt. To improve the prospecting efficiency of such deposits, the feasibility of applying the hydrocarbon-mercury gas measurement method in the prospecting of sedimentary copper deposits was studied in the Mabende-Likasi area of the Democratic Republic of Congo. As indicated by the test results, two known ore bodies show remarkable anomalies of multiple indicators of hydrocarbon and mercury, but the anomaly distribution is controlled by the occurrence of orebodies. Based on these findings, this study summarized the anomaly pattern of hydrocarbon-mercury gas and primarily explored the anomaly causes. Moreover, this study conducted the prospecting prediction of concealed copper (cobalt) deposits in the study area. An industrial copper orebody was discovered through drilling in the delineated favorable target area, thus achieving achieved prospecting results.

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Hydrochemical characteristics and significance of the Hongshan Lake in the Tianshuihai area, Xinjiang, China
XIAO Rui, PANG Shou-Ji, ZHU You-Hai, ZHANG Shuai, ZOU Yi
Geophysical and Geochemical Exploration. 2023, 47 (1): 39-46.   DOI: 10.11720/wtyht.2023.2569
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Focusing on the spring and lake water in the Hongshan Lake in the Tianshuihai area, Xinjiang, China, this study explored the formation process of the hydrochemical components in the water and the geochemical characteristics and sources of the water bodies through hydrogeochemical testing and analyses. Accordingly, the hydrocarbon-related hydrogeochemical information was obtained. The results are as follows: The spring water in the Hongshan Lake is weakly alkaline in general and dominated by brackish water. The mass concentration of main ions in the water bodies increases with increasing salinity. The water has a hydrochemical type of Na-HCO3 and is mainly charged by atmospheric precipitation, which interacts with the surrounding rocks during the deep circulation along faults or fractures. The salinity, hydrochemical type, and characteristic coefficient of spring water indicate that the groundwater in this area features weak hydrodynamic force and deep metamorphic degree, which are similar to the characteristics of the formation water associated with hydrocarbon in oil fields. Therefore, it can be inferred that the geological environment in this area is conducive to the generation and preservation of hydrocarbon resources.

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Division of the geochemical landscapes in Morocco
WU Fa-Fu, LIU Jiang-Tao, WANG Jian-Xiong, HU Peng, CHENG Xiang, LI Fu-Lin, ZHAO Kai, ZENG Guo-Ping, WANG Cheng-Gang, XIANG Peng
Geophysical and Geochemical Exploration. 2023, 47 (1): 47-54.   DOI: 10.11720/wtyht.2023.2670
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Based on the characteristics of the physical geography,topography,and hydroclimatology of Morocco and years of experience in the geochemical survey in Morocco, this study divided the geochemical landscapes in Morocco and plotted the geochemical landscape zoning map of Morocco. As a result, Morocco was divided into six first-order geochemical landscape areas, namely a forest coverage area, a semi-arid high mountain area, a humid-semi-humid middle-low mountain and hill area, an arid-semi-arid middle-low mountain and hill area, an arid desert and gobi area, and a desert coverage area. According to the elevation and surface cutting intensity, the humid-semi-humid and arid-semi-arid middle-low mountain and hill areas were subdivided into four second-level landscape areas each, namely a hill area, a low mountain area,a shallow-cutting middle mountain area,and a medium-deep-cutting middle-mountain area. Based on this division scheme, this study proposed several suggestions for geochemical surveys in Morocco.

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Core characteristics and Quaternary stratigraphic division of borehole QK4 in southern Lubei Plain
ZHOU Yong-Gang, DAI Li-Ming, TIAN Zhen-Huan, YU Chun-Nan, ZHANG Zhen-Fei, LIU Wei, PEI Lun-Pei
Geophysical and Geochemical Exploration. 2023, 47 (1): 55-64.   DOI: 10.11720/wtyht.2023.1005
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The establishment of the Quaternary stratigraphic framework is of great significance for the study of regional stratigraphic correlation and paleogeographic environment evolution. The sedimentary strata since the Late Pleistocene have been extensively studied, but the research on the complete Quaternary stratigraphic framework is not yet sufficient. Therefore, paleomagnetic, AMS 14C, OSL, well logging, and lithostratigraphic studies were conducted on borehole QK4 (depth: 285.98 m) in the Lubei Plain. Based on the systematic paleomagnetic sampling (398 samples), processing, and testing, it is considered that the cores from borehole QK4 recorded Brunhes normal polarity chron, Maruyama reversed polarity chron, Gauss normal polarity chron, and some of their polarity subchrons. Based on the magnetic age framework, as well as MS 14C, OSL, well logging, and lithostratigraphic characteristics, the Quaternary strata revealed by borehole QK4 were divided, and it was determined that the bottom boundaries of the Holocene, Upper Pleistocene, Middle Pleistocene, and Lower Pleistocene strata have depths of 4.11 m, 23.49 m, 118.70 m, and 147.35 m, respectively. Moreover, as the strata revealed, the strata revealed by borehole QK4 include the Cenozoic Heituhu, Dazhan, Pingyuan, and Minghuazhen formations from top to bottom. The results allowed for the establishment of the Quaternary stratigraphic framework in the southern Lubei Plain, thus providing reliable petrological, chronological, and paleomagnetic evidence for the Quaternary stratigraphic division and correlation and palaeogeographic environmental evolution in the southern Lubei Plain.

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Target area prediction and drilling verification of the tectonic fissure-hosted geothermal water in Meixian County, Guanzhong Plain based on the integrated geophysical exploration
HAN Yuan-Hong, SHEN Xiao-Long, LI Bing, XU De-Cai, JIA Zhi-Gang, WU Da-Lin, WANG Wei, Lyu Jun
Geophysical and Geochemical Exploration. 2023, 47 (1): 65-72.   DOI: 10.11720/wtyht.2023.1209
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To achieve the goals of peak carbon dioxide emissions and carbon neutrality, geothermal energy has great prospects for utilization as a type of widely distributed green and clean energy. The tectonic fissure-hosted geothermal water is regarded as an important type of hydrothermal energy for development and utilization because of its high water yield and easy reinjection. This study systematically analyzed the regional structures, formation lithology, water storage space, and water yield property of the urban area of Meixian County in the west of Guanzhong Plain through the regional integrated geophysical exploration, aiming to guide the target area prediction and well placement of geothermal wells. The results show that three concealed faults are present in the target area, of which two faults with favorable water yield property and large scale can be regarded as the faults of the target area. Based on this, geothermal wells were arranged near the fault prediction lines on the hanging wall of the faults, and the weathered zones of the bedrock surfaces were penetrated vertically along the dip angles of the faults. Given the actual geological conditions, such as the faults and the burial depth of the bedrock surface, the geothermal wells had an average drilling depth of 500 m from the bedrock surface. The drilling results show that there are dual-structure thermal reservoirs in the target area, including thermal reservoirs of pore water in the Neogene clastics and those of the bedrock fissure water. Among the eight geothermal wells, seven wells have a water yield of more than 100 m?/h, which mainly originates from the bedrock fissure water, and only one well has a relatively low water yield, which is mainly sourced from the pore water in the Neogene clastics.

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Resistivity of moraine deposits in the Tangbu section, Dongcuoqu, southeastern Tibet
JIANG Shou-Jin, CHEN Yong-Ling, LI Huai-Yuan, HU Jun-Feng
Geophysical and Geochemical Exploration. 2023, 47 (1): 73-80.   DOI: 10.11720/wtyht.2023.1107
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Glacial landforms, such as cirques, razorback ridges, horn peaks, and alpine lakes, are commonly developed in the surrounding areas of the Tangbu section of Dongcuoqu in the Nujiang River Basin in southeastern Tibet, indicating that intensive glacial activities once occurred in this area. However, field surveys show that proluvium and alluvial-diluvial deposits are mainly distributed in the Quaternary surface of this section. The comprehensive analysis of the audio-frequency magnetotellurics and high-density measurement results of this area show that the electrical characteristics of the Quaternary in this section are highly consistent with the moraine deposit structure. Combined with the commonly developed glacial landforms in the surrounding area, it can be inferred that the Quaternary stratum in this section is mainly dominated by moraine deposits, which are covered with a layer of proluvium and alluvial-diluvial deposits. From the perspective of the electrical structure characteristics of the geophysical exploration results, the resistivity results of the audio-frequency magnetotellurics can effectively reflect the structural characteristics including the thickness of the moraine deposits, glacial valleys on the bedrock surface, and moraine lenses, and the resistivity results from high-density measurement can well reflect the characteristics of moraine melange, moraine lenses, and the long axis direction of large boulders.

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Reservoir lithology identification method based on multi-scale time-frequency-space feature combination
WANG Zong-Ren, WEN Chang, XIE Kai, SHENG Guan-Qun, HE Jian-Biao
Geophysical and Geochemical Exploration. 2023, 47 (1): 81-90.   DOI: 10.11720/wtyht.2023.1020
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Conventional methods for reservoir lithology identification suffer low precision and efficiency since reservoir lithologies have various types and complex compositions and alternate frequently.This study proposed a reservoir lithology identification method based on multi-scale time-frequency-space feature combination.Based on the original logging characteristics,this method introduced the multi-scale frequency-domain components from the complementary ensemble empirical mode decomposition (CEEMD) to improve the longitudinal resolution of log curves.Moreover,a multi-scale convolutional neural network-bidirectional gated recurrent unit-attention mechanism (CNN-BiGRU-AT) model was constructed to extract the spatio-temporal features of log data containing multi-scale frequency-domain components.In this way,the joint learning of time-frequency-space features of log data was realized.Finally,the model output was optimized using the attention mechanism to reduce the propagation of error information.To verify the reliability of this method,an experimental analysis was conducted using the data from five wells that have relatively complete data.As revealed by the analysis results,the identification accuracy of training and verification sets containing multi-scale frequency-domain components was increased by 9.50% and 8.66%,respectively in the comparative experiments of different data combinations.The method proposed in this study yielded sample identification accuracy of 94.11%.Compared with support vector machine (SVM),backpropagation (BP) neural network,convolutional neural network (CNN),bidirectional gated recurrent unit (BiGRU),and CNN-BiGRU fusion models, the identification accuracy of this method increased by 16.21%,14.54%,11.69%,5.05%,and 3.38%,respectively.

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Joint Q-compensated least-squares reverse time migration using primary and diffracted waves
XU Lei-Liang, ZHAO Guo-Yong, ZHANG Jian, ZHONG Tian-Miao, GU Jia-Ying, YOU Jian, QU Ying-Ming
Geophysical and Geochemical Exploration. 2023, 47 (1): 91-98.   DOI: 10.11720/wtyht.2023.2636
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Poor illumination poses great challenges to the imaging of small-scale faults and pores.Subsurface attenuation leads to amplitude loss and phase distortion of seismic waves,and ignoring such attenuation during imaging will blur migration amplitudes.The Q-compensated least-squares reverse time migration (QLSRTM) can improve the imaging of these small-scale structures,but it requires a huge amount of iterations and computational cost.To improve the imaging effect of these small-scale structures,this study proposed a geological-target-oriented joint QLSRTM (J-QLSRTM) that fully utilizes diffracted waves.In this method,a new objective function and gradient formula was constructed.Moreover,the Q-compensated wavefield propagation operators,Q-compensated adjoint operators,and Q-attenuated demigration operators were derived for both primary and diffracted waves based on the inversion and adjoint theories.The numerical examples verified that the proposed J-QLSRTM is superior to the conventional QLSRTM and the acoustic J-LSRTM.

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Application of the integrated engineering geophysical exploration technology in the predrilling stage of shale gas well platforms in southern Sichuan Province
YU Chang-Heng, ZHENG Jian, ZHANG Xu-Lin, ZHOU Hao, WANG An-Ping, LIU Lei, LI Yi
Geophysical and Geochemical Exploration. 2023, 47 (1): 99-109.   DOI: 10.11720/wtyht.2023.3530
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Southern Sichuan Province has widely developed karsts and densely distributed coal mine goafs, which cannot be accurately detected and identified using a single existent exploration method. Consequently, large-scale and industrial drilling for shale gas is prone to induce failures and complex events. In light of the complex topographic and geological conditions in southern Sichuan, this study conducted tests and comparative analysis using multiple engineering geophysical exploration methods including electrical resistivity imaging, shallow seismic method, transient electromagnetic method, audio-magnetotelluric method, and microtremor survey method. As a result, an integrated engineering geophysical exploration technology for shale gas well platforms in southern Sichuan was formed and applied to the construction of shale gas well platforms. As indicated by drilling results, the integrated technology can effectively identify unfavorable geological bodies (e.g., shallow karsts, coal mine goafs, and overburdens) at a depth of less than 1000 m and provide technical support for siting shale gas well platforms, optimizing casing programs, predicting drilling risks, shortening drilling cycles, and protecting ecological environment, with remarkable economic, social, and ecological benefits having been achieved. Moreover, this integrated technology provides a technical guarantee for the construction of both the Changning-Weiyuan national shale gas demonstration zone and the southern Sichuan shale gas exploration and development pilot zone and accelerates the shale gas development in southern Sichuan.

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Evaluation of the saturation of carbonate reservoirs by combining the nuclear magnetic resonance logging and the Thomeer model
CHEN Xing-He, ZHANG Chao-Mo, ZHU Lin-Qi, ZHANG Chong, ZHANG Zhan-Song, GUO Jian-Hong
Geophysical and Geochemical Exploration. 2023, 47 (1): 110-119.   DOI: 10.11720/wtyht.2023.2606
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Carbonate reservoirs have various pores and complex pore structures.However,the microstructure of rocks cannot be characterized using conventional saturation evaluation models,making it extremely difficult to perform the saturation evaluation of carbonate reservoirs.Given this,this study proposed a Thomeer saturation model combined with the nuclear magnetic resonance (NMR) logging based on the data of capillary pressure curves and NMR logging.Specifically,information about the structure of the pore system in the mercury injection data was analyzed,and then the capillary pressure curves of multiple pore types were obtained through fitting using the Thomeer function.Finally,the complex pore structure was characterized using multiple Thomeer curves.The NMR logging is the only logging method that can continuously and quantitatively characterize the pore structure of reservoirs.The Thomeer parameters Bv,Pd,and G and the modal element Porositon of the maximum pore throat diameter were calculated using the logarithmic mean of T2 transverse relaxation time for NMR (T2LM) and the NMR total porosity (MPHS),as well as the classification of pore throat R35.Accordingly,the saturation evaluation model for carbonates reservoirs with complex pore structures was constructed.This model allows for the continuous evaluation of formation pore structure that cannot be achieved using experimental methods.This model was applied to the saturation evaluation of the carbonate reservoirs with complex pore structures in oilfield X in the Middle East.By comparison with the J function model and Archie's formula,this model decreased the relative error from 0.496 and 0.442,respectively to 0.272,better characterized the variation trend,and achieved encouraging application effects regardless of the saturation of reservoirs.Therefore,this model can minimize the impacts of carbonate reservoirs with complex pore structures and improve the precision of the reservoir saturation evaluation.

