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  20 June 2022, Volume 46 Issue 3 Previous Issue   
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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
Abstract   HTML ( 7 )   PDF (1810KB)

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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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
Abstract   HTML ( 0 )   PDF (2209KB)

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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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
Abstract   HTML ( 2 )   PDF (1945KB)

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
Abstract   HTML ( 1 )   PDF (2828KB)

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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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
Abstract   HTML ( 1 )   PDF (3263KB)

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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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
Abstract   HTML ( 3 )   PDF (1469KB)

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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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
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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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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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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
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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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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
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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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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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Geochemical characteristics and genesis of hydrocarbons in superficial soil in continental permafrost regions in China
YANG Zhi-Bin, ZHOU Ya-Long, ZHANG Fu-Gui, ZHANG Shun-Yao, SUN Zhong-Jun
Geophysical and Geochemical Exploration. 2022, 46 (3): 628-636.   DOI: 10.11720/wtyht.2022.1244
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This study analyses the geochemical characteristics, genesis, and properties of hydrocarbon components using data of surface soil samples collected from the permafrost regions in the Qiangtang Basin, the Qilian Mountains, and the Mohe Basin. The results revealed that the hydrocarbon gases in the superficial soils in the permafrost regions mainly comprise methane, as well as a small amount of ethane, ethylene, propane, butane, and pentane. The hydrocarbon gases in the Qiangtang and Mohe basins are mainly of pyrolytic genesis and their types include soil-formed gas and the mixed gas of soil-formed gas and coalbed methane. In contrast, hydrocarbon gases in the superficial soil in the permafrost zone in the Qilian Mountains are of pyrolytic and biogenic genesis and their types include soil-formed gas, coalbed methane, and biogenetic gas. The study provides a basis for exploring oil and gas resources such as natural gas hydrates in the continental permafrost regions in China.

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Application of automated mineral analysis systems in geochemical exploration of carbonatite-related REE deposits
LIU Dong-Sheng, CHEN Yuan-Yuan
Geophysical and Geochemical Exploration. 2022, 46 (3): 637-644.   DOI: 10.11720/wtyht.2022.1381
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In recent years, China has been strengthening the exploration of rare earth resources in order to secure the status of China as a large rare earth resource country. Geochemical exploration is an important means of mineral exploration, This paper summarizes the geochemical exploration of rare earth, finds out the existing problems and puts forward solutions. The carbonatite related rare earth anomalies are characterized by low contrast and small scale, the reasons are: ① the industrial grade of rare earth ore is enriched to a low degree relative to the abundance of the earth's crust, which is easily diluted by non-mineral anomalies caused by granite, etc.; ②the size of rare earth ore-forming indicator minerals are small and difficult to sort by traditional method, thus the epigenetic migration and enrichment pattern is not well understood, and it is difficult to develop a targeted sampling method. The automatic mineral analysis system based on scanning electron microscopy and energy spectrum can realize the quantitative statistics of chemical composition and morphological parameters of rare earth minerals at the micron level, which provides the basis for the study of epigenetic migration pattern of rare earth minerals. In recent years, in the field of geochemical exploration, previous research on the variation pattern of micro scale grain mineral content in the ore body-stream sediment system using the automatic mineral analysis system has shown the good application prospect of this method. In the future, the automatic mineral analysis system can be used to carry out:①research on the change of rare earth mineral size during weathering process; ②research on the migration and enrichment of rare earth minerals in the ore body-aqueous sediment system. Thus, the distribution characteristics and migration and enrichment rules of rare earth indicative minerals in ore-body, soil-stream sediment system are clarified, providing theoretical support for geochemical exploration of rare earth.

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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
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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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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
Abstract   HTML ( 2 )   PDF (2327KB)

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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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
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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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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
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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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Near-surface response of hydrocarbon-consuming microorganisms to the fault-karst reservoirs in Shunbei oil and gas field
CAO Fei, YANG Min, BAO Dian, CHEN Yin-Jie, WANG Guo-Jian
Geophysical and Geochemical Exploration. 2022, 46 (3): 678-684.   DOI: 10.11720/wtyht.2022.1060
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As an ultra-deep fault-karst reservoir located in the Tarim Basin of Xinjiang,the Shunbei oil and gas field prosses the characteristics of the large burial depth and fault development in the target formations.This oil and gas field is difficult to explore due to the low signal-to-noise ratio and low resolution of seismic signal data since seismic signals are absorbed by the desert surface and thereby suffer severe attenuation.The microbial prospecting developing based on the theory of vertical hydrocarbon microseepage can detect the oil and gas-bearing properties of fault zones.This technology,combined with geophysical exploration,can improve the success rate of the prediction of the oil and gas-bearing properties of fault zones.This experimental study of microbial prospecting in fault zone No.5 in the Shunbei oil and gas field shows that the abundance anomalies of hydrocarbon-consuming microorganisms show good near-surface response to fault-karst reservoirs.Compared to areas with vegetation,hydrocarbon-consuming microorganisms (including methane- and butane-oxidizing bacteria) as indicators of microbial prospecting in desert areas are characterized by low measured values and slight fluctuation.However,hydrocarbon-consuming microorganisms can better reflect the near-surface information induced by the vertical microseepage of deep-buried oil and gas since they are less disturbed by other microbial communities due to the special ecological conditions in desert areas.According to the application results,the high-amplitude anomalies of both methane- and butane-oxidizing bacteria are primarily distributed in the vicinity of fault zone No.5,and favorable anomalies also occur in the vicinity of fault zone No.1 in the Shunbei oil and gas field.Furthermore,the strike of these anomalies roughly coincides with that of fault zones,indicating that the microbial anomaly zones correlate strongly with fault-karst reservoirs.Therefore,the microbial prospecting for hydrocarbons has great application prospects in the exploration of the fault-karst reservoirs.

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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
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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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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
Abstract   HTML ( 3 )   PDF (6493KB)

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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Suppression of random noise in deep seismic reflection data using adaptive threshold-based Shearlet transform
WANG Tong, Liu Jian-Xun, WANG Xing-Yu, LI Guang-Cai, TIAN Mi
Geophysical and Geochemical Exploration. 2022, 46 (3): 704-713.   DOI: 10.11720/wtyht.2022.1187
Abstract   HTML ( 2 )   PDF (13829KB)

Deep seismic reflection is one of the most effective means of studying the deep geological structure of the Earth.However,the energy of seismic waves exponentially decreases due to the filtering by the Earth,resulting in weak energy of effective deep seismic reflection signals.In this case,deep seismic reflection data are liable to be seriously disturbed by background noise,and thus it is difficult to obtain accurate images of deep geological structures.According to the study on the differences in the distribution of effective signals and random noise of deep seismic reflection data on different scales in the Shearlet domain,seismic signals on different scales are affected by random noise to different extents.Furthermore,with the signal-to-noise ratio,the L2 norm of Shearlet coefficients,and the residual errors of random noise in deep seismic reflection data as the parameters for threshold estimation,this study developed a random noise suppression method that is adaptive to different scales to minimize the effects of random noise.Theoretical model data and actual tests of deep seismic reflection data verified that this method can effectively eliminate the disturbance of random noise,improve the overall signal-to-noise ratio of seismic sections,and realize the accurate imaging of weak deep seismic reflection signals.

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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
Abstract   HTML ( 0 )   PDF (5457KB)

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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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
Abstract   HTML ( 0 )   PDF (6151KB)

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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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
Abstract   HTML ( 2 )   PDF (3548KB)

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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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
Abstract   HTML ( 2 )   PDF (2643KB)

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 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
Abstract   HTML ( 3 )   PDF (2912KB)

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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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
Abstract   HTML ( 0 )   PDF (4057KB)

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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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
Abstract   HTML ( 0 )   PDF (9225KB)

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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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
Abstract   HTML ( 0 )   PDF (4084KB)

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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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
Abstract   HTML ( 0 )   PDF (556KB)

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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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.  
Abstract2462)      PDF (4180KB)(4724)      


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
Abstract1140)   HTML145)    PDF (12833KB)(4181)      

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.  
Abstract3232)      PDF (431KB)(3277)      

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.  
Abstract2864)      PDF (1014KB)(3217)      

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.  
Abstract6621)      PDF (532KB)(2969)      

 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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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
Abstract2215)      PDF (964KB)(2467)      
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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CALCULATION OF THE ANOMALY AREA
Zhao Rongjun
Geophysical and Geochemical Exploration    2000, 24 (2): 154-156.  
Abstract1439)      PDF (346KB)(2465)      

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 CHOICE OF GRIDDING METHODS FOR GEOPHYSICAL DATA
LIU Zhao-Ping, YANG Jin, WU Wei
Geophysical and Geochemical Exploration    2010, 34 (1): 93-97.  
Abstract3043)      PDF (1939KB)(2360)      

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.  
Abstract4415)      PDF (659KB)(2324)      

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.  
Abstract1617)      PDF (673KB)(2245)      

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.  
Abstract4188)      PDF (403KB)(2169)      

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.  
Abstract3000)      PDF (2717KB)(2160)      

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

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

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

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

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

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

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RESEARCH AND APPLICATION ON NUMERICAL INTEGRATIONOF HANKEL TRANSFORMS BY DIGITAL FILTERING
ZHANG Wei, WANG Xu-Ben, QIN Qing-Yan
Geophysical and Geochemical Exploration    2010, 34 (6): 753-755.  
Abstract3616)      PDF (363KB)(2117)      

 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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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.  
Abstract3647)      PDF (643KB)(2080)      

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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PARAMETER SELECTION IN VIBROSEIS SEISMIC EXPLORATION
XUE Hai-Fei, DONG Shou-Hua, TAO Wen-Peng
Geophysical and Geochemical Exploration    2010, 34 (2): 185-190.  
Abstract3424)      PDF (3477KB)(1973)      

 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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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.  
Abstract2747)      PDF (1927KB)(1963)      

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 INVERSED PROBLEM IN GRAVITY AND MAGNETICEXPLORATION: A REVIEW
Zeng Hualin
Geophysical and Geochemical Exploration    1990, 14 (3): 182-190.  
Abstract1937)      PDF (737KB)(1960)      

