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New progress in the technology and applications of SOTEM XUE Guo-Qiang Geophysical and Geochemical Exploration    2024, 48 (5): 1165-1168.   DOI: 10.11720/wtyht.2024.0325 Abstract （367）   HTML （9）    PDF （380KB）（369）       Knowledge map    The artificial source electromagnetic method is an important technique for deep resource exploration. The key challenge is to improve the depth and precision of detection through innovative technology. The detection mode of electromagnetic methods is evolving from far-field to near-field, and the study of near-source electromagnetic methods has become an international research frontier in recent years. Building on the recent advancements in wide-field electromagnetic methods and multi-channel transient electromagnetic methods, the short-offset transient electromagnetic method (SOTEM) has been further developed and proposed. The distinguishing features of SOTEM are its stronger signals and wider bandwidth, which are advantageous for achieving the detection requirements of greater depth and higher precision. This special issue presents eight articles covering the methods, techniques, software, and applications of SOTEM, providing strong support for the growing need for high-resolution subsurface detection. Reference | Related Articles | Metrics

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Analysis of critical parameters in the field acquisition of short-offset transient electromagnetic data CHEN Wei-Ying, XUE Guo-Qiang, LI Hai Geophysical and Geochemical Exploration    2024, 48 (5): 1169-1175.   DOI: 10.11720/wtyht.2024.1197 Abstract （197）   HTML （5）    PDF （2409KB）（241）       Knowledge map    The grounded-source short-offset transient electromagnetic (SOTEM) method involves many parameters in field data acquisition. The selection of these parameters is closely associated with the signal quality and detection sensitivity of measured data. Based on the relevant provisions in the organization standard, Technical specification for grounded-source short-offset transient electromagnetic method (T/CGS 002—2021), issued by the Chinese Geophysical Society, numerical emulations, and practical cases, this study analyzed and expounded the selection criteria of critical parameters like transmitting source length, transmitting fundamental frequency, offset, device type, and observation component. The insights obtained in this study are significant for guiding the field construction of the SOTEM device and leveraging its detection performance. Table and Figures | Reference | Related Articles | Metrics

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Geochemical characteristics and formation mechanism of thermal spring water in the Chuhe fault zone in Anhui Province WANG Guo-Jian, HU Wen-Hui, LI Guang-Zhi, ZHU Huai-Ping, HU Bin, XIAO Peng-Fei, ZHANG Ying Geophysical and Geochemical Exploration    2024, 48 (5): 1223-1231.   DOI: 10.11720/wtyht.2024.1145 Abstract （139）   HTML （5）    PDF （3297KB）（149）       Knowledge map    Several thermal springs associated with tectonic activity occur along the Chuhe fault zone. Except for the Bantang thermal spring at the southern end, other springs along the fault zone exhibit unideal utilization of thermal energy. This affects the development of local industries. Therefore, it is necessary to delve into the geochemical characteristics and formation mechanism of typical thermal springs along the Chuhe fault zone. The purpose is to provide scientific evidence for the rational utilization and exploration methods of geothermal resources in the thermal spring groups in the future. Therefore, this study investigated thermal springs in the Bantang, Zhaoguan, and Xiangquan areas along the Chuhe fault zone, where nine samples of thermal spring water, cold well water, and surface water were collected individually. For these samples, the composition tests of 25 indices, including anions, cations, and major and trace elements, were tested, and the hydrogen and oxygen isotope values were determined. The analyses of the 25 measured indices, along with the investigation of the geothermal water source and controlling factors through hydrogen and oxygen isotope tracing, indicate that the thermal spring water in the three areas tends to be of the CaSO4 type and is all closely related to the interactions between groundwater and surrounding rocks. The thermal spring water, cold well water, and surface water in Bantang and Zhaoguan show consanguinity, with geothermal water being directly recharged with local precipitation and surface water. In contrast, the thermal spring water, surface water, and cold well water in the Xiangquan area show weaker consanguinity, indicating different sources for the underground cold water runoff and geothermal water. This should be noted when determining the primary factors controlling the thermal spring in this area. The temperatures calculated using a chalcedony geothermometer were close to the temperatures of the hot water recovered on the surface. In contrast, the temperatures calculated using a quartz geothermometer approached the temperatures of deep geothermal reservoirs. The results of this study preliminarily reveal the geochemical characteristics, recharge relationships, and water-rock interactions of thermal spring water in the Chuhe fault zone and propose effective geochemical geothermometers for the study area. These contribute to deeper insights into the mechanisms and controlling factors of the thermal springs along the fault zone, as well as providing practical value and a methodological model for enhancing thermal spring functionality and geothermal resource exploitation and utilization in the future. Table and Figures | Reference | Related Articles | Metrics

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Spatiotemporal changes of soil organic matter in the Songnen and Sanjiang plains of Heilongjiang Province over 40 years YANG He-Ping, ZHAO Xiao-Jing, SUN Jiang-Jun Geophysical and Geochemical Exploration    2024, 48 (4): 1103-1113.   DOI: 10.11720/wtyht.2024.0129 Abstract （69）   HTML （1）    PDF （5288KB）（176）       Knowledge map    The spatiotemporal changes in soil organic matter (SOM) hold great significance forthe elevation of both regional soilquality and the potential of soil carbon sequestration. Based on two periods of soil data from the second soil reconnaissance surveyof Heilongjiang Province in 1980 and thesoil geochemical survey of Heilongjiang Province in 2020, this study analyzed the spatiotemporal changes in SOM content in surface soil (0~20 cm) in the Songnen and Sanjiang plains in Heilongjiang Province over 40 years through spatial analysis in GIS. Furthermore, this study summarized the distribution patterns of SOM lossof different soil types in various cities and counties. The results indicate that the average SOM content in the surface soil in the major two plains decreased by 5.68×10-3over 40 years, generallyexhibiting a downward trend. Areas with decreased SOM are primarily distributed in Qiqihar, Daqing, western Suihua of the Songnen Plain, along with Hegang and western Jiamusi of the Sanjiang Plain, with the largest decreased amplitudeobserved in the Qiqihar Zhaoyuan area along the Nenjiang River basin. Regarding soil types, swampsoils exhibited the highestSOM loss rate (-44.68%), while grassland soilsexhibited a contribution rate for SOM of 44.14%, which established these soilsas the soil type making the most significant contribution to SOM in both plains. The SOM loss area in Wangkui County, Zhaoyuan County, and Daqing City accounted for over 72.11% of the total. This study determines the spatiotemporal changes in SOM in the major two basins in Heilongjiang Province on a scale of 40 years, providing a theoretical basis for the primary prevention and control targets of regional black soil degradation. Table and Figures | Reference | Related Articles | Metrics