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Current field distribution characteristics and detection influencing factors of the focusing DC IP method for tunnels
ZHAO Jun, MENG Xin-Jia, LI Bing, LIU Zhi-Min
Geophysical and Geochemical Exploration. 2023, 47 (1): 120-128.   DOI: 10.11720/wtyht.2023.1116
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This study aims to explore the current field distribution characteristics and detection influencing factors of the focusing DC induced polarization (IP) method for tunnels. The study processes are as follows: the normal and anomalous potentials of the spatial electric field were calculated using the finite element method; a homogeneous 3D geoelectric detection model was constructed using the Comsol software, the model was divided into grid cells using the adaptive algorithm for tetrahedral mesh generation, and the numerical calculation precision was compared and analyzed; the distribution and change patterns of the focusing current field were investigated, and the range of the current ratio of the focusing effect was determined, and a 3D geoelectric model was constructed for anomalous geological structures in front of the tunneling section, and the influences of factors such as the area of the tunneling section, interference bodies, and current ratio coefficient of focusing effect on the IP effect parameters were simulated through the forward modeling using the equivalent resistivity method. The results are as follows: the focusing DC IP method was highly sensitive to the detection of the unfavorable geological bodies in front of the tunneling section; the impact of the interference bodies in the tunnel cavity on the detection of the anomalous target bodies can be ignored; the farther the lateral anomalous interference bodies from the tunnel floor, the less the impact on the detection of the anomalous target bodies, and the exploration distance can be effectively increased by increasing the area of the tunneling section and the current ratio coefficient of the focusing effect. This study can be utilized as a basis and reference for the inversion using the focusing DC IP method and is greatly significant for promoting the development of the focusing electrical exploration theory.

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Evaluation of the external coincidence precision of the aeromagnetic survey system
WANG Yun-Peng, LIU Xiao-Gang, QIU Xue-Feng, SONG Ying
Geophysical and Geochemical Exploration. 2023, 47 (1): 129-134.   DOI: 10.11720/wtyht.2023.2682
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The precision evaluation of an aeromagnetic survey system is an important part of a magnetic survey. This study obtained airborne and ground magnetic data through flight experiments in a certain survey area of Inner Mongolia. Then, the high-precision ground magnetic survey data was upward-continued to the height of the flight course using the interpolation-iteration and equivalent source methods. Finally, the external coincidence precision of the aeromagnetic survey system was evaluated by comparison with the aeromagnetic survey data. The precision evaluation results of the two continuation methods are better than 5 nT, reflecting the actual precision level of the aeromagnetic survey system. Therefore, the research methods in this study can provide references for the evaluation of the external coincidence precision of an aeromagnetic survey system and can also be used for online calibration of the scale factor, deviation, and other parameters of newly developed aerial magnetometers.

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Differences in the characteristics of geomagnetic diurnal variation in different periods and their influence on correction of geomagnetic diurnal variation
LI Xing-Kang, FU Yong-Tao, ZHOU Zhang-Guo, YANG An
Geophysical and Geochemical Exploration. 2023, 47 (1): 135-145.   DOI: 10.11720/wtyht.2023.1138
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The phase difference (i.e., time difference) and amplitude difference between the geomagnetic data of the offshore work area and the geomagnetic diurnal variation data of the remote stations are still challenges to the precision of the marine magnetic survey network. Based on the stations on both sides of the East China Sea and three stations in Europe at higher latitudes, this study analyzed and made statistics on the numerical differences in morphological characteristics, phase differences, and amplitude differences of the diurnal variation curves during the daytime, nighttime, and the periods of intense magnetic disturbance. The results are as follows. During the daytime, the phase difference between the stations is constantly changing, resulting in a large amplitude difference around noon. During the nighttime, the data of the stations have consistent phases, and the amplitude difference is mostly less than 4 nT. During strong magnetic disturbance activities such as magnetic storms, the phases of the stations are consistent, and the amplitude difference is even smaller than that during quiet days. According to the survey data of the ocean, the absolute value of the difference at intersections between the survey lines during magnetic storms and quiet days is less than 3.2 nT. The variation characteristics of the phase difference and amplitude difference of the geomagnetic diurnal data between stations facilitate the diurnal variation correction of the marine geomagnetic data.

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Audiomagnetotelluric data: Influence of terrain and the inversion considering terrain
CHENG Zheng-Pu, GUO Shu-Jun, WEI Qiang, ZHOU Le, LEI Ming, LI Shu
Geophysical and Geochemical Exploration. 2023, 47 (1): 146-155.   DOI: 10.11720/wtyht.2023.1033
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This study designed a group of 2D peak-valley comprehensive terrain models with different widths and slopes and investigated the influence of differently undulating terrains in mountainous areas on the audiomagnetotelluric (AMT) data and corresponding distortion characteristics from seven aspects, namely polarization modes, frequency, positions of measurement points, the width of a mountain top, the elevation difference and slope of terrain, and phase curves. The results are as follows. The transverse magnetic mode (TM mode) is more susceptible to terrain than the transverse electric mode (TE mode). The undulating terrain has little influence on the high-frequency parts of AMT data but has a great influence on their low-frequency parts. The apparent resistivity and phase of different frequency points at a measurement point reflect the comprehensive influence of all terrains within the skin depth level rather than just the influence of a single mountain peak or valley near the measurement point. Measurement points located at the mountain peaks are more easily affected by terrains than those in the valleys. Moreover, narrower mountain tops correspond to greater elevation differences of terrain, and steeper terrain exerts greater influence. In addition, the comparison of the 2D_TE results of the inversion considering and not considering terrains show that the 2D inversion considering terrains can effectively eliminate the influence of terrain. The 2D inversion considering terrains was carried out for measured AMT data. As indicated by the inversion results, the 2D inversion considering terrains can effectively eliminate the false high and low resistance anomalies and relieve the "hanging surface" phenomenon of signals, and the results corresponded well with the horizons with encountered manganese of three boreholes.

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A compensation model of aeromagnetic gradient tensor data based on low-temperature superconducting
HOU Rui-Dong, GUO Zi-Qi, QIAO Yan-Chao, LIU Jian-Ying
Geophysical and Geochemical Exploration. 2023, 47 (1): 156-161.   DOI: 10.11720/wtyht.2023.2553
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In the compensation of the aeromagnetic gradient tensor data based on superconducting, the simulation results of the compensation model often differ from the compensation results of the survey data. To establish a model that is valid for measured data, this study analyzed the sources of errors, proposed a comprehensive compensation model by combining magnetic interference, installation errors, and the degree of unbalance, and determined the method to solve the model. Moreover, this study compensated the measured data using the comprehensive compensation model proposed and verified the compensation effects. The experimental results show that the comprehensive compensation model is applicable to the compensation of measured data since it can not only effectively reduce the influence of external interference but also can improve the quality of magnetic gradient tensor data and achieve significant compensation effects.

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Amethod for determining the optimal height for upward continuation of gravity anomalies
SUN Zheng, WANG Jun, DING Peng, TAN Xin
Geophysical and Geochemical Exploration. 2023, 47 (1): 162-170.   DOI: 10.11720/wtyht.2023.2356
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Upward continuation is one of the important methods used to separate gravity anomalies. However, how to quantitatively select an appropriate upward-continuation height has always been a problem in the application of this method. Given this, this paper proposes a curvature analysis method based on the least square method to quantitatively determine a reasonable upward-continuation height. The steps of this method are as follows. Perform upward continuation to different adjacent heights for observation data, and then use the least square method to estimate the least square error of the upward continued value of adjacent heights.There is a maximum curvature in the least square curve of upward-continued values of all adjacent heights.At the point of the maximum curvature, the local anomalies are attenuated to the greatest extent, while the regional anomalies are preserved as far as possible. Therefore, this point can be approximately regarded as the optimal upward-continuation height. As indicated by tests using the data of a theoretical model, the method proposed in this paper can be used to qualitatively determine a suitable upward-continuation height, thus providing an important reference for the selection of upward-continuation height in practical applications.

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A C#-based study and application of data files from MTU series magnetotelluric sounders
HE Jing-Long, WANG Zhan-Bin, KOU Shao-Lei, YANG Kai
Geophysical and Geochemical Exploration. 2023, 47 (1): 171-178.   DOI: 10.11720/wtyht.2023.1064
Abstract   HTML ( 1 )   PDF (3218KB)

The MTU series magnetotelluric sounders produced by Phoenix Geophysics Ltd. in Canada have been widely used in various fields of earth exploration because of their advantages, such as small weight and stable and reliable data acquisition. However, their special data formats make the data processing troublesome. At present, most of the data processing depends on the SSMT-2000 software developed by Phoenix Geophysics, which is not conducive to the improvement and application of data processing methods. By studying the formats of data files of MTU series magnetotelluric sounders, this study used the UltraEdit software to analyze the structure and rules of the data files and analyzed and studied TBL, CLB, CLC, and TS files based on the C# programming language. As a result, this study transcoded the data files from indigestible binary files into plain files that are easy to understand and provided the modification and editing module of TBL parameter files, the data analysis module of CLC and CLB files, and the transformation module of TS files. The data measured in the field were edited using the program developed in this study. The test results verify that the program can modify TBL file parameters, analyze CLB and CLC files, and convert TS files. Therefore, this study provides a new idea and method for studying such binary files.

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Comparison of deep learning algorithms for geochemical anomaly identification
LI Mu-Si, CHEN Li-Rong, XIE Fei, GU Lan-Ding, WU Xiao-Dong, MA Fen, YIN Zhao-Feng
Geophysical and Geochemical Exploration. 2023, 47 (1): 179-189.   DOI: 10.11720/wtyht.2023.2667
Abstract   HTML ( 1 )   PDF (6584KB)

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

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Genetic mechanisms and prediction of the deep abnormal high pressure in the Ledong area,Yinggehai Basin
AI Neng-Ping, SONG Peng, LI Wei, WU Yun-Peng, LI Hu
Geophysical and Geochemical Exploration. 2023, 47 (1): 190-198.   DOI: 10.11720/wtyht.2023.1007
Abstract   HTML ( 1 )   PDF (3738KB)

The deep strata in the Ledong area of the Yinggehai Basin have a complex pressure structure.As indicated by the surveyed pressure data,strata at different depths and horizons have greatly different pore pressure.Especially in the Huangliu Formation,the pore pressure shows a large transverse span.Moreover,it tends to reduce at the top but rises rapidly at the bottom,with a pressure coefficient of up to 2.3,indicating the presence of significant pressure mutation.Pressure prediction using only the undercompaction model yields large errors and thus is prone to induce engineering accidents.To effectively predict the formation pressure,it is necessary to determine the genetic mechanisms of overpressure.This study effectively identified the genetic mechanisms of the overpressure using the cross plots of vertical effective stress vs logging response.The identification results show that the genetic mechanisms of the deep overpressure in the Ledong area mainly include mechanical unbalanced compaction,chemical compaction,vertical pressure transmission along faults,and hydrocarbon-generating pressurization.A proper pressure prediction method was established based on the defined genetic mechanisms,thus improving the prediction precision and ensuring the smooth construction of drilling engineering.

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Seismic noise suppression using non-local means algorithm based on the Shearlet transform
WANG Jin-Gang, AN Yong, XU Zhen-Wang
Geophysical and Geochemical Exploration. 2023, 47 (1): 199-207.   DOI: 10.11720/wtyht.2023.2630
Abstract   HTML ( 0 )   PDF (6298KB)

Owing to the limitations of both the field environment for seismic data acquisition and the performance of instruments,the seismic signals collected in seismic exploration are inevitably mixed with strong noise,thus greatly affecting the subsequent processing and interpretation.In recent years,multi-scale geometric analysis methods have become an important topic in noise suppression owing to their unique advantages.This study proposed suppressing the seismic noise using a non-local mean (NLM) algorithm in the Shearlet domain.First,the non-subsampled Shearlet transform (NSST) was performed for seismic signals.Then,the decomposed coefficient subset was further processed using the NLM method,and the weight function was improved by using eight Sobel operators to approximate the omnidirectional structure.Finally,the inverse Shearlet transform was performed for the coefficients to obtain the denoised seismic signals.Experimental results show that this combined algorithm can effectively suppress the random noise and preserve the weak events,thus showing high practicability in the seismic data processing.

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Multiple suppression in the S-transform domain based on the similarity of seismic signals
ZHANG Hong-Zhi, WANG Da-Long, ZHANG Chun-Niu, HAN Jian, HUANG De-Zhi, YANG Fei-Long
Geophysical and Geochemical Exploration. 2023, 47 (1): 208-216.   DOI: 10.11720/wtyht.2023.2639
Abstract   HTML ( 1 )   PDF (9800KB)

Multiple suppression is the key to marine seismic data processing.Efficient and accurate identification and suppression of multiples while protecting primary reflected waves is the focus of seismic data processing.This study carried out the multiple suppression in the S-transform domain using the CMP stacking based on the similarity of seismic signals between the common midpoint (CMP) gather and the stack trace.First,the initial multiple subtraction was completed through the normal moveout (NMO) correction of multiple velocity and subtracting the stack trace data from the CMP gather data.As a result,the residual multiples in the wave field exist in the form of random noise.Then,the NMO correction was conducted for the velocity of primary reflected waves of the seismic wave field, for which multiples were subtracted.Afterward,the similarity filtering was conducted for the S-transform spectra of the CMP gather,with the stack trace of the primary reflected wave velocity as the initial model.In this way,the residual multiples were eliminated.The validity tests based on both the theoretical data and the actual data show that the method proposed in this study can efficiently suppress multiples and improve the imaging precision of reflected waves.