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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RECENT ADVANCES IN THE RESEARCH AND DEVELOPMENT OF QUANTUM MAGNETOMETERS
ZHANG Chang-da
Geophysical and Geochemical Exploration    2005, 29 (4): 283-287.  
Abstract1645)      PDF (376KB)(1940)      

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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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.  
Abstract3372)      PDF (2025KB)(1937)      

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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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.  
Abstract3562)      PDF (830KB)(1931)      

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.  
Abstract3092)      PDF (1060KB)(1924)      

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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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.  
Abstract2867)      PDF (2969KB)(1895)      

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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YANG Li-De
Geophysical and Geochemical Exploration    2009, 33 (6): 741-742.  
Abstract2093)      PDF (240KB)(1879)      
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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.  
Abstract2449)      PDF (2110KB)(1861)      

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.  
Abstract2109)      PDF (690KB)(1848)      

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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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.  
Abstract3600)      PDF (534KB)(1836)      

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

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THE 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.  
Abstract2711)      PDF (608KB)(1835)      

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 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.  
Abstract3429)      PDF (572KB)(1830)      

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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SOME PROBLEMS CONCERNING THE CONVERSIONOF MAPS BETWEEN SURFER AND MAPGIS
QIN Lin-Jiang
Geophysical and Geochemical Exploration    2010, 34 (5): 677-680.  
Abstract5290)      PDF (865KB)(1811)      

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 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
Abstract1033)   HTML147)    PDF (11771KB)(1797)      

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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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.  
Abstract3757)      PDF (1006KB)(1791)      

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 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.  
Abstract3171)      PDF (1351KB)(1784)      

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

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

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

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

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

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THE 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
Abstract4647)      PDF (1427KB)(1775)      
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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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.  
Abstract2479)      PDF (2180KB)(1741)      

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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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.  
Abstract2017)      PDF (749KB)(1704)      

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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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.  
Abstract2710)      PDF (811KB)(1679)      

 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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THE APPLICATION OF THE RAYLEIGH SURFACE WAVE TECHNIQUE TO RAILWAYS
LI Hai
Geophysical and Geochemical Exploration    2002, 26 (2): 160-162.  
Abstract1853)      PDF (480KB)(1678)      

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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GEOPHYSICAL-GEOCHAMICAL PROSPECTING MODEL OF THE CAIJIAYING Pb-Zn-Ag DEPOSIT, HEBEI PROVINCE
Zhang Sulan, Yao Jingjin, Cao Lohua
Geophysical and Geochemical Exploration    1999, 23 (3): 161-169174.  
Abstract1801)      PDF (1652KB)(1658)      

Based on the study of geological, geophysical and geochemical characteristics of the background field, ore district and ore belt that the Caijiaying ore deposit lies in, the authors have formulated the structural geological geophysical-geochemical-prospecting model,and summed up the optimum combinational process of geophysical and geochemical prospecting techniques.

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THE EXPERIMENTAL PROBING STUDY OF GROUND PENETRATING RADAR IN THE FRESHWATER AREA OF SHALLOW WATER
WANG Guo-qun
Geophysical and Geochemical Exploration    2011, 35 (4): 565-568.  
Abstract2520)      PDF (556KB)(1653)      

Based on analyzing three cases, i.e., water stone riprap exploration of bank protection embankment, underwater exploration of concrete grid and gravel layer, and river waters yard landslide detection, the authors tried to illustrate the effect of the geological radar exploration in the freshwater of shallow water. The impacts of conductivity, dielectric constant and frequency detection were studied by using the antenna to an environment that the object detection is in. GPR fills the gaps of engineering investigation in the shallow water, and research on GPR and test in the non-ater area are of reference value.

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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.  
Abstract2900)      PDF (1404KB)(1650)      

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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Review on the study of grounded-source transient electromagnetic method
ZHANG Ying-Ying
Geophysical and Geochemical Exploration    2021, 45 (4): 809-823.   DOI: 10.11720/wtyht.2021.1513
Abstract737)   HTML528)    PDF (729KB)(692)      

Grounded-source transient electromagnetic method (TEM) has many advantages such as deep exploration, flexible arrangement in rough terrain and high working efficiency. Recently it has got much attention and a series of new methods are available, ranging from surface to airborne and borehole method. In this paper, the authors review the research history of long-offset TEM (LOTEM), short-offset TEM (SOTEM), multi-channel TEM(MTEM), grounded-source semi-airborne TEM and grounded-source surface to borehole TEM, and summarize their research status in forward modeling, system design, inversion, imaging and field working. The results show that, as a well-developed grounded-source TEM, LOTEM has accumulated many research achievements. Although some progress has been made, the researches on other grounded-source TEMs are still in a primary stage and still need further improvement. Valuable research results in LOTEM, for example, noise suppression technology, high dimensional inversion and point interpretation, can be introduced to these newly developed electromagnetic methods, which can help provide solutions for high working efficiency and high resolution deep exploration.

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The application of integrated geophysical prospecting to the exploration of buried faults in the high and steep fault-fold zone in eastern Sichuan
PENG Ming-Tao, WANG Lei, ZENG Ming-Yong, XIE Bing-Bing, MO Wei-Tao
Geophysical and Geochemical Exploration    2021, 45 (4): 882-889.   DOI: 10.11720/wtyht.2021.1378
Abstract412)   HTML237)    PDF (3269KB)(443)      

The eastern region of Sichuan basin is located between Huaying Mountain and Qiyaodan Mountain. After multiple periods of complex structural superposition and transformation, high and steep tectonic belts and faults were formed. It is difficult to detect and distinguish hidden faults in the high and steep tectonic belts in geophysical exploration. Based on the forward and inverse simulation results of gravity, magnetic and electric detection methods, the authors have reached the conclusion that buried faults in high and steep fault folds can be detected and recognized. Combined with the practical application effect of gravity, magnetic and electric integrated geophysical prospecting methods in high and steep fault folds in eastern Sichuan, the authors summarized the abnormal morphology and abnormal characteristics of buried faults . At the same time, the experimental results of field data acquisition interference suppression and the forward inversion processing method of fault fracture zone anomalies were also summarized. The results obtained by the authors provide a reference basis and experience accumulation for geological exploration in eastern Sichuan.

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The application of integrated geophysical prospecting methods to the exploration of urban buried fault
LIU Wei, HUANG Tao, WANG Ting-Yong, LIU Yi, ZHANG Ji, LIU Wen-Tao, ZHANG Qi-Bin, LI Qiang
Geophysical and Geochemical Exploration    2021, 45 (4): 1077-1087.   DOI: 10.11720/wtyht.2021.1525
Abstract408)   HTML278)    PDF (4078KB)(510)      

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

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Valley system soils geochemical characteristics and metallogenic prediction of the Yue'e tin polymetallic mining area in Xieng Khouang Province, Laos
SHI Qi, ZHAO Yan-Peng, CHI Zhan-Dong, GE Hua, KANG Tie-Suo, LI Fa-Xing, WEI Xiang-Yu, LU Jian-Kun, YANG Ren-Yi
Geophysical and Geochemical Exploration    2021, 45 (4): 824-834.   DOI: 10.11720/wtyht.2021.1268
Abstract406)   HTML212)    PDF (2758KB)(341)      

The tin-polymetallic mining area of the Yue'e ore district, XiengKhouang Province, Laos, is located in the west of the XiengKhouang Laos-Changshan Vietnam tectonic magmatic belt. Based on the 1:25 000 valley system soil geochemical survey, combined with an analysis of the characteristics of element variation coefficients and concentration coefficients, the correlation of elements, anomaly verification, and gold and other polymetallic ore prospecting potentials, the authors optimized multiple target and prospects areas. The position of the mineralized body was inferred based on geochemical exploration anomalies in key target areas. Through trench verification and drilling engineering verification, good prospecting results were achieved. The area is considered to have copper, tin, lead, zinc, tungsten. It is shown that this method can quickly delineate the prospecting target area and distant scenic area in the thick coverage area and extensive blank research area of Southeast Asian tropical monsoon climate, and can provide an effective basis for the next exploration work.

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Elements enrichment and dilution characteristics and deep metallogenic prognosis in the Haiyu gold deposit, Jiaodong Peninsula
ZHANG Liang-Liang, ZHU Li-Xin, MA Sheng-Ming, LIN Shao-Yi, DAI Chang-Guo, ZHOU Ming-Ling, HUO Guang, XU Zhong-Hua, XI Ming-Jie, ZHANG Tao
Geophysical and Geochemical Exploration    2021, 45 (4): 835-845.   DOI: 10.11720/wtyht.2021.1099
Abstract349)   HTML212)    PDF (7770KB)(348)      

The Haiyu gold deposit, as a superlarge gold deposit with gold reserves of 470 t and average grade of 4.30×10-6, is a typical Jiaojia-type gold deposit. The authors carried out the rock geochemical survey by the samples from drillholes, and detected the enrichment of Au, Cu, Pb, Zn, Ag, As, Sb, Cd, Bi, S and Fe2O3 and the depletion of Na2O, Ba and Sr in the ore-hosting tectonic alteration zone. The authors systematically summarized the geochemical marks used for exploration. The enrichment of S and Au, or called the positive S and Au anomalies, is the typical geochemical mark of the source rock. The enrichment of S, Au, Ag and Bi and the depletion of Na2O and CaO are typical geochemical marks of the tectonic alteration zone. Based on the above elements and their anomalies, the authors constructed the ore-induced anomaly model of the Haiyu gold deposit, which provides a useful reference for the exploration of the peripheral and deep-seated gold deposits. It is proposed that the main gold orebodies of the ore-forming zone of the sea field may be along ZK2403, ZK3008, and ZK3814 boreholes spread in NEE direction.

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The application of ANSYS to TEM 3D forward modeling
ZHI Qing-Quan, WU Jun-Jie, WANG Xing-Chun, SUN Huai-Feng, YANG Yi, ZHANG Jie, DENG Xiao-Hong, CHEN Xiao-Dong, DU Li-Ming
Geophysical and Geochemical Exploration    2021, 45 (4): 1037-1042.   DOI: 10.11720/wtyht.2021.1456
Abstract346)   HTML100)    PDF (1430KB)(282)      

The forward modeling is an effective way to study the characteristics of transient electromagnetic (TEM) responses. The high precision and fast 3D forward modeling technology is a hot spot in the study of TEM forward modeling. The multiphysics module in ANSYS software is suitable for the forward modeling of TEM. In this paper, the application method of ANSYS software in TEM 3D forward modeling is introduced by some model examples, including the preprocessing, loading, solution setting and post-processing. The numerical results show that the simulation of TEM forward modeling by using ANSYS software has high accuracy. The TEM forward modeling using ANSYS can improve the efficiency of forward simulation calculation and provide a strong support for analyzing and understanding the characteristics of TEM response.

