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  20 August 2022, Volume 46 Issue 4 Previous Issue   
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Research progress in the geological characteristics and material sources of fluorite deposits in the Heyu-Checun area, western Henan Province
ZHANG Kai-Tao, BAI De-Sheng, Li Jun-Sheng, LIU Ji-Feng, XU Dong, SU Yang-Yan, FAN Kang
Geophysical and Geochemical Exploration. 2022, 46 (4): 787-797.   DOI: 10.11720/wtyht.2022.1438
Abstract   HTML ( 17 )   PDF (4836KB)

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

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

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

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2D seismic and high-density resistivity sounding reveal the shallow three-dimensional geological structure characteristics of Xiong'an New Area
LONG Hui, XIE Xing-Long, LI Feng-Zhe, REN Zheng-Wei, WANG Chun-Hui, GUO Shu-Jun
Geophysical and Geochemical Exploration. 2022, 46 (4): 808-815.   DOI: 10.11720/wtyht.2022.1319
Abstract   HTML ( 10 )   PDF (4550KB)

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

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Airborne electromagnetic characteristics and deep prospecting of a ringed molten rock mass in eastern Tianshan
YANG Bo, SUN Dong-Hua
Geophysical and Geochemical Exploration. 2022, 46 (4): 816-823.   DOI: 10.11720/wtyht.2022.1196
Abstract   HTML ( 4 )   PDF (2541KB)

A ringed molten rock mass in eastern Tianshan, Xinjiang is closely related to Au-Pb-Zn mineralization. Since the mineralization occurs in the fault fracture zone near the outer contact zone between the rock mass and strata, it is necessary to find out the spatial distribution of the rock mass and the development of the fault structure. The processing and analysis of the 1∶25 000 high-resolution airborne transient electromagnetic and aeromagnetic data yielded the following airborne electromagnetic characteristics of the rock mass. The ringed molten rock mass displayed positive and negative alternating ringed aeromagnetic fields. There were four NWW-trending banded zones with strong electromagnetic responses along the ringed molten rock mass, with a time constant of generally 0.07~0.18 ms. Seven NWW-trending faults were inferred and interpreted using the high-value band of the electromagnetic response of the 23rd trace of the dB/dt X component and the aeromagnetic anomaly zone with amplitude of 5~10 nT. By combining the airborne electromagnetic characteristics and three-dimensional inversion results of magnetic vectors, the lithology and structures of the study area were inferred and interpreted again, roughly ascertaining the three-dimensional distribution characteristics of the diorites. Based on these results as well as the known metallogenic geological conditions and the airborne electromagnetic characteristics, two prospecting favorable areas were delineated in the areas with strong electromagnetic responses to the west and southwest of the ringed molten rock mass. This study provides important information on the deep prospecting of the rock mass.

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Application of comprehensive geophysical prospecting method in well siting for shale gas exploration in carbonate areas in east China
LUO Wei-Feng, HU Zhi-Fang, GAN Fu-Ping, ZHANG Qing-Yu, KANG Hai-Xia, ZHANG Yun-Xiao
Geophysical and Geochemical Exploration. 2022, 46 (4): 824-829.   DOI: 10.11720/wtyht.2022.1505
Abstract   HTML ( 5 )   PDF (1739KB)

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

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

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

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Application of geothermal measurement in the geothermal exploration
WANG Ming-Peng, YANG Jun-Song, LIU Yan-Hua
Geophysical and Geochemical Exploration. 2022, 46 (4): 838-844.   DOI: 10.11720/wtyht.2022.3270
Abstract   HTML ( 6 )   PDF (6488KB)

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

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Application of comprehensive geophysical exploration in geothermal resources on the eastern margin of Yinchuan Basin
HU Xin-Jun, CHEN Xiao-Jing, WU Yang, AN Bai-Zhou, NI Ping
Geophysical and Geochemical Exploration. 2022, 46 (4): 845-853.   DOI: 10.11720/wtyht.2022.1409
Abstract   HTML ( 10 )   PDF (12127KB)

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

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Application of radioactive prospecting in exploration of rare metal minerals: A case study of a uranium anomaly in the Nancha area
Wang Rui, Li Zhan-Long, Ma Tao
Geophysical and Geochemical Exploration. 2022, 46 (4): 854-861.   DOI: 10.11720/wtyht.2022.2500
Abstract   HTML ( 3 )   PDF (4560KB)

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

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Basement structure characteristics of the Lingwu depression in southern Yinchuan Basin
CHEN Xiao-Jing, HU Xin-Jun, BAI Ya-Dong, WU-Yang , CHEN Tao-Tao, CAO Yuan-Yuan, NI-Ping
Geophysical and Geochemical Exploration. 2022, 46 (4): 862-867.   DOI: 10.11720/wtyht.2022.1314
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The Lingwu depression,located in the southeastern part of the Yinchuan Faulted Basin,has a complex geological tectonic framework and serves as the turning and intersection part of structures due to the two Himalayan tectonic stresses,namely the EW-direction tensile stress of the Ordos block and the NE-direction compressive stress of the Qinghai-Tibet Plateau. Since 1970, more than 3000 earthquakes with magnitudes of greater than 2.0 have been monitored in the Yinchuan Basin and its periphery. Among them, most of the small and moderately strong earthquakes occurred in the Lingwu depression, which, therefore, has serious hidden risks of earthquake disasters. Previous studies indicate that fault structures are the cause for the earthquakes and that strata serve as the main reason for the earthquake secondary disasters in this depression. To interpret the geological structures in the basement of the Lingwu depression, this study finely characterized the basement characteristics of the Lingwu depression using the 2.5D human-computer interactive inversion technology based on the 1∶50,000 regional gravity data and the constraints of data on drill holes, seismic profiles, magnetotelluric sounding, and controlled source audio-frequency magnetotellurics (CSAMT) profiles, thus providing a basis for the prevention and control of earthquake disasters.

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Geophysical prospecting mode and metallogenic model of the Weiquan silver-copper polymetallic deposit in Xinjiang
Feng Jun, Jiang Wen, Zhang Zheng
Geophysical and Geochemical Exploration. 2022, 46 (4): 868-876.   DOI: 10.11720/wtyht.2022.0055
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The Weiquan silver-copper polymetallic deposit has received extensive attention because of its unique genesis. This study analyzed the anomaly characteristics shown in the integrated gravity-magnetic-electrical geophysical planes and sections of the Weiquan silver-copper polymetallic deposit. Then, it obtained the interpretation model of geophysical anomalies through the forward and inverse calculations of the typical sections. Based on the distribution pattern of existing ore bodies and the metallogenic model summarized in previous studies, this study established the geological-geophysical prospecting mode of this area. Moreover, this study proposed the geological-geophysical prospecting model of this area, aiming to provide a basis for prospecting prediction.

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An analysis of influencing factors of visco-acoustic reverse time migration imaging in borehole seismic
YANG Hong-Wei, WANG Ji-Chuan, KONG Qing-Feng, GU Bing-Luo, SUN Wei-Guo, LI Zhen-Chun
Geophysical and Geochemical Exploration. 2022, 46 (4): 877-886.   DOI: 10.11720/wtyht.2022.1307
Abstract   HTML ( 3 )   PDF (5714KB)

At present,the targets of oil and gas exploration have transformed from simple structural oil and gas reservoirs into deep complex structural oil and gas reservoirs.The small thickness,wide distribution,and hidden occurrence state of the reservoirs pose great challenges to seismic migration imaging technology.Compared with ground seismic,the seismic sources of the borehole seismic are located in wells and close to target layers.Meanwhile,the times that wave field induced by the borehole seismic passes through the low-velocity zone reduce by one.Therefore,the borehole seismic has the advantages of high signal-to-noise ratio (SNR) of data and strong reservoir identification in theory and thus can serve the purpose of the fine imaging of the reservoirs around wells.However,the special observation method makes it difficult to directly apply mature ground seismic imaging technology to the borehole seismic.In addition,due to the weak source energy of the borehole seismic,the formation absorption attenuation effect produces stronger impacts on the borehole seismic than on the ground seismic.Therefore,it is necessary to develop a targeted migration imaging method for borehole seismic.This study applied the visco-acoustic reverse-time migration imaging method to the borehole seismic and discussed the influence of various factors on the migration imaging effect of borehole seismic through model calculation,aiming to provide theoretical and technical support for the practical application of borehole seismic technology.