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An analysis of the temporal and spatial changes in soil monitoring indices based on GIS and statistics
WANG Yuan-Yuan, HUA Ming, JIN Yang, CUI Xiao-Dan, XU Wei-Wei, LI Wen-Bo, LIU Wei-Jing, WANG Zi-Yi, WEN Yu-Bo
Geophysical and Geochemical Exploration. 2023, 47 (1): 217-227.   DOI: 10.11720/wtyht.2023.2687
Abstract   HTML ( 1 )   PDF (6279KB)

Soil monitoring is of significance for guiding the determination of the ecological quality of soil, the active ecological restoration and prevention of soil pollution, and the sustainable monitoring and utilization of land resources. To investigate the temporal and spatial changes in the soil monitoring indices in Yixing City, Jiangsu Province, this study collected the geochemical data on 426 soil samples taken during the multi-purpose geochemical survey of Yixing City in 2004 and 4 458 soil samples taken during the 1∶50 000 land quality geochemical survey in 2015. Based on these data, this study analyzed the changes in important soil environmental parameters of the study area using the geographic information system (GIS) and statistics. Moreover, it determined the changes in the parameters or element concentrations using box-whisker plots and t-tests, conducted an error analysis using the nugget value (C0) based on the semivariance function, and evaluated and analyzed different spatial variables. The results are as follows. From 2004 to 2015, the organic matter (OM) and nutrient elements such as nitrogen, phosphorus, and boron showed an upward trend; the pH of soil showed a significant downward trend; the contents of selenium and heavy metals such as cadmium, copper, lead, and zinc showed an upward trend, and the arsenic content did not change significantly.

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A preliminary study of Se-rich soil in the Shizuishan area, Ningxia and its potential for application
WANG Zhi-Qiang, YANG Jian-Feng, SHI Tian-Chi
Geophysical and Geochemical Exploration. 2023, 47 (1): 228-237.   DOI: 10.11720/wtyht.2023.2412
Abstract   HTML ( 1 )   PDF (3202KB)

Based on the statistical analysis of the Se distribution in 8,835 soil samples and 240 sets of crop-root soil samples, as well as related survey data in the Shizuishan area of Ningxia, this study summarized the element geochemical characteristics of the local Se-rich soil and explored the development and utilization prospects of the soil and related issues. The study results are as follows. ① The newly delineated Se-rich land (soil with Se content of ≥0.222×10-6; local standard of Ningxia) covers a total area of more than 1,000 km2, including more than 25% of Se-rich farmland, and the effective Se content is mostly over 10% of Se in the soil; ② The Se-rich soil has pH of greater than 7.5 and organic matter content of less than 10.26%, without heavy metal pollution. There are significant positive correlations between the Se content and the contents of organic matter, B, Mn, Mo, Cu, and Zn and a negative correlation between the Se content and pH; ③ The correlation coefficient between effective Se and Se in the soil is r = 0.39, and those between effective Se and OM, CEC, and N are 0.33 to 0.5; ④ Among the 10 types of Se-rich agricultural products (i.e., Se-rich wheat) obtained in Se-enrich soil through spot check, the wheat has been proven to have the strongest capacity to absorb Se, with an average bioconcentration coefficient of 0.12; ⑤ Since the unique Se-rich soil resources in this area is of great value in development and utilization, it is necessary to strengthen the R&D of characteristic Se-rich crops (i.e., wheat, rice, wolfberry, and grape) and the development of relevant Se-rich standards through scientific research and reasonable planning.

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Characteristics of bioavailable selenium in different types of selenium-rich soils
YAO Ling-Yang, XIE Shu-Yun, BAO Zheng-Yu, MA Ming, WAN Neng
Geophysical and Geochemical Exploration. 2023, 47 (1): 238-246.   DOI: 10.11720/wtyht.2023.2660
Abstract   HTML ( 5 )   PDF (3059KB)

Bioavailable selenium (Se) is an important indicator used to evaluate the supply capacity of Se in the soil to plants. There is a lack of national standard methods for testing bioavailable Se in the soil in China presently. This study used ten different chemical extractants to extract bioavailable Se from the soil. The results show that the extraction capacity of extractants was in the order of NaOH (10.57%) > SOL-Se+EX-Se (8.10%) > AB-DTPA (6.79) > NaHCO3 (4.99%) > K2SO4 (4.57%) > KH2PO4-K2HPO4 (4.33%) > KH2PO4 (3.05%) > SOL-Se (2.28%) > EDTA (1.40%) > NH4F-HCl (1.22%). Among them, the bioavailable Se extracted from the soil by KH2PO4, NaHCO3, SOL-Se, KH2PO4-K2HPO4, and AB-DTPA was significantly correlated with the Se content of crops. As revealed by the relationship between the percentage content of bioavailable Se in soil and soil properties, the percentage content of bioavailable Se in soil significantly correlated with indicators such as the chemical index of alteration (CIA), LOI, pH, Eh, P, and SiO2. Among them, pH and Eh mainly affect the existence form of Se in the soil, while indicators such as CIA, LOI, P, and SiO2 reflect the alteration degree of soil and the effect of adsorbates on bioavailable Se in soil. The results of this study can provide data support and a scientific basis for the development of Se-based ecological agriculture and the development and utilization of Se-rich land resources.

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Selenium contents in surface soil and agricultural products in Minhou County
ZOU Shan-Jin-Hong
Geophysical and Geochemical Exploration. 2023, 47 (1): 247-256.   DOI: 10.11720/wtyht.2023.2683
Abstract   HTML ( 1 )   PDF (2714KB)

Based on the evaluation data of agricultural geological surveys in Minhou County, Fujian Province, this study investigated the distribution of selenium contents in the surface soil of the cultivated land and garden plots in Minhou County and its major controlling factors. Moreover, it analyzed the selenium contents in agricultural products. The results are as follows. The selenium content in the surface soil is controlled by the geological setting. The areas with Late Jurassic concealed granite porphyries occurring have significantly higher soil selenium content than other areas. Moreover, different landforms, soil types, and land uses have certain effects on selenium content in the soil. Most of the agricultural products in the study area have low selenium content. The main selenium-rich crop is rice, which has a selenium accumulation rate of 78.6% according to the preliminary evaluation. However, some rice samples had excessive As or Cd content. Therefore, attention should be paid to the risk of excessive heavy metals in the development and utilization of selenium-rich rice. Based on the distribution of clean selenium-rich soil and the selenium-rich characteristics of agricultural products, this study determined nine potential areas of natural selenium-rich land in the study area.

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Application of the microtremor B-mode ultrasound technology in detecting the hidden hazards of dams
QI Juan-Juan, FAN Hong-Qiang, LI Jing-Lun, CHEN Zi-Jian, HUANG Xiao-Tong, ZHANG Shu-Tong
Geophysical and Geochemical Exploration. 2023, 47 (1): 257-263.   DOI: 10.11720/wtyht.2023.1027
Abstract   HTML ( 7 )   PDF (3955KB)

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

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Application of the natural source surface wave technique to the evaluation of the site of an urban planning area
CHEN Shi, JIN Rong-Jie, LI Yan-Qing, LI Chong-Bo, HU Zun-Ping
Geophysical and Geochemical Exploration. 2023, 47 (1): 264-271.   DOI: 10.11720/wtyht.2023.2702
Abstract   HTML ( 4 )   PDF (6410KB)

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

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Application of the high-density resistivity method in detailed exploration of superficial paleochannels in Xiong'an New Area
SU Yong-Jun, CAO Zhan-Ning, ZHAO Geng-Xin, HU Xiang-Yun, FAN Jian, ZHANG Jing, FAN Cui-Song, HUANG Zhong-Feng
Geophysical and Geochemical Exploration. 2023, 47 (1): 272-278.   DOI: 10.11720/wtyht.2023.1245
Abstract   HTML ( 2 )   PDF (4223KB)

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

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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.  
Abstract2536)      PDF (4180KB)(4764)      


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
Abstract1217)   HTML145)    PDF (12833KB)(4204)      

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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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.  
Abstract3297)      PDF (431KB)(3378)      

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.  
Abstract2897)      PDF (1014KB)(3286)      

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.  
Abstract6675)      PDF (532KB)(3041)      

 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.  
Abstract1512)      PDF (346KB)(2569)      

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 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
Abstract2269)      PDF (964KB)(2481)      
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 CHOICE OF GRIDDING METHODS FOR GEOPHYSICAL DATA
LIU Zhao-Ping, YANG Jin, WU Wei
Geophysical and Geochemical Exploration    2010, 34 (1): 93-97.  
Abstract3092)      PDF (1939KB)(2428)      

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 UTILIZATION OF EXCEL TO THE PERFORMANCE OF R-MODE CLUSTER ANALYSIS
CHUN Nei-ya
Geophysical and Geochemical Exploration    2007, 31 (4): 374-376.  
Abstract4500)      PDF (659KB)(2416)      

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 APPLICATION OF ATOM INTERFEROMETER TO THE MEASUREMENT OF GRAVITATIONAL ACCELERATION
ZHANG Chang-da
Geophysical and Geochemical Exploration    2000, 24 (5): 321-326.  
Abstract1684)      PDF (673KB)(2355)      

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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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.  
Abstract4244)      PDF (403KB)(2235)      

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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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.  
Abstract3024)      PDF (2717KB)(2168)      

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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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.  
Abstract3687)      PDF (643KB)(2161)      

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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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.  
Abstract3675)      PDF (363KB)(2143)      

 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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RECENT ADVANCES IN THE RESEARCH AND DEVELOPMENT OF QUANTUM MAGNETOMETERS
ZHANG Chang-da
Geophysical and Geochemical Exploration    2005, 29 (4): 283-287.  
Abstract1685)      PDF (376KB)(2121)      

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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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.  
Abstract2921)      PDF (2969KB)(2086)      

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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PARAMETER SELECTION IN VIBROSEIS SEISMIC EXPLORATION
XUE Hai-Fei, DONG Shou-Hua, TAO Wen-Peng
Geophysical and Geochemical Exploration    2010, 34 (2): 185-190.  
Abstract3456)      PDF (3477KB)(2054)      

 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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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.  
Abstract3653)      PDF (534KB)(2036)      

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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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.  
Abstract2779)      PDF (1927KB)(2024)      

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.  
Abstract3596)      PDF (830KB)(2019)      

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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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.  
Abstract3119)      PDF (1060KB)(1986)      

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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THE INVERSED PROBLEM IN GRAVITY AND MAGNETICEXPLORATION: A REVIEW
Zeng Hualin
Geophysical and Geochemical Exploration    1990, 14 (3): 182-190.  
Abstract1963)      PDF (737KB)(1983)      

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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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.  
Abstract3483)      PDF (572KB)(1955)      

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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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.  
Abstract3398)      PDF (2025KB)(1947)      

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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YANG Li-De
Geophysical and Geochemical Exploration    2009, 33 (6): 741-742.  
Abstract2137)      PDF (240KB)(1902)      
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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.  
Abstract2537)      PDF (2180KB)(1895)      

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 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.  
Abstract2475)      PDF (2110KB)(1894)      

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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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.  
Abstract2139)      PDF (690KB)(1891)      

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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SOME PROBLEMS CONCERNING THE CONVERSIONOF MAPS BETWEEN SURFER AND MAPGIS
QIN Lin-Jiang
Geophysical and Geochemical Exploration    2010, 34 (5): 677-680.  
Abstract5368)      PDF (865KB)(1880)      

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 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.  
Abstract2743)      PDF (608KB)(1859)      

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 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
Abstract4752)      PDF (1427KB)(1855)      
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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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.  
Abstract3197)      PDF (1351KB)(1827)      

 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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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.  
Abstract3811)      PDF (1006KB)(1827)      

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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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
Abstract1090)   HTML147)    PDF (11771KB)(1807)      

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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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.  
Abstract2066)      PDF (749KB)(1756)      

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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Geophysical and Geochemical Exploration    1982, 6 (3): 154-156.  
Abstract1098)      PDF (190KB)(1748)      
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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.  
Abstract1880)      PDF (480KB)(1744)      

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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THE APPLICATION OF ELEMENT AND LEAD ISOTOPE TRACING TO THALLIUM CONTAMINATION IN SOIL OF THE YUNFU PYRITE MINE
LIU Jing-yong, CHANG Xiang-yang, TU Xiang-lin
Geophysical and Geochemical Exploration    2006, 30 (4): 348-353.  
Abstract1748)      PDF (896KB)(1731)      

The environmental pollutant has the same lead isotope composition as its source, and hence we can determine the accurate contaminative source through the study of lead isotope composition. In recent years lead isotope tracing has been playing its unique role in studying the source and migration of heavy metals in soil. As Tl and Pb have similar geochemical characteristics, the distribution and migration of Tl in the surface soil of the Yunfu pyrite mine have good correlation with Pb. In this study, therefore, the element and lead isotope tracing was used to study the migration of thallium in soil. Element and lead isotope tracing shows that thallium pollutants are mainly accumulated in top soil of about 0-16.5 cm, and that the soil is subjected less pollution in deeper soil. The soil around the slags at the depth of some 44 cm is affected by Tl leaching from the slags.

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THE MAGNETIC FIELD DATA PROCESSING AND INTERPRETATION METHODS BASED ON WAVELET ANALYSIS
ZHANG Heng-Lei, LIU Tian-You
Geophysical and Geochemical Exploration    2009, 33 (6): 686-690.  
Abstract2920)      PDF (1404KB)(1710)      

In order to analyze characteristics of underground sources of the high accuracy magnetic data in an effective way, the

authors employed wavelet transform to make a multiscale analysis of the magnetic data. Based on the inversion and

interpretation of the plane and profile data, this paper built a geophysical model for the working area by using the 2.5D

inversion method. Tests show that the wavelet method can separate the information of different underground sources effectively

and has reliable calculation accuracy and higher resolution than traditional extension and filtering methods.

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THE APPLICATION OF INTEGRATED ELECTRIC METHODS
TO THE EXPLORATION OF DEEP CONCEALED ORE BODIES
ZHANG Jian-Jin, YANG Jin
Geophysical and Geochemical Exploration    2010, 34 (1): 40-43.  
Abstract2726)      PDF (811KB)(1695)      

 An integrated application of such means of the intermediate gradient installment as the timedomain IP method, controlled source audiofrequency magnetotelluric sounding method and phase IP method was tested in the exploration of metallic ore deposits in the Deerbugan polymetallic ore belt in northeastern Inner Mongolia, with excellent result obtained. This test shows that the application of multiple parameters to the integrated analysis is characterized by mutual supplement and mutual verification, has abundant information, reduces the multisolution possibility in geophysical exploration and improves the reliability of geological integration.