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A case analysis of multielectrode resistivity method for determining a well location in groundwater prospecting in the ore concentration area of Guyang County, Baotou City
WANG Wen-Jie, HAO Yi, BO Hai-Jun, WANG Hai-Long, XU Hao-Qing, LI Yong-Li, MAO Lei, Liu Yong-Xin, YUAN Shuai
Geophysical and Geochemical Exploration    2021, 45 (4): 869-881.   DOI: 10.11720/wtyht.2021.0068
Abstract316)   HTML198)    PDF (6772KB)(493)      

In order to find out the stratigraphic structure and groundwater pollution in the ore concentration area of Guyang County, Baotou City, it is necessary to carry out hydrogeological drilling around typical mines in the ore concentration area. In this paper, according to different types of groundwater-finding targets and the advantages of different measuring devices in resolution and signal-to-noise ratio, the multielectrode resistivity method was employed to study and analyze the electrical structure characteristics and well forming pattern of groundwater around south concentrator of Wengeqi iron deposit, Hongchang concentrator and Shangshierfenzi gold deposit. The result shows that comprehensive analysis of the hydrogeological conditions of the study area and utilization of different arrays of multielectrode resistivity method seem to be effective technical means for carrying out water resources investigation, which can achieve the target, reduce the multi-solution of geophysical inversion and interpretation, greatly improve the efficiency of searching for groundwater resources by using single geophysical method and provide a technical basis for water exploration and well determination in the ore concentration area of Guyang County, Baotou City.

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An experimental study of geochemical exploration methods for concealed deposits in loess overburden area: A case study of the Zhonghedi polymetallic deposit in Henan Province
DOU Bei, ZHANG Bi-Min, YE Rong, CHI Qing-Hua
Geophysical and Geochemical Exploration    2021, 45 (4): 933-941.   DOI: 10.11720/wtyht.2021.1324
Abstract313)   HTML138)    PDF (3995KB)(249)      

As it is difficult to collect the weathering stream sediments of bedrock in the loess overburden area,the effect of regional geochemical exploration is often not ideal; therefore, regional geochemical exploration work has not been carried out in many loess overburden areasof China. In this paper, the deep-penetrating geochemistry method was used to carry out the experimental study of geochemical prospecting techniques for concealed deposits in the loess overburden area in the Zhonghedi silver-lead-zinc polymetallic deposit in Xiaoshan, Henan Province. The results of fine-grained soil prospecting method and metal mobile extraction measurement show that both methods can well indicate the anomalies of underlying polymetallic orebodies in the loess overburden area and, at the same time, the mobile extraction method further enhances the abnormal indication of ore-forming elements to the orebody, so both methods can be used as effective means in search for concealed polymetallic deposits in the loess overburden area.

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Application of airborne geophysical survey in antarctica
LI Xiao, TONG Jing, ZHANG Wan, YAO Guo-Tao, ZHANG Xuan-Jie
Geophysical and Geochemical Exploration    2022, 46 (1): 12-21.   DOI: 10.11720/wtyht.2022.1076
Abstract312)   HTML42)    PDF (2664KB)(326)      

Airborne geophysical techniques represent a cost-effective way for obtaining insights into the crustal geology of the Antarctic. Based on the analysis of the history of Antarctic airbrone geophysical survey and development of facilities and fly-platform applied in the survey, this paper gives a review of the leading scientific application topic of airborne geophysical data i.e.,the crustal structure of Antarctica,the reconstruction and restoration of ancient terrains, magmatism and volcanism identification,and the interaction between Antarctica Ice Shelf and bed rock, which shows that airborne geophysical survey provides effective technical support for Antarctica geosciences research.Our research shows that there is still a blank area for geophysical survey. Based on out review, the combination of airborne magnetic, airborne gravity and ice radar data has provide a new solution to the interaction study of Antarctic Ice shelf and bedrock.

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Research progress of methane microseepage in petroliferous basins and its significance for oil-gas exploration
ZOU Yu, WANG Guo-Jian, YANG Fan, CHEN Yuan
Geophysical and Geochemical Exploration    2022, 46 (1): 1-11.   DOI: 10.11720/wtyht.2022.1150
Abstract310)   HTML1437)    PDF (1474KB)(341)      

Great progress has been made in the formation mechanisms of surface characteristics of gas microseepagesince the start of the 21st century, which is significant for oil-gas exploration. The microseepage in petroliferous basins is dominated by methane, which migrates nearly vertically from source rocks or reservoirs toward ground surface. The chemical, physical, and biological variation characteristics produced on the ground surface approximately reflect the oil reservoirs underground. Therefore, the methane microseepage is an objective and important part of the petroleum seepage system and has replaced microseepage as the most effective window for the tracing of underground reservoirs on the ground surface at present. Methane microseepage can be directly monitored on ground surface and in water and atmosphere, and the component concentrations and isotopic composition of methane-bearing hydrocarbon gases serve as the first-hand important data for the assessment of underground oil and gas. The data indirectly monitored mainly source from microorganisms, vegetation, minerals, radioactivity, and magnetism on the ground surface. Similar to the geochemical exploration data directly obtained, these abnormal data canbe distinguished from the background values of the ground surface far away from the oil reservoirs, and the distribution areas of the anomalies will become important targets of favorable exploration areas. It will play an increasingly important role in the future integrated oil and gas explorationto gain in-depth understanding of methane microseepage mechanisms, avoid single monitoring method and one-sided understanding, transform ideas to adoptsurface integrated monitoring methods, and establish new mathematical analysis systems.

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The application of high-precision aeromagnetic survey to the investigation of oil-gas geological structure in Southwest Tarim Basin
CUI Zhi-Qiang, XU Zhi-Li, LI Fei
Geophysical and Geochemical Exploration    2021, 45 (4): 846-858.   DOI: 10.11720/wtyht.2021.1455
Abstract303)   HTML128)    PDF (3968KB)(273)      

Influenced by the difficulty of exploration and poor seismic quality, the exploration of oil-gas resources in the southwest of Tarim Basin has not achieved a substantial breakthrough after decades of work. Based on the latest high-precision aeromagnetic data obtained in Southwest Tarim Basin in recent years, this paper discusses the geological problems related to oil-gas accumulation, such as basement structure of basin, distribution and characteristics of depressions, main fault structures and their controlling rules for oil-gas migration and accumulation, local anomalies and favorable local structures of oil-gas as well as their distribution characteristics. The results of the study can provide important reference for the further strategic selection of oil-gas exploration and deep resource evaluation in Southwest Tarim Basin.

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Application of integrated geophysical exploration in deep spatial structures: A case study of Jiaodong gold ore concentration area
CHEN Da-Lei, WANG Run-Sheng, HE Chun-Yan, WANG Xun, YIN Zhao-Kai, YU Jia-Bin
Geophysical and Geochemical Exploration    2022, 46 (1): 70-77.   DOI: 10.11720/wtyht.2022.1102
Abstract290)   HTML141)    PDF (2056KB)(372)      

Jiaodong area is one of the major gold producing areas in China, and the deep prospecting in this area is to seek deep breakthroughs and blind spots at present. With the gold concentration area in Jincheng Town in Laizhou City and Ershilidian Town in Haiyang City as an example and based on the prediction and assessment theory and method of deep gold resources, this study summarizes the deep spatial characteristics and relationships of the Archaeozoic-Mesozoic intrusive rocks, Precambrian metamorphic basement, and the strata in Jiaolai Basin in the area and the deep morphology and characteristics of major ore-controlling structures in the area. To this end, section measurement was carried out using the integrated geophysical exploration of high-precision gravity survey, high-precision magnetic survey, and magnetotelluric sounding. Meanwhile, the obtained gravity, magnetic, and resistivity data were comprehensively researched and analyzed in combination with previous results. This study will provide a basis for the late prospecting prediction of deep gold deposits and related researches of the area.

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Integrated geophysical exploration of the Wei concubine in the Tang-dynasty Zhao Mausoleum
SHI Zhao-Yang, GAO Wei-Qiang, ZHANG Li-Ming, ZHANG Lin, FENG Xu-Liang, HE Tao, ZHENG You-Wei
Geophysical and Geochemical Exploration    2021, 45 (6): 1617-1624.   DOI: 10.11720/wtyht.2021.1303
Abstract278)   HTML152)    PDF (2419KB)(322)      

Tomb of Wei Concubine is the nearest to Zhao mausoleum and the highest level in all the Tomb in Zhao Mausoleum,as also, it is the only construction tomb in Mountain of the Tang Dynasty that has been compouded,so,it is improtant to research and protect Tang-dynasty mausoleum.We survey the tomb of the Wei concubine with uav lidar survey, ground high-precision gravity and magnetic survey, high-density electrical survey, GPR and soil radon gas survey for evaluating the results. Ground high precision gravity and magnetic survey combined with soil radon measurement can effectively delineate the plane position of underground place. The high density electric method accurately delineates the space position under ground. The GPR has clearly detected the fine structure of the tomb with a resolution of up to sub-meter level, These resoults provide valuable information for exploration of Zhao Mausoleum’s underground palace in the future.

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Oil shale exploration based on seismic ambient noise
LI Hong-Xing, TAN Shun-Jia, YAO Zhen-An, HUANG Guang-Nan, XU Pei-Yuan, ZHOU Jie, FAN Li-Fei
Geophysical and Geochemical Exploration    2021, 45 (4): 898-905.   DOI: 10.11720/wtyht.2021.1320
Abstract271)   HTML130)    PDF (4006KB)(269)      

As oil shale is an important unconventional oil and gas resource,its exploration and development has received increasing attention.Microtremor exploration based on seismic ambient noise is a passive,efficient and low-cost method of seismic exploration,which can be used to image the shear wave velocity of underground medium and can become a potential new exploration method for oil shale more in line with the requirements of "environmental protection".For the first time,the authors applied microtremor method to oil shale exploration based on the spatial cross correlations of common central panel and conducted a study of the identification of oil shale in Songliao Basin.The results show that the geometry of microtremor method can be flexible according to the real situation,the shear wave velocity profile corresponds well with the results of borehole cataloging near the survey line and the main stratum is well divided.The second member of the Nenjiang Formation,which is mainly oil-bearing shale,exhibits low velocity characteristics.