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Fractal model-based 2.5 D finite element modeling of complex resistivity method
Long Xiu-Jie, Chen Han-Bo, Mo Ya-Jun, Ou Xiao-Yi, Lu Sheng-Hui
Geophysical and Geochemical Exploration. 2022, 46 (4): 887-896.   DOI: 10.11720/wtyht.2022.1377
Abstract   HTML ( 4 )   PDF (7643KB)

This study proposed the variational problem of 2.5D finite element forward modeling of the complex resistivity method and detailed the process of solving stiff matrix of finite equations. The Fractal model was introduced as a research model for studying the equivalent induced polarization anomalies of spectra. Furthermore, the complex conductivity and complex potential of a grid unit were linearly interpolated. Then, to obtain anomalous complex potential, finite element linear equations were solved using the biconjugate gradient stabilized method with incomplete LU decomposition. The results of three typical geoelectric models validated the correctness and accuracy of the algorithm proposed in this study. Furthermore, this study analyzed the abnormal response characteristics of 2.5D complex resistivity under different frequencies.

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Joint application of active and passive surface wave in 3D imaging of loess covered area
SHAO Guang-Zhou, LI Yuan-Lin, YUE Liang
Geophysical and Geochemical Exploration. 2022, 46 (4): 897-903.   DOI: 10.11720/wtyht.2022.1546
Abstract   HTML ( 5 )   PDF (4096KB)

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

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Turbidite reservoir identification technology based on prestack multi-parameter sensitivity factor fusion
SHANG Wei, ZHANG Yun-Yin, KONG Xing-Wu, LIU Feng
Geophysical and Geochemical Exploration. 2022, 46 (4): 904-913.   DOI: 10.11720/wtyht.2022.1473
Abstract   HTML ( 3 )   PDF (9379KB)

Turbidite reservoirs have always been an important exploration type in the Jiyang depression.After years of exploration and development,the turbidites are mainly of the heterogeneous isomorphic type.The sandstone reservoirs of this type of turbidites have similar velocity,density,and seismic waveforms to those of non-reservoirs and thus are difficult to identify using conventional seismic attributes and poststack impedance.Therefore,a reservoir description method based on prestack multi-parameter sensitivity factor fusion was established.This method mainly included three steps.Firstly,major factors affecting the accuracy of shear wave estimation were analyzed,and then the multi-mineral-component shear wave prediction technology based on a modified xu-white model was established to improve the accuracy of shear wave prediction and lay a foundation for the accurate prediction of elastic parameters. Secondly,a quantitative evaluation method of sensitivity factors was proposed based on reflection coefficient ratios to obtain three sensitive elastic parameters,namely Murho,Lambrho,and POIS.The fusion index F of sensitivity factors was constructed by using the three elastic parameters.The purpose is to reduce the strong multiplicity of solutions of a single parameter and accurately identify rock properties.Thirdly,the prestack inversion technology was used for the inversion of sensitive elastic parameters.The three sensitivity parameters of sandstone information were fused using the fusion model of the RGB primary color information to realize a fine-scale prediction of lithology.This method was applied to the exploration of a deep-water turbidite reservoir around well-Tuo-71 in the Jiyang depression.The distribution of deep-water turbidite fan reservoirs in the study area was accurately predicted.The coincidence degree between the prediction results and the actual drilling reached 85%,indicating the improved accuracy of reservoir identification and description.The results of this study have contributed to an interpreted favorable sand body area of 9.5 km2 and the deployment of more than 10 exploration and development wells.Among these wells,five have yielded industrial oil flow after competition and being put into operation,and their new production capacity is expected to be 2×104 t。

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An experimental study on the high-resolution single-channel seismic exploration technology for inland shallow waters
YUE Hang-Yu, ZHANG Ming-Dong, ZHANG Bao-Wei, WANG Guang-Ke, WANG Xiao-Jiang, LIU Dong-Ming
Geophysical and Geochemical Exploration. 2022, 46 (4): 914-924.   DOI: 10.11720/wtyht.2022.1479
Abstract   HTML ( 3 )   PDF (14954KB)

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

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Suppression of magnetotelluric square wave noise based on a LSTM recurrent neural network
YANG Kai, TANG Wei-Dong, LIU Cheng, HE Jing-Long, YAO Chuan
Geophysical and Geochemical Exploration. 2022, 46 (4): 925-933.   DOI: 10.11720/wtyht.2022.1572
Abstract   HTML ( 4 )   PDF (5389KB)

Denoising is an important part of magnetotelluric data processing. To enrich and develop the denoising method of magnetotelluric time series, this study introduced the LSTM network-one of the recurrent neural networks-into the square wave noise processing of the magnetotelluric time series. Different from previous studies, the measured magnetotelluric time series without human interference superimposed on simulated square wave noise were used as the input of the LSTM network, and the noise-free original time series were used as the target output of the network. After training for 1,500 epochs, the normalized cross-correlation coefficient between the time series extracted from the simulated noise signals by the network and the original time series reached 0.9718, indicating that the network has effectively learned the characteristics of the noise-free magnetotelluric time series. Finally, the denoising test results of measured square wave noise signals show that the proposed method can effectively suppress the interference of square wave noise and improve the estimation quality of impedance. This study provides a new idea for the processing of magnetotelluric time series based on deep learning.

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Design and test of the parallel ultra-small transmitter loop used in the transient electromagnetic method
WU Bei-Chen, PAN Yang-Run-Yi, CHENG Jiu-Long, WANG Hui, YAO Di, PANG Xiao-Yin
Geophysical and Geochemical Exploration. 2022, 46 (4): 934-939.   DOI: 10.11720/wtyht.2022.1424
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In the shallow or mine prospecting using the transient electromagnetic method (TEM), the transmitting magnetic moment is limited by the limited supply voltage of the transmitting system, and the stray inductance of the transmitter loop causes a long turn-off time. To solve these problems, this study designed a parallel transmitter loop of ultra-small coils used in TEM. Using these coils, the transmitting magnetic moment can be increased by the parallel connection of the coils, and the turn-off time can be reduced by additional resistance. The equivalent circuit models of the conventional transmitter coils and the parallel transmitter coils were established and analyzed theoretically. Moreover, the comparative test between the parallel transmitter coils and the conventional transmitter coils were carried out. The results show that the parallel transmitter coils can effectively increase the magnetic moment and reduce the turn-off time. Therefore, this design is greatly significant for reducing the blind area and increasing the prospecting depth in shallow or mine prospecting using TEM.

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Application of autocorrelation filtering to iron ore prospecting in Qihe-Yucheng area, Shandong Province
WU Cheng-Ping, YU Chang-Chun, XIONG Sheng-Qing, XU Jian-Chun, QIAO Chun-Gui
Geophysical and Geochemical Exploration. 2022, 46 (4): 940-945.   DOI: 10.11720/wtyht.2022.1493
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Deeply concealed iron ores cause relatively weak geophysical anomalies on the ground surface in the Qihe-Yucheng area, Shandong Province, a typical thickly covered area. Therefore, it is the key to the ore prospecting in this area to extract local weak anomalies caused by iron ores. Autocorrelation filtering can extract local weak anomalies by reducing the influence of a regional field using a high-pass filter of a certain wavelenth. The steps of the method are as follows. First, establish a model of incline plutons generating background field and models of iron ores of different scales and depths. Based on this, obtain the superimposed magnetic field through forward modeling. Then carry out autocorrelation filtering processing of the superimposed magnetic field to effectively extract the weak anomalies of iron ores. The autocorrelation filtering method was used to process the measured data in the Qihe-Yucheng area and the processing results were compared to the borehole data, verifying that the autocorrelation filtering method is effective. The extraction of weak anomalies using the autocorrelation filtering method allows for the ore prospecting scope to be reduced, which can provide guidance on the determination of prospecting favorable locations and drilling verification.

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Property analysis and application of multi-scale wavelet decomposition of gravity potential field
MENG Qing-Kui, ZHANG Wen-Zhi, GAO Wei, SHU Qing, LI Rui, XU Guang-Jing, ZHANG Kai-Song
Geophysical and Geochemical Exploration. 2022, 46 (4): 946-954.   DOI: 10.11720/wtyht.2022.2552
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Multi-scale wavelet decomposition is one of the common methods for gravity potential field separation. The biggest advantage is that it breaks through the traditional concept of dichotomy gravity anomalies and achieves the multiple decomposition of gravity anomalies. However, no systematic study has been carried out on the limitations and properties of the multi-scale wavelet decomposition. To systematically investigate the multi-scale wavelet decomposition and provide guidance for its practical application, this study, starting from the definition of multi-scale wavelet decomposition of gravity potential field based on profiles and grids, expounded three important properties such as the criterion that low-order wavelet keeps details invariant. Then, it analyzed the definition and properties of multi-scale wavelet by designing simple and complex theoretical models. Afterward, this study compared the multi-scale wavelet decomposition with the interpolation cutting method using field data. The results show that multi-scale wavelet decomposition can achieve multi-layer separation of gravity potential field and estimate the burial depths of source bodies. In addition, the multi-scale wavelet decomposition can provide some ideas for solving the limitations pointed out in this study, such as abnormal scale aliasing and difficulty with the determination of scale coefficients. The above basic research can provide a certain degree of references for the processing and interpretation of gravitational potential field data.