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Metalleogenic geochemistry:Science problems and research ideas XI Xiao-Huan Geophysical and Geochemical Exploration    2024, 48 (4): 891-917.   DOI: 10.11720/wtyht.2024.0282 Abstract （144）   HTML （5）    PDF （791KB）（259）       Knowledge map    In geoscientific field, the essential object of all the research problems is the physical world which is derived from the crust-mantle interaction and has deeply influenced globally the environment and resources. The metallogenic geochemical theory believes that the metallogenic materials are the internal factors for the metallogenic system to influence the metallogenic process, and taking metallogenic materials as the main body to study the problems of metallogenic materials and metallogenic processes is the basic meaning of the metallogenic geochemical theory, and the core subject of the studies of metallogenic rules and theories. During the mineralization process of metallogenic system, metallogenic materials formed into metallogenic series of corresponding scale. This paper outlines several scientific topics of the metallogenic geochemical studies, among which, the topic of global metallogenic system mainly studies the metallogenic processes and relations of the series of metallogenic regions, provinces and belts formed by metallogenic materials in the context of global metallogenic process; the topic of regional metallogenic system mainly studies the metallogenic processes and relations of ore field series in the context of regional metallogenic process; the topic of ore field metallogenic system mainly studies the metallogenic processes and relations of mineral deposit series in the context of ore field metallogenic process; the topic of mineral deposit metallogenic system mainly studies the metallogenic processes and relations of ore-body series in the context of mineral deposit metallogenic process. The basic research ideas concerning above mentioned studies are discussed in this paper, including the metallogenic materials' geneses and sources, migration and evolution, differentiation and concentration, as well as the zoning relations of each level's metallogenic system and series of the world during the metallogenic processes. The purpose is to summary the metallogenic rules, explore the metallogenic mechanism and guide the mineral resources exploration. Supported by modern technologies and methods of IT(information technology), modeling and AI(artificial intelligence), the metallogenic geochemical theory uses the earth system scientific ideas to study the problems of metallogenic system and metallogenic series, construct the theoretical framework for metallogenic geochemical research, and provide a theoretical basis for the mineral resources exploration, evaluation and development technics and methods. Table and Figures | Reference | Related Articles | Metrics

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Bedrock surface and fault structures in the Rongcheng uplift revealed from reflection seismic profiles and their implications for the geothermal origin LIU Hong-Kai, GAO Lei, ZHANG Jie, HOU He-Sheng, XIE Min-Ying, LI Hong-Qiang Geophysical and Geochemical Exploration    2024, 48 (4): 934-944.   DOI: 10.11720/wtyht.2024.1316 Abstract （97）   HTML （6）    PDF （9585KB）（232）       Knowledge map    The Rongcheng uplift in North China boasts abundant geothermal resources. Research indicates that the Rongcheng uplift exhibits significantly different physical properties between the bedrock surface and the overlying Cenozoic strata. Moreover, the bedrock surface serves as the primary top boundary of the geothermal reservoir in the Wumishan Formation. Investigating the fine-scale structures, burial depths, and faults of the bedrock surface in the Rongcheng uplift holds critical significance for understanding the distribution and enrichment of geothermal resources in the area and guiding their exploration and production. Through elaborative processing of the north-south reflection seismic profile data of the Rongcheng uplift, collected by the Chinese Academy of Geological Sciences in 2018, this study obtained the high-precision geometric structure of the Rongcheng uplift within a depth of 4 km. The geometric structure was calibrated using geothermal borehole data before interpretation. Key findings are as follows: (1) The Cenozoic sedimentary strata overlying the bedrock surface of the Rongcheng uplift exhibit a nearly horizontal layered distribution, serving as cap rocks of the Rongcheng geothermal field; (2) The bedrock surface of the Rongcheng uplift manifests burial depths ranging from 700 to 3 000 m, with gentle changes in the central portion, and rapidly deepening to around 3 000 m towards the periphery; (3) The Niunan and Rongdong faults converge in the deep part, constituting a fault system along with other medium and small faults, thus facilitating the conduction of water and heat; (4) The geometric structure of the Rongcheng uplift on the bedrock surface contributes to the convergence of heat flow beneath the uplift. Table and Figures | Reference | Related Articles | Metrics

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Research and application of the log-based comprehensive identification method for low-contrast oil layers:A case study of the Lufeng oilfield in the Pearl River Mouth Basin LIU Wei-Nan, GUAN Yao, LIU Dao-Li, SHI Lei, SONG Wei Geophysical and Geochemical Exploration    2024, 48 (3): 573-583.   DOI: 10.11720/wtyht.2024.1164 Abstract （207）   HTML （15）    PDF （7267KB）（241）       Knowledge map    The accurate identification of fluid properties is critical for reservoir evaluation.However,for the Paleogene low-porosity and low-permeability reservoirs in the Lufeng area,Pearl River Mouth Basin,the low contrast between oil and water layers in conventional logs due to the presence of high-resistivity water layers complicates the identification of oil and water layers.This study first ascertained the reservoir characteristics and genetic analysis of low-contrast oil layers.Then,it developed the Flair gas logging response equation and the Flair logging response correction method,aiming to overcome the challenge that gas logging response values of low-porosity and low-permeability reservoirs are significantly influenced by factors such as drilling rate and porosity.Given the differences in the properties and components of various fluids,this study constructed new oil-bearing and water-content indices using Flair gas logging curves.Moreover,this study characterized the geochemical chromatogram using a gamma probability distribution function and extracted the shape and scale factors to describe the chromatogram characteristics.Based on sensitivity parameters,this study plotted the characteristic parameter-based fluid property identification chart.The practical application shows that the log-based comprehensive fluid property identification method can yield satisfactory effects,achieving a compliance rate of 91.3%.Therefore,this method can be popularized. Table and Figures | Reference | Related Articles | Metrics

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Multi-source frequency-domain seismic exploration technique and its application SUN Hong-Lin, LIU Tie-Hua, LIU Tie, ZHANG Zhan-Rong, CHEN Zhi-Xing Geophysical and Geochemical Exploration    2024, 48 (3): 618-628.   DOI: 10.11720/wtyht.2024.1317 Abstract （202）   HTML （3）    PDF （5836KB）（312）       Knowledge map    Due to various strong electromagnetic mechanical interference and traffic barriers, many geophysical exploration techniques are ineffective in urban geophysical exploration.Based on transient surface waves,microtremor arrays,and microtremor spectral ratios,this study synthetically extracted two kinds of characteristic curves for joint inversion from the multi-source frequency-domain seismic data obtained by multi-point three-component low-frequency sensors.Consequently,this study achieved multi-source frequency-domain seismic exploration that integrated three techniques and developed the two-source synthetic dispersive spectrum extraction technique,the two-source characteristic curve joint inversion technique,and the equivalent homogeneous medium forward modeling technique based on inhomogeneous media.Engineering practice results demonstrate the improvements in the exploration accuracy and efficiency. Table and Figures | Reference | Related Articles | Metrics

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Exploring the shear-wave prediction method for complex lithologic assemblages of the Fengcheng Formation in the Mahu sag ZHONG Hou-Cai, LIU Zhen-Yu, ZHU Zhe, QU Lin, ZHANG Shan, YAO Yan-Fei, FAN Rong-Rong Geophysical and Geochemical Exploration    2024, 48 (3): 736-746.   DOI: 10.11720/wtyht.2024.1179 Abstract （134）   HTML （1）    PDF （9611KB）（190）       Knowledge map    Research on shear-wave prediction for complex lithologic assemblages of the Permian Fengcheng Formation in the Mahu sag is critical but challenging for accurately identifying hydrocarbon accumulation zones in the sag.The key to the prediction is to make breakthroughs in petrophysical modeling based on different lithologies.Given various lithologic types and intricate mineral compositions,this study delved into petrophysical modeling based on different lithologies.Consequently,this study developed an interval-,lithology-,and model-specific shear-wave prediction technique for complex lithologies.Furthermore,it established a technique for building a dry rock matrix for alkali lake-type dolomitized tight reservoirs by highlighting the major rock mineral compositions and merging the same types of rock mineral compositions.Additionally,the self-consistent model was selected for shear-wave calculation in the petrophysical modeling of dolomitized sandstone reservoirs.These techniques have been applied in the Fengcheng Formation of the Mahu Sag,achieving encouraging application results in both the shear-wave prediction of complex lithologic assemblages and the prediction of sweet spots.This study will provide a basis for well deployment and reserves determination in the area and offer valuable experience for oil and gas exploration in similar areas. Table and Figures | Reference | Related Articles | Metrics