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New understanding of the distribution characteristics of the Yellow River fault on the eastern margin of Yinchuan Basin
HU Xin-Jun, CHEN Xiao-Jing, LI Ning-Sheng, WU Yang, CHEN Tao-Tao
Geophysical and Geochemical Exploration    2021, 45 (4): 913-922.   DOI: 10.11720/wtyht.2021.1445
Abstract261)   HTML67)    PDF (2975KB)(234)      

As one of the important regional faults in northern Ningxia, the Yellow River fault has controlled the formation and evolution of Yinchuan Basin. This fault is one of the inevitable key points for studying the law of seismic activity and geothermal resource enrichment in Yinchuan plain. At present, the study of the Yellow River fault is very insufficient, and the work is mainly concentrated on surface survey with shallow geophysical exploration in some areas. In this paper, the authors used geological outcrop data as clues and, based on regional 1:200000 gravity data, used advanced geophysical data processing techniques such as wavelet demarcation and oblique derivative to clearly depict the phenomenon that the Yellow River fault has obvious characteristics of "flying geese" plane distribution. The fault is divided into four sub-segments: Lingwu section, Linhe section, Yueyahu section and Lihe section. The CSAMT data of Linhe section and Lingwu section reveal that the main fault and its secondary faults of the Yellow River descend gradually from east to west, i.e., "staircase", with obvious "grading" characteristics. The undercut depth of the Yellow River main fault reaches the upper crust, and the combination of the secondary-scale faults on the profile exhibits a typical "broom" shape. The "seat-like" space of "upward steep, moderately gentle, and downward steep" of each fault is obviously present. Compared with the existing research results, it is found that there are three differences between them, i.e., spreading characteristics, spreading position, and spreading relationship.

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Stochastic inversion of surface wave dispersion curves based on Bayesian theory
LIU Hui, LI Jing, ZENG Zhao-Fa, WANG Tian-Qi
Geophysical and Geochemical Exploration    2021, 45 (4): 951-960.   DOI: 10.11720/wtyht.2021.1100
Abstract259)   HTML99)    PDF (4903KB)(282)      

Surface wave dispersion curve inversion is an important geophysical method for obtaining the velocity and thickness distribution of underground shear wave.Conventional linear inversion methods,such as iterative least squares,relying on the initial model and multiple solution,are easy to fall into local minimum and low inversion accuracy.The stochastic inversion method based on Bayesian theory is a nonlinear inversion method which can integrate prior information.This method does not need initial model,only uses prior information to sample the model randomly,and selects and accepts the appropriate inversion model according to the probability distribution.It achieves the accurate estimation of the detail information.In this paper,the authors present a Bayesian Markov Monte Carlo (MCMC) stochastic inversion method based on GPR data constraints to invert the Rayleigh-waves dispersion curve.In the inversion process,by randomly changing the model parameters and calculating the likelihood function of the dispersion curve and the actual dispersion curve,researchers can choose whether to accept the new model parameters,repeat this process continuously,and finally get the best fitting result with the actual dispersion curve and the posterior probability density distribution of the VS solution.The typical numerical model test and field seismic data demonstrate that,compared with the conventional unconstrained stochastic inversion,the proposed method can effectively reduce the multiple solution and improve the efficiency and accuracy.

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Application of shallow seismic reflection surveys in the exploration of urban underground space in Jinan
XIAO Guan-Hua, ZHANG Wei, CHEN Heng-Chun, ZHUO Wu, WANG Yan-Jun, REN Li-Ying
Geophysical and Geochemical Exploration    2022, 46 (1): 96-103.   DOI: 10.11720/wtyht.2022.2375
Abstract258)   HTML70)    PDF (9157KB)(301)      

Shallow seismic reflection (SSR) surveys are an indispensable method in the exploration of urban underground space.Their exploration effects are affected by many aspects such as excitation,receiving factors,acquisition parameters,and processing methods,which should be systematically scientifically demonstrated and selected according to geological tasks.Taking an underground space exploration project in Jinan as an example,the authors discussed the method of improving the resolution of SSR surveys.Through the comprehensive analysis of the collected data,a reasonable seismic geological model was established.Based on this model,the forward analysis and illumination analysis were performed using the fluctuation equation of seismic data acquisition parameters,obtaining a high-density two-dimensional seismic observation plan.Meanwhile,high-resolution reflection images were obtained through the study on targeted data processing techniques such as pre-stack denoising,deconvolution,and velocity field optimization.Excellent exploration results have been achieved in the project.This study will provide reliable geophysical exploration data for the construction of the smart city in Jinan,and can serve as references for the implementation of SSR exploration in this area in the future.

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Geological characteristics and prospecting direction of rare earth element deposits in North China
ZHAO Ze-Lin, LI Jun-Jian, ZHANG Tong, NI Zhen-Ping, PENG Yi, SONG Li-Jun
Geophysical and Geochemical Exploration    2022, 46 (1): 46-57.   DOI: 10.11720/wtyht.2022.1040
Abstract258)   HTML118)    PDF (1069KB)(280)      

Based on the systematic collection of information of rare earth element (REE) deposits in North China, this paper analyzes the current situation of REE resources and the temporal-spatial distribution regulation of REE deposits in North China.The mineralization types of the REE deposits in North China mainly include sedimentary and metamorphic type, igneous carbonate magma type, magmatic hydrothermal type, pegmatite type, andion-adsorption type. Given thegeotectonic locations and ore-controlling factorsof REE deposits in North China, the geodynamic background favorable for the formation of the REE deposits includes the ancient metamorphic basement, Archean-Paleoproterozoic rift zones on continental margins, Middle Proterozoic rift zoneson continental margins, and Yanshanian active continental margins in coastal areas of the West Pacific. Thetectonic-sedimentary-magmatic prospecting favorable conditions include volcanic-sedimentary events during the early development of regional deep faults and geosynclines and the magmatic activitiesof alkaline syenitesand alkaline granites. Meanwhile, the geochemical background favorable for REE mineralization consists of high precipitation amount, alluvial plains, and brown soil distribution areas.

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The parameter selection of middle and shallow seismic exploration based on vibrator
XIE Xing-Long, MA Xue-Mei, LONG Hui, LI Qiu-Chen, GUO Shu-Jun, CHENG Zheng-Pu
Geophysical and Geochemical Exploration    2021, 45 (4): 1004-1013.   DOI: 10.11720/wtyht.2021.1145
Abstract257)   HTML121)    PDF (18105KB)(295)      

The vibrator has been widely used in petroleum,coal field and other seismic exploration,and the corresponding technical means are relatively mature;nevertheless,there is no reference basis for the parameter selection of middle and shallow seismic exploration with vibrator.In order to study how to obtain high quality data in middle and shallow seismic exploration,the authors carried out a series of "vibrator excitation,high frequency geophone reception" experiments in Xiong'an.Based on a large number of experimental data and using qualitative analysis of original single shot and quantitative analysis of frequency spectrum,this paper systematically discusses the influence of the selection of parameters such as vibration number of vibrator,sweep length,starting frequency,ending frequency,drive level,slope length and natural frequency of geophone on data quality.This paper clarifies the key points and basis of parameter selection,puts forward the concept of high cutoff frequency,and summarizes the strategy of parameter selection for middle and shallow seismic exploration,which provides some reference for the use of vibrator in middle and shallow seismic exploration.

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Seismic imaging of high-steep structural zone in Biyang Depression
DUAN Ying, ZHANG Gao-Cheng, TAN Ya-Li
Geophysical and Geochemical Exploration    2021, 45 (4): 981-989.   DOI: 10.11720/wtyht.2021.2492
Abstract253)   HTML42)    PDF (7963KB)(176)      

Seismic imaging of the high-steep structural zone in southern Biyang Depression is difficult.In order to improve imaging accuracy,in this paper,the authors studied and applied tomographic static correction technology of undulating surface in the piedmont zone,employed prestack multi-domain noise suppression technology based on low-frequency fault surface waves protection,velocity modeling technology of high-steep structure in the piedmont zone and reverse-time migration technology of undulating surface,and thus improved the seismic imaging accuracy of complex structures in the high-steep structure zone in this area.As a result,large boundary fault zone characterization is more accurate,and the stratigraphic contact relation and structure imaging are clear.

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The application of tectonogeochemical cuttings survey to gold prospecting in Nanshan area of Danghe, Gansu Province
ZHAO Ji-Chang, FAN Ying, LEI Yi-Lan, YAO Bin-Bin
Geophysical and Geochemical Exploration    2021, 45 (4): 923-932.   DOI: 10.11720/wtyht.2021.0098
Abstract248)   HTML125)    PDF (6756KB)(236)      

Danghe Nanshan is one of the important gold metallogenic areas in Gansu Province. A number of important gold deposits have been discovered there, such as Jiagongtai, Heicigou and Langchagou, suggesting that the metallogenic conditions are very favorable. However, due to the special geochemical landscape of this area, the peripheral prospecting effect is not good. When carrying out the 1:50 000 mineral prospect survey project in Heidaban-Danghe Nanshan area and aiming at the low and gentle anomalies in the area, the authors introduced the 1:10 000 tectono-geochemical debris survey method into the gold prospecting work for the first time, and analyzed the geochemical characteristics and element combination characteristics in this area. Combined with the metallogenic geological background, 13 comprehensive geochemical anomalies were delineated, and it was found that the main metallogenic elements Au, Pb and Pb and exploration elements As and Sb are intensively enriched in favorable structural positions. Through trenching, 6 new gold mineralization zones were discovered and 15 gold orebodies were delineated. This method was further applied to the gold prospecting in adjacent areas, with good prospecting results achieved. The successful application of this method is of great significance for prospecting in the geochemical landscape area of shallow covered Alpine desert.