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The precision of airborne gravimetry under the condition of long baselines
Li Rui, Shu Qing, Luo Yao, Wang Chen-Yang, Gao Wei, Zhou Jian-Xin
Geophysical and Geochemical Exploration. 2022, 46 (4): 955-960.   DOI: 10.11720/wtyht.2022.0073
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It is difficult to set up GPS base stations for airborne gravimetry in offshore and far seas, leading to long baselines. Given this, this study analyzed the impacts of long baselines on the precision of airborne gravimetry based on the principle of airborne gravimetry and the real measurement data. Moreover, this study comprehensively analyzed the effects of long baselines on differential positioning precision and evaluated the internal coincidence precision of airborne gravity anomaly. Compared to the precision required for airborne gravimetry, it is believed that long baselines (600-800 km) have limited and almost negligible impacts on the precision of airborne gravimetry. This study can provide technical support for further development of airborne gravimetry in offshore and far seas.

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Automatic detection of multiple pavement layers based on the cosine of instantaneous phase of ground penetrating radar data
ZHOU Dong, LIU Mao-Mao, LIU Zong-Hui, LIU Bao-Dong
Geophysical and Geochemical Exploration. 2022, 46 (4): 961-967.   DOI: 10.11720/wtyht.2022.1363
Abstract   HTML ( 2 )   PDF (4200KB)

Horizon characteristics are important information in pavement detection using ground penetrating radar (GPR) data.However,current horizon picking methods based on manual work or related algorithms have problems such as strong subjectivity and heavy workload and they can only track one horizon each time.Therefore,this study proposed a multi-layer auto-tracking method based on the cosine of the instantaneous phase of GPR data.The specific steps of this method are as follows.Firstly,obtain the cosine of the instantaneous phase of GPR data through complex signal analysis.Secondly,carry out the correlation analysis of wavelet cosine matrix data and then calculate the cosine of the instantaneous phase of these data,aiming to enhance the transverse continuity of phase data along the cophase axis.Thirdly,obtain the spatial positions,amplitude,and polarity of the phase data,and automatically track the transversely continuous horizon lines under a series of constraints such as signal amplitude and cophase axis characteristics.Finally,determine the horizon data and their polarity by comparing the RMS values of the amplitude of adjacent horizon lines along the depth direction,and extract the horizon line data with continuous high amplitude by setting horizon and amplitude thresholds.Numerical simulation and field case analysis have verified the effectiveness and adaptability of the method proposed in this study.

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Prestack inversion of anisotropic coefficients and its application in fracture prediction
XIE Rui, YAN Jian-Guo, CHEN Qi
Geophysical and Geochemical Exploration. 2022, 46 (4): 968-976.   DOI: 10.11720/wtyht.2022.1369
Abstract   HTML ( 3 )   PDF (4776KB)

The forward modeling of wave field response characteristics of wide-azimuth seismic data shows that the reflection coefficient has apparent azimuth anisotropy when the P-waves propagate in underground geologic bodies.It has become a research hotspot at home and abroad to make a fracture prediction using azimuth anisotropy.This study analyzed the response characteristics of the changes in seismic P-waves with azimuth using forward modeling.Based on the analytical results combined with the relationship between the anisotropy parameters of fluid-bearing fractures proposed by Bakulin et al.,this study approximately simplified the Ruger formula,deduced the equation between anisotropic parameter γ that can be used to characterize fracture development and reflection coefficient,and proposed a fracture prediction method based on anisotropic parameter inversion.The validity and applicability of the method have been proven using theoretical models and practical data application.Therefore,this study provides a feasible method and technology for fracture prediction using wide-azimuth prestack seismic data.

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Total variation regularized full waveform inversion based on gradient projection method
YAO Han, XU Hai
Geophysical and Geochemical Exploration. 2022, 46 (4): 977-981.   DOI: 10.11720/wtyht.2022.1320
Abstract   HTML ( 1 )   PDF (3053KB)

To reduce the ill-posedness of seismic full waveform inversion,a common method is to introduce prior information to regularize the inversion problem.Traditional regularization methods still face challenges even when they contain multiple prior information.This study proposed an extended full waveform inversion formula,which includes the convex set constraints on models.Specifically,this study showed how to constrain the total variation of the slowness square while forcing the constraint to keep it within a physical reality range.To verify the applicability of the algorithm proposed in this study,numerical experiments on simple models and international standard geological models were carried out.The results show that the introduction of total variation regularization can improve the reconstruction of high-speed disturbances under smooth background models.

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Local tomographic velocity modeling of deep anhydrite-bearing rocks
QI Peng
Geophysical and Geochemical Exploration. 2022, 46 (4): 982-987.   DOI: 10.11720/wtyht.2022.1512
Abstract   HTML ( 2 )   PDF (8294KB)

The deep parts of complex prospecting areas such as piedmont zones and ultra-deep strata are usually accompanied by anhydrite-bearing rocks,leading to great challenges to velocity modeling and affecting the final imaging quality and reliability.It is difficult for the conventional grid tomography method to adapt to the severe lateral velocity changes of special geological bodies.To this end,this study introduced a local tomographic velocity modeling method for deep anhydrite-bearing rocks.By constructing a new tomographic objective function for velocity anomalies,the local remaining residuals below the rocks were converted into the velocity update amount of the special lithologic bodies through tomography in order to further improve the accuracy of the velocity model and effectively improve the quality of imaging below the rocks.The actual data processing results have verified the effectiveness of the local tomography method,which will provide effective technical support for oil and gas prospecting in complex prospecting areas.

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Accessing the distribution and ecological risks of heavy metals in soil in Hong’an County, Hubei Province through ecological geological surveys
JU Zi-Long, QIN Zhi-Jun, Wan Xiang, YUAN Hang, ZHANG Xiao-Bo, WANG Deng
Geophysical and Geochemical Exploration. 2022, 46 (4): 988-998.   DOI: 10.11720/wtyht.2022.1398
Abstract   HTML ( 1 )   PDF (7362KB)

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

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Geochemical characteristics and influencing factors of soil in Hulu River Basin in the southern mountainous region of Ningxia
LI Yong-Chun, SU Ri-Li-Ge, ZHOU Wen-Hui, TAI Su-Ri-Ga-La, CHEN Guo-Dong, WANG Yong-Liang, GAO Qi, ZHANG Xiang, ZHANG Dong
Geophysical and Geochemical Exploration. 2022, 46 (4): 999-1010.   DOI: 10.11720/wtyht.2022.1408
Abstract   HTML ( 2 )   PDF (5276KB)

Based on the data derived from the geochemical survey of land quality in the Guyuan region, Ningxia, this study studied the background values of 30 elements (indicators) in the surface soil using mathematical statistics. This study compared the distribution and enrichment (or dilution) characteristics of elements in different parent materials (parent rocks) and land use types and further analyzed the factors restricting the distribution of the elements from the perspective of element association characteristics using the principal component analysis method. The results show that the contents of iron-philic element Ni, tungsten-philic element Mo, alkaline (earth) metal elements Na2O, MgO, CaO, halogen elements I, F, and copper-philic element As were all higher than corresponding national background values, while the contents of the biophilic elements such as Hg, Se, organic matter, N, and Pb were lower than corresponding national background values. Parent materials (parent rocks) were the main factor controlling the characteristics of element contents in soil. In the process of soil formation, natural and man-made influences have caused the enrichment or dilution of some elements. N, Mo, I, organic matter, and S are significantly controlled by the laterite parent material and their parent rocks, and the erosion of Ca2+ and Na+ causes weathering and leaching due to hydrodynamic effects. The element contents in the soil in the river valley plain were between those of laterite and those of loess parent material. In a supergene environment, Na2O, K2O, and Cl, which are prone to dissolve in water, are rich in estuaries and valleys due to hydrodynamic action. P, Hg, Se, and Mo elements are locally rich due to human interference. The factor analysis shows that parent materials (parent rocks), weathering, leaching, and bioaccumulation in the process of soil formation, and human production activities all affect the background values of the surface soil in the study area. The study results will provide basic geochemical information for the assessment of the regional resources and environment.