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A review of thirty years of airborne geophysical surveys in the Qiangtang Basin and future prospect ZHOU Dao-Qing, XIONG Sheng-Qing, WANG Bao-Di, CAO Bao-Bao, GUO Zhi-Hong, HU Yue, ZHENG Yu-Zhou, ZHAO Rui, WEI Yan-Yan, XIAO Meng-Chu, HU Xia-Wei, YAN Qiao-Juan Geophysical and Geochemical Exploration    2024, 48 (2): 287-295.   DOI: 10.11720/wtyht.2024.1413 Abstract （276）   HTML （15）    PDF （7354KB）（385）       Knowledge map    Airborne geophysical surveys, characteristic of being green, economical, efficient, and subjected to less influence by surface factors, serve as the one of most effective means of basic surveys and scientific research on the Qinghai-Tibet Plateau. This study reviewed the progress in the airborne geophysical surveys in the Qiangtang Basin of the Qinghai-Tibet Plateau in the past thirty years, systematically summarizing the progress and geological interpretation results of comprehensive airborne geophysical surveys in the basin. Furthermore, this study presented research progress and understanding of major basic geological issues of the basin, such as the basin's boundaries, central uplift zone, basement properties, deep structures, and cover characteristics, as well as the identification of favorable structural areas for oil and gas exploration. Finally, based on an analysis of the developmental trends of airborne geophysical surveys in the Qiangtang Basin, this study proposed opinions and suggestions for key research directions in the future. Table and Figures | Reference | Related Articles | Metrics

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Practices and future research directions of geophysical exploration for normal-pressure shale gas in complex structural areas,southeastern Chongqing HE Xi-Peng, LIU Ming, XUE Ye, LI Yan-Jing, HE Gui-Song, MENG Qing-Li, ZHANG Yong, LIU Hao-Juan, LAN Jia-Da, YANG Fan Geophysical and Geochemical Exploration    2024, 48 (2): 314-326.   DOI: 10.11720/wtyht.2024.1202 Abstract （174）   HTML （8）    PDF （7986KB）（354）       Knowledge map    Southern China boasts great potential for normal-pressure shale gas resources,with distribution areas primarily including the peripheral complex structural areas and the extrabasinal fold belts of the Sichuan Basin.These areas exhibit intricate surface and subsurface geological conditions,leading to poor seismic acquisition quality,low imaging accuracy,and unclear varying patterns of sweet spot parameters.This study systematically summarized the research achievements and technical advances in the seismic acquisition,image processing,and reservoir prediction for normal-pressure shale gas in southeastern Chongqing,including:①The development of variable-density 3D observation system design technique and the seismic excitation and reception technique for complex mountains with limestone surfaces,ensuring sufficient sampling of the reflected wave field in complex subsurface structures and improving data quality and construction efficiency;②The optimization of prestack seismic preprocessing technique for complex mountains,imaging techniques for complex structures in basin-margin transition zones, and imaging techniques for synclinal structures in extrabasinal fold belts,achieving resulting profiles with high signal-to-noise ratios,wide effective frequency bands,and high structural imaging accuracy;③The quantitative prediction of the thickness,formation pressure coefficient,and brittleness of high-quality shales based on research on petrophysical characteristics;the quantitative prediction of the organic carbon content,gas content,and porosity of shales based on statistical petrophysics;the quantitative prediction of fractures formed due to the superimposed effect of multi-stage structural modifications based on the paleo-stress field evolution revealed using the finite element simulation technique;and the ascertainment of the distribution patterns of the current in-situ stress field using the current stress field prediction technique developed using the combined spring model.The above breakthroughs have effectively guided the sweet spot prediction,exploration,and production of normal-pressure shale gas,providing a basis for the discovery of the Nanchuan normal-pressure shale gas field.Subsequent research should focus on more scientific and reasonable seismic acquisition techniques based on seismic reception using 5G wireless nodes,high-precision automatic image processing technologies for high-steep structures in complex mountains,and integrated geology-engineering-economy seismic evaluation methods for sweet spots. Table and Figures | Reference | Related Articles | Metrics

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Advances in research on the distributed optical fiber acoustic sensing system in the field of geophysical exploration ZHOU Shao-Yu, BAO Qian-Zong, SHI Wei Geophysical and Geochemical Exploration    2024, 48 (2): 411-427.   DOI: 10.11720/wtyht.2024.1304 Abstract （370）   HTML （5）    PDF （7793KB）（411）       Knowledge map    Distributed acoustic sensing (DAS) technology, one of the most advanced sound field detection technologies, can achieve distributed, long-distance, and high-precision real-time detection of the ambient vibration and sound field information interacting with optical fiber. The optical fiber exploration system of the DAS technology solves the problems of high cost and deployment difficulty of conventional geophones in complex geological environments. In recent years, the DAS technology has experienced rapid development, especially in monitoring application scenarios that require long-term and large-scale deployment. However, its systematic understanding is insufficient due to divergent research results. To further understand the research advances of the DAS technology in geophysical exploration for more effective subsequent research, this study systematically classified and summarized the development history of the DAS technology and its recent research results in geophysical exploration based on the oil and gas, marine, and environmental engineering application scenarios through literature research. This study focused on the development process of the DAS technology in different directions, the research advances in data processing, and relevant literature with specific results. Finally, this study generalized the development trend and urgent problems of the DAS acquisition system, analyzing the DAS development prospect. Table and Figures | Reference | Related Articles | Metrics

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Application of natural thermoluminescence measurement technique in natural gas hydrate exploration in permafrost areas WANG Hui-Yan, TANG Rui-Ling, BI Jing Geophysical and Geochemical Exploration    2024, 48 (1): 24-30.   DOI: 10.11720/wtyht.2024.1037 Abstract （155）   HTML （5）    PDF （2704KB）（265）       Knowledge map    Since natural gas hydrates (NGHs) in permafrost areas feature complex formation mechanisms and multiple sources, there is an urgent need to develop multiple techniques for micro-leakage information capture in order to increase the exploration success rate. This study applied the natural thermoluminescence measurement technique to NGH exploration in a permafrost area for the first time. Specifically, it tested the thermoluminescence intensity in soil samples from the Muli permafrost area of the Qilian Mountains using an RGD-6 thermoluminescent dosimeter. Then, it summarized the heating procedure for NGH exploration in the area, as well as size fractions for sampling. The results show that the soil samples from the Muli permafrost area demonstrated optimal size fractions for sampling ranging from -60~100 meshes, an optimal heating rate of 5 ℃/s, and an optimal heating range of 50~400 ℃. Based on the anomaly characteristics of the natural thermoluminescence intensity in soil samples, this study determined the anomaly boundary of NGHs on the surface of the permafrost area. It revealed that the natural thermoluminescence intensity displayed anomalies on the top, which correspond well to the hydrocarbon anomaly mode. The natural thermoluminescence measurements of soil, unaffected by microorganisms and boasting high sensitivity, can be popularized as a promising method for NGH explorations in permafrost areas. Table and Figures | Reference | Related Articles | Metrics