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Geochronology and geochemistry of the granodiorite intrusion in Yangkang area of Qinghai Province and its geological significance
FANG Yong-Kun, Cao Cheng-Gang, DONG Jun-Lin, LI Ling-Gui
Geophysical and Geochemical Exploration    2021, 45 (6): 1367-1377.   DOI: 10.11720/wtyht.2021.1185
Abstract244)   HTML458)    PDF (2334KB)(349)      

The formation age and petrogenesis of the Yangkang granites in the Qilian block remain controversial. In this study, LA-ICP-MS zircon U-Pb dating and whole-rock geochemical analysis were conducted to constrain the petrogenetic and tectonic processes during the formation of the granites. The results show that U-Pb age of granodiorite in Yangkang pluton is 444±1.2Ma, (MSWD=1.14), indicating that it was formed in the early Late Ordovician and that the rocks belong to weak peraluminous-strong peraluminous I-type granite.The rocks are enriched with large ion lithophile elements (K,Ba, Rb) and Light Rare Earth Elements (LREEs) and Th, but depleted in the high field strength elements (e.g., Ta-Nb). The above results show that Yangkang granites were derived from partial melting of continental crust. Combined with the regional data, the authors suggest that the Yangkang granites were probably formed in an active continental margin during Late Ordovician.

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Neural network seismic prediction of sand and mudstone lithology of Pinghu Formation in Xihu Sag
ZHANG Peng-Fei, ZHANG Shi-Hui
Geophysical and Geochemical Exploration    2021, 45 (4): 1014-1020.   DOI: 10.11720/wtyht.2021.1297
Abstract242)   HTML61)    PDF (5329KB)(182)      

The traditional seismic P-wave impedance inversion method has the problems of low lithologic resolution and multi-solution,and it is hence difficult for the inversion results to meet the requirements of finely characterizing the lithologic distribution.In this paper,by constructing a normalized pseudo-gamma curve containing lithology and P-wave impedance information as a lithology index indicator curve,the neural network method is used to convert seismic data into a gamma data volume which is more closely related to lithology.Through the neural network seismic inversion,the sand and mudstone lithologic inversion data volume is obtained.This method was used to invert the sand and mudstone lithology of the Pinghu Formation in the Xihu Sag.Compared with traditional methods,the prediction accuracy of the mudstone thickness is up to 93%,which more accurately characterizes the distribution of underground sand and mudstone,and provides a basis for later oil and gas exploration.

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An analysis of the detection effect of cross-well electromagnetic wave CT in coal mine goaf
ZHAO Xu-Chen, LI Xue-Jian, CAO Fang-Zhi, LEI Xiao-Dong, LI Chen, HAN Yu-Da
Geophysical and Geochemical Exploration    2021, 45 (4): 1088-1094.   DOI: 10.11720/wtyht.2021.0067
Abstract242)   HTML95)    PDF (4594KB)(264)      

In an open-pit coal mine in Hulun Buir of Inner Mongolia, the main mining coal seams are buried in depths ranging from 39m to 90m. Before coal mine integration, predatory mining has left many mined areas with unknown geological data, and the existence of mined-out areas has brought huge safety hazards to open-pit mining stripping. In order to find out the specific location and connectivity of the underground goaf, the authors used the cross-hole electromagnetic wave CT method to probe into the inside of the goaf in detail, and obtained a lot of real and reliable geophysical data. The analytical result shows that relatively complete rock formation electromagnetic wave absorption coefficient is in the range of 0.44~0.51Nper/m, and no water-filled goaf electromagnetic wave absorption coefficient is in the range of 0.29~0.40 Nper/m. According to the difference of electromagnetic wave absorption coefficient between goaf and surrounding rocks, the authors drew the morphological interpretation map of the goaf, and the results are basically consistent with the drilling data.

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Wide field electromagnetic data processing and interpretation platform based on MySQL
ZHU Yun-Qi, LI Di-Quan, WANG Jin-Hai
Geophysical and Geochemical Exploration    2021, 45 (4): 1030-1036.   DOI: 10.11720/wtyht.2021.1549
Abstract238)   HTML101)    PDF (3124KB)(286)      

Aiming at tackling the current shortcomings of wide field electromagnetic method data processing software such as low integration, cumbersome operation and inability to manage data in a unified manner, the authors developed wide field electromagnetic method data processing and interpretation software. The software adopts client-server architecture and modular design. The project management module developed based on MySQL database can realize the automatic storage and management of project data. The data processing module of wide field electromagnetic method developed by the scientific computing library based on Python can meet the data processing requirements. Based on visualization and interactive operation, this software can greatly simplify the operation process and improve the efficiency of data processing. This software was applied to actual projects and, as a result, large quantities of data were processed, and good results were achieved.

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Physical simulation experiment for detecting water-filled goaf of coal mine under complex conditions bases on transient electromagnetic method
PEI Xiao-Ming, FENG Guo-Rui, QI Ting-Ye
Geophysical and Geochemical Exploration    2021, 45 (4): 1055-1063.   DOI: 10.11720/wtyht.2021.0055
Abstract237)   HTML83)    PDF (4751KB)(300)      

After the formation of water-filled goaf in coal mines, the distribution patterns and locations are different and unclear. Therefore, it can easily cause serious water hazards. In order to accurately locate the water-filled goaf and study its electromagnetic response characteristics, the authors chose the Datong Majiliang coal mine as the engineering background, used acrylic glass shelves as the experimental platform, and took similar simulation materials as each rock layer to design the physical experiment of transient electromagnetic detection in the water-filled goaf under different water accumulation and existence situations of collapsed rock masses. The results demonstrate that, when the goaf is filled with water, the induced electromotive force curve will be affected by the low resistance effect during the attenuation process and produce an abnormal "upward" phenomenon, and the greater the water filling, the more obvious the abnormal amplitude is. The existence of collapsed rock mass will limitedly weaken the abnormal interference of low resistance. When the goaf is not filled with water, the induced electromotive force curve decays normally, and the impact of the collapsed rock mass is negligible.

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The application of unmanned helicopter aeromagnetic method to the survey of the iron deposit in Xiangshannan-Dadiantang area, Ma’anshan City, Anhui Province
CHEN Wei, ZHAO Guo-Feng, FEI Zhen-Zheng, LUO Ding, PENG Jiang-Ying, HUANG Yan, JIA Shuo
Geophysical and Geochemical Exploration    2021, 45 (4): 890-897.   DOI: 10.11720/wtyht.2021.1382
Abstract233)   HTML89)    PDF (2584KB)(325)      

With Xiangshan South-Dadiantang area of the Ningwu volcanic basin as an example, the authors used the methods of geology and unmanned helicopter aeromagnetic to explore the prospecting work in the deep and peripheral parts of the old mine. Comprehensive analysis and fine inversion of aeromagnetic anomalies were conducted to determine the location of the borehole. All the drill holes intersected ores in the depth of the old mine, which proves the effectiveness of this method. The result also provides a reference for the rapid and effective development of prospecting work in the deep and peripheral areas of old mines in areas with similar working conditions in the future.

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Research and application of seismic forward simulation technology in deep reflection seismic profile detection
WANG Guang-Wen, WANG Hai-Yan, LI Hong-Qiang, LI Wen-Hui, PANG Yong-Xiang
Geophysical and Geochemical Exploration    2021, 45 (4): 970-980.   DOI: 10.11720/wtyht.2021.1122
Abstract232)   HTML107)    PDF (13560KB)(444)      

Seismic wave forward modeling technology is widely used in shallow exploration.This method can combine geological model and seismic model organically to verify and guide the acquisition,processing and interpretation of seismic data.The deep reflection seismic profile detection technology based on the oil reflection seismic technology has been very mature after decades of development and application.But up to now,the application of seismic wave forward modeling in deep reflection seismic profile is very insufficient.In this paper,the deep reflection seismic profile across Sichuan Basin was used to carry out forward modeling.By comparing and fitting the horizon of forward simulation data and actual seismic data,the parameters such as velocity and horizon were constantly modified,and the final depth domain geological model was established,which provides more accurate stratigraphic information such as crustal thickness and Moho depth for structural profile.Through the geological model in depth domain,it is revealed that the angle of Neoproterozoic paleosubduction in the northwest margin of Yangtze plate was about 30 °,and the depth of subduction reached 60 km.

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Forward modeling of MT tipper based on 3D complex anomalous body model
TIAN Yu, YUE Biao
Geophysical and Geochemical Exploration    2021, 45 (4): 1021-1029.   DOI: 10.11720/wtyht.2021.1459
Abstract230)   HTML5)    PDF (2763KB)(162)      

Tipper is very sensitive to the lateral inhomogeneity of the geoelectric structure and can be used to characterize the complex structure. In this paper, based on the three-dimensional complex anomalous body model of magnetotelluric sounding, the formula for calculating the three-dimensional tipper is derived according to the definition of the dump, and three-dimensional anomalous volume models with different combinations are constructed for forward modeling. Forward modeling studies show that the tipper data better reflect the abnormal body boundary, and it is also more accurate to reflect the boundary of several abnormal bodies, whereas the low resistivity body sensitively reflects a high resistance abnormal body. The study of tipper data further explains the characteristics and laws of tipper data and provides a theoretical basis for the application of tipper data.

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The application of multi-channel energy spectrum survey to the exploration of granite type rare metal deposits in eastern Hebei
CHENG Li-Qun, ZHANG Wen-Yu, WANG Kai, WANG Bin, PEI Ming-Xing
Geophysical and Geochemical Exploration    2021, 45 (4): 942-950.   DOI: 10.11720/wtyht.2021.1562
Abstract227)   HTML9)    PDF (3375KB)(180)      

There are many Yanshanian granite intrusions in eastern Hebei, which constitute a good metallogenic background of granite-type rare metal deposits. In order to study the metallogenic prospects of these rock masses, the authors chose the Hanerzhuang granitic body in this area as the research object, and carried out the multi-channel energy spectrum survey to analyze the characteristics of radioactive parameters of different lithologies, the characteristics of radioactive anomalies and their relationship with rare metal mineralization. The results show that the average content of U, Th and total trace in the monzogranite is 9 times, 8.5 times and 3.9 times the background value in the whole area, respectively. The distribution characteristics of the anomaly field are basically consistent with the surface outburst form of the monzogranite. Combined with the results of petrogeochemical study and artificial heavy sand, the authors hold that the monzogranite whole rock has a good mineralization of rare metals. The rocks contain a large number of U, Th and Hf minerals such as yttrium-brown niobium ore and monazite, and these minerals have a symbiotic relationship with Nb, Ta, Rb and other rare metal minerals. According to the distribution of anomaly field and the characteristics of thorium potassium, thorium uranium, uranium potassium ratio and other parameters, the favorable areas of rare metal mineralization can be directly delineated to guide the arrangement of prospecting engineering. The effective implementation of this method provides a convenient, efficient and cheap means for the exploration of rare metals in the granite area in the future.