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Research progress in the geological characteristics and material sources of fluorite deposits in the Heyu-Checun area, western Henan Province
ZHANG Kai-Tao, BAI De-Sheng, Li Jun-Sheng, LIU Ji-Feng, XU Dong, SU Yang-Yan, FAN Kang
Geophysical and Geochemical Exploration    2022, 46 (4): 787-797.   DOI: 10.11720/wtyht.2022.1438
Abstract488)   HTML55)    PDF (4836KB)(432)      

Based on the data on the geology, minerals, exploration, and geochemistry of more than 30 fluorite deposits in the Heyu-Checun area, western Henan Province, this study summarized the types, spatial distribution, and geochemical characteristics of fluorite deposits in the area and explored the genesis and material sources of the deposits. The fluorite deposits in this area have simple types and are distributed in Yanshanian granites and along the fault zone of the external contact zone of the granites. The formation ages of the Heyu and Taishanmiao plutons are 124.7~148.2 Ma and 115~123.1 Ma, respectively. The mineralized age of fluorites is 120~126.8 Ma, indicating that the mineralization occurred in the late stage of the intrusion of the Heyu pluton and the early stage of the intrusion of the Taishanmiao pluton. The ore-forming fluids belong to the NaCl-H2O system with a medium-low temperature, a low salinity, and a low density, indicating that the deposits in the area are medium-low-temperature supergene hydrothermal fluorite deposits. The chondrite-normalized REE patterns of fluorites in the area can be divided into slightly leftward, flat, and rightward types dominated by the rightward type. Moreover, the rightward chondrite-normalized REE patterns of fluorites are similar to those of the Yanshanian granites, both showing strongly negative Eu anomalies and weakly negative Ce anomalies. This finding indicates that the Yanshanian granites provide materials for the formation of fluorites. The metallogenic element F may mainly originate from the Heyu and Taishanmiao plutons, while the metallogenic element Ca partly comes from granites as surrounding rocks.

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Joint application of active and passive surface wave in 3D imaging of loess covered area
SHAO Guang-Zhou, LI Yuan-Lin, YUE Liang
Geophysical and Geochemical Exploration    2022, 46 (4): 897-903.   DOI: 10.11720/wtyht.2022.1546
Abstract344)   HTML47)    PDF (4096KB)(483)      

Due to the strong attenuation effect of loess cover on seismic and electromagnetic waves, the successful application of seismic reflection wave method and electromagnetic wave method in loess covered area is limited.In view of the characteristics of large thickness and fine stratification of loess cover, the active source and passive source surface wave methods are combined in this paper, so that the advantages of the two surface wave methods are complementary and the geological stratification of loess covered area can be accurately detected.The study area is located in the suburb of Fengxiang County,Weihe Basin.It is a typical loess covered area, and the thickness of loess cover is 80~120 m.By processing the measured data of active and passive surface waves in the study area, the positions of the main strata on the 2D shear wave velocity profile are basically consistent with the actual borehole test results, and the 3D stratum structure in the study area is also obtained.The results of joint imaging show that it is feasible and effective to use passive and active surface wave joint exploration for stratification of loess covered area, which provides technical support and beneficial idea for geological mapping of loess covered area.

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A Python-based scheme of Rayleigh-wave dispersion inversion
WU Wei-Zhi, LOU Li, WANG Peng, WANG Bin
Geophysical and Geochemical Exploration    2022, 46 (3): 743-749.   DOI: 10.11720/wtyht.2022.1238
Abstract314)   HTML45)    PDF (2912KB)(241)      

This study developed a workflow of Rayleigh-wave dispersion inversion using the Python programming language, and the detail is as follows.First,carry out the forward modeling of the dispersion curves on a horizontal layered model using the pysurf96 software package.Second,create an objective function used to describe the fitting degree of the dispersion curves.Third,complete the dispersion curve inversion using the heuristic algorithm in the scikit-opt software package.The problems encountered in the function call in the workflow were proposed and solved.The results show that the Python-based dispersion curve inversion of Rayleigh wave in multilayered media is reliable and offers a certain computational efficiency.In this way,this study built a Python-based inversion platform of underground layered structures using the wave dispersion,thus providing a method for other researchers to do inversion using open-source software.Finally,this study carried out the inversion of the crust and upper mantle structures using the dispersion curves extracted from the study of Yi-bo Peng on the noise in the Hailar Basin,achieving ideal results.

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Online insulation monitoring technology for a marine controlled source electromagnetic transmitter system
DENG Ming, WANG Meng, WU Wen, MA Xiao-Xi, LUO Xian-Hu
Geophysical and Geochemical Exploration    2022, 46 (3): 537-543.   DOI: 10.11720/wtyht.2022.1460
Abstract247)   HTML1867)    PDF (1810KB)(329)      

The marine controlled source electromagnetic (MCSEM) method is widely used in the exploration of natural gas hydrate, seabed oil and gas resources, and seabed geological structures. In the process of marine operation, the shipborne power supply unit transmits high-voltage and high-power electric power to a marine controlled source electromagnetic transmitter on the seabed through deep towing cables, during which it is necessary to carry out the automatic and real-time measurement and monitoring of the insulation resistance in the high-voltage power supply circuit to ensure the safe transmission of electric energy and timely deal with the abnormal power supply. This study collected the leakage current between the high-pressure end and the ground using high-voltage broadband couplers, insulation detection modules, remote data transmission units, and PC monitoring software. Meanwhile, this study amplified the leakage current using an analog amplifier and then calculated the insulation resistance by measuring voltage, thus achieving the automatic measurement and monitoring of the insulation resistance between the high voltage circuit and the ground. As verified by offshore tests, the automatic online insulation monitoring technology can meet the requirements of the MCSEM system and achieve the ideal online evaluation of the insulation performance of the system, thus providing a useful reference for the research and development of similar functions of marine instruments.

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2D seismic and high-density resistivity sounding reveal the shallow three-dimensional geological structure characteristics of Xiong'an New Area
LONG Hui, XIE Xing-Long, LI Feng-Zhe, REN Zheng-Wei, WANG Chun-Hui, GUO Shu-Jun
Geophysical and Geochemical Exploration    2022, 46 (4): 808-815.   DOI: 10.11720/wtyht.2022.1319
Abstract243)   HTML52)    PDF (4550KB)(388)      

The Xiong'an New Area is located in the middle part of the Jizhong Plain.The Cenozoic strata in the underground structure of the area have a large thickness,good stratification,and relatively stable tectonic activities.To finely determine the shallow geological structures,ascertain the fault structure characteristics,and improve the shallow exploration accuracy,this study combined two-dimensional seismic surveys and high-density resistivity sounding and made the following important progress.①This study finely determined the geological structure and the spatial distribution characteristics of fault structures at a depth of less than 200 m in the Xiong'an New Area;②This study constructed a three-dimensional visualized geological structure model,which intuitively displays the stratigraphic fluctuation pattern of Cenozoic strata and the spatial distribution of main fault structures;③This study analyzed and summarized the application of geophysical methods under the background of urbanization-induced high disturbance,including their exploration depths,horizontal and vertical resolution,response characteristics of geological bodies,and applicability.This study effectively supports and serves the planning,construction,and underground-space development and utilization in the Xiong'an New Area and serves as a reference for the geophysical exploration of urban underground space in hugely thick sedimentary basins.

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Application of geochemical survey of lithic fragments in ore prospecting in arid Gobi desert of the Beishan area, Gansu Province: A case study of the discovery of the gold-arsenic deposit in Sanbaidun area
LEI Zi-Qiang, CHEN Jie, CHEN Shi-Ming, FANG Cheng-Hao, YANG Zhen-Xi, WANG-Zhen
Geophysical and Geochemical Exploration    2022, 46 (3): 585-596.   DOI: 10.11720/wtyht.2022.1246
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Based on the landscape characteristics of the arid Gobi desert in the Beishan area, Gansu Province, this study carried out a 1:50,000 stream sediment survey in the Sanbaidun area and delineated 10 integrated anomalies. Then, the As-3 anomaly was preferentially selected for detail inspection by taking lithic fragments with grain sizes of 2~20 mm at multiple locations within 1/3 line spacing using a grid density of 100 m × 20 m. As a result, three integrated anomalies of lithic fragments were delineated and their characteristics were investigated. The dominant ore-forming elements were identified as As and Au, and two integrated anomalies were preferentially selected for detailed inspection using methods such as geochemical profile and trenching. Consequently, four Au orebodies, two As orebodies, one Au mineralized body, and one As mineralized body were found. The prospecting results indicate that the geochemical survey of lithic fragments can achieve ideal prospecting effects in the arid Gobi desert landscape area of Beishan and that 1:10,000 surveys of lithic fragments can be used to verify the anomalies of 1:50,000 stream sediment surveys.

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Key techniques for seismic data processing of deep metal deposits:A case study of the Chaganhua molybdenum orefield in Inner Mongolia
YUE Hang-Yu, WANG Xiao-Jiang, WANG Lei, CHEN Xiao-Qiang, JIANG Chun-Xiang, LI Pei, ZHANG Bao-Wei
Geophysical and Geochemical Exploration    2022, 46 (6): 1315-1326.   DOI: 10.11720/wtyht.2022.1453
Abstract202)   HTML172)    PDF (24023KB)(181)      

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

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Fine Interpretation of the exploration results of diamond-bearing rock masses in Maping area, Guizhou using the 3D AMT forward modeling and inversion technologies
HE Shuai, YANG Bing-Nan, RUAN Shuai, LI Yong-Gang, HAN Yao-Fei, ZHU Da-Wei
Geophysical and Geochemical Exploration    2022, 46 (3): 618-627.   DOI: 10.11720/wtyht.2022.1189
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The "Dongfang No.1" rock mass in the Maping area, Zhenyuan County, Guizhou is the parent rock of a primary diamond-bearing deposit discovered in China for the first time. Studies have shown that the rock mass found in the Maping area is of the shallow facies of the kimberlite magmatic system, and large-scale concealed rock pipes or buckets may exist in the deep part. To reveal the spatial distribution of deep diamond-bearing concealed rock pipes or buckets in the Maping area, this study carried out the audio-magnetotelluric (AMT) data acquisition in the area using a high grid density of 80 m × 40 m. Then it simulated the pure terrain response in the study area using the 3D forward modeling and deducted the pure terrain response from the measured data. The obtained qualitative interpretation results restored the distribution morphology of AMT impedance phase invariants to some extent that was distorted by static effects. Afterward, this study performed the 3D inversion of the data using the AR-QN quasi-Newtonian inversion method. Based on the lithologic statistical results of the study area, the resistivity variation intervals of the underground units were set during the inversion, obtaining a reliable 3D electrical structure. Finally, this study carried out a fine interpretation of the geoelectric model of this area based on geological data such as rock tubes found on the surface and multiple dikes revealed by boreholes, outlining the morphology of concealed rock pipes or buckets. This study will provide a geophysical basis for the future prospecting and prediction of primary diamond deposits in this area.

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Application of comprehensive geophysical exploration in geothermal resources on the eastern margin of Yinchuan Basin
HU Xin-Jun, CHEN Xiao-Jing, WU Yang, AN Bai-Zhou, NI Ping
Geophysical and Geochemical Exploration    2022, 46 (4): 845-853.   DOI: 10.11720/wtyht.2022.1409
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A geothermal field has been discovered in the Tianshan Sea World on the eastern margin of the Yinchuan Basin, revealing that the region has high-quality geothermal resources. The geological conditions for the formation of the geothermal field are significantly different from those of the conduction-type geothermal resources within basins, providing a new direction for the study of clean energy in the Yellow River Basin in Ningxia. This study processes and analyzes the data of 1∶50,000-scaled gravity surveys, controlled source audio-frequency magnetotellurics (CSAMT), and microtremor survey based on regional geological and geophysical characteristics. The results of the study are as follows. The uplifting zone of the Ordovician basement lies on the east side of the Lingwu Sag and spreads in an "S" shape along the Yellow River Fault. This zone reaches its highest part in the Tianshan Sea World, where it merges with the NW-trending local uplift. The Ordovician of the deep reservoirs in the geothermal field is characterized by medium-high resistance. The Carboniferous-Permian of the first cap rock at a moderate depth shows medium-low resistance and low seismic velocity. The Paleogene-Neogene of the second shallow cap rock corresponds to the formation with low resistance and low seismic velocity. Using these results, three prospective areas for developing and utilization of geothermal resources have been predicted.

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Application of the microtremor B-mode ultrasound technology in detecting the hidden hazards of dams
QI Juan-Juan, FAN Hong-Qiang, LI Jing-Lun, CHEN Zi-Jian, HUANG Xiao-Tong, ZHANG Shu-Tong
Geophysical and Geochemical Exploration    2023, 47 (1): 257-263.   DOI: 10.11720/wtyht.2023.1027
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To quickly and effectively detect the hidden hazards of dams,this study proposed the microtremor B-mode ultrasound technology based on linear arrays.Most of the (earth) dams also act as highways,and the vibration signals generated from running vehicles propagate along dams.Therefore,this study proposed deploying linear arrays along the dams,with the vibration propagation direction consistent with the signal receiving direction.In this way,abundant vibration sources can be provided for detecting hidden hazards of the dams.The results of this study show that the data on multiple exploration points can be simultaneously acquired using the multi-channel acquisition technique based on linear arrays,thus improving the efficiency of field data acquisition.Moreover,the influence of source differences can be avoided,and the lateral resolution and the accuracy of exploration results can be improved.The technology proposed in this study was applied to the pre-flood safety inspection of a dam in Jiujiang,Jiangxi Province.Three low-velocity hidden hazards were identified in this dam and were presumed to be the weak layers of the dam foundation and the loose media of the dam body.Practices have proved that this technology effectively counteracts the deficiencies (i.e.,low efficiency and lateral resolution) of the previous microtremor exploration.Moreover,this technology allows scanning at a spacing of 1 m or 0.5 m,thus improving the lateral resolution.This study will provide efficient and accurate guidance for dam safety management.