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Two-dimensional joint inversion based on the marine controlled-source electromagnetic method and seismic full-waveform KONG Fan-Xiang, TAN Han-Dong, LIU Jian-Xun Geophysical and Geochemical Exploration    2024, 48 (1): 67-76.   DOI: 10.11720/wtyht.2024.2583 Abstract （188）   HTML （1）    PDF （5740KB）（265）       Knowledge map    To reduce the limitations and the multiplicity of solutions of a single geophysical inversion method, this study investigated the two-dimensional joint inversion based on the marine controlled-source electromagnetic (MCSEM) method and seismic full-waveform inversion. The MCSEM method employs the data-space Occam’s algorithm, while the seismic full-waveform inversion utilizes the gradient algorithm. By incorporating a cross-gradient function for the mutual coupling of the two types of physical property parameters, this study developed a two-dimensional joint inversion method, whose accuracy was verified using three different models. As indicated by the results, compared to a single inversion method, the MCSEM-based joint inversion yielded significantly improved inversion results, predominantly in terms of the morphology characterization of anomalous bodies, as well as the reconstruction of their structure and textures and their physical property values. Therefore, the full-waveform inversion can enhance the reliability of the MCSEM inversion results. Table and Figures | Reference | Related Articles | Metrics

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A petrophysical model of shales considering soft-mineral aspect ratios and its application YANG Qi-Yu, LI Jing-Ye, WU Fan, LI Wen-Jin, CUI Jin-Ming Geophysical and Geochemical Exploration    2024, 48 (1): 98-104.   DOI: 10.11720/wtyht.2024.2567 Abstract （108）   HTML （1）    PDF （3776KB）（261）       Knowledge map    Previous petrophysical modeling of shale reservoirs often ignored the influence of pore types and soft-mineral aspect ratios on the elastic modulus.This study built a petrophysical model for transversely isotropic shales considering pore types and shapes,and soft-mineral aspect ratios.In this study,solid minerals were divided into hard and soft minerals,and soft minerals'anisotropic characteristics and shape changes were considered.According to the actual conditions of reservoirs, pores were categorized into intragranular,organic,and intergranular pores,and they were classified into stiff and soft pores based on their shapes.Finally,the input parameters were inverted using the particle swarm optimization algorithm to further calculate compressional and shear wave velocities,anisotropy parameters,and rock mechanical parameters.Combined with the actual data application,the results of this study were compared with the known results of shear wave velocity and isotropic rock mechanical calculation,suggesting that the model in this study is effective. Table and Figures | Reference | Related Articles | Metrics

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Gravity field characteristics and boundaries of geotectonic units on the northeastern margin of the Linyi uplift, Shandong Province WANG Run-Sheng, WU Bin, ZHANG Hai-Rui, YU Jia-Bin, DONG Yan-Long, GUO Guo-Qiang, KANG Yi-Ming Geophysical and Geochemical Exploration    2023, 47 (2): 279-289.   DOI: 10.11720/wtyht.2023.1144 Abstract （1166）   HTML （27）    PDF （9602KB）（866）       Knowledge map    The northeastern margin of the Linyi uplift is located at the eastern end of the Luxi Block and immediately adjacent to the Yishu fault in the east. The main structural framework of the study area is controlled by the NE-trending Tangwu-Gegou fault and the NW-trending Mengshan fault. Covered by the Cenozoic sediments, the boundaries of main tectonic units in the study area are almost all concealed, and it is necessary to further investigate the change in the strike of the eastern end of the Mengshan fault as well as the distribution of the angular unconformity along the northern boundary of the Linyi uplift. Using the latest 1:50,000 high-precision gravity data, this study mainly investigated the positions and intersection relationships of the boundaries of tectonic units based on the qualitative analysis of gravity field, the interpretation of multiple gravity potential field conversion, and the division scheme of geotectonic units in Shandong Province. The analysis results are as follows. The Mengshan fault at the junction of the Mengshan uplift and the Pingyi sag transitions from the NW trending to nearly-EW trending in the east of Bancheng Town, significantly cuts the NE-trending Tangwu-Gegou fault, and shows a NW-trending turn to the east again. The angular unconformity at the junction of the Linyi uplift and the Pingyi sag neither ends in the Mengshan fault in the north nor turns southward but extends to the Tangwu-Gegou fault in the east. This unconformity also controls the southern boundary of the Pingyi sag, making the NW-trending banded gravity anomalies of the sag turn eastward. Consequently, the boot-shaped low-value gravity anomalies were formed in the study area. Based on the high-precision gravity boundary identification, this study determined the fault system and tectonic division of the northeastern margin of the Linyi uplift, providing high-precision gravity data for the basic geological study in the study area and laying a good foundation for further mineral geological survey. Table and Figures | Reference | Related Articles | Metrics

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Seismic characteristics of the paleo-underground river system in Ordovician carbonate paleo-buried hills in the western Lungu area DAN Guang-Jian, ZHOU Cheng-Gang, LIU Yun-Hong, LI Xiang-Wen, ZHANG Liang-Liang, ZHANG Ming, WANG Chun-Yang Geophysical and Geochemical Exploration    2023, 47 (2): 290-299.   DOI: 10.11720/wtyht.2023.1052 Abstract （526）   HTML （17）    PDF （8684KB）（546）       Knowledge map    Many karst fracture-vug reservoirs have been found in the Ordovician carbonate paleo-buried hills in the Lungu area,Tarim Basin.Hydrocarbons are mainly enriched in these fracture-vug reservoirs,which are mainly related to the paleo-underground river system in carbonate paleo-buried hills.The paleo-underground river system is well developed,especially in the western Lungu area.The fracture-vug reservoirs related to the paleo-underground river system have strong longitudinal and lateral heterogeneity,and ascertaining the seismic and geological characteristics of the paleo-underground river system in this area is the key to the efficient development of fracture-vug reservoirs in this area.Based on the characteristics of modern karst underground rivers and the log and drilling data of this area,this study established a geological model of underground rivers for forward modeling.The study results are as follows.The underground river system developing under the tight limestone setting showed continuously linear strong reflections on the seismic profile.The seismic amplitude decreased as the height and width of underground rivers decreased,and higher seismic amplitude corresponded to larger underground river caves and lower filling velocity.The amplitude can accurately characterize the horizontal range of the underground river on the seismic profile.Meanwhile,the frequency and phase can describe the outline of the underground river on the seismic profile,but the outline described was larger than that of the real underground river.The main channels of the underground river system were prone to be filled with mud.By contrast,the branch channels had a low filling probability and thus serve as the main areas for both the occurrence of underground river reservoirs and the hydrocarbon accumulation. Table and Figures | Reference | Related Articles | Metrics