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The application of low-amplitude structure based on low-frequency reduction
XIA Hong-Min, ZHENG Xiao-Wen, HUANG Han-Dong, XIAO Yan-Hui, DONG Jin-Chao, LIAO Jun
Geophysical and Geochemical Exploration    2021, 45 (4): 998-1003.   DOI: 10.11720/wtyht.2021.1167
Abstract224)   HTML4)    PDF (5599KB)(190)      

With the continuous improvement of exploration degree,more and more attention has been paid to low-range structural oil and gas reservoirs.Current methods for identifying low-amplitude structures cannot effectively eliminate low-frequency structural background information contained in seismic data,and cannot accurately identify low-amplitude structures.In this paper,on the basis of de-frequency reduction,the trend decomposition method was used in the search for structural inflection points,and the low-amplitude structure was graphed. Combined with the wavelet decomposition method,the continuity in the large-scale time-frequency domain is good.The inverse transform finally obtains a low-amplitude structure explanatory diagram that eliminates the low-frequency background of the structure.The practical application in the northern part of E Basin shows that the low-amplitude structure identification method based on de-frequency reduction enhances the local micro-structural characteristics,and also makes up for the influence of structural elevation difference and random factors on low-amplitude structures.The purpose of the complete and detailed map is of great guiding significance for the exploration and development of complex oil and gas reservoirs with low structural amplitude.

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Application of microtremor survey method in detection of urban land subsidence
XU Hao, WU Xiao-Ping, SHENG Yong, LIAO Sheng-Zhu, JIA Hui-Tao, XU Zi-Qiao
Geophysical and Geochemical Exploration    2021, 45 (6): 1512-1519.   DOI: 10.11720/wtyht.2021.0053
Abstract222)   HTML63)    PDF (7432KB)(380)      

Urban land subsidence is liable to induce ground fractures or even collapse,thus causing safety accidents.However,traditional geophysical methods cannot be applied in cities due to the strong human interference and high requirements for safety and environmental protection in the urban environment.The microtremor survey method is a passive,efficient,and environment-friendly geophysical method and it can be used to detect the underground geological conditions in the urban environment with strong interference.Taking Xiegang Primary School in Hefei City as the research site,this paper focuses on the applicability and effectiveness of the microtremor survey method in detecting the causes of land subsidence.Based on the microtremor survey data collected,the dispersion curve was extracted using the F-K method and then the underground shear wave velocity structure was obtained through inversion,thus revealing the underground geological conditions.Finally,verification was conducted through drilling.The results show that the microtremor survey is an effective geophysical method for detecting the information such as the position and scale of underground unconsolidated soil,and thus the secondary accidents in subsidence areas can be eliminated.

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Research on 3D modeling of fully mechanized mining face based on UPSO-Kriging
ZHANG Xiao-Yan, XU Hui, JIANG Shui-Jun
Geophysical and Geochemical Exploration    2021, 45 (4): 1071-1076.   DOI: 10.11720/wtyht.2021.0087
Abstract221)   HTML4)    PDF (2242KB)(142)      

Kriging interpolation algorithm is the basis of 3D modeling of coal seam occurrence form in fully mechanized mining face based on traditional geostatistics. However, the variation function model selected and fitted by Kriging interpolation algorithm cannot reflect the actual geological characteristics and the variation trend of spatial data. In this paper, UPSO-Kriging interpolation method is thus proposed: PSO algorithm is optimized to solve the problems of slow convergence and easily falling into local solution, and the optimized algorithm UPSO is then introduced into Kriging interpolation to solve the variation parameters and fit the variation function model, thus realizing the height prediction of each layer in the coal seam structure of working face. In addition, with DEM model established on regular grid method, the three-dimensional visualization of the occurrence form of coal seam in fully mechanized mining face is realized by using Three.js, which provides scientific basis for transparent mining, intelligent mining and quality mining of coal enterprises.

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Online sequential extreme learning machine for transient electromagnetic nonlinear inversion
LI Rui-You, ZHANG Huai-Qing, WU Zhao
Geophysical and Geochemical Exploration    2021, 45 (4): 1048-1054.   DOI: 10.11720/wtyht.2021.1514
Abstract210)   HTML5)    PDF (2487KB)(121)      

The traditional transient electromagnetic inversion method using artificial neural network based on gradient descent method is inefficient and can not guarantee global convergence. In order to solve these problems, this paper proposes a transient electromagnetic inversion method based on on online sequential extreme learning machine (OSELM). This approaches is used for inversion of high-dimensional exploration data obtained by transient electromagnetic method. Firstly, the hidden layer parameters (input weight and deviation) are randomly set to simplify the learning process of the model. Then, the prediction samples obtained from the test are added to the training samples as the next update information, and the online sequential extreme learning machine prediction model is established to maximize the inverse accuracy. Finally, the inversion results of two classical TEM layered geoelectric models and a quasi two-dimensional geoelectric model show that the proposed method can solve the problem of nonlinear modeling and high-dimensional data for TEM inversion, and a comparison with extreme learning machine (ELM) shows that this method has more accurate inversion, better generalization ability and higher calculation efficiency, which provides a new idea for the application of neural network in geophysical inversion.

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The application of information entropy subinterval area median contrast filtering method to extracting the abnormal soil gas radon concentrations: A case study of Huahai basin, Ganshu Province
LEI Bo, LAN Ming, HE Feng, LU Bao-Long, LUO Cai-Wu
Geophysical and Geochemical Exploration    2021, 45 (4): 1064-1070.   DOI: 10.11720/wtyht.2021.1323
Abstract208)   HTML2)    PDF (3082KB)(157)      

Huahai basin is in the western edge of the corridor basin group in Gansu Province. Based on the results of soil gas radon concentration measurement and the background structural and evolution law of Huahai basin, the authors analyzed the characteristics of the abnormal fields by the Information Entropy Subinterval Area Median Contrast Filtering (SAMCF) Method. The results were different with the different m and n paraments by using SAMCF method. It also showed that the entropy varied from 2.5 to 3.6. The relationship of entropy and m and n was complexity. However, it varied like a "U" sharp with the incease of k parament. When the k varied from 15 to 20, the minimum entropy was gotten showing the western party of the study area with anomaly radon gas in the soil, is the favorable area for deep uranium exploration.

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The application of multi-seismic hydrocarbon detection technology to gas identification in B oilfield
MA Liang-Tao, FAN Ting-En, XU Xue-Liang, DONG Jian-Hua, CAI Wen-Tao
Geophysical and Geochemical Exploration    2021, 45 (4): 961-969.   DOI: 10.11720/wtyht.2021.1175
Abstract201)   HTML3)    PDF (8835KB)(199)      

The target field is in the early stage of development with few drilling wells.Unclear boundary of gas reservoir in the target area affects accurate calculation of oil field reserves and well pattern deployment for later development.To solve this problem,the authors analyzed the seismic response characteristics of gas-bearing reservoirs in the target area by spectral decomposition energy attenuation,AVO analysis and pre-stack elastic parameter inversion technology,and then predicted the boundary of gas-bearing reservoirs in the target area.The result shows that the gas-bearing reservoir in the target area is characterized by "low frequency resonant and high frequency attenuated".That means the increase of low frequency energy and the decrease of high frequency energy due to the attenuation of seismic wave.Through AVO forward analysis of drilled well,it can be determined that the gas-bearing reservoir in the target area belongs to class III AVO anomaly,and its seismic positive amplitude increases with the increase of offset distance.Among the petrophysical parameters,Lame's coefficient,Poisson's ratio and P-S wave velocity ratio are sensitive to gas-bearing sandstone.Besides,Poisson's ratio is the best one for distinguishing gas-bearing sandstone and can reveal the gas-bearing reservoir and predict its plane distribution.Applying spectral decomposition energy attenuation,AVO analysis and pre-stack elastic parameter inversion technology,the authors detected gas-bearing reservoirs. With the application of multi-technology,the prediction precision of gas-bearing reservoir boundary can be improved and this would provide support for accurate calculation of reserves and development of well pattern deployment in the target area.

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Evolution characteristics and potential area prediction of shale in Wuerxun Sag
YANG Song-Lin, LI Yan, LIU Ya-Xuan, YANG Xue, JIANG Wen-Bo
Geophysical and Geochemical Exploration    2021, 45 (4): 906-912.   DOI: 10.11720/wtyht.2021.1391
Abstract195)   HTML2)    PDF (1996KB)(183)      

Wuerxun Sag is an important oil-bearing area in the south of Hailaer basin, which has great exploration potential. This paper determines the main source rocks in Wuerxun Sag by oil source correlation, analyzes the development characteristics of source rocks in different regions and geochemical indicators such as organic matter abundance and type, evaluates the oil generation maturity and accumulation stage of main source rocks in Wuerxun Sag, and judges the oil and gas filling history and predicts the preferred exploration potential position by measuring the homogenization temperature of fluid inclusions. It is found that the oil source in different areas of Wuerxun Sag is not identical. The oil reservoir in the north of Wuerxun Sag is derived from the parent material of mud shale rock of Nantun formation. In the south of Wuerxun Sag, besides the mud shale of Nantun formation, there is oil flow from dark mudstone of Tongbomiao formation. Wuerxun Sag has two stages of hydrocarbon accumulation: The first stage is from the later Yimin formation to the early Qingyuangang formation; The second stage is the late structural activity of Qingyuangang formation, which makes the early oil reservoir redistribute and inject new traps. It is considered that the west side of Wubei sag and the east side of Wunan sag are two important exploration potential zones.