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Scale effects of spatial variations in SOM and STN in semi-arid regions: A case study of Yan'an
WANG Peng, ZHAO Jun, LIU Tuo, ZHOU Yi-Fan, WEI Jin-Ping, WANG Lei
Geophysical and Geochemical Exploration. 2022, 46 (4): 1011-1020.   DOI: 10.11720/wtyht.2022.1404
Abstract   HTML ( 1 )   PDF (5421KB)

Taking high-density sampling data as a dataset, the sampling spatial distribution scenarios on different scales were simulated through resampling analysis. Spatial analysis methods, such as Moran's I index, semi-variance function value, and fractal dimension FD, were used to explore the scale effects of spatial variations in soil organic matter (SOM) and soil total nitrogen (STN) and to analyze the conversion of influencing factors between different scales. The results are as follows. With an increase in scale, the spatial agglomeration decreased, and the spatial variation of SOM and STN in general increased first and then tended to be stable. By contrast, the random variation decreased gradually and the structural variation increased first and then decreased as the scales increased. The spatial variation generated on small scales consisted of a large proportion of random variation and a small proportion of structural variation, while the opposite is true on large scales. Different influencing factors had different distinguishing degrees for the spatial variations in SOM and STN. Their distinguishing degrees were in the order of height<factors such as soil type, vegetation index, annual average temperature, and humidity<precipitation. The influencing factors of the spatial variations in SOM and STN had scale effects. Specifically, with an increase in scale, the random variation caused by small-scale factors decreased gradually, while the structural variation caused by large-scale factors increased first and then weakened until the large-scale factors were transformed into relatively small-scale factors. The coordination mechanism of the effects of each factor on the SOM and STN contents was quite different between different scales, causing the random and structural variations to fluctuate between different scales. As a result, the spatial variations showed the law of decreasing first and then tending to stabilize.

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Characteristics and risk assessment of the heavy metals in stream sediments of Heze City
XU Xiong, SUN Yan-Ting, XIAO Fang, XIAO Pei-Ping, DONG Ying-Shang, LI Min
Geophysical and Geochemical Exploration. 2022, 46 (4): 1021-1029.   DOI: 10.11720/wtyht.2022.1421
Abstract   HTML ( 2 )   PDF (4931KB)

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

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Assessing the distribution and ecological risks of heavy metals in surface sediments of the Maowei Sea estuary, Guangxi
YAN Kun, PANG Guo-Tao, LI Wei, MAO Fang-Song
Geophysical and Geochemical Exploration. 2022, 46 (4): 1030-1036.   DOI: 10.11720/wtyht.2022.1470
Abstract   HTML ( 2 )   PDF (2717KB)

A total of 13 surface sediment samples were collected from estuaries of the Maoling, Dalan, and Qinjiang rivers for heavy metal analysis, aiming to study the distribution characteristics and ecological risk of heavy metals in the surface sediments of the Maowei Sea estuary. The results are as follows. The average contents of heavy metals As, Cd, Cr, Cu, Hg, Pb, and Zn in Maowei Sea sediments were 7.78×10-6, 0.14×10-6, 37.6×10-6, 18.9×10-6, 0.0048×10-6, 22.5×10-6, and 54.7×10-6, respectively. They are all lower than the class-I standard specified in GB18668—2002. The heavy metals in the sediments show quite different spatial distribution, with high content of heavy metals concentrating in the industrial zone to the east of the Maowei Sea and near the Maoling River to the west of the Maowei Sea. The analysis of heavy metal pollution shows that most elements are at levels of no pollution to moderate pollution, and Cr is at a medium pollution level. As indicated by the ecological risk analysis, the heavy metals generally show potentially low potential risks, and Hg and Cd in the industrial zone to the east show moderate ecological risks. The sources of heavy metal pollutants were explored through correlation analysis, cluster analysis, and principal component analysis. The results show that heavy metal pollution is mainly controlled by rivers, and Hg, As and Cd are also affected by wastewater discharged from the port industrial zone. This comprehensive study shows that the Maowei Sea has a good ecological environment overall, but it is recommended to focus on the drainage of heavy metal pollution in the industrial zone to the west of the Maowei Sea.

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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.  
Abstract2508)      PDF (4180KB)(4751)      


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
Abstract1190)   HTML145)    PDF (12833KB)(4193)      

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.  
Abstract3270)      PDF (431KB)(3330)      

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.  
Abstract2883)      PDF (1014KB)(3261)      

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.  
Abstract6652)      PDF (532KB)(3005)      

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

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CALCULATION OF THE ANOMALY AREA
Zhao Rongjun
Geophysical and Geochemical Exploration    2000, 24 (2): 154-156.  
Abstract1483)      PDF (346KB)(2539)      

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

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THE APPLICATION OF THE GRADIENT SOUNDING PROFILE METHOD TO THE GOLD PROSPECTING IN THE YINAN GOLD MINE
DU Li-ming, WU Jun-jie, YANG Jin-duo, WANG Peng, YU Bao-xian
Geophysical and Geochemical Exploration    2013, 37 (2): 225-228.   DOI: 10.11720/j.issn.1000-8918.2013.2.07
Abstract2249)      PDF (964KB)(2472)      
IP is an important method for mineral resources exploration, but it can only be applied in a few pivotal places because its difficult performance, and hence the information obtained from the survey area is very limited. The aim of this study is to find a simple and effective IP method with which we can get much valuable information form the survey area so as to improve the exploration effect. In the Yinan gold ore district, the authors applied the gradient sounding profile method, calculated 2D resistivity and obtained the IP model. The results show that the gradient sounding profile method is simple and effective.
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THE CHOICE OF GRIDDING METHODS FOR GEOPHYSICAL DATA
LIU Zhao-Ping, YANG Jin, WU Wei
Geophysical and Geochemical Exploration    2010, 34 (1): 93-97.  
Abstract3076)      PDF (1939KB)(2372)      

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.  
Abstract4484)      PDF (659KB)(2350)      

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.  
Abstract1662)      PDF (673KB)(2320)      

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.  
Abstract4221)      PDF (403KB)(2208)      

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.  
Abstract3019)      PDF (2717KB)(2163)      

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.  
Abstract3656)      PDF (363KB)(2126)      

 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.  
Abstract3676)      PDF (643KB)(2106)      

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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RECENT ADVANCES IN THE RESEARCH AND DEVELOPMENT OF QUANTUM MAGNETOMETERS
ZHANG Chang-da
Geophysical and Geochemical Exploration    2005, 29 (4): 283-287.  
Abstract1677)      PDF (376KB)(2037)      

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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PARAMETER SELECTION IN VIBROSEIS SEISMIC EXPLORATION
XUE Hai-Fei, DONG Shou-Hua, TAO Wen-Peng
Geophysical and Geochemical Exploration    2010, 34 (2): 185-190.  
Abstract3444)      PDF (3477KB)(2009)      

 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.  
Abstract2769)      PDF (1927KB)(1988)      

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

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

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

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

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

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

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

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

considerably improved.

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THE AUTOMATIC FORMATION OF THE SUFFER SOFTWARECONTOUR LEVEL FILE BASED ON AREA STATISTICS
REN Lei, CHEN Hua-Gen
Geophysical and Geochemical Exploration    2009, 33 (5): 595-598.  
Abstract3590)      PDF (830KB)(1985)      

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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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.  
Abstract2899)      PDF (2969KB)(1982)      

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

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THE INVERSED PROBLEM IN GRAVITY AND MAGNETICEXPLORATION: A REVIEW
Zeng Hualin
Geophysical and Geochemical Exploration    1990, 14 (3): 182-190.  
Abstract1953)      PDF (737KB)(1968)      

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

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WAVE FIELD SEPARATION NUMERICAL MODELING OF SECOND ORDER ELASTIC WAVE EQUATION BY HIGH-PRECISIONSTAGGEREDGRID FINITE DIFFERENCE SCHEME
CHEN Ke-Yang, YANG Wei, LIU Hong-Lin, WU Qing-Ling
Geophysical and Geochemical Exploration    2009, 33 (6): 700-703.  
Abstract3114)      PDF (1060KB)(1965)      

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

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

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

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

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

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

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

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PML ABSORBING BOUNDARY CONDITION FORNUMERICAL MODELING OF RAYLEIGH WAVE
XIONG Zhang-Qiang, TANG Sheng-Song, ZHANG Da-Zhou
Geophysical and Geochemical Exploration    2009, 33 (4): 453-457.  
Abstract3391)      PDF (2025KB)(1942)      

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 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.  
Abstract3632)      PDF (534KB)(1920)      

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 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.  
Abstract3463)      PDF (572KB)(1899)      