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The spatial variations of elements and element associations in the primary geochemical halos:A case study of the Zhajiatongna gold deposit in Qinghai province
HOU Zhen-Guang, YUAN Zhao-Xian
Geophysical and Geochemical Exploration    2022, 46 (4): 798-807.   DOI: 10.11720/wtyht.2022.1444
Abstract186)   HTML41)    PDF (5123KB)(258)      

The primary geochemical halos, which exist in nearly all types of deposits, especially in hydrothermal deposits, serve as an essential geochemical indicator for deep prospecting. Many studies have been presently carried out on the elemental enrichment/depletion and component zoning in primary geochemical halos. However, there is a lack of reports on the spatial variations of elements and associated elements. This study collected geochemical data from 2,279 samples of the boreholes in the Zhajiatongna gold deposit and then calculated the enrichment factors and conducted a multivariate analysis to characterize the spatial variations of elements and element associations of the deposit. The element associations representing the components of surrounding rocks and mineralized components were extracted from all samples including surrounding rock samples, mineralized surrounding rock samples, and ore samples. They reflect that the deposit was formed by the superposition of mineralized components on the components of surrounding rocks in essence. Moreover, high-medium- and medium-low-temperature element associations were extracted from the ore samples, and high- and medium-low-temperature metallogenic element associations were extracted from the mineralized surrounding rock samples, indicating mineral precipitation mechanisms and the differences in the precipitation time and space. As suggested by the results, the primary geochemical halos of the Zhajiatongna deposit show the following variations from the periphery to the mineralization center: the mineralization-related elements generally exhibit an increasing trend in terms of enrichment degree and the number of enriched element types quantitatively, and the high-medium-temperature-medium-low-temperature and high-temperature-medium-low-temperature metallogenic element associations are superimposed on the surrounding rocks - mineralized element associations.

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Key points of the design of a nodal acquisition system for seismic exploration
YAN Wei
Geophysical and Geochemical Exploration    2022, 46 (3): 570-575.   DOI: 10.11720/wtyht.2022.1462
Abstract180)   HTML45)    PDF (1469KB)(299)      

The requirements for the design and manufacturing of nodal devices are relatively low. The most basic modules of a nodal device include controllers, acquisition circuits, GNSS timing circuits, geophones, batteries, interfaces, downloading cabinets, data downloading & compositing servers, optional testing circuits, signal generators, and QC manuals. As mature supply chains are available for all the above modules, manufacturers pay more attention to organically integrating the above modules into products that can stably work and meet the needs for the signal acquisition of seismic exploration. However, the absence or neglect of some details in some products on the market due to design or cost considerations will cause difficulties in the field application of seismic data acquisition. The data acquisition quality of the nodal devices relies entirely on the independent performance and stability of each nodal device, which further rely entirely on the manufacturers’ understanding of signal acquisition for seismic exploration and data acquisition operations and the resultant design. The requirements of oil and gas exploration and development in new situations must be considered in the design of nodal devices. The focus of oil and gas exploration and development is constantly shifting to deep and ultra-deep parts with more complex ground surfaces, and thus high precision and resolution are required for signal pickup. As a result, nodal devices should be more capable of acquiring weak signals and broadband signals, which cannot be compromised in the design. This paper elaborates on the fundamental details of signal acquisition, test functions, circuit design, storage, batteries, profile, auxiliary systems, quality control, and auxiliary devices in order to avoid problems such as signal distortion, coupling, and EMC.

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Application of complex resistivity method to the exploration of marine shale gas in the Nanling Basin, Anhui Province
YIN Qi-Chun, WANG Yuan-Jun, ZHOU Dao-Rong, ZHANG Li, SUN Tong
Geophysical and Geochemical Exploration    2022, 46 (3): 668-677.   DOI: 10.11720/wtyht.2022.1336
Abstract174)   HTML45)    PDF (3471KB)(178)      

The main part of the Nanling Basin in Anhui Province is a red Mesozoic continental basin, under which the distribution of marine strata is still undetermined and the potential of shale gas resources is unidentified. Based on the physical property characteristics that the Permian organic-rich shale reservoirs around the study area contain pyrite, this study carried out a geological survey of shale gas using the complex resistivity method. Specifically, this study designed an observation system suitable for the different geological characteristics inside and outside the basin, conducted fitting and inversion using Cole-Brown and Cole-Cole models, and plotted maps of near-field parameters electromagnetic resistivity and apparent charging rate. The results show that: (1) The Permian organic-rich shale contains high carbonaceous content and rich pyrite particles and has distinct characteristics of low resistivity and high polarizabi-lity. Therefore, it can be effectively distinguished from its surrounding rocks, which is favorable for the shale gas exploration using the complex resistivity method; (2) Polarizability is an effective parameter that can be used to identify deep organic-rich shale strata and even shale gas reservoirs; (3) Drilling tests were carried out based on the exploration results obtained using the complex resistivity method, successfully discovering the Triassic carbonate strata and predicting that below the red basin in the Nanling Basin is the favorable area of Permian shale gas reservoirs. This study demonstrates that the complex resistivity method can detect pyrite-bearing shale strata with a depth of greater than 2,000 m and a cumulative thickness of about 200 m in the Nanling Basin and is the only method that can directly indicate shale gas reservoirs in electromagnetic exploration. Therefore, the complex resistivity method can be applied to the geophysical prospecting of the marine shale gas in the Nanling Basin with complex geological conditions and even Southern China. The results of this exploration also provide a basis for the further exploration of the marine shale gas in the Nanling Basin.

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Application of geothermal measurement in the geothermal exploration
WANG Ming-Peng, YANG Jun-Song, LIU Yan-Hua
Geophysical and Geochemical Exploration    2022, 46 (4): 838-844.   DOI: 10.11720/wtyht.2022.3270
Abstract173)   HTML39)    PDF (6488KB)(255)      

Geothermal measurement is the most direct method to study the distribution of geothermal field. The intensity and distribution of geothermal heat sources directly affect the distribution of the soil temperature field in the surface layer of the earth's crust, especially the existence of thermal reservoirs and thermal transport channels can cause anomalies in the distribution of the geothermal field. Geothermal measurements were carried out in 16 civil wells and 32 boreholes in the study area to analyze the distribution of geothermal field and the pattern of underground hot water activity, and the results were obvious.The results show that the geothermal field at shallow depths is laterally consistent with that at deep depths, with the temperature tending to increase toward the northeastern corner of the study area, and that the anomalous geothermal areas are distributed as a NNE-oriented strip, with a width of about 700 m, which is consistent with the NNE-oriented faults. The highest geothermal point is located at the intersection of the NW and NNE-trending faults.. The vertical geothermal distributions in the study area are distinct. The geothermal water is limited to a narrow area. The low-temperature groundwater inflows into the tectonic faults and karsts, with volumes controlled with the development degrees of them, leading to an abnormal geothermal gradient. This anomaly also indicated that the geothermal water in the Lasozi Mountain area is mainly stored in fissures and karst caves of limy dolomite or breccia rocks, with fissures and caves providing good pathways for the geothermal water to flow. The geothermal measurement method has traced the range of geothermal anomalies in the study area, which provides an important basis for further geothermal investigation.

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Prediction and identification of gas-bearing properties of tight sandstone reservoirs through simultaneous pre-stack inversion:A case study of block S in Sulige gas field
ZHANG De-Ming, LIU Zhi-Gang, ZANG Dian-Guang, LIAO Xian-Feng, LIU Zhi-Yi, LIU Guo-Bao
Geophysical and Geochemical Exploration    2022, 46 (3): 645-652.   DOI: 10.11720/wtyht.2022.2581
Abstract169)   HTML25)    PDF (8667KB)(179)      

Owing to the small impedance difference with surrounding rock and complex gas-water relationships,it is difficult to identify high-quality reservoirs in block S in the Sulige gas field through the post-stack P-wave impedance inversion.According to the petrophysical analysis of the study area,the pre-stack parameter vp/vs ratio can be used to effectively identify lithology and gas-bearing properties.This study firstly determined the seismic response characteristics of the reservoirs through forward modeling.Secondly,it conducted petrophysical modeling and the prediction of shear-wave velocities using the Xu-White model suitable for sandstone and mudstone and accordingly established a petrophysical model.Thirdly,the CRP gathers were optimized using the processing methods such as linear denoising and residual amplitude compensation.Finally,the thickness and gas-bearing properties of the reservoirs in block S in the Sulige gas field were quantitatively predicted through simultaneous pre-stack inversion.The results are as follows.(1)The top boundary of the reservoirs in the study area shows the seismic reflection characterized by strong trough reflection,while the bottom boundary of the reservoirs shows unapparent seismic reflection;(2)The vp/vs ratio of less than 1.68 can be used to effectively determine sandstone.This combined with the P-wave impedance of less than 12200 g·cm-3 ·m·s-1 can be used to predict the reservoirs in the study area. Moreover, a vp/vs of less than 1.57 can be used to identify the gas-bearing properties;(3)Reservoir distribution and the predicted gas-bearing range have similar trends but differ locally.The development degree of reservoirs is not necessarily positively correlated with the gas content.The method proposed in this paper is expected to provide strong technical support for delineating the favorable gas-bearing reservoir area and deploying well locations in the future.

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Direct current resistivity method and the transparency of mining face
RAO Rong-Fu, SU Ben-Yu
Geophysical and Geochemical Exploration    2022, 46 (3): 563-569.   DOI: 10.11720/wtyht.2022.1459
Abstract169)   HTML39)    PDF (3263KB)(228)      

The transparency of the fully mechanized mining face achieved using advanced exploration equipment and technology can make the information on coal seams more comprehensive and accurate and can lay a solid foundation for the intelligent production of the fully mechanized mining face. DC resistivity method is a common method for geophysical exploration. Owing to the high stability, great anti-interference performance, and sensitive responses to low- and high-resistance bodies, the DC resistivity method is one of the key means of achieving the transparency of the mining face. To explore the application effects of the method in the transparency of the mining face, this study used different working methods to conduct three-dimensional forward and inverse modeling of the response characteristics for solving proven water-bearing structures of the mining face and frontal advanced detection of roadways. The results show that the distribution laws of 3D DC inversion data obtained by corresponding working methods were basically consistent with those of the initial model, and the DC resistivity method can well distinguish between high- and low-resistivity bodies. Therefore, this study can guide the application of the DC resistivity method in the transparency of mining face in practical engineering.

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A collaborative airborne, ground, and borehole exploration technology system for concealed magmatic copper-nickel deposits
HUANG Xu-Zhao, FAN Zheng-Guo, HE Jing-Zi, GE Teng-Fei, WANG Si-Xun, MAN Yi, WANG Peng, LI Jun, WANG Heng
Geophysical and Geochemical Exploration    2022, 46 (3): 597-607.   DOI: 10.11720/wtyht.2022.1562
Abstract164)   HTML99)    PDF (11503KB)(450)      

In recent years, prospecting in coverage areas has become an important topic in China due to the strong demand for energy and mineral resources, and there is an urgent need for new targeted methods and technologies of prospecting. This study put forward a technology system for the collaborative and rapid prospecting of copper-nickel deposits in coverage areas that combines airborne-ground-borehole prospecting methods and technologies. Meanwhile, this study established the framework and description of the collaborative, rapid, and effective exploration technology system. Taking the terrain and geology of coverage areas, as well as the distribution characteristics of deep mineral resources in the area as preconditions, this technology system mainly uses the methods of aero geophysics combined with ground and borehole geophysical exploration and focuses on big data fusion, weak information extraction, and geophysical-geological modeling methods. Meanwhile, it takes geological structure and metallogenic theory as guidance. This technical system has been verified in the exploration of the concealed magmatic copper-nickel deposit in the Qixin area, Ruoqiang County, Xinjiang, achieving positive results.

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Geochemical characteristics and genesis of selenium in soil in Xuancheng City, Anhui Province
XING Run-Hua
Geophysical and Geochemical Exploration    2022, 46 (3): 750-760.   DOI: 10.11720/wtyht.2022.1335
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This study investigates the geochemical characteristics and genesis of selenium (Se) in the soil in Xuancheng City, Anhui Province using the samples of surface and deep soil collected through a 1:250 000 multi-purpose geochemical survey. The results are as follows. The Se content in the surface soil in Xuancheng City is (0.12~8.80)×10-6, with an average of 0.44×10-6. Se-sufficient and Se-rich soils are widely distributed in the study area, accounting for 61.90% and 35.63%, respectively. Se-rich soils are mainly distributed in the Ningdun Town in Ningguo City-Fulingtown in Jixi County, Yangong Town in Jingxian County-Baikeshu area in Xuanzhou District, Chencun Village-Chikeng Mountain in Jingxian County, and Xinhang Town in Guangde County. The Se content in the soil is mainly controlled by parent rocks and soil-forming parent materials. Se content is high in soils in the distribution areas of carbonaceous shale and carbonaceous siliceous mudstones, such as the SinianLantian Formation and Cambrian Hetang and Yangliugang formations, as well as Permian, Triassic, Carboniferous, Cambrian, and Ordovician limestone distribution area. In contrast, Se content is low in Yanshanian intermediate-acid intrusive rocks and Quaternary distribution area. In terms of soil-forming parent materials, Se content is higher in soils with parent materials of carbonate, light clastic rocks, and epimetamorphic rocks than that in soils with parent materials of Late Pleistocene loess, alluvium, and acid rocks. In terms of soil type, Se content is higher in limestone soil, skeleton soil, stonysoil, and red soil than paddy soil, yellow-cinnamon soil, and fluvo-aquic soil. Se content in soil is correlated closely with physicochemical indices, such as V, Cd, Ba, Ag, Zn, Mo, U, Ni, Sb, P, S, and organic matter. Meanwhile, total Se content is correlated closely with bioavailable Se content. Furthermore, all the 47 rice samples collected in the study area are rich in selenium, with a selenium accumulation rate of 100%. However, tea and maize are not rich in Se, and some types of vegetables are rich in Se. Therefore, different types of crops have different absorption capacities of Se in the soil.