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Identification of footwalls and roofs of coal seams in underground coal mines using borehole radar LIU Si-Xin, SHI Wei, SONG Zi-Hao, CHEN Chun-Lin, DAI Zheng Geophysical and Geochemical Exploration    2023, 47 (2): 365-371.   DOI: 10.11720/wtyht.2023.1392 Abstract （280）   HTML （17）    PDF （3287KB）（367）       Knowledge map    In coal mining, the accurate determination of the locations of the footwalls and roofs of coal seams and the identification of the geological structures that threaten the safety of excavation are important measures to ensure safe coal mining. This study proposed a technique for detecting the footwalls and roofs of coal seams, which consisted of a mining face-based borehole radar detection method for underground coal mines and a data processing process. Then, this study applied this technique to the Xinyuan coal mine. Specifically, radar profiles were denoised and enhanced through the correction of zero-moment point, DC elimination, band-pass filtering, direct wave removal, and gain processing of measured borehole radar data of boreholes along a mining face of the Xinyuan coal mine. Then, the locations of the roofs and footwalls of coal seams in the underground coal mines were identified and presented through a series of processing and interpretation, including velocity pickup, reflective surface extraction, and diffraction stack migration, as well as time-depth conversion, flipping, splicing, and the correction of borehole trajectories. The technique proposed in this study serves as an effective means for the safe operation of coal mines and thus is of value for promotion. Table and Figures | Reference | Related Articles | Metrics

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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 （488）   HTML （45）    PDF （3192KB）（518）       Knowledge map    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. Table and Figures | Reference | Related Articles | Metrics

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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 （371）   HTML （23）    PDF （6873KB）（531）       Knowledge map    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. Table and Figures | Reference | Related Articles | Metrics

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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 Abstract （806）   HTML （75）    PDF （4836KB）（902）       Knowledge map    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. Table and Figures | Reference | Related Articles | Metrics

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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 Abstract （690）   HTML （65）    PDF （4096KB）（964）       Knowledge map    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. Table and Figures | Reference | Related Articles | Metrics

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Epigenetic anomaly in soil or regolith and deep-penetrating geochemistry ZHAO Yang, WANG Ming-qi, Zhang He Geophysical and Geochemical Exploration    2021, 45 (2): 257-265.   DOI: 10.11720/wtyht.2021.1573 Abstract （1347）   HTML （475）    PDF （637KB）（976）       Knowledge map    Syngeneic and epigenetic components in soil or regolith were discussed from definition. Epigenetic anomalies were classified as lateral and top anomalies,and top epigenetic anomalies are the base for deep penetration technology design. The principle of deep penetrating geochemical exploration technology is to extract the epigenetic components related to deep mineralization without destroying or less destroying the soil matrix (syngeneic components). The authors use a case study to illustrate what the epigenetic anomalies are and why conventional geochemical exploration (total) cannot be used for mineral exploration in overburden areas. From the perspective of extracting epigenetic anomalies in soil, the history, updates and problems of various deep penetration technologies are analyzed. Table and Figures | Reference | Related Articles | Metrics

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The application of frequency division ant tracking based on synchronous extrusion improvement of short time Fourier transform in crack detection HUANG Wei, ZHOU Jie, GAO Li-Jun, WANG Sheng-Li, YAN Hai-Tao Geophysical and Geochemical Exploration    2021, 45 (2): 432-439.   DOI: 10.11720/wtyht.2021.1022 Abstract （817）   HTML （124）    PDF （4303KB）（784）       Knowledge map    Since the application of the time-frequency analysis method in the field of geophysics,it has been favored by geophysicists and is widely used to detect faults and cracks.Therefore,seeking for time-frequency analysis methods with higher precision has become the goal pursued in the field of seismic signal processing.The improved short-time Fourier transform method has low accuracy of time-frequency analysis due to its own window function limitation.In order to improve the time-frequency resolution to a greater extent,the authors squeezed the time-spectrum values after the improved short-time Fourier transform,and developed synchronous extrusion improved short-time Fourier transform.The synthetic signal analysis results show that synchronous squeeze improved short-time Fourier transform has higher time-frequency convergence,and can more accurately characterize the time-frequency characteristics of the signal.The theory shows that the high-frequency components of seismic data can accurately engrave tiny secondary cracks,and ant tracking technology is an effective means to detect crack and fault information.Therefore,based on the high-resolution time-frequency analysis method and the ant tracking technology,the authors predicted the three-dimensional data volume of the South China Sea by cracks.The results show that the method can describe the micro-cracks and associated folds well,and the recognition accuracy is obviously improved as compared with the algorithm of the traditional ant tracking method,thus proving the effectiveness and practicability of the proposed method. Table and Figures | Reference | Related Articles | Metrics

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Distribution feature of soil selenium in west Sanjiang plain and its influencing factors NIU Xue, HE Jin, PANG Ya-Jie, MING Yuan-Yuan Geophysical and Geochemical Exploration    2021, 45 (1): 223-229.   DOI: 10.11720/wtyht.2021.2596 Abstract （684）   HTML （144）    PDF （2152KB）（711）       Knowledge map    In recent years, precious selenium-rich land has been discovered in Sanjiang plain, Heilongjiang Province; nevertheless, studies of the distribution and the controlling factors of soil selenium content have been rarely reported. Geochemical investigation of land quality in the western part of Sanjiang plain has revealed that the surface soil in this area is mainly sufficient, without selenium poisoning. The selenium-rich soil is mainly distributed in the alluvial lacustrine low plain area between the front of Wanda Mountain and the Naoli River, and secondarily distributed in the lacustrine denudation platform in the north of Luobei County. The selenium-deficient and selenium-potential-deficient areas mainly existalong the Songhua River and the ancient course of Luobei River in Luobei area. Based on the combination of statistical correlation analysis, factor analysis, clustering analysis and the selenium spatial distribution, the authors consider that the selenium content in the surface soil of Sanjiang plain is mainly affected by the adsorption of organic matter and clay minerals in the surface soil. Oxides of iron, manganese and other elements as well as soil pH have a relatively weaker effect on selenium enrichment.The comprehensive evaluation of soil environmental quality shows that Sanjiang plain area is mostly a risk-free area, which is a precious clean land resource. Green selenium-rich agriculture can be developed by relying on selenium-rich land. Table and Figures | Reference | Related Articles | Metrics

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Exploration and analysis of geophysical methods in curtain grouting water control WEI Hai-Min, LI Xing, SUN Bang-Tao, ZHOU Sheng, NIU Jie Geophysical and Geochemical Exploration    2021, 45 (1): 245-251.   DOI: 10.11720/wtyht.2021.1146 Abstract （615）   HTML （144）    PDF （3596KB）（859）       Knowledge map    Taking the Maoping mining area of Yilang in Yunnan Province as an example, the authors used the opposing coils transient electromagnetic method (OCTEM) and the audio-frequency magnetotelluric (AMT) method to detect the development of water-bearing fault zone within 700 m below the axis of curtain grouting project, with the intention to provide guidance for curtain grouting water control project. Through the comprehensive analysis of geophysical exploration, 7 anomalies with water-rich were delineated. The results show that OCTEM method can identify small water-bearing joints or cracks, AMT method is more sensitive to large-depth water-bearing fracture zone, and the combination of the two has obvious effect on the detection of bad water-bearing geological bodies. It can be seen that the application effect of integrated geophysical exploration in curtain grouting water control is good, the deep extension of water-bearing channel is effectively identified, and the target area is provided for curtain grouting water control. Table and Figures | Reference | Related Articles | Metrics