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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YANG Li-De
Geophysical and Geochemical Exploration    2009, 33 (6): 741-742.  
Abstract2129)      PDF (240KB)(1895)      
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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.  
Abstract2466)      PDF (2110KB)(1874)      

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.  
Abstract2126)      PDF (690KB)(1867)      

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 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.  
Abstract2725)      PDF (608KB)(1856)      

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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SOME PROBLEMS CONCERNING THE CONVERSIONOF MAPS BETWEEN SURFER AND MAPGIS
QIN Lin-Jiang
Geophysical and Geochemical Exploration    2010, 34 (5): 677-680.  
Abstract5333)      PDF (865KB)(1854)      

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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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.  
Abstract2503)      PDF (2180KB)(1821)      

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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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.  
Abstract3790)      PDF (1006KB)(1814)      

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.  
Abstract3191)      PDF (1351KB)(1804)      

 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
Abstract4711)      PDF (1427KB)(1804)      
This paper has summed up the progress of the ERI method over the past decade of years as well as its future development trend in the following aspects: ① A comparison of the performances of the main ERI instruments used at present shows that the ERI instruments tend to develop in the multi-channel, multi-parameter, multi-functional, high-power direction; ② ERI measurement environment has changed from surface measurement to water surface, underwater and cross-hole measurements, with the last three kinds of measurements analyzed in this paper; ③ On the basis of analyzing ERI data processing method and inverse development status, this paper describes three-dimensional and four-dimensional inversion theory of ERI with practical examples; ④ ERT applications are summed up, and several new applications are introduced. It is concluded that, with the improvement of the probing depth and observation precision as well as the diversification of the observation models, the application field of ERI will become broader and broader, and this technique will surely have wide development prospect.
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The application of 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
Abstract1076)   HTML147)    PDF (11771KB)(1802)      

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

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CHAMP, GRACE AND GOCE: THREE SATELLITES FOR SENSING AND/OR MEASURING THE EARTH'S GRAVITY FIELD
ZHANG Chang-da
Geophysical and Geochemical Exploration    2005, 29 (5): 377-382.  
Abstract2050)      PDF (749KB)(1738)      

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 THE RAYLEIGH SURFACE WAVE TECHNIQUE TO RAILWAYS
LI Hai
Geophysical and Geochemical Exploration    2002, 26 (2): 160-162.  
Abstract1872)      PDF (480KB)(1708)      

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

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THE APPLICATION OF ELEMENT AND LEAD ISOTOPE TRACING TO THALLIUM CONTAMINATION IN SOIL OF THE YUNFU PYRITE MINE
LIU Jing-yong, CHANG Xiang-yang, TU Xiang-lin
Geophysical and Geochemical Exploration    2006, 30 (4): 348-353.  
Abstract1742)      PDF (896KB)(1689)      

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

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THE 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.  
Abstract2719)      PDF (811KB)(1688)      

 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 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.  
Abstract2913)      PDF (1404KB)(1674)      

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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AN ATTEMPT TO REDUCE AMBIGUITY IN GEOPHYSICAL INTERPRETATION
LIU Shi-Yi, TIAN Qian-Ning, ZHAO Jin-Shui, HE Xian-Ming, JIAO Meng-Mei, HU Lin-Zhen, LIU Ling
Geophysical and Geochemical Exploration    2010, 34 (6): 691-696.  
Abstract4479)      PDF (912KB)(1674)      

Exemplified by the utilization of geophysical data in search for a concealed iron deposit and based on the deduction and interpretation of the gravitational, magnetic and electrical cross-shaped profile data in a certain area, this paper sums up the train of thought and working methods for reducing the ambiguity in the geophysical anomaly interpretation. It is held that various kinds of constraint data should be accurately and completely collected during the field work and data acquisition so as to reduce the ambiguity, and that the one-by-one judgment and exclusive method seems to be an effective way for this purpose.

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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
Abstract473)   HTML273)    PDF (2419KB)(424)      

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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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
Abstract407)   HTML310)    PDF (2056KB)(476)      

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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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
Abstract398)   HTML243)    PDF (2664KB)(426)      

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
Abstract383)   HTML2882)    PDF (1474KB)(409)      

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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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
Abstract359)   HTML290)    PDF (1069KB)(383)      

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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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
Abstract330)   HTML206)    PDF (9157KB)(387)      

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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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
Abstract296)   HTML130)    PDF (7432KB)(461)      

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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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
Abstract292)   HTML783)    PDF (2334KB)(404)      

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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Research progress in the geological characteristics and material sources of fluorite deposits in the Heyu-Checun area, western Henan Province
ZHANG Kai-Tao, BAI De-Sheng, Li Jun-Sheng, LIU Ji-Feng, XU Dong, SU Yang-Yan, FAN Kang
Geophysical and Geochemical Exploration    2022, 46 (4): 787-797.   DOI: 10.11720/wtyht.2022.1438
Abstract283)   HTML17)    PDF (4836KB)(269)      

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

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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
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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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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
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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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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
Abstract251)   HTML115)    PDF (2234KB)(300)      

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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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
Abstract249)   HTML143)    PDF (3536KB)(260)      

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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Geochemical characteristics and ecological health-related ranges of Copper in soil in Huaying Mountain-Xicao in Linshui County, Sichuan Province
ZHAO Xiao-Yuan, YANG Zhong-Fang, CHENG Hui-Yi, MA Xu-Dong, WANG Jue, LI Zhi-Kun, WANG Chen, LI Ming-Hui, LEI Feng-Hua
Geophysical and Geochemical Exploration    2022, 46 (1): 238-249.   DOI: 10.11720/wtyht.2022.1317
Abstract242)   HTML180)    PDF (5910KB)(312)      

Copper (Cu) is an essential trace element for the human body. However, there is no recommended value for Cu content in crops in China, and there is no standardon Cu content in soil for developing Cu-rich land resources. This paper takes the Huaying Mountain-Xicao cultivated land areas in Linshui County, Sichuan Province as the study area. Based on the survey results of the Cu contents in surface soil, crops, and root soil obtained from the 1∶50 000 land quality geochemical survey, this study investigated the contents and distribution of Cu in soil and crops and analyzed the influencing factors of the biological enrichment coefficient (BAF) of Cu in corn seeds. Moreover, it established a BAF prediction model of Cu in corn seeds and proposed the optimal ranges of Cu contents for developing Cu-rich corn and land resources. The study results are as follows. The Cu content in the surface soil of the study area ranges from 3.33×10-6 to 173×10-6, with an average and a median of 26.85×10-6 and 25.60×10-6, respectively. The soil with high Cu content is mainly distributed in the areas in Huaying Mountain in Linshui County where basalts, carbonate rocks, and carbonaceous shales are soil-forming rocks. In contrast, the soil with low Cu content is distributed in areas in Xicao where Jurassic sandshaleserves as soil-forming rocks. The Cu content in corn seeds in the study area ranges from 0.80×10-6 to 2.71×10-6, with an average and a median of 1.76×10-6 and 1.82×10-6 respectively. To ensure the safety of human beings in terms of Cu intake, the optimal Cu contents in corn seeds and soil in the study area should be 0.756×10-6~10.080×10-6 and 12.67×10-6~169.00×10-6, respectively.

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TEM response characteristics of borehole in goaves of old coal mines
ZHANG Jian-Zhi, HU Fu-Hang, LIU Hai-Xiao, XING Guo-Zhang
Geophysical and Geochemical Exploration    2022, 46 (1): 191-197.   DOI: 10.11720/wtyht.2022.1243
Abstract242)   HTML69)    PDF (5314KB)(223)      

The transient electromagnetic (TEM) method is widely used in coalfield hydrogeological exploration and goaf investigation in China. However, due to the characteristics of the method itself, the vertical resolution of the ground device is low, and thus it is impossible to realize the fine detection of goaves. In a goaf exploration project of a coal mine in Shanxi Province, a simple goaf model of coal measure strata was established according to the study on cores and logging curves, as well as previous experience of electrical exploration. Based on this, numerical simulation was conducted for the ground TEM response of goaves with and without water in a homogeneous half-space and the ground-well TEM response of three-dimensional horizontal thin plates. As confirmed by the characteristics of the ground and ground-well TEM response of goaves in some practical cases, the ground-well TEM has high vertical resolution, which provides an idea for fine exploration of goaves.