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An instance of comprehensive geophysical prospecting features and quantitative interpretation of a quartz-vein-type gold deposit in Northwest China
FENG Jun, JIANG Wen, ZHANG Zheng
Geophysical and Geochemical Exploration    2022, 46 (3): 661-667.   DOI: 10.11720/wtyht.2022.0079
Abstract163)   HTML46)    PDF (1792KB)(216)      

Gold deposits of the quartz-vein-type are the product of post-magmatic hydrothermal and metamorphic hydrothermal processes and are generally controlled by major and secondary faults. Their metallogenic materials originate from the surrounding rocks. The assemblages and contents of metal sulfides in ores of various deposits differ with geological setting and ore-forming and controlling conditions. Moreover, sulfide-gold-quartz ores predominate. The gold deposits of this type have distinct comprehensive geophysical prospecting features, and various physical prospecting methods yield a high degree of regularity. Taking a gold deposit of the quartz-vein-type in northwest China as an example, this study carried out comprehensive physical prospecting of deposits of this type, performed a quantitative prediction based on forward modeling, and conducted interpretation and analysis by combining theories related to geophysical prospecting.

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Channel calibration calculation program for OBEMs
QIAO Yu, CHEN Kai, YANG Qin
Geophysical and Geochemical Exploration    2022, 46 (3): 550-556.   DOI: 10.11720/wtyht.2022.1466
Abstract162)   HTML180)    PDF (1945KB)(142)      

An ocean bottom electromagnetic receiver (OBEM) is primarily designed to measure the submarine electromagnetic signal. In order to verify the function of the instrument and improve the accuracy of result, the instrument is self-checked by a built-in channel calibration before OBEM enters the water. OBME-Ⅲ needs to export the calibration file generated by channel calibration from the instrument, and then use the Matlab program on the PC side to perform calibration calculation, which has shortcomings such as complex offshore operations and low calculation efficiency. In order to solve these problems, the author developed a calibration calculation program based on the ARM-Linux platform. By entering the relevant commands, the channel calibration calculation can be realized locally in OBEM-Ⅲ, reducing the trouble of exporting data for calculation on multiple platforms. The mixed-base fast Fourier transform calculation method adopted reduces the calculation time from 90 s to 11 s while ensuring the calculation accuracy, which greatly improves the calculation speed and improves the efficiency of the instrument's offshore operations. In the magnetotelluric scientific research mission carried out in the southwest of the South China Sea from July to August 2020, the program performed well and successfully obtained high-quality submarine magnetotelluric sounding data.

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Preliminary exploration into the monitoring technology for distributed weak electric field during hydraulic fracturing for shale gas extraction
WU Wen, WANG Meng, YANG Di-Kun, CHEN Mo, REN Lin-Bin
Geophysical and Geochemical Exploration    2022, 46 (3): 557-562.   DOI: 10.11720/wtyht.2022.1461
Abstract162)   HTML42)    PDF (2828KB)(190)      

In the process of hydraulic fracturing for shale gas extraction, the injection, flowback, retention, and absorption of fracturing fluids will cause changes in electric fields in the case of the excitation by the electromagnetic field from an artificial source in a far area or the excitation by the geoelectric field. The time-dependent change in the information on fracturing can be reflected by monitoring the change in weak electric fields above the hydraulic fracturing area. To meet the needs of the real-time monitoring of the fracturing field, this study focuses on the preliminary study of the monitoring technology based on the nodal acquisition devices of distributed weak electric fields. The monitoring system only collects two horizontally orthogonal electric field signals, monitors the real-time information on the electric field within a certain range, and transmits the preliminarily processed data back to the data center in a wireless way. Test results show that the monitoring system has stable performance, a standby time of more than 10 days, and high sealing performance, and is applicable to complex field environments. Therefore, this monitoring system can provide important technical support for obtaining images of fracturing fluid migration in the future.

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Calibration of magnetotelluric sounding based on resistivity logging curves
ZHAO Li-Fang, LI Ai-Yong, WANG Dao-Li, ZHANG Ming-Peng, ZHOU Xi-Ming
Geophysical and Geochemical Exploration    2022, 46 (3): 737-742.   DOI: 10.11720/wtyht.2022.1494
Abstract159)   HTML48)    PDF (2643KB)(203)      

The distortion correction of magnetotelluric sounding curves is critical to magnetotelluric exploration. Based on the comparison between the resistivity logging curves of basin D and the basin's inversed sounding curves before and after being corrected through magnetotelluric sounding translation, this study constructed a transformation function and calibrated magnetotelluric sounding curves using logging curves. The magnetotelluric inversion results improved using the calibration technology proposed in this study are highly consistent with the verification boreholes. Finally, this study effectively revealed the structural characteristics of basin D by combining drilling, seismic, gravitational, and magnetic data.

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A data decoupling analysis of different devices in time-domain IP sounding
LI Zhong-Ping, HAO Feng-Yun, WU Hong-Fei, ZHANG Rui-Fang, ZHU Zhao-Ming, JIA Quan-Shan, LIU Shuang
Geophysical and Geochemical Exploration    2022, 46 (3): 722-728.   DOI: 10.11720/wtyht.2022.1373
Abstract157)   HTML48)    PDF (6151KB)(211)      

This study aims to eliminate the electromagnetic coupling interference in IP sounding. Based on the theory that frequency-and time-domain data can be mutually converted, this study achieved rapid decoupling while retaining the IP information to the greatest extent by using decoupling methods including static IP inversion, the full waveform IP inversion of Cole-Cole parameters, and delay inversion. This study investigated a gold deposit in Yinan County, Shandong Province and conducted the inversion of time-domain IP sounding data before and after decoupling. The results are as follows. The electromagnetic coupling effect of symmetrical quadrupole devices and unconventional electrode array increases with an increase in the distance between adjacent electrodes, and its influencing depth is mostly less than 150 m in the inversion results of time-domain IP sounding; the electromagnetic coupling interference produced by the unconventional electrode array that adopts a collinear device of dislocation multipoles (tripoles, quadrupoles, and dipoles) is apparently greater than that of symmetrical quadrupole devices and monopole-dipole devices; noncollinear monopole-dipole devices generate slight electromagnetic coupling effect in the process of time-domain IP sounding.

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Application of radioactive prospecting in exploration of rare metal minerals: A case study of a uranium anomaly in the Nancha area
Wang Rui, Li Zhan-Long, Ma Tao
Geophysical and Geochemical Exploration    2022, 46 (4): 854-861.   DOI: 10.11720/wtyht.2022.2500
Abstract156)   HTML39)    PDF (4560KB)(225)      

The mineralization of deposits of rare metals such as tantalum and niobium in China is mostly related to granite pegmatite. The enrichment of rare metals in these deposits is accompanied by the formation of radioactive minerals, such as albite, monazite, and high-grade uranium, and these deposits have paragenetic and associated minerals uranium deposits. Therefore, radioactive prospecting has become the most convenient and effective method to explore deposits of rare metals such as REEs, Nb, and Ta. Based on the close correlation between mineralization and radioactivity of rare earth minerals, this study fully investigated the parameter characteristics of the surveyed energy spectrum data through the combination of airborne radioactivity measurement and ground gamma spectrometry measurement to determine prospecting indicators. A new niobium-tantalum-rubidium polymetallic mineralized point was discovered in the Nancha area, Yichun City using the radioactive prospecting method, which was thus proven effective.

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Design and test of the parallel ultra-small transmitter loop used in the transient electromagnetic method
WU Bei-Chen, PAN Yang-Run-Yi, CHENG Jiu-Long, WANG Hui, YAO Di, PANG Xiao-Yin
Geophysical and Geochemical Exploration    2022, 46 (4): 934-939.   DOI: 10.11720/wtyht.2022.1424
Abstract155)   HTML19)    PDF (2732KB)(177)      

In the shallow or mine prospecting using the transient electromagnetic method (TEM), the transmitting magnetic moment is limited by the limited supply voltage of the transmitting system, and the stray inductance of the transmitter loop causes a long turn-off time. To solve these problems, this study designed a parallel transmitter loop of ultra-small coils used in TEM. Using these coils, the transmitting magnetic moment can be increased by the parallel connection of the coils, and the turn-off time can be reduced by additional resistance. The equivalent circuit models of the conventional transmitter coils and the parallel transmitter coils were established and analyzed theoretically. Moreover, the comparative test between the parallel transmitter coils and the conventional transmitter coils were carried out. The results show that the parallel transmitter coils can effectively increase the magnetic moment and reduce the turn-off time. Therefore, this design is greatly significant for reducing the blind area and increasing the prospecting depth in shallow or mine prospecting using TEM.

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Research progress of SmNiO3 and feasibility analysis of applying SmNiO3 in ocean electric field sensors
XIAO Yue-Tong, WANG Meng, WANG Xing-Zhuo, CHEN Kai, SHI Zong-Yang, ZHAO Yi-Yu, FU Yue-Si
Geophysical and Geochemical Exploration    2022, 46 (2): 418-423.   DOI: 10.11720/wtyht.2022.1255
Abstract153)   HTML56)    PDF (1135KB)(90)      

Ocean electric field signals are widely used in the fields of geological tectonics, water target detection, physical ocean, and the analysis of ocean physical characteristics. It is of great scientific value to collect the ocean electric field signals, while the ocean electric field is measured using ocean electric field sensors. In recent years, perovskite-type composite oxides have become a research hot spot as new materials. Among these composite oxides, SmNiO3 is the one that possesses some unique properties including metal-insulator phase transition, strong stability in seawater, and high sensitivity to low-frequency electric field signals. Therefore, it is expected to become a new type of electrode materials in ocean electric field sensors. Domestic and foreign researchers have carried out some studies on SmNiO3, which mainly focus on the electrical properties (especially the metal-insulator phase transition and optical properties) and preparation process of SmNiO3. This paper systematically reviews the above research contents and preliminarily explores the feasibility of applying SmNiO3 in marine electric field sensors.

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Moving-footprint-based large-scale model decomposition method for forward modeling of gravity and gravity gradient anomalies
SHI Ze-Yu, ZHANG Zhi-Hou, LIU Peng-Fei, FAN Xiang-Tai
Geophysical and Geochemical Exploration    2022, 46 (3): 576-584.   DOI: 10.11720/wtyht.2022.1468
Abstract153)   HTML44)    PDF (2387KB)(188)      

The computational efficiency of the forward modeling for gravity and gravity gradient anomalies determines the feasibility of inverse modeling. It also forms the basis for the efficient building of sufficient and diverse deep learning sample data. Inspired by the application of moving-footprint—a fast forward modeling method in the aerospace electromagnetic field and based on the fast space-domain forward modeling of geometric lattice functions of grid points, the authors proposed a computation method for the forward modeling of gravity and gravity gradient anomalies by applying “moving-footprint”, aiming to further improve the speed of the forward calculation for gravity and gravity gradient anomalies. Specifically, this method selects the subspace in a certain effective range directly below an observation point in the underground half-space. The observation point anomaly approximates the total anomalies of the cuboid units in the corresponding subspace while ignoring the anomalies produced by the cuboid units outside the subspace. When the observation point moves, the corresponding subspace moves accordingly. Therefore, the large-scale underground half-space cuboid model can be decomposed into the subspace corresponding to each calculation point for the forward calculation. As shown by the results of a model test, when 32×32×15 subspace was selected in the underground half-space of a 256×256×15 rectangular parallelepiped model for calculation, the relative average error of gravity anomalies and partial gradient anomalies was less than 10% and the calculation speed was increased by 19 times. Moreover, the calculation time of 1024×1024×15 rectangular parallelepiped model is approximately 32 minutes. Compared with the existing algorithms with a bottleneck in the ultra-conventional calculations, the method proposed in this study has significant advantages regarding computation.

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MicrOBEM: a micro-ocean-bottom electromagnetic receiver
LUO Xian-Hu, DENG Ming, QIU Ning, SUN Zhen, WANG Meng, JING Jian-En, CHEN Kai
Geophysical and Geochemical Exploration    2022, 46 (3): 544-549.   DOI: 10.11720/wtyht.2022.1478
Abstract152)   HTML182)    PDF (2209KB)(162)      

Ocean bottom electromagnetic receivers (OBEMs) are mainly used for high-precision observation and measurement of magnetotelluric signals and controlled-source electromagnetic signals at the sea bottom. To overcome the shortcomings of large volume, high power consumption, and high cost of the existing OBEMs (OBEM-Ⅲ type), this study conducted technical research regarding miniaturization, low power consumption, and low cost. As a result, the overall power consumption of the existing OBEMs (OBEM-Ⅲ type) has been reduced from 1 600 mW to 500 mW or less (by equipment of inductive magnetic sensors) due to the development of a low-power control unit and preamplifier, the installation of low-power fluxgate sensors, and adoption of advanced power management technology. Traditional acoustic releasers are expensive and bulky and require more suitable buoyant materials. By integrating the underwater acoustic communication module and being equipped with the external erosion wearing release device, the MicrOBEMs make release and recovery possible using only a 17-inch glass sphere, thus greatly reducing the volume and hardware cost of the instrument and improving the integration and operation efficiency of devices. Compared to the OBEM-Ⅲ type, the volume, power consumption, and cost of the newly developed MicrOBEMs are reduced by 3/4, 2/3, and 1/2, respectively. A deep-water geomagnetic test was conducted in March 2021 in the southern South China Sea, preliminarily verifying the geomagnetic measurement function of the MicrOBEMs and reflecting that the MicrOBEMs have the advantages of small size, low power consumption, and low cost.

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Application of comprehensive geophysical prospecting in investigation of coal mine goaves
WANG Qiang, Tian Ye, LIU Huan, ZHU Chun-Guang, BAI Chao-Kun, HAO Sen
Geophysical and Geochemical Exploration    2022, 46 (2): 531-536.   DOI: 10.11720/wtyht.2022.1202
Abstract152)   HTML34)    PDF (2788KB)(192)      

There are many small coal mine goaves in Huazi Town-Xidayao Town in Dengta City, Liaoyang City, Liaoning Province. They are distributed in villages and towns and their surrounding areas, posing great threats to the ground buildings and resident life. Furthermore, the vegetation around the mining area is sparse, and a large amount of coal slag has been piled up at will, which causes serious damage to the ecological environment. However, owing to the limitations of a single geophysical method, it is difficult to completely eliminate interference and observation errors through the goaf investigation using a single geophysical method. Based on the selection and exploration of geophysical methods from the aspects of anti-interference and effectiveness, this study conducted the coal mine goaves in the study area by applying the geophysical prospecting methods including gravity survey, high-density resistivity method, and shallow seismic reflection method. As verified through drilling, ideal results were achieved.