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Joint application of surface nuclear magnetic resonance and high-density resistivity method in the exploration of potassium ore in salt lake brine in Tibet
HE Sheng, MA Wen-Xin, GAN Bin
Geophysical and Geochemical Exploration    2021, 45 (6): 1409-1415.   DOI: 10.11720/wtyht.2021.0005
Abstract195)   HTML31)    PDF (1900KB)(269)      

Surface nuclear magnetic resonance (SNMR) can be used to directly find groundwater (brine), and the high-density resistivity method is suitable to distinguish brine from fresh water. This study introduces the joint exploration using the above two geophysical methods in two major salt lake study areas in Tibet-Chagcam Caka and Chalico salt lakes, in order to make full use of the advantages of the two methods while avoiding the limitations and one sidedness of a single method. As a result, the distribution of underground brine in the two salt lakes was identified, thus providing a basis for the overall layout of the exploration and development of potassium ore in brine in the two salt lakes. Furthermore, the joint exploration results of the two geophysical methods were highly consistent with the geological survey results of shallow wells. It can be concluded that the joint application of the above two geophysical methods in Tibet serves as an efficient and accurate exploration mode for the exploration of underground brine.

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A discussion on quality monitoring and evaluation methods for oil and gas geochemical analysis and testing
HU Bin, LI Guang-Zhi
Geophysical and Geochemical Exploration    2021, 45 (4): 1043-1047.   DOI: 10.11720/wtyht.2021.1482
Abstract190)   HTML3)    PDF (355KB)(138)      

The quality monitoring and evaluation of oil and gas geochemical analysis and testing are not detailed enough in the current standards and specifications, and there are also some differences in quality requirements. Based on a comparison of related contents of the effective national standards, industry standards and enterprise standards and combined with many years of experience in quality management, this paper systematically analyzes and evaluates the monitoring and evaluation methods commonly used in oil and gas geochemical analysis and testing.At the same time,based on the comparative study of the allowable error and the qualified rate of each standard, it is pointed out that the other standards are lower than the national standards in quality and need to be revised in time. This paper also calls for speeding up the development of standard samples for oil and gas geochemical exploration, ensuring the accurate tracing of quantitative values, and promoting and improving the quality monitoring level of oil and gas geochemical analysis and testing.

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Research into the pore structure of tight reservoirs:A review
CHEN Xiu-Juan, LIU Zhi-Di, LIU Yu-Xi, CHAI Hui-Qiang, WANG Yong
Geophysical and Geochemical Exploration    2022, 46 (1): 22-31.   DOI: 10.11720/wtyht.2022.1190
Abstract188)   HTML14)    PDF (3536KB)(198)      

With the increasing demand for oil and gas resources,the exploration and development of oil and gas fields have shifted from conventional to unconventional fields,and tight oil and gas reservoirs have become the current and future focus of the exploration and development of unconventional oil and gas.Most of the tight reservoirs in China are continental sediments with poor lateral continuity,strong vertical heterogeneity,complex lithology,and large changes in physical properties.All these make it difficult to effectively characterize the pore structure of tight reservoirs.The pore structure of reservoirs not only affects the occurrence of oil and gas but also seriously restricts the seepage and efficient exploitation of oil and gas.To analyze the pore structure characteristics of tight reservoirs in a targeted manner,this study systematically investigates relevant literature on the assessment methods of pore structure of tight reservoirs and organizes indirect measurement methods such as semi-permeable plate,direct observation methods such as casting thin sections,and digital core method.Moreover,it dissects the logging-based assessment methods of the pore structure of tight reservoirs,explores the applicability,advantages,and disadvantages of these methods,and further proposes the development trend of pore structure study based on the current status.

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Analyses of internal structure of slopes using multi-channel transient surface wave exploration and microtremor survey
LI Qiao-Ling, ZHANG Hui, LEI Xiao-Dong, LI Chen, FANG Hao, GUAN Wei, HAN Yu-Da, ZHAO Xu-Chen
Geophysical and Geochemical Exploration    2022, 46 (1): 258-267.   DOI: 10.11720/wtyht.2022.2498
Abstract178)   HTML129)    PDF (4589KB)(296)      

According to the characteristics of thin eluvium and poor topographic conditions in research area,this paper analyzes the suitability and effectiveness of multi-channel transient surface wave and microtremor survey technology in investigating slope internal structure of the typical slope in Luniao Town,Yuhang District,Hangzhou Ctity.The dispersion curve is extracted using frequency-wave number (F-K) and spatial autocorrelation method(SPAC).Based the velocity profile,the surface silty clay with breccia,completely weathered tuff,strongly weathered tuff and medium-slightly weathered tuff is interpreted.The results show that the surface wave exploration can effectively distinguish the internal structure of slope covered by thin eluvium.Both multi-channel transient surface wave and microtremor survey have a high accuracy in depth interpretation of the interface between strongly weathered and medium-slightly weathered tuff,which is well consistent with the borehole data,and there is a little bit of error in depth interpretation of the interface between surface silty clay with breccia and completely weathered tuff.The data analysis also shows that the fitting relationship between spatial autocorrelation function and Bessel function J0 is good when frequency less than 15 Hz,and the accuracy lose when it is higher than 15 Hz.Furthermore,the microtremor survey velocity is generally lower than the multi-channel transient surface waves exploration velocity.

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A comparative study on polymetallic metallogenic characteristics of Xiangshan and Lengshuikeng ore fields
PANG Wen-Jing, CHEN Bei-Bei, ZHOU Tao, HUANG Rou-Rui, ZHOU Yun-Yun, GUO Fu-Sheng, WU Zhi-Chun, XIE Cai-Fu
Geophysical and Geochemical Exploration    2021, 45 (6): 1416-1424.   DOI: 10.11720/wtyht.2021.0362
Abstract166)   HTML1)    PDF (5537KB)(142)      

More than 20 uranium deposits and polymetallic mineralization have been discovered in the Xiangshan ore field at present. However, breakthroughs in polymetallic prospecting are yet to be made in the ore field.This paper compared the Xiangshan ore field with the Lengshuikeng lead-zircon-silver polymetallic ore field at a high exploration level in terms of regional geological setting, strata, magmatic rocks, ore body characteristics, and wall-rock alteration. Based on this, it is found that the Xiangshan and Lengshuikeng ore fields are similar in geological conditions, the geochemical characteristics of rare earth elements (REEs) and trace elements, and the characteristics of ore bodies and alternation. Regarding lithology, both are mainly composed of volcanic rock series of the Cretaceous Ehuling and Daguding formations, which are present as high high-K calc-alkaline basalts and possess quasi-aluminous-weakly peraluminous characteristics. The REE-distribution patterns and trace element spider diagrams of the two ore fields are notably rightward, indicating the enrichment of light REEs, low content of Ba and Sr, and obvious Eu depletion. Therefore, the sediments in the two ore fields mainly originate from the crust. Meanwhile, the magmatic rocks feature a high crystallization differentiation degree, and the wall-rock alteration is dominated by chloritization, sericitization, silicification, and carbonation.By referring to the metallogenic model of the Lengshuikeng ore field, it is considered that the future polymetallic prospecting in the Xiangshan ore field should focus on the porphyry-type polymetallic ore in small rock masses and strata-bound, superimposed polymetallic ore at the K1d1 horizon. In this manner, breakthroughs are expected to be made in polymetallic prospecting in the Xiangshan ore field.

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Application effect analysis of UAV aeromagnetic survey technology in desert and semidesert regions
WANG Meng, LIU Yuan-Yuan, WANG Da-Yong, DONG Gen-Wang, TIAN Liang, HUANG Jin-Hui, LIN Man-Man
Geophysical and Geochemical Exploration    2022, 46 (1): 206-213.   DOI: 10.11720/wtyht.2022.1224
Abstract165)   HTML8)    PDF (3000KB)(163)      

The UAV aeromagnetic survey technology has continuously developed and gradually applied to different geomorphic landscape areas. This study aims to verify the application effects of the UAV aeromagnetic survey technology in the desert and semidesert regions in China. To this end, the applicability tests of UAV types were performed according to the characteristics of the natural environment in the desert and semidesert regions. Then the applicability of multi-rotor UAVs and vertical take-off and landing fixed-wing UAVs in the desert and semidesert regions was assessed from the ability to resist wind, terrain-following ability, battery life, efficiency, and the quality of data acquisition. Through the qualitative and quantitative comparative analysis of the results obtained from UAV aeromagnetic surveys and ground magnetic surveys, the practicability and reliability of the UAV aeromagnetic survey technology in the desert and semidesert regions in West China was measured. It is considered that UAV aeromagnetic survey technology enjoys the advantages of high precision of data collection and high efficiency compared to the ground magnetic survey. Therefore, the UAV aeromagnetic survey technology is worthy of widespread application as a geophysical prospecting method and technique.

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The research of reservoir parameters forecasting based on KICA and SVM
WANG Wei-Qiang
Geophysical and Geochemical Exploration    2021, 45 (4): 990-997.   DOI: 10.11720/wtyht.2021.1170
Abstract164)   HTML2)    PDF (7055KB)(150)      

In order to improve the accuracy of prediction of reservoir parameters,the paper proposes the approach for reservoir parameters forecasting based on KICA and Support vector machine (SVM).The KICA attribute optimization technology reflects the non-linear relationship and high order statistical properties of the attributes,extract the reservoir information of mutual statistical independence which reflects the reservoir parameters of the subsurface.SVM technology based on structural risk minimization principle,which can solve problems of the nonlinear systems for the small sample,high dimensional and local minimum.KICA combined the SVM,which accurately predict the reservoir parameter distributions through the huge attribute space and less well data.Through the model and actual data, it shows that reservoir parameter prediction technology has good effect of application, and high prediction.