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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
Abstract241)   HTML1230)    PDF (3000KB)(244)      

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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Application of iTilt-Euler deconvolution in gravity data processing and fault system interpretation
CHEN Qing, SUN Shuai, DING Cheng-Yi, HUANG Xiao-Yu, CHEN Hao, SHEN Peng, LUO Gang, WEI Yao-Cong
Geophysical and Geochemical Exploration    2021, 45 (6): 1578-1587.   DOI: 10.11720/wtyht.2021.0284
Abstract238)   HTML1)    PDF (4071KB)(226)      

In order to improve the convergence and stability of Euler inverted results, the iTilt-Euler method, which do not depend on the structure index, is used for the calculation. Furthermore, the data points are constrained by the peak values of tilt angle of the total horizontal derivative (TAHG) to optimize the solutions. The method has been demonstrated with synthetic and real data. For synthetic data, the convergence of iTilt-Euler inversion results constrained by the TAHG method is improved effectively to detect the fault structures with deeper depth. Application to gravity data for the ANZA basin in Kenya shows that the iTilt-Euler inversion results constrained by peak values of TAHG have good continuity. The results distribute generally along NW direction, followed by NE direction, and these characteristics are consistent with the identifying features of fault in the second-order vertical derivative and total horizontal derivative anomaly maps. Furthermore, the inversion depth results show that the solutions along NW direction are extend to large scale and with higher values, which is reflected as a basement fault that controls the boundary of the main tectonic units in the study area and usually cut by the superficial faults with NE extension. It is worth noting that a large deep fault with NNE extension is developed in the southeast of the study area, which cuts the north-west direction and the north-east direction fault. It is speculated that it may control the southeast boundary of the regional tectonic unit. We can conclude that the iTilt-Euler deconvolution combined with the peak constraint method can provide a reliable method for fault system interpretation, and has good practicability.

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Generation mechanism of ghost wave in marine seismic exploration and ghost wave attenuation from marine seismic data
MA De-Zhi, WANG Wei, JIN Ming-Xia, WANG Hai-Kun, ZHANG Ming-Qiang
Geophysical and Geochemical Exploration    2022, 46 (1): 175-181.   DOI: 10.11720/wtyht.2022.2337
Abstract235)   HTML54)    PDF (3050KB)(183)      

In marine oil and gas exploration,for the purpose of accurately acquiring the high-precision and high-resolution reflection information of the exploration target and realizing more delicate imaging,broadband acquisition and processing technology of marine seismic has been greatly innovated and developed in recent years.In this paper,the generation mechanism of ghost wave,the classification and characteristics of ghost wave and its manifestation in actual seismic data are studied.The high-resolution radon transform in frequency domain is used as the main processing method to attenuate ghost wave in a broad-band data of a straight slant cable.After the ghost wave suppression processing,the source ghost wave and cable ghost wave of seismic data have been greatly attenuated,and the notch energy has been significantly enhanced.The broadband processing not only broadens the low-frequency component of seismic data,but also broadens the high-frequency component of seismic data;especially,the low-frequency component energy has been significantly enhanced.This method has achieved good results in the application of marine seismic data.

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Major controlling factors of low-resistance shale gas reservoirs
CUI Rui-Kang, SUN Jian-Meng, LIU Xing-Jun, WEN Xiao-Feng
Geophysical and Geochemical Exploration    2022, 46 (1): 150-159.   DOI: 10.11720/wtyht.2022.1123
Abstract227)   HTML59)    PDF (7367KB)(222)      

The Longmaxi Formation is one of the major exploration horizons of shale in China at present. The gas-bearing sediments in the Lower Paleozoic Longmaxi Formation in the Yangtze area, South Sichuan are characterized by low resistivity. Therefore, it is difficult to distinguish the gas-bearing sediments from aquifers only using logging response. Given this, this study investigated the genetic mechanisms of low-resistivity gas-bearing sediments in the study area in depth using existing data of conventional logging, core drilling, and production-related dynamic conditions, as well as a large number of core analyses and experiments, including casting thin sections, QEMSCAN, and X whole-rock diffraction. According to the study results, three major controlling factors in the low-resistivity gas-bearing sediments of the Lower Paleozoic Longmaxi Formation in the Yangtze region, South Sichuan include the additional conductivity of clay minerals, the complete graphitization of over-mature organic matter, and the distribution pattern of organic matter laminae. The practical application results indicate that the low-resistivity gas-bearing sediments in the study area were formed due to the organic matter laminae developing and the partial graphitization of organic matter. That is, the low resistivity of the shale gas reservoirs tends to be caused by the mutual superimposition and effects of multiple factors. Therefore, it is necessary to analyze the geological, logging, and core data according to various zones and horizons and employ the correlation between upper and lower horizons and between adjacent wells to determine the major controlling factors of the low resistivity of the shale gas reservoirs.

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Successive regression for determining the optimum terrain correction density in mountainous areas
GAO Wei-Qiang, SHI Zhao-Yang, ZHANG Li-Ming, FENG Xu-Liang
Geophysical and Geochemical Exploration    2021, 45 (6): 1530-1538.   DOI: 10.11720/wtyht.2021.0294
Abstract227)   HTML2)    PDF (5814KB)(222)      

Bouguer gravity anomaly is constantly correlated with terrain in mountainous areas, which is unserviceable to geological interpretation of gravity data. This phenomenon is mainly caused by inaccurate terrain correction density. We ascertain the terrain correction density in mountainous areas based on regression analysis. We obtain the terrain correction density by analyzing the relationship between the free-air gravity anomaly and the elevation, and modify the density according to the relationship between the calculated Bouguer gravity anomaly in each step and the elevation. Based on this, we adjust the terrain correction density of topographic correction successively until we obtain the optimum terrain correction density and the corresponding Bouguer gravity anomaly. We have adopted the proposed method for the terrain correction of the gravity data in the Jiuzongshan mountain and obtained the optimum terrain correction density after 5 iterations, and thus the Bouguer gravity anomaly was calculated. The results of Jiuzhongshan mountain confirmed the correctness of our proposed method.

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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
Abstract226)   HTML157)    PDF (2585KB)(322)      

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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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
Abstract226)   HTML155)    PDF (2566KB)(349)      

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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The approach to gravity forward calculation of 3D Tesseroid mesh model and its parallel algorithm
WANG Bo, GUO Liang-Hui, CUI Ya-Tong, Wang Xiang
Geophysical and Geochemical Exploration    2021, 45 (6): 1597-1605.   DOI: 10.11720/wtyht.2021.0078
Abstract225)   HTML1)    PDF (3253KB)(259)      

The forward modeling of a 3D mesh model is the basis of gravity data inversion. High precision and high efficiency forward modeling is helpful to the improvement of the quality of inversion interpretation. In order to solve the problem of high precision and high efficiency gravity forward modeling based on a large-scale surface observation area, this paper presents the gravity anomaly forward modeling method and parallel algorithm of a 3D Tesseroid mesh model in the spherical coordinate system. The forward modeling uses the improved Gauss-Legendre Quadrature integration method to realize the high-precision gravity anomaly calculation based on a large-scale surface observation area, and also uses the MATLAB task parallel algorithm based on OpenMP to realize the high-efficiency forward modeling. The test on the 3D theoretical model and the Eastern China lithospheric model has verified the validity of the proposed method. This method can provide technical support for efficient large-scale gravity field simulation and 3D inversion.

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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
Abstract220)   HTML70)    PDF (4734KB)(157)      

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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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
Abstract219)   HTML76)    PDF (5537KB)(199)      

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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Research on the method of shear wave prediction based on rock physics modeling
LIU Lan-Feng, YIN Long, HUANG Han-Dong, ZHOU Zhen-Ya, DONG Jin-Chao
Geophysical and Geochemical Exploration    2021, 45 (6): 1482-1487.   DOI: 10.11720/wtyht.2021.1164
Abstract217)   HTML3)    PDF (3640KB)(172)      

Shear wave velocity plays an important role in seismic forward modeling,fluid prediction and AVO analysis.However,due to the high cost of shear wave logging,there are no shear wave velocity logging data in some work areas.The prediction method of shear wave based on rock physics modeling is specific and accurate.In this paper,the method of calculating effective elastic modulus proposed by Sabrina is adopted,and the assumption conditions of CAO for shear wave prediction by this method are extended,rock physics modeling is performed,and the measured porosity is used to calculate the pore compliance so as to further predict the shear wave.Finally,combined with the actual data,the cross velocity data are used to conduct verification,and the results show that the effect is fairly good.