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The prediction of Archean buried hill fracture reservoir in BZ-A structure of the Bohai oilfield LI Yao, ZHANG Xiao-Jie, LIU Gong-Li, GONG Min Geophysical and Geochemical Exploration    2021, 45 (1): 37-45.   DOI: 10.11720/wtyht.2021.2569 Abstract （535）   HTML （128）    PDF （9647KB）（617）       Knowledge map    Drilling has revealed that the Archean buried hill of BZ-A has great potential for natural gas exploration.In the target area,the metamorphic rock fracture reservoir in Archean buried hill has many problems such as great buried depth,strong heterogeneity of the reservoir and rapid lateral changes,which pose challenges to the exploration.Based on the study of the genetic mechanism of fractured reservoirs in buried hill,the authors comprehensively analyzed the features of the weathered fractured zone and the inner fractured zone,and established a targeted technical system for the description of fractured reservoirs in buried hill.For the weathered zone fractured reservoir,the pre-stack fracture reservoir porosity prediction technology based on the double-parameter was innovatively used,and the fracture reservoir porosity was predicted by the 3D elastic parameter analysis,and the distribution of the fractured reservoir in the weathered zone was finely described.For the inner fractured zone,the F-K domain coherence enhancement technique was used to improve the imaging of the buried hill.The method of edge enhanced crack detection based on clustering analysis was used to comprehensively characterize the distribution of reservoir in the inner fracture zone.Through the comprehensive application of targeted geophysical techniques, the exploration evaluation of BZ-A has been strongly promoted,thus providing a strong basis for the further exploration evaluation of the target area. Table and Figures | Reference | Related Articles | Metrics

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Geochemical characteristics and geological significance of uranium-rich granites in Lincang area TIAN Jian-Min, XU Zheng-Qi, YIN Ming-Hui, LI Tao, SUN Kang Geophysical and Geochemical Exploration    2020, 44 (5): 1103-1115.   DOI: 10.11720/wtyht.2020.1554 Abstract （1282）   HTML （131）    PDF （5345KB）（641）       Knowledge map    Petrographic and geochemical study and U-Pb dating of uranium-rich granite bodies in Lincang area were carried out for Shuangjiang 701 and Fengqing 901 uranium mines, with the purpose of exploring the relationship between petrogenesis type, diagenetic tectonic background and uranium mineralization. The results show that Lincang uranium-rich granite body has high Si (up to 90.11%, averaging 71.6%), rich alkali, high potassium and high Ca, thus belonging to high Al and high potassium calcium alkaline series rocks. U-Pb zircon dating yielded 214±12 Ma, and thus Lincang uranium-rich granite body was formed in Late Indochina. Rare earth elements show a slightly rightward "V" shape, with obvious fractionation of light and heavy rare earth elements (w(LREE)/w(HREE) 7.26 on average), obvious negative Eu anomaly (δEu=0.28 ~ 0.49), relative enrichment of Rb, U and Th, and relative loss of Ba, Nb, Sr, Ti and Eu. Comprehensive analysis shows that Lincang uranium-rich granite belongs to S-type granite with obvious differentiation, which must have originated from melting of upper crust material and was formed in a mountain-building and rift environment in late collision, belonging to the simultaneous collision of granite related to the Lancang River collision zone. Its high content of uranium provided part of the uranium source for the uranium mineralization process. Uranium elements were transported to the vicinity of the fault fracture zone and was enriched to form granite-type uranium deposits by leaching. Table and Figures | Reference | Related Articles | Metrics

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Density interface inversion method in spherical coordinates and its application in the South China mainland WANG Xiang, GUO Liang-Hui Geophysical and Geochemical Exploration    2020, 44 (5): 1161-1171.   DOI: 10.11720/wtyht.2020.0067 Abstract （592）   HTML （135）    PDF （4704KB）（557）       Knowledge map    The density interface inversion method has been playing an important role in the oil and gas exploration, regional structure inference studies as well as crustal crystal basement surface and Moho undulations researches. Most of the density interface inversion methods are generally based on the Cartesian coordinate system. When large regional or even global scale data are dealt with, the influence of earth curvature cannot be ignored, and the density interface inversion method based on Tesseroid model of spherical coordinate system needs to be considered. However, due to the limitations of calculation accuracy and efficiency, the existing density interface inversion method based on Tesseroid cannot be well applicable to the surface gravity observation data. In this paper, on the basis of previous studies, a density interface inversion method of spherical coordinate system suitable for surface observation data is proposed. Firstly, the gravity Gauss-Legendre integral formula in the spherical coordinate system is simplified to improve the forward calculation efficiency. Then, an optimized adaptive subdivision algorithm is introduced to enhance the calculation accuracy. According to the previous forward calculation and by using Cordell iterative optimization algorithm, the authors propose a density interface inversion method for the surface observation data in the spherical coordinate system. The proposed inversion method in this paper can be verified through the synthetic data test. The inversion results show that the proposed method can overcome the limitation of calculating precision and efficiency of the surface observation data. In addition, the inversion results based on spherical coordinate system are better than those based on cartesian coordinate system. Finally, tests on real data from South China mainland verify the feasibility of the presented methods. The results show that Moho depth rises gradually from the west to the east, with the western part uplifting dramatically and the eastern part uplifting gently. Between Wuling Mountain and Guizhou-Guangxi border, there is an obvious NNE-Moho step. Table and Figures | Reference | Related Articles | Metrics

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New research progress in theory and application of wide field electromagnetic method HE Ji-Shan Geophysical and Geochemical Exploration    2020, 44 (5): 985-990.   DOI: 10.11720/wtyht.2020.0192 Abstract （919）   HTML （175）    PDF （453KB）（1177）       Knowledge map    Mineral resources are the lifeblood of national economic development. Electromagnetic method is one of the most effective methods to search for mineral resources.With the depletion of shallow resources, developing a both large-depth and high-precision electromagnetic method has become big challenge for all countries in the world, which is also the research hotspots. Aiming at the problems of shallow depth and low precision of the original artificial source frequency domain electromagnetic methods,from theory, method, technology to application, the author carried out systematic research and invented WIDE FIELD ELECTROMAGNETIC METHOD. It is a great leap forward for the development of frequency domain electromagnetic method from coarse to fine. As a result, the achievements of "large depth and high precision wide field electromagnetic exploration technology and equipment" have been formed, it won the First Prize of National Technological Invention in 2018.Wide field electromagnetic method provides a new technical means for oil and gas exploration, deep prospecting, coal mine water disaster detection, geological disaster prevention, fracturing monitoring and urban geophysical exploration. It has strongly supported the "deep ground" strategy oriented to the major needs of the country.The papers collected in this column are mainly distributed in the technical research fields of solid mineral, shale gas and geothermal exploration, fracturing monitoring and airborne geophysical application. This paper focuses on these papers and discusses the development of the theory and application of wide field electromagnetic method. Reference | Related Articles | Metrics