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Big data based studies of the variation features of Chinese soil’s background value versus reference value: A paper written on the occasion of Soil Geochemical Parameters of China’s publication
XI Xiao-Huan, HOU Qing-Ye, YANG Zhong-Fang, YE Jia-Yu, YU Tao, XIA Xue-Qi, CHENG Hang-Xin, ZHOU Guo-Hua, YAO Lan
Geophysical and Geochemical Exploration    2021, 45 (5): 1095-1108.   DOI: 10.11720/wtyht.2021.0302
Abstract162)   HTML269)    PDF (3015KB)(255)      

The research on the soil’s geochemical background value and reference value is an important basic work in the field of geosciences. The publication of Soil Geochemical Parameters of China is an important result achieved on the basis of the China’s nation-wide multi-target regional geochemical survey and the high quality and precision big data studies. This paper outlines some basic requirements including the geochemical investigation method and the sample testing quality, and explains the acquisition means and accuracy level of the big data. We mainly discuss on a macro-scale the variation features of Chinese soil’s background value versus reference value, including:① to study the ratio feature between Chinese soil’s geochemical background value and the continental crust abundance of the world, and explain the overall characteristics and basic rules of Chinese soil element(oxide)background value versus the global continental crust abundance;② through comparing the soil element(oxide)background values of Liaohe river, yellow river, Yangzi river and Zujiang river catchment areas with the continental crust abundance, to study the variation features of soil element(oxide)background values of each large river catchment area from north China to south China versus the global continental crust abundance;③ through comparing the soil background value of the above mentioned large river catchment areas with Chinese nationwide soil background value, to study the soil background value’s variation features of each large river catchment area relative to Chinese nationwide overall soil background value;④ taking the soil background value of the “first environment”, which represents the natural background with almost no human influence, as the baseline, to study soil’s geochemical enrichment characteristicsof the “second environment” which is deeply influenced by human activities;⑤ through comparing the ratio features of “first environment” soil geochemical background versus “second environment” soil geochemical background of each large river catchment area and region in China, to study enrichment and depletion rules of the element index under different natural environment and geographic landscape of the whole China. The study of Soil Geochemical Parameters of China is on the basis of geochemical big data. With huge amount of information and very rich connotation, this study represents China’s high quality and accuracy, and is an unprecedented academic achievement and milestone in China’s geochemical research history. This study will provide basic information for many scientific fields including the pedology, ecology, environment science and biology; provide important basis for the research of major scientific subjects such as global change, global environment and global governance; and provide evaluation criteria for the scientific management and decision-making of China’s natural resources, ecological & environmental protection, agricultural & rural development and health sectors. Only by exploring some problems on a macro-scale in this paper, we have found many ecological information, natural rules and scientific questions which need us to make in-depth research and application practice. It is predictable that along with the in-depth research and extensive application of Chinese soil’s geochemical parameters, the geochemical research will be further involved into China’s economic and social development, make positive contributions to our country, and geochemical problems will be more concerned by China’s economic and social development sectors.The result of this investigation and research project is a concentration of many geo-scientists’ hard work and wisdom, shows us these geoscientists’ rigorous scientific spirit and respectable dedication and responsibility, demonstrates China’s high quality and accuracy, and represents the high quality geo-scientific advancement of China.

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Development of multi-parameter parallel measuring high-density electrical system for urban underground space exploration
DING Wei-Zhong, SUN Fu-Wen, LI Jian-Hua, ZHENG Cai-Jun, LIN Pin-Rong, QI Fang-Shuai
Geophysical and Geochemical Exploration    2021, 45 (6): 1448-1454.   DOI: 10.11720/wtyht.2021.1531
Abstract160)   HTML36)    PDF (2585KB)(274)      

On the basis of summing up the advantages and disadvantages of the existing high-density resistivity instruments and combining with the requirements of urban underground space exploration, a set of multi-parameter parallel measuring high-density electrical system is developed. It has the characteristics of transmitting signal at one time, receiving signal by multiple electrodes at the same time, and measuring multiple parameters at the same time. Compared with the traditional high-density electrical instrument, it can effectively improve the working efficiency. the field test shows that the performance of the new electrical system achieves the desired effect. At the end of the article, the paper summarizes the advantages of the new electrical system and showed the suggestions on the development of high-density electrical instrument.

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Application of 3D geological modeling in screening of sites preselected for geological disposal of high-level radioactive wastes: A case study of Tianhu preselected site, Xinjiang
LUO Hui, JIANG Shi, ZHAO Hong-Gang, LI Ya-Wei, TIAN Xiao
Geophysical and Geochemical Exploration    2021, 45 (6): 1488-1496.   DOI: 10.11720/wtyht.2021.0525
Abstract160)   HTML3)    PDF (4734KB)(123)      

Based on the theories and methods of 3D geological visualization models and the geological data of the Tianhu preselected site, a geological model of the site was established in this study using the Deep Insight TM geoscience modeling software. It describes the 3D tectonic morphology of the preselected site, carries out 3D visual analysis of the geological conditions of the study area from 2D to 3D, from overall to local, and from macroscopic to microscopic aspects,and intuitively expresses the distribution regularity of geological information in the main rockmass used for the disposal of high-level radioactive wastes. The granite rock massatthe Tianhu site occurs in equiaxed rock stocks, with simple lithology and large volume.There is only an NW-tending fault with a length of 2 km developing in the southeastern part of the rock mass. Besides, veins and alteration zones are relatively developed in the rock mass, which affects the integrity of the rock mass to a certain degree. The model can be used to query and update geological data at any time, analyze the distribution characteristics and laws of various geological information in the whole model, and improve the understanding of geological laws. All these willassist in better guiding the site selection, assessment, and construction of disposal repositories.

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Potential assessment of gold, copper, lead, zinc, tungsten, and tin deposits in Kyrgyzstan based on 1∶1 000 000 scale geochemical data
WANG Bin, LUO Yan-Jun, MENG Guang-Lu, ZHANG Jing, ZHANG Hai-Di, CHEN Bo, HE Zi-Xin
Geophysical and Geochemical Exploration    2022, 46 (1): 58-69.   DOI: 10.11720/wtyht.2022.2594
Abstract159)   HTML10)    PDF (2234KB)(228)      

As an important part of the Tianshan metallogenic belt in Central Asia, Kyrgyzstan boasts rich mineral resources and completely types of mineral resources. The national scale (1∶1 000 000) geochemical mapping of Kyrgyzstan covers an area of about 170 000 km2 across the country and the analyses and tests of 69 elements. It has filled in the blank of national geochemical mapping in Kyrgyzstan and will provide basic geochemical data for studies on basic geology, mineral development, environmental protection, and agricultural production inthe country. According to the regional geologic and structural evolution and geochemical background, the study area is divided into five structural geochemical regions. According to the geological background and the statistical analysis of geochemical parameters of major metallogenic elements, it is considered that Kyrgyzstan is a metallogenic favorable region of Au, Cu, Pb, Sb, Sn, W, and Ag, with notably distributed geochemical anomalies. In detail, the northern Tianshan Mountain shows high anomalies of Au, Cu, Pb, Zn, Ag, Be, and As. The middle Tianshan Mountaincan be divided into the eastern and western parts with the Fergana fault as the boundary. Among them, the western part is rich in Au, Cu, Cr, Mo, and Co, while the eastern part is rich in Au, W, Sn, Co, Cr, and Ni. As for the southern Tianshan Mountain, the western part is characterized by the concentrated distribution of Cu, Co, Cr, Ni, Au, As, Sb,and Hg, while the eastern part is characterized by the distribution of W, Sn, and Bi associations. The analytical results of metallogenic significance are as follows.The Chattkar area in middle Tianshan Mountain is considered the area with the highest prospecting potential in Kyrgyzstan. It has enormous potential for the prospecting of Cu, Pb, Au, and W. It is followed by the Zarejaz area in the eastern part of the southern Tianshan Mountain, which also has great prospecting potential and is highly favorable forthe prospecting of Au, CU, W, and Sn. Besides, the western part of the southern Tianshan Mountain and the Talas-Narun area also enjoygood prospecting potential and are prospecting favorable areas of gold, copper, lead, and zinc polymetallic deposits.

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Ore prospecting on northwestern margin of Hengyang Basin using geophysical and geochemical information
CHEN Yun-Tao, LIU Jun-Feng, CAO Chuang-Hua, WANG Dang
Geophysical and Geochemical Exploration    2021, 45 (5): 1189-1195.   DOI: 10.11720/wtyht.2021.1332
Abstract154)   HTML1)    PDF (1964KB)(372)      

The Hengyang Basin is a junction zone between the Yangtze Plate in South China and the Cathaysian Plate. It is expected to have great potential for rich mineral resources given its complex geological tectonic movement history. This paper aims to deeply analyze and explore the stratigraphic framework and deposit occurrence mechanisms on the northwestern margin of the Hengyang Basin. To this end, a series of geophysical surveys in this area were carried out. Firstly, a multi-method survey of a long section spanning the Ziyunshan and Nanyue rock masses was conducted and the structure of the northwestern margin of the Hengyang Basin was accordingly analyzed. Secondary, large-scale fine detections of subsections in the key sections/blocks were carried out using induced polarization (IP) sounding. Meanwhile, the characteristics of the IP response of the Changshou-Hengyang-Guanyin’ge fault were analyzed especially, and the genesis and metallogenic prospect of the fault were explored. Finally, the migration rules of ore-forming materials on the margin were investigated based on comprehensive information such as regional geological and gravity anomalies. The combined results confirmed that the Hengyang Basin is a typical sub-mantle plume-mantle branch system.

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Problems and improvements of Tunnel Seismic Prediction in geological prediction of tunnels under high geotemperature and high in-situ geostress
FAN Zhan-Feng, CAI Jian-Hua, ZHAO Wei
Geophysical and Geochemical Exploration    2022, 46 (1): 268-274.   DOI: 10.11720/wtyht.2022.1167
Abstract154)   HTML57)    PDF (2566KB)(276)      

The Sichuan-Tibet Railway under construction has a large number of tunnels under high geotemperature and high in-situ geostress.How to improve the accuracy of advanced geological prediction of these tunnels is a major difficulty in railway construction.Taking the Tunnel Seismic Prediction (TSP) method for advanced geological prediction as an example,analyses reveal that there are two major problems in the detection of the tunnels.On is that the use of emulsion explosives and plastic detonating tubes in blastholes under a high rock-temperature is liable to cause misfires,thus affecting data acquisition.The other is that the wave velocity differences between the excavated and unexcavated areas of tunnels under high in-situ geostress are not considered in data processing.Targeting these problems,this paper proposes six improvement measures,namely researching and developing detonation packs with a thermal insulation bag,establishing intelligent engineering assessment systems based on multiple geological information,changing the models of shock initiation of the TSP,popularizing new technologies and methods of advanced geological prediction,researching and developing advanced geological prediction systems suitable for Tunnel Boring Machines (TBMs),and improving the organizational management of geological prediction.All these measures can provide references for efficient detection of advanced geological prediction of tunnels in areas with high geotemperature and high in-situ geostress.

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