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Geochemical characteristics and bioavailability of selenium in alkaline soil in Shizuishan area, Ningxia
WANG Zhi-Qiang, YANG Jian-Feng, WEI Li-Xin, SHI Tian-Chi, CAO Yuan-Yuan
Geophysical and Geochemical Exploration    2022, 46 (1): 229-237.   DOI: 10.11720/wtyht.2022.1166
Abstract212)   HTML60)    PDF (1211KB)(238)      

Based on the comprehensive collection of samples from the alkaline soil in the Shizuishan area, Ningxia, this study analyzes the geochemical indicators of selenium and available selenium in soil in the area.The results are as follows. The seleniumin soil in the study area is mainly originated from the black rock series in the Helan Mountain area, followed by siltation brought in by the agricultural irrigation water diverted from the Yellow River. The bioavailability of selenium in the study area is at a relatively high level, and the effective selenium enrichment and above covers 79.2% of the whole study area, with an area of about 777.2 km2. The content of different forms of selenium is in the order ofresidualselenium>strongly organic matter-bound selenium>humic acid-bound selenium>ion exchangeableselenium≈water-soluble selenium > carbonate-bound selenium≈iron manganese oxide-boundselenium. The total selenium content is limited, while thewater-soluble selenium content is relatively high. The higher the total nitrogen and organic matter content in soil, the higher the total selenium and available selenium content. As the salt content in soil in the study area increases, the bioavailability of seleniumtends to gradually increase. The irrigation-silted soiland thefluvo-aquic soil with a pH value between 7.5 and 9 have moderate total selenium content and high available selenium content, and they are high-quality areas for planting selenium-rich agricultural products.

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Distribution and influencing factors of selenium content in soil in karst areas in Mashan County, Guangxi, China
ZHANG Chun-Lai, YANG Hui, Huang Fen, CAO Jian-Hua
Geophysical and Geochemical Exploration    2021, 45 (6): 1497-1503.   DOI: 10.11720/wtyht.2021.1598
Abstract210)   HTML81)    PDF (1787KB)(231)      

This study aims to investigate the distribution characteristics of the total selenium content in soil in karst areas in Mashan County, Guangxi and to explore the effects of different soil parent materials, land uses, and soil types on the selenium content in soil. To this end, 492 samples of surface soil (0~20 cm) were collected from the northern part of Mashan County and the distribution of the total selenium content in the samples were studied by statistical methods. The results are as follows. The total selenium content in the soil varies from 0.20×10-6 to 3.54×10-6, with an average value of 0.76×10-6. Meanwhile, the selenium-rich area accounts for 98.29% and the coefficient of variation is 34.49%. The soil in the Permian Heshan formation bearing black shales and coal-measure strata has the highest selenium content, with an average of 1.17×10-6, while the Carboniferous Maping formation has the lowest selenium content, with an average of 0.64×10-6. In terms of different soil types, the lateritic red soil has the highest selenium content, with an average value of 1.04×10-6, while the fluvo-aquic soilhas the lowest selenium content, with an average value of 0.56×10-6. In terms of land use types,the forestland and orchard have a high selenium content in soil, while the paddy field, grassland, and arid land have a low selenium content. Therefore, the selenium content in soil in the study area is mainly affected by soil parent materials, with the selenium enrichmentin soil being affected by the organic matter content to a certain extent.

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Gravity characteristics and hydrocarbon prospect of Trinidad Basin
XING Jin-Cheng, YUAN Bing-Qiang, ZHANG Chun-Guan, FENG Xu-Liang, DUAN Rui-Feng, XUE Jian, JIA Hong-Yang, LI Xiang
Geophysical and Geochemical Exploration    2021, 45 (6): 1606-1616.   DOI: 10.11720/wtyht.2021.0274
Abstract209)   HTML1)    PDF (3489KB)(173)      

Trinidad Basin, which is located in the northern part of Venezuela in South America and the southern margin of the Caribbean Sea has a good prospect for oil and gas resources. The formers have studied the tectonic evolution, sedimentary characteristics of the basin, the work was mainly focused on the southeastern basin, there is lack of research on the characteristics of the structure of the entire basin. In order to study systematically the distribution of faults and basement characteristics of the basin, predict the prospective areas of hydrocarbon, and provide a basis for further hydrocarbon exploration and development in the basin. This paper uses ship log gravity data and satellite gravity data provided by GETECH to analyze and study the characteristics of the gravity field of the basin, infer the fault structure system of the basin. With the constraints of the three existing seismic profiles, the three gravity profiles with the same position as the above seismic profiles were fitted, the basement depth of the basin is calculated combined with correlation analysis and Parker, the structural units and favorable hydrocarbon exploration areas of the basin are predicted. The results show that the structure of Trinidad basin is complex, there are mainly two groups of faults in NE direction and NW direction, the NE-oriented main faults control the scope of the basin and the development of stratum in the basin. The basement of the basin is undulating and can be divided into six structural units: the eastern subbasin, the northern subbasin, the central uplift belt, the central nappe belt, the western subbasin and the western uplift. The eastern sub-basin, the north sub-basin and the western sub-basin are favorable areas for hydrocarbon exploration.

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Exploration and practice of non-uniform time-lapse seismic key technology in Shengli Oilfield
RUI Yong-Jun, SHANG Xin-Min
Geophysical and Geochemical Exploration    2021, 45 (6): 1439-1447.   DOI: 10.11720/wtyht.2021.1219
Abstract208)   HTML1)    PDF (7797KB)(279)      

Time-lapse seismic survey is an effective technique for reservoir dynamic description,but it has not been widely used since its success in the last century due to the high cost and the limitation of its application range.Since 2007,Shengli Oilfield has put forward the idea of non-uniform time-lapse seismic survey in view of the current situation of the secondary acquisition seismic survey in high mature exploration area.Aiming at tackling a series of technical problems,such as how to evaluate and eliminate the influence of non-uniform acquisition system, how to detect the small difference of monitor changes and how to comprehensively use the time-lapse results,researchers have spent more than ten years to innovate the key technologies,i.e.,the matching technology of non-uniform time-lapse seismic acquisition system,the pre-stack cross equalization technology based on well data,the joint optimization technology of pre-stack and post-stack sensitive attributes,and the comprehensive interpretation technology of time-lapse seismic based on reservoir value.The time-lapse seismic technology of water-drive complex fault block reservoir,small-scale gas reservoir boundary monitoring and steam huff and puff heavy oil reservoir has been formed.The application demonstration of six blocks with an area of 300 square kilometers has been carried out,which shows the broad prospect of the achievements and broadens the ability of reservoir geophysical technology to solve the development problems.

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Capabilities of airborne electromagnetic methods to detect permafrost
SUN Si-Yuan, YU Xue-Zhong, XIE Ru-Kuan, HE Yi-Yuan, SHAN Xi-Peng, LI Shi-Jun
Geophysical and Geochemical Exploration    2022, 46 (1): 104-113.   DOI: 10.11720/wtyht.2022.2480
Abstract204)   HTML91)    PDF (4295KB)(302)      

It is critical for climate, water resources, ecology, and engineering construction in China to accurately assess the three-dimensional distribution and periodic change of permafrost. Permafrost is mainly distributed in high-elevation regions in China. Therefore, the surface geophysical prospecting suffers from low efficiency, high cost, and poor transportation in determining the thickness of permafrost in China. In contrast, the airborne electromagnetic methods using resistivity difference enjoy great advantages. This study established a geoelectric model based on the thickness and resistivity of permafrost in Qilian area, Qinghai Province. Then, by simulating the thickness and resistivity of permafrost, low resistance layer under permafrost, flight height, and changes in the angles of receiver coils, this study analyzed the differences in electromagnetic responses under different conditions obtained from one-dimensional forward modeling using time-domain and frequency-domain airborne electromagnetic systems AeroTEM and Impulse. Based on this, this study assessed the capability of airborne electromagnetic methods to detect the top and bottom interfaces of permafrost. According to the simulation results, frequency-domain airborne electromagnetic system Impulse can determine the top interface of the permafrost covered by a marsh, wetland, or moist meadow according to the thickness of melted permafrost under a low noise level. In comparison, time-domain airborne electromagnetic system AeroTEM can determine the bottom interface of the permafrost, with the determination accuracy significantly improving when low-resistivity layers occur beneath the permafrost. Therefore, the top and bottom interfaces of permafrost can be jointly determined using frequency and time-domain airborne electromagnetic data. The results of this study will provide theoretical support for the future application of airborne electromagnetic methods to permafrost surveys in China.