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The application of wide field electromagnetic method to shale gas exploration in Wuling Mountain area: A case study of Tongzi area in northern Guizhou LI Di-Quan, WANG Zhen-Xing, HU Yan-Fang, WANG Han, SU Yu-Di Geophysical and Geochemical Exploration    2020, 44 (5): 991-998.   DOI: 10.11720/wtyht.2020.1570 Abstract （586）   HTML （155）    PDF （4513KB）（821）       Knowledge map    After the major breakthrough in oil and gas was obtained from the Well Anye 1, the Ministry of Natural Resources increased the residual shale gas and oil and gas exploration and development of 7,800 square kilometers in the Wuling Mountain. The Wulong Mountain area has complex geological structures, undulating terrain and large areas of carbonate rock, which has led to great challenges to traditional oil and gas exploration methods based on seismic exploration. Wide field electromagnetic method has the characteristics of green, high efficiency and low cost, and hence has become one of the powerful methods for oil and gas exploration and is now being widely used in shale gas exploration in southern China. It is a favorable method for shale gas exploration in southern China. The strata in Tongzi Guizhou are relatively stable, and the organic carbon content in the upper Ordovician Wufeng-Lower Silurian Longmaxi Formation is high. Through surface sample collection and well logging data analysis, the organic shale in this formation shows obvious low resistivity characteristics, which has the physical conditions of electromagnetic exploration. The wide field electromagnetic method was used to carry out shale gas exploration in Tongzi area of northern Guizhou, which overcame the complex influence of topography, carbonate rocks and structure. It is found that the structure pattern of Tongzi area is characterized by "depression and uplift" from northeast to southwest. The spatial distribution characteristics of the Wufeng-Longmaxi Formation in the target layer were detected, and four favorable areas for shale gas exploration were delineated. The prediction of shale gas exploration target area by wide area electromagnetic method is expected to help realize the breakthrough of shale gas exploration and development from point to surface in Wuling Mountain area and promote the development of clean energy industry along the river. Table and Figures | Reference | Related Articles | Metrics

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The application of multiple non-seismic methods to geothermal exploration in Qihe, Shandong Province Hui ZHANG, Shao-Qiang SUI, Luo-Ran QIAN, Xin-Wei WANG Geophysical and Geochemical Exploration    2020, 44 (4): 727-733.   DOI: 10.11720/wtyht.2020.1413 Abstract （810）   HTML （160）    PDF （4897KB）（801）       Knowledge map    Non-seismic methods have been proved to be effective in geothermal exploration.This paper describes a two-step method for investigating the geothermal potential in Fountain Village,Rongsheng,Qihe,Shandong Province.The geological background of the target area is very complicated;for instance,many complex faults are developed and the formations usually have strong horizontal anisotropic property,which enhances the difficulty of exploration.The two-step method put forward by the authors utilizes the electrical and elastic features in different formations to solve these difficulties.The first step is to investigate the location of huge fault structure and the depth of resources by using electromagnetic method,which can locate the water-rich regions.The second step focuses on the more precise features of faults based on microtremors method. This method can help locate the sweet spot area more accurately and bring constructive suggestions to well location determination.Drilling results have testified the feasibility and applicability of this two-step method,which opens up a new path in complex geothermal exploration. Table and Figures | Reference | Related Articles | Metrics

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Geochemical characteristics and influential factors of soil selenium in typical agricultural area, Chongqing YU Fei, ZHANG Feng-Lei, ZHANG Yong-Wen, WANG Rui, WANG Jia-Bin Geophysical and Geochemical Exploration    2020, 44 (4): 830-838.   DOI: 10.11720/wtyht.2020.1471 Abstract （585）   HTML （146）    PDF （1906KB）（727）       Knowledge map    Nanchuan District is a typical agricultural area in Chongqing. The authors investigated the geochemical characteristics and influential factors of soil Se from Nanchuan District of Chongqing City to provide some scientific bases for the survey of environment background and regional production as well as human health. More than 8 496 soil samples from the topsoil layers(0~20 cm)all over the Nanchuan District were collected and analyzed for content and distribution of soil Se and their relationships with parent material, soil properties (pH and Corg), altitude and human factors. The research results show that the content of total selenium ranges from 0.056×10-6 to 10.80×10-6 with a mean value of 0.46×10-6, which indicates that the most of the soils are in the category of Se-sufficiency to Se-abundance, with 42.31% being Se-enrichment. The spatial characteristics of soil Se content in Nanchuan District show "high in the south and low in the north", and the soil Se enrichment areas are mainly distributed in Shuijiang Town, Nanping Town, Nanchuan urban area and Jinfo Mountain. Among the types of soils existing in the Nanchuan District, Se content is the highest in industrial and mining land soil and the lowest in farmland. The spatial characteristics of soil Se content and strata show a similar variation pattern. The soil Se enrichment is mainly distributed in Permian, Triassic (Feixianguan Formation and Jialingjiang Formation), Silurian, Ordovician and Cambrian strata, which indicates that the soil Se content is mainly controlled by parent materials in Nanchuan District. In addition, Se content in soil is significantly positively correlated with soil organic matter and altitudes, but significantly negatively correlated with soil pH. Table and Figures | Reference | Related Articles | Metrics

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The result analysis of the comparison between SAG-2M and KSS31M marine gravimeters Fei-Fei ZHANG, Jian-Wei SUN, Bo HAN, Run-Lin DU, Wan-Yin WANG Geophysical and Geochemical Exploration    2020, 44 (4): 870-877.   DOI: 10.11720/wtyht.2020.0077 Abstract （628）   HTML （152）    PDF （1743KB）（787）       Knowledge map    A comparison for the marine gravimeters on the same vessel was carried out between SAG-2M marine gravimeter developed by China and KSS31M marine gravimeter designed by Germany in order to test the technical performance and data reliability of SAG-2M marine gravimeter. The raw gravity data acquired from these two marine gravimeters were preprocessed according to the standards of marine geologic survey to obtain the free air gravity anomalies, and the comparison and relativity for those two types of gravity data were studied by analyzing the cross-point differences, survey lines and grid data. The result shows that the SAG-2M marine gravimeters have the same level of measurement accuracy with the KSS31M marine gravimeter because there is a highly linear relationship between the data from two marine gravimeters with an approximately similar variation trend. Based on the results of comparison, it is concluded that the self-developed SAG-2M marine gravimeter shares the similar standard of measurement accuracy with the KSS31M marine gravimeter with a stabilized technical performance, which provides an important reference for the future application of SAG-2M marine gravimeter. Table and Figures | Reference | Related Articles | Metrics

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Geochemical survey method of land quality in hilly areas:A case study of the geochemical survey of land quality in Ganzhou Guo-Guang CHEN, Xiao-Hong LIANG, Jie ZHANG, Zhong-Fang YANG Geophysical and Geochemical Exploration    2020, 44 (3): 463-469.   DOI: 10.11720/wtyht.2020.1566 Abstract （830）   HTML （182）    PDF （1742KB）（875）       Knowledge map    In view of the characteristics of obvious changes in topography, geologic background and significant influence on geochemical element content in hilly area, this paper puts forward a method for geochemical investigation of land quality in hilly areas based on geological background analysis, with emphasis on soil geochemical survey of arable land, garden andgentle-slope land.According to the geological and geographical features of Ganzhou, detailed sample method laying in basins, valleys and mountains are,the method of plot-assignment based on geological background, the combination of eco-geological investigation and soil geochemical survey, the method of combining the pollution-free se-enriched concentration and the land quality files as the core. Table and Figures | Reference | Related Articles | Metrics