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Eco-geochemical survey and evaluation of heavy metals and other elements in soil in Anning City, Yunnan Province
FAN Chen-Zi, YUAN Ji-Hai, LIU Cheng-Hai, GUO Wei, SUN Dong-Yang, LIU Wei, ZHAO Jiu-Jiang, HU Jun-Dong, ZHAO Ling-Hao
Geophysical and Geochemical Exploration    2022, 46 (3): 761-771.   DOI: 10.11720/wtyht.2022.1367
Abstract149)   HTML46)    PDF (9225KB)(197)      

Anning City, Yunnan Province, China is an important area of economic development and ecological civilization construction in central Yunnan on the upper reaches of the Yangtze River. This study investigated the contents and enrichment degrees of elements including heavy metals in the surface soil samples that were systematically collected in the Anning area from 2018 to 2020. Then, this study assessed the ecological risks of heavy metals in the soil using the geoaccumulation index and the assessment indices of potential ecological risks and analyzed the sources of heavy metals using the methods of the Pearson correlation and principal component analysis. The results show that heavy metals Cr, Zn, As, Cd, Pb, Hg, and radioactive element U in the soil in the study area have significantly higher contents than corresponding background values of soil in Yunnan Province and show high-degree variation and uneven spatial distribution. Moreover, Cr has the highest accumulation degree of geological anomalies, elements As, Cd, and Hg have high potential ecological risks, and ecological risks are mainly concentrated in the phosphate mining area and the vicinity of steel plants and chemical plants in the Tanglangchuan basin. In terms of sources, Cr, Ni, and Cu may mainly originate from soil parent materials; areas with high Cd, Pb, Zn, and As contents are significantly affected by human activities, and Hg may have a composite pollution source. These results will provide a scientific basis for understanding the sources of heavy metals in soil in Anning City and for the management and protection of local land resources.

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An application test of broadband magnetotelluric method (BMT) for the evaluation of uranium resources in the Erlian Basin
WU Xian-Hong, XU Di-Qiao, LI Mao
Geophysical and Geochemical Exploration    2022, 46 (4): 830-837.   DOI: 10.11720/wtyht.2022.1429
Abstract146)   HTML38)    PDF (4298KB)(243)      

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

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Geophysical prospecting mode and metallogenic model of the Weiquan silver-copper polymetallic deposit in Xinjiang
Feng Jun, Jiang Wen, Zhang Zheng
Geophysical and Geochemical Exploration    2022, 46 (4): 868-876.   DOI: 10.11720/wtyht.2022.0055
Abstract145)   HTML31)    PDF (7928KB)(249)      

The Weiquan silver-copper polymetallic deposit has received extensive attention because of its unique genesis. This study analyzed the anomaly characteristics shown in the integrated gravity-magnetic-electrical geophysical planes and sections of the Weiquan silver-copper polymetallic deposit. Then, it obtained the interpretation model of geophysical anomalies through the forward and inverse calculations of the typical sections. Based on the distribution pattern of existing ore bodies and the metallogenic model summarized in previous studies, this study established the geological-geophysical prospecting mode of this area. Moreover, this study proposed the geological-geophysical prospecting model of this area, aiming to provide a basis for prospecting prediction.

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An experimental study on the high-resolution single-channel seismic exploration technology for inland shallow waters
YUE Hang-Yu, ZHANG Ming-Dong, ZHANG Bao-Wei, WANG Guang-Ke, WANG Xiao-Jiang, LIU Dong-Ming
Geophysical and Geochemical Exploration    2022, 46 (4): 914-924.   DOI: 10.11720/wtyht.2022.1479
Abstract143)   HTML33)    PDF (14954KB)(331)      

With the advantages of flexible configuration,convenience,high efficiency,and resolution,the single-channel seismic detection technology has been widely used in marine geological surveys and offshore engineering geophysical prospecting.However,there are few cases of the application of this technology in inland rivers and lakes.Therefore,an experimental study on the high-resolution single-channel seismic detection technology targeting the inland shallow waters of Baiyangdian Lake,Xiongan New Area,Hebei Province was conducted.The application effects using key acquisition parameters,including excitation energy,excitation interval,sailing speed,and the number of receiving units,were compared to determine the optimal parameter combination.A set of single-channel seismic data processing processes and methods for inland shallow waters were developed to gradually attenuate all kinds of noises and improve the signal-to-noise ratio and resolution to the greatest extent.The experimental results show that the single-channel seismic detection technology for inland shallow waters can finely divide the shallow stratigraphic structure in the waters.Moreover,the division effects agree well with drilling data.Therefore,this technology can effectively support the investigations of environment,geology,and geologic hazards in inland rivers and lakes.

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Application of comprehensive geophysical prospecting method in detecting concealed karst collapses
ZHANG Jian, FENG Xu-Liang, YUE Xiang-Ping
Geophysical and Geochemical Exploration    2022, 46 (6): 1403-1410.   DOI: 10.11720/wtyht.2022.1566
Abstract141)   HTML18)    PDF (3908KB)(188)      

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

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Application of comprehensive geophysical prospecting method in well siting for shale gas exploration in carbonate areas in east China
LUO Wei-Feng, HU Zhi-Fang, GAN Fu-Ping, ZHANG Qing-Yu, KANG Hai-Xia, ZHANG Yun-Xiao
Geophysical and Geochemical Exploration    2022, 46 (4): 824-829.   DOI: 10.11720/wtyht.2022.1505
Abstract140)   HTML44)    PDF (1739KB)(205)      

The drilling engineering for shale gas in carbonate areas in China is facing prominent carbonate karst. It is necessary to carry out near-surface geophysical prospecting before drilling and reasonably select the well locations in order to ensure the safety of the well site and reduce the drilling engineering risks. Taking the siting of Well Guirongye-1 in Rong'an County, Liuzhou City, Guangxi Province as an example, this study conducted the application research of well siting before drilling comprehensively using three geophysical prospecting methods, namely the high-density resistivity method, the audio-frequency magnetotellurics method, and radon survey, achieving satisfactory results. Well Guirongye-1 did not encounter a fault fracture zone near the surface, which is basically consistent with the interpretation results of comprehensive geophysical prospecting. This result indicates that the comprehensive geophysical prospecting method is feasible and effective in the siting of shale gas exploration wells in the carbonate areas in south China. This study will provide a certain reference for the well siting before drilling in similar areas in the future.

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Property analysis and application of multi-scale wavelet decomposition of gravity potential field
MENG Qing-Kui, ZHANG Wen-Zhi, GAO Wei, SHU Qing, LI Rui, XU Guang-Jing, ZHANG Kai-Song
Geophysical and Geochemical Exploration    2022, 46 (4): 946-954.   DOI: 10.11720/wtyht.2022.2552
Abstract139)   HTML41)    PDF (5207KB)(169)      

Multi-scale wavelet decomposition is one of the common methods for gravity potential field separation. The biggest advantage is that it breaks through the traditional concept of dichotomy gravity anomalies and achieves the multiple decomposition of gravity anomalies. However, no systematic study has been carried out on the limitations and properties of the multi-scale wavelet decomposition. To systematically investigate the multi-scale wavelet decomposition and provide guidance for its practical application, this study, starting from the definition of multi-scale wavelet decomposition of gravity potential field based on profiles and grids, expounded three important properties such as the criterion that low-order wavelet keeps details invariant. Then, it analyzed the definition and properties of multi-scale wavelet by designing simple and complex theoretical models. Afterward, this study compared the multi-scale wavelet decomposition with the interpolation cutting method using field data. The results show that multi-scale wavelet decomposition can achieve multi-layer separation of gravity potential field and estimate the burial depths of source bodies. In addition, the multi-scale wavelet decomposition can provide some ideas for solving the limitations pointed out in this study, such as abnormal scale aliasing and difficulty with the determination of scale coefficients. The above basic research can provide a certain degree of references for the processing and interpretation of gravitational potential field data.

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Technology for suppressing "black triangle" high-energy noise in vibroseis seismic data acquisition in a desert area
SU Yun, YOU Hong-Wen, LI Ling-Xi, MENG Fan-Bing, LI Min-Jie, TANG Juan, XIE Jin-Li
Geophysical and Geochemical Exploration    2022, 46 (2): 410-417.   DOI: 10.11720/wtyht.2022.2419
Abstract137)   HTML70)    PDF (12149KB)(170)      

The special topographic and geomorphic conditions in the desert exploration area of the Guaizihu sag in the Yin'e Basin produce adverse effects on the excitation and reception of seismic data.The surface of the area is covered by hugely thick loose sand,with the thickness of the sand dunes varying in the range of 50~100 m.In the process of vibroseis data acquisition in this area,"black triangle" noise is formed in the near-trace scope due to the dual effects of the mechanical characteristics of the vibroseis and the near-surface structure,resulting in a low signal-to-noise ratio of seismic records.Since the "black triangle" noise features high energy,wide frequency range,wide distribution,and great morphological difference,it is difficult to make accurate statistics of its amplitude (intensity) in a single arrangement of the common shot domain and the common receiver domain,thus resulting in too much residual noise after the suppression of the "black triangle" noise.Given this,this paper proposes a method,in which data rearrangement is firstly conducted based on the shot-offset domain and then denoising is performed.As verified by the application of actual vibroseis data of the Guaizihu area in the Yin'e Basin,this method can effectively protect the near-trace reflection signals(especially the deep weak reflection information) while effectively suppressing the "black triangle" noise and it is effective in improving the signal-to-noise ratio of seismic data.

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Exploring the standards of Se-rich soil in Qinghai Province
MA Qiang, ZHANG Ya-Feng, HUANG Qiang, JI Bing-Yan, Miao Guo-Wen, MA Feng-Juan, MA Ying
Geophysical and Geochemical Exploration    2022, 46 (3): 772-780.   DOI: 10.11720/wtyht.2022.1285
Abstract136)   HTML37)    PDF (4084KB)(181)      

The acid-base properties and Se background values of the soil in Qinghai Province were obtained by analyzing the pH and Se content of the soil based on the data derived from the geochemical survey of land quality conducted in Qinghai Province. The Se enrichment models of root soil and crops such as wheat, rapeseed, pea, garlic, and forage were established accordingly. The recommended values of Se-rich soil in Qinghai were calculated by combining the recommended in take of Se in the population with the standard value of Se content in Se-rich agricultural and livestock products in Qinghai Province. It is recommended that the lower limit of Se-rich soil for alkaline soil and neutral and acidic soil in Qinghai Province should be 0.23×10-6 and 0.25×10-6, respectively. This study is greatly significant for the formulation of the local standards for Se-rich soil in Qinghai Province and for guiding the development of the selenium industry.

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Exploration of the genesis of regional geothermal resources in Guizhou Province
WANG Liang, HU Cong-Liang, ZHANG Jia-Wei, CHEN Guo-Yong, ZHANG Mei-Xue, YANG Wu, ZHANG Ying-Wen
Geophysical and Geochemical Exploration    2022, 46 (2): 304-315.   DOI: 10.11720/wtyht.2022.1228
Abstract132)   HTML82)    PDF (1751KB)(111)      

Regarding the genesis of the geothermal resources in Guizhou Province, most researchers tend to think that the geothermal resources were formed from the temperature rise induced by the mechanical energy of the “geothermal gradient” controlled by seismic activities and faults and that the geothermal resources do not possess from magma heat sources nor have the conditions of radioactive heat generation. Based on the research on the previous achievements, the characteristics of geothermal reservoirs and cap rocks, and regional gravity and magnetic data, the inference of the deep faults and intermediate-acid and basic-ultrabasic rock masses, and the analysis of regional distribution characteristics of natural geothermal resources and geothermal wells, this study proposes two possible basic genetic models of the geothermal resources in Guizhou. One is that automatic temperature rise and cyclic heat generation caused by the “geothermal gradient” controlled by deep faults. The groundwater with continuous temperature rise driven by this model is the most developed. The other genesis is the waste heat of magmatic rocks. It is inferred as a new type of heat generation and genesis supplement. As an important regional metallogenic region of uranium and thorium in China, Guizhou Province has only been researched at a low level and on a small scale, with a small amount of available data. Therefore, it is not clear whether there are basic conditions of radioactive heat generation in Guizhou Province. The in-depth study on the genesis of geothermal resources can provide relevant bases for the accurate surveys of geothermal resources and the expansion of prospecting direction in Guizhou Province in the future.

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Ground penetrating radar imaging mechanisms of underground square cavities
HAN Jia-Ming, NIU Yu-Kai, LIU Ming-Ming, GUO Ya-Nan, JIN Chao
Geophysical and Geochemical Exploration    2022, 46 (3): 685-692.   DOI: 10.11720/wtyht.2022.1313
Abstract132)   HTML25)    PDF (2462KB)(188)      

Owing to geographical factors and historical reasons,the urban underground square cavities show increasing number,density,and chaotic state,leading to unclear interpretation results of the ground penetrating radar(GPR) images of these underground square cavities.This study divided the left side of an image(with the symmetry axis as a boundary) of square cavities obtained from the GPR scanning close to the ground into three stages based on the whole process of ground penetrating radar scanning detection.Then,this study established the relationships between horizontal distance and echo delay of each stage.Furthermore,it systematically analyzed the changes in the GPR images of square cavities with different burial depths and sizes.Finally,this study obtained the scientific explanation of geological radar imaging mechanisms of underground square cavities based on GPR detection examples.It is concluded that the three stages of the left side of a GPR scanning image of the underground square cavities in uniform media include a continuous straight line with a constant slope,a monotonically decreasing continuous concave curve,and a continuous horizontal straight line unrelated to the horizontal distance.With an increase in the burial depth and cavity size,the curve tends to be gentle and its open radian tends to increase.

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Characteristics and risk assessment of the heavy metals in stream sediments of Heze City
XU Xiong, SUN Yan-Ting, XIAO Fang, XIAO Pei-Ping, DONG Ying-Shang, LI Min
Geophysical and Geochemical Exploration    2022, 46 (4): 1021-1029.   DOI: 10.11720/wtyht.2022.1421
Abstract130)   HTML28)    PDF (4931KB)(196)      

This study aims to investigate the characteristics, pollution sources, and ecological risks of heavy metals in the stream sediments in Heze City, which is an important catchment area in the east route of the South-to-North Water Diversion Project. To this end, stream sediment samples were collected from 25 sites of three major river basins in Heze City, and the contents of Cu, Zn, Ni, Cr, Cd, and Pb in the samples were analyzed. Moreover, this study assessed the ecological risks of these heavy metal elements using the pollution load index (PLI), potential ecological risk index (RI), and logarithmic regression model and determined the pollution sources of these heavy metal elements through correlation and principal component analysis. The results are as follows. The contents of the six heavy metal elements in the stream sediment samples were generally higher than their background values. The Ni and Cd contents at all investigated sites exceeded their background values, especially the Cd content at 40% of the investigated sites, which was more than three times the background value. The heavy metals in the stream sediments of the three river basins are unevenly distributed. The maximum values of the six heavy metals all originated from the samples of the Zhuzhaoxin River basin, of which the PLI, RI, and toxicity ratio Y were 1.67, 123 and 0.367, respectively. These values were higher than those of the other two basins, indicating that the heavy metals in sediments of the Zhuzhaoxin River basin reach moderate pollution and have high ecological risks and potential harm to aquatic organisms. The principal component analysis shows that the petroleum refining and related chemical enterprises in industrial parks are the main contributors to the enrichment of the six heavy metal elements.

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Metallogenic prediction of gold deposits in Laowan area, Henan Province using the weight of evidence model and MRAS
WEI Cong-Ling, CHEN Jian-Li, GUO Peng
Geophysical and Geochemical Exploration    2022, 46 (3): 653-660.   DOI: 10.11720/wtyht.2022.1337
Abstract129)   HTML29)    PDF (2327KB)(118)      

The Laowan area in Henan Province is an important gold minerogenetic area in the Tongbai-Dabie noble nonferrous metal metallogenic belt. Based on the comprehensive analysis of the metallogenic factors of the area, the authors extracted and established nine predictive variables, i.e., strata, ductile shear zones, brittle fault zones, magmatic rocks, gold-related alteration zones, and single-element anomalies of gold, arsenic, antimony, and sliver in stream sediments. Then, the authors predicted metallogenic prospect areas of gold in this area using the weight of evidence model and the MRAS software. Grid cells with a size of 0.10 km×0.10 km were used for prediction, and they were divided into classes A, B, and C in terms of prospecting prediction through the prior probability calculation, weight statistics, independence tests, and posterior probability calculation of each prediction variable. Based on the distribution characteristics of various classes of prediction grid cells and the geological characteristics of gold deposits in the study area, this study delineated four first- and four second-order prospecting target areas. According to comprehensive analysis, most of the known gold deposits or gold ore occurrences fall into the prediction blocks of classes A and B and the prediction blocks of class C lie around the prediction blocks of classes A or B. This analytical result is consistent with the gradual changes of the metallogenic belt from the center to the edges. Gold deposits or ore occurrences have been discovered in all the delineated first-order prospecting target areas, and the posterior probabilities have a high average. Therefore, first-order prospecting target areas have great gold prospecting potential.

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Determination of the optimal factors of seismic excitation and reception on the ground surface of carbonate mountainous areas in Pengshui area and its seismic acquisition effects
XUE Ye, YANG Fan, LIU Hou-Yu, LIU Ming, ZHAO Su-Cheng, LAN Jia-Da
Geophysical and Geochemical Exploration    2022, 46 (3): 608-617.   DOI: 10.11720/wtyht.2022.1251
Abstract129)   HTML39)    PDF (8487KB)(185)      

The Pengshui area,located in the Wuling fold belt at the southeast margin of Sichuan Basin,has a typical karst mountain landform and very complex near-surface structures.Such a geological setting leads to a poor seismic acquisition effect and a low signal to noise ratio (SNR),which seriously affects the oil and gas exploration in this area.This study carried out the excitation tests and research,such as charge type,excitation mode,excitation well depth,and excitation dose,as well as receiving tests on interference wave investigation and geophone types and their combination means on the ground surface in the mountainous areas with exposed carbonate rocks.Furthermore,this study selected a set of excitation and receiving parameters with a strong economy and maneuverability and established the technology used to determine the optimal excitation point location for complex mountainous terrain.Compared with the previous data,this study achieved significantly improved energy,SNR,and first-grade product rate of the newly acquired single-shot records.Moreover,the new data processing profiles obtained in this study show rich information,clear reflection characteristics,and high SNR and display a distinct seismic tectonic pattern of carbonate rock area.

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Speciation and distribution of heavy metals in sediments in Haihe River Basin and their effects on ecological risk assessment
LI Sheng-Qing
Geophysical and Geochemical Exploration    2022, 46 (3): 781-786.   DOI: 10.11720/wtyht.2022.1074
Abstract128)   HTML22)    PDF (556KB)(137)      

Since a large amount of domestic and industrial wastewater containing heavy metals has been discharged into the Haihe River Basin, many heavy metals enter the water environment and accumulate in the sediments. Traditional ecological risk assessment methods ignore the speciation and distribution of heavy metals, leading to the low reliability of ecological risk assessment. This study investigated the plain section of the Haihe River Basin and researched the speciation and distribution of heavy metals in the sediments in the Haihe River Basin and carried out the ecological risk assessment. Sediment samples were collected at the collection points deployed in the Haihe River Basin. Afterward, the samples were processed using mixed acids at the laboratory. Then, the contents of heavy metals in the samples were determined using atomic absorption spectrometry, and the speciation and distribution of heavy metals in the sediments were analyzed. For the ecological risk assessment, abundance calculation was adopted to improve the ecological risk assessment indices and design the ecological risk assessment standard of heavy metals. The experimental results show that the obtained evaluation of the sampling points and various heavy metals were closer to the actual situation, has higher reliability, and displayed better evaluation performance compared to results obtained using traditional assessment methods.

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Development and performance tests of maintenance-free ultra-low noise solid nonpolarizing electrodes
WANG Hui, FU Shu-Ji, GE Shuai-Yin, MA Fang-Yuan, SONG Bao-Jia, LUO Jing-Cheng
Geophysical and Geochemical Exploration    2022, 46 (3): 714-721.   DOI: 10.11720/wtyht.2022.1386
Abstract127)   HTML28)    PDF (5457KB)(103)      

To overcome the shortcomings of traditional nonpolarizing electrodes, such as the poor stability of potential difference, high low-frequency noise, short life, and requiring regular maintenance, the authors researched and developed maintenance-free ultra-low noise Pb-PbCl2 nonpolarizing electrodes after over a decade of development and constant tests. Lab test results show that the new nonpolarizing electrodes have a potential difference drift within one month of less than ±0.06 mV and a temperature coefficient of less than 20 μV/℃, which are 5% and less than one-fifth of those of the PMS9000 electrodes exported from France, respectively; under the ideal condition of the distance between two adjacent electrodes of 100 m, the signal-to-noise ratios relative to the natural induced electric field are 40dB@103s, 20dB@104s, and 10dB@105s. The field comparative tests show that the newly developed solid nonpolarizing electrodes can significantly improve the acquisition accuracy of geoelectric field signals and the data quality of dead and low magnetotelluric frequency bands.

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Selenium speciation in surface soil in Yaling Town, Yichuan County—Xiaodian Town,Ruyang County in Luoyang City
HOU Jin-Kai, SONG Yan-Bin, ZHU Rui-Zhen, XIN Feng-Pei, ZHOU Jian-Chuan, LU Fu-Lan, YAO Jie
Geophysical and Geochemical Exploration    2022, 46 (2): 511-517.   DOI: 10.11720/wtyht.2022.1242
Abstract126)   HTML67)    PDF (725KB)(152)      

Surface soil samples in Yaling Town, Yichuan County -Xiaodian Town, Ruyang County in Luoyang City were collected and analyzed to study the selenium (Se) speciation and its influencing factors. The study results are as follows. Existing Se in the surface soil of the study area mainly occurs in humic acid, residue, and strong organic states, while the sum of Se in water-soluble and ion-exchange states only accounts for 2.70% of total Se in the surface soil. Therefore, the Se in the study area shows the characteristics of the low content of water-soluble Se and a significantly high proportion of organic Se in total Se. The Se speciation in the surface soil is affected by the total Se content, pH, organic matter content, and type of soil. Specifically, the proportion of bioavailable Se in alkaline soil is significantly higher than that in neutral and acidic soils, and the bioavailable selenium content increases with increasing soil pH. Especially, the organic matter content in the soil has the most significant effects on organic Se but has no significant effect on bioavailable Se. For different types of soils, the proportion of the sum of Se in water-soluble and ionic-exchange states in total Se is in the order of red clay>paddy soil>brown soil>skeleton soil>fluvo-aquic soil>lime concretion black soil.

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Accessing the distribution and ecological risks of heavy metals in soil in Hong’an County, Hubei Province through ecological geological surveys
JU Zi-Long, QIN Zhi-Jun, Wan Xiang, YUAN Hang, ZHANG Xiao-Bo, WANG Deng
Geophysical and Geochemical Exploration    2022, 46 (4): 988-998.   DOI: 10.11720/wtyht.2022.1398
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This study selected the Jinsha Lake and the Miersi Industry Park as key survey areas to study the distribution of heavy metals in soil in Hong’an County, Hubei Province. Samples were collected from surface soil and vertical soil profiles to assay the contents of eight heavy metals, i.e., Cu, Pb, Zn, Cr, Ni, Cd, As, and Hg. Both the single factor pollution index method and the potential ecological hazard index method were used to assess the distribution and the ecological risk of heavy metals. The study results are as follows:The average contents of the above eight heavy metals were 21.48×10-6, 21.75×10-6, 63.60×10-6, 53.24×10-6, 20.25×10-6, 0.13×10-6, 5.44×10-6, and 0.04×10-6,respectively. The cumulative Cu, Cr, Ni, and Cd are relatively enriched in the soil and their pollution is slight. The heavy metals show distinct distribution patterns. Minor pollution exists in the Gaoqiao-Yongjiahe basic-ultrabasic melange zone and around the Miershi Industrial Park, while severe pollution exists in Mn-Co mineralized points scattered in the northeastern Baliwan. Pb and Hg are enriched in the surface layer but decrease in the deep layer, Cr and Ni show an inverse trend, while other elements show indistinct distribution patterns. Cd and Hg have high potential ecological risk individually in the soil in the surveyed areas. The comprehensive ecological risk assessment based on Cd and Hg shows that the surrounding area of the Jinsha Lake Chengguan Town, the basic-ultrabasic melange zone, the surrounding area of the Miersi Industrial Park, and the Baliwan manganese-cobalt mineralization zone are areas with moderate potential ecological risks, where ecological supervision and protection should be strengthened. This study can provide a scientific basis for later ecological management in Hongan. It also serves as a good soil reference for other ecological geological surveys.

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A comparative study of Mur second-order absorbing boundary condition and unsplit recursive convolutional perfectly matched layer method under multi-source concurrency
CUI Fan, CHEN Yi, XUE Han-Peng, PENG Su-Ping, DU Yun-Fei
Geophysical and Geochemical Exploration    2022, 46 (3): 693-703.   DOI: 10.11720/wtyht.2022.1180
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Plane beam signals form when multiple excitation sources simultaneously emit pulses with the same center frequency (multiple-source concurrency),thus enhancing the quality of data records.This paper compares and analyzes the electromagnetic wave absorption effects of unsplit recursive convolutional perfectly matched layer (PML) as the absorbing boundary condition and Mur second-order absorbing boundary condition under multi-source concurrency through numerical simulation.According to study results,the traditional Mur second-order absorbing boundary condition did not perform well in absorbing electromagnetic waves under the conditions of multi-source concurrency and multi-angle grazing,and it will cause waveform distortion and spurious reflections in the case of large offsets.For the unsplit recursive convolutional perfectly matched layer as the absorbing boundary condition under multi-source concurrency,coordinate scale factors were introduced into the finite-difference time-domain (FDTD) algorithm.Then,the PML equation for coordinate stretching was transformed from frequency domain into time domain through the inverse Fourier transform.Finally,the electric and magnetic field values were solved using the recursive convolution method in the discrete state,thus avoiding the complicated calculation involved in directly determining the numerical solution of convolution.This allows less memory space and high calculation efficiency while ensuring accuracy.Therefore,the unsplit recursive convolutional perfectly matched layer method improves the electromagnetic wave absorption effect at the positions where the grid terminate without inducing wave-field splitting.

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Multi-scale full waveform inversion method using combined source encoding
GUO Yun-Dong
Geophysical and Geochemical Exploration    2022, 46 (3): 729-736.   DOI: 10.11720/wtyht.2022.1216
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Full waveform inversion (FWI) is one of the most accurate velocity inversion tools.It can be used to obtain high-precision subsurface structures through iterative inversion and provide a more accurate velocity field for prestack imaging technology,thus satisfying the increasingly complex demand for petroleum exploration and development.However,FWI requires accurately estimated source wavelets,which are very difficult to extract from the seismic data collected in the field.Furthermore,in the inversion process,there is a strong nonlinear relationship between model parameters and observed data,which is liable to induce cycle skipping.To overcome the cycle skipping and the difficulty in extracting seismic wavelets in the inversion process of medium-low wavenumber,this paper developed a multi-scale waveform inversion method using combined source encoding.Specifically,the wavelets and seismic data were combined by applying time-shift stacking,and gradients can be determined through only one calculation of reverse time migration.According to the calculation results using a model,the FWI method using combined source encoding can be used to achieve multi-scale inversion and obtain more stable inversion results.Meanwhile,relatively accurate inversion results can be obtained by combining this method with a source-independent method.

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A review of foreign system integration technologies for airborne geophysical prospecting (2015~2020)
JIN Jiu-Qiang, YU Chang-Chun, SHI Lei, XU Ming, ZHANG Jing-Mao, GUO Liang, JIANG Jiu-Ming
Geophysical and Geochemical Exploration    2022, 46 (2): 285-295.   DOI: 10.11720/wtyht.2022.1045
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This paper summarizes the current status and progress of major system integration technologies for airborne geophysical prospecting used abroad from 2015 to 2020. During this period, some old systems were improved, while some became obsolete. Meanwhile, new system integration methods constantly emerged during this period. Specifically, towed birds using geomagnetic gradient began to be widely applied. At the same time, with the significant improvement of flight control and load capacity, UAVs were widely applied in magnetic, electromagnetic, gravity, and gamma-ray spectrometry fields. SQUID magnetic tensor gradiometers and FTG gravity tensor gradiometers were successively put into commercial airborne geophysical prospecting. The signal-to-noise ratio of electromagnetic systems was significantly improved, and CsI (Tl) scintillators were preferred by companies producing gamma-ray spectrometry instruments.

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