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The calculation method of full tensor geomagnetic gradient based on IGRF model Yang ZHONG, Yan-Wu GUAN, Jia-Qiang SHI, Feng XIAO Geophysical and Geochemical Exploration    2020, 44 (3): 582-590.   DOI: 10.11720/wtyht.2020.1416 Abstract （906）   HTML （167）    PDF （3448KB）（1077）       Knowledge map    The international geomagnetic reference field (IGRF) is a general international model for describing the earth’s main magnetic field. At present,this model can be used to calculate the seven elements of geomagnetic field at any point. However,with the development of aeronautical full tensor magnetic measurement technology,there is an urgent need for full tensor geomagnetic gradient data. In this paper,the calculation principle of the IGRF model is summarized and the expression of the full tensor geomagnetic gradient with spherical harmonic expansion is derived. The calculation of the seven elements of geomagnetic field and the full tensor geomagnetic gradient at any given point is realized. Comparing with the calculated data from the website of the National Oceanic and Atmospheric Administration of the United States (NOAA),the results are accurate and reliable. The contour map of the full tensor geomagnetic field in a region is drawn, and the results were in accordance with the Laplace equation. It provides the theoretical basis for the selection of learning flight working area and flight height in the aeromagnetic survey. Table and Figures | Reference | Related Articles | Metrics

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A review of seismic tomography methods Chang LIU, Zhen-Chun LI, Ying-Ming QU, Yi-Peng XU, Wei-Jie ZHAO Geophysical and Geochemical Exploration    2020, 44 (2): 227-234.   DOI: 10.11720/wtyht.2020.1243 Abstract （1514）   HTML （950）    PDF （550KB）（1694）       Knowledge map    As a method for effectively reducing the velocity model of the subsurface media,seismic tomography provides a reliable initial velocity model for full waveform inversion.The finite frequency characteristics of seismic wave propagation are realized from primitive ray toe to phase shift travel time tomography and instantaneous travel time tomography.From the acoustic wave equation to the elastic wave equation and from the isotropic medium to the VTI,TTI media,the simulation of the real underground medium is realized.The morbidity of mitigating tomographic inversion has also been a research hotspot.The commonly used methods have regularization,and the sensitive nucleus of Gaussian beam tomography has replaced the traditional ray-sensitive nucleus.Furthermore,in order to avoid the dependence of the accuracy of the imaging results on the true depth of the reflection bits on the common imaging gather,the angular domain double differential reflection tomography can converge stably and efficiently to the accurate migration velocity model.At present,tomography is gradually transitional to anisotropic media,data used are transitional from VSP to WVSP,and a single waveform is developed into multiple waveforms combined inversion.However,problems related to resolution and computational efficiency still require attention. Reference | Related Articles | Metrics

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The identification of gravity anomaly body based on the convolutional neural network Yi-Chen WANG, Lin-Tao LIU, Hou-Ze XU Geophysical and Geochemical Exploration    2020, 44 (2): 394-400.   DOI: 10.11720/wtyht.2020.1504 Abstract （1042）   HTML （133）    PDF （1573KB）（890）       Knowledge map    This study combines the deep learning with the identification of gravity anomaly body. Based on the CNN (convolutional neural network) which has been gaining its use in the past several years in the field of image identification, the contour image of gravity signal is taken as the unidentified image, while the space parameters of the gravity anomaly body will be identified through CNN. In the training phase, a large number of the 3D anomaly bodies are generated with random variation of parameters, then the network is fed with parametric labels and the computed gravity contour images. The testing is performed with generated testing models to estimate the performance of the trained model. The trained CNN accuracy shows excellent accuracy in the identifications. Then the CNN model is tested with measured main gravity anomaly data of Kauring area in West Australia, and the identified parameters of the 3D anomaly body are compared with known results. It is shown that the generalization of CNN can handle identification of the measured gravity data. Table and Figures | Reference | Related Articles | Metrics

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Inversion of gravity gradient tensor based on unstructured grids Tian-Tong HUANG, Xin-Fa PENG, Zi-Qiang ZHU Geophysical and Geochemical Exploration    2020, 44 (1): 132-140.   DOI: 10.11720/wtyht.2020.2256 Abstract （535）   HTML （128）    PDF （3191KB）（590）       Knowledge map    Gravity gradient tensor is the second derivatives of gravitational field. Compared with the traditional gravitational exploration, gravity gradient tensor can reach a better resolution. Gravity gradient tensor has 5 independent components, so they can contain more geological information. Therefore, gravity gradient tensor can be used to recover the causative bodies in the subsurface with high accuracy. Due to strong adaptability and flexibility of the unstructured grid, it can smoothly approximate the irregular and complex boundaries of anomalous source. Compared with the structured grid, the unstructured grid can provide researchers with more accurate discretization and calculation with less computation time. In order to reduce the ambiguity of the inversion, the authors chose to jointly and simultaneously invert all gravity gradient components based on tetrahedron grids with the help of the so called generalized objective function which is widely used in geophysical inverse problems. The authors applied the algorithm to each gravity tensor component at the beginning to ensure that the depth weighting function makes a difference in the inversion. It turns out that the depth weighting function works well. To explore all components of the gravity gradient tensor as much as possible, the authors described the joint-inversion in detail in this paper. The inversion results show that 3D inversion of gravity gradient tensor based on unstructured grids can obtain the position of causative bodies in the subsurface and the density distribution. Based on a comparison with rectangular grid inversion results, the authors highlighted the advantages of unstructured grid inversion. And the practicability of the method was verified through two synthetic models. Table and Figures | Reference | Related Articles | Metrics

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Ecological risk assessment and source analysis of heavy metals in sediments of Liujiang River Catchment Xiao-Yu ZHONG, Tian-Sheng WU, Jie LI, Guo-Dong ZHEN, Xiao-Xiong ZHUO, Dong-Chao GUAN, Lei WANG, Bing-Ji MO Geophysical and Geochemical Exploration    2020, 44 (1): 191-199.   DOI: 10.11720/wtyht.2020.1210 Abstract （626）   HTML （143）    PDF （1827KB）（793）       Knowledge map    In this study, 91 sediment samples were collected from the middle and lower reaches of Liujiang River. The geochemical characteristics of As, Cd, Cr, Cu, Hg, Ni, Pb, Zn and other elements were analyzed. The current pollution situation and potential risks were predicted and evaluated, and the sources of heavy metals were analyzed. The results show that: The spatial dispersion of elements in the sediments of Liujiang River Catchment is relatively large, and the distribution of heavy metal elements shows strong regional characteristics.Distribution of heavy metal elements in Liujiang River Catchment shows strong regional characteristics.As, Cr, Cu, Hg and Ni are mainly from natural sources, while Cd and Pb are mainly from human sources. The high-value areas of Cd natural source contribution mainly distribute in Longjiang River Catchment, while the high-value areas of industrial and mining sources contribution mainly distribute around Jincheng River and Liuzhou District of Liujiang River. Table and Figures | Reference | Related Articles | Metrics

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