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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
Abstract204)   HTML9)    PDF (2912KB)(166)      

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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Tracing and identification of concealed Luoboling copper-molybdenum deposit in Fujian Province using trace elements and isotopes in fine-grained surface soils
LI Jian-Ting, LIU Xue-Min, WANG Xue-Qiu, HAN Zhi-Xuan, JANG Yao
Geophysical and Geochemical Exploration    2022, 46 (1): 32-45.   DOI: 10.11720/wtyht.2022.2585
Abstract203)   HTML73)    PDF (4571KB)(282)      

This paper collected surface soil above the known concealed deposit the Luoboling porphyry-type copper-molybdenum deposit and acquired samples of ore and surrounding rocks from typical boreholes of the deposit. Then, it analyzed the changes in the contents of six trace elements (Cu, Mo, Ba, Pb, Zn, and V) and the isotopic composition of S and Pb, aiming to verify the ore prospecting effects of the measurement technology of mobile forms of metals in soil and full analysis of fine-grained soil in concealed deposits and to identify the sources of surface geochemical anomalies according to the isotopic composition of Pb and S. The study results are as follows. The total analysis of fine-grained soil showed the best effects in indicating deep ore bodies in the Luoboling deposit, and the areas with high contents of Cu, Ba, and Mo correlated strongly with the distribution of deeply concealed ore bodies. Both the mobile forms of metals in the soil and the total analysis of fine-grained soil showed that it is quite possible that concealed ore bodies occur below sampling points No.14 and 15. Meanwhile, the changes in the contents of V, Pb, and Zn obtained using both methods can accurately delineate the scopes of mineralized rock masses close to the ground surface. However, most of the total sulfur isotopic composition in the soil of anomaly zones inherits from the non-ore-hosting surrounding rocks and masked the contribution from the deep ore bodies. Consequently, sulfur isotopes showed poor effects in indicating the sources of anomalies in the surface soil in the Luoboling deposit. Therefore, it is more reasonable to measure the sulfur isotopic composition according to the mobile forms of metals in the soil. In contrast, the total Pb isotopes in the soil of the anomaly zones inherit the characteristics of the Pb isotopes of deep ore bodies. This serves as direct evidence of full analysis of fine-grained soil in the mineral exploration of coverage areas.Moreover, the changes in the 206Pb/204Pb ratio in the full analysis of surface fine-grained soil correlated strongly with the distribution of underlying concealed ore bodies and thereby can effectively indicate the deep concealed ore bodies.

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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
Abstract203)   HTML1825)    PDF (1810KB)(262)      

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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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
Abstract203)   HTML7)    PDF (9692KB)(188)      

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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Geochemical background and management target values of heavy metals in soil in northwestern Guizhou Province
MENG Wei, MO Chun-Hu, LIU Ying-Zhong
Geophysical and Geochemical Exploration    2022, 46 (1): 250-257.   DOI: 10.11720/wtyht.2022.1077
Abstract198)   HTML180)    PDF (1851KB)(298)      

Based on the heavy metal content data of 1 308 deep soil samples taken from the 1∶250 000 geochemical survey of land qualityin the Bijie area, Guizhou Province, the content distribution and geochemical background characteristics of heavy metals in soil in the area were studied. The geochemical background values of heavy metals in soil in northwestern Guizhou Provinceare significantly higher than those in soil nationwide but are close to those in soil in southwestern China. The heavy metal content in soil in northwestern Guizhou is closely related to the geological background and is significantly different between different geological units. The soil developing in Carboniferous strata has high geochemical background values of Pb and Zn, while the Middle Permian soil formed due to weathering hashigh geochemical background values of Cd and Hg. All these mean that besides heavy metal pollution in soil caused by zinc melting using indigenous methods,another important factor causing the heavy metal enrichment is the high geochemical background values of heavy metals in soil.The statistics show that the management target value of Cd in the Middle Permian weathered soil in northwestern Guizhou is higher than thecontrol value (2.0×10-6) of Cd stipulated in the Risk Management Standard for Agricultural Land for Soil Pollution in China. It is considered that the differences in geochemical background values of heavy metals in soil between different geological units and their impacts on the ecological environment should be fully considered when determining the management target values of heavy metals in soil in northwestern Guizhou Province.

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Application of multi-attribute fusion in quantitative prediction of reservoirs: A case study of Yangshuiwu buried hill in Langgu sag
WANG Cheng-Quan, WANG Meng-Hua, ZHOU Jia-Yi, WANG Sheng-Liang, YANG Zhou-Peng, LIU Hui, ZHANG Hong-Wen
Geophysical and Geochemical Exploration    2022, 46 (1): 87-95.   DOI: 10.11720/wtyht.2022.2371
Abstract196)   HTML40)    PDF (5111KB)(182)      

The Yangshuiwu buried hill is located in the northern part of the Langgu sag,where fractured porous reservoirs are well developed.As indicated by comprehensive geological studies,it is in the direction favorable for hydrocarbon migration and accumulation.However,owing to the deep reservoirs and low imaging accuracy of seismic data,it is difficult to predict effective reservoirs using conventional attributes and the obtained prediction results feature strong multiplicity of solution.Based on full analyses of the geophysical response characteristics of existing drilled wells,this study selects three optimal attributes sensitive to the response of effective reservoirs,namely mean amplitude,variance,and arc length,and calculates the correlation coefficient between the thickness of effective reservoirs and each of the optimal attributes.Then it determines the fusion weight of each attribute according to corresponding correlation coefficient,and finally obtains the fused attribute than can reflect the thickness of effective reservoirs.The fused attribute can be used to effectively reduce the multiplicity of solution compared with single attribute prediction and quantitatively predict effective reservoirs.Practice has proved that the multi-attribute fusion technology is effective and practical and has achieved accurate application results in the Yangshuiwu buried hill.

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An EMI array sensor based on differential reception
WU Yan-Min, PENG Zheng-Hui, YUAN Yong-Hu, ZHU Jin-Xiang, LIU Chuang, GE Wei, LING Guo-Ping
Geophysical and Geochemical Exploration    2022, 46 (1): 214-220.   DOI: 10.11720/wtyht.2022.1036
Abstract193)   HTML53)    PDF (3070KB)(194)      

This study proposes an EMI array sensor based on differential reception, which can effectively improve the comprehensive performance of the EMI system on a vehicle or robot in terms of soil adaptability, positioning accuracy, and anti-interference ability. The EMI array sensor consists of a large transmitting coil and multiple receiving coils, which are horizontally arranged in the transmitting coil. Meanwhile, the receiving coils are a kind of double-D coils to realize differential reception. In this manner, the detection efficiency of unexploded ordnances (UXO) can be effectively improved using the EMI array sensor. The simulated minefield detection test results show that the array sensor proposed in this study can be used for UXO detection and positioning.

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A discussion on the processing method of high density single point seismic acquisition data
WANG Fei, SUN Ya-Jie, PEI Jin-Mei, SONG Jian-Guo, LI Wen-Jian
Geophysical and Geochemical Exploration    2021, 45 (6): 1469-1474.   DOI: 10.11720/wtyht.2021.1226
Abstract193)   HTML4)    PDF (4649KB)(204)      

In the past seismic exploration in Qaidam Basin,large combination receiving has been often used in order to achieve the purpose of suppressing noise.However,as the exploration goes deeper,the disadvantages of the big combination gradually emerge.The single detector receiver can combine the channels in the post-processing of the data,which can not only suppress the interference but also eliminate the influence of statics in the large combinations,which is beneficial to the resolution, fidelity and imaging accuracy of the data.Based on the data of a survey line in the area of the peak mountain in the basin,this paper deals with and analyzes the trace combination,discusses the method,process and problems that should be paid attention to in the process of the trace combination,completes the function of the field detector combination,and shows the effect of the trace combination treatment.

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Stretch correction method based on Curvelet sparse transform
LIU Shi-You, ZHANG Ming-Lin, SONG Wei-Qi
Geophysical and Geochemical Exploration    2022, 46 (1): 114-122.   DOI: 10.11720/wtyht.2022.1328
Abstract190)   HTML63)    PDF (8528KB)(210)      

NMO correction is an important step in seismic data processing, but it will produce the wavelet stretching distortion effect in the process of correction. With the increase of offset, the dominant frequency will decrease and the amplitude will increase.Due to stretch distortion, the in-phase axis is not leveled, leading to non-in-phase stacking, which will lead to frequency distortion and resolution decrease of horizontal stacking profile. Therefore, stretch correction is the key to improve the resolution of horizontal stacking profile.The stretching distortion of wavelet is incoherent in the curved sparse domain, and the stretching correction can be regarded as a nonlinear optimization process.By measuring the sparsity of the data in the sparse domain, a fast and effective algorithm is used to optimize the nonlinear problem generated by the wavelet stretching distortion, and finally the purpose of eliminating the wavelet stretching distortion is realized.The curved sparse transform stretching correction method can eliminate the wavelet stretching distortion caused by NMO correction, recover the high frequency information at the far offset and level the in-phase axis.Combining model data and actual data processing, the curved wave sparse stretch correction method can significantly improve the resolution of horizontal superposition profile.

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Suppression method of multi-source harmonic noise in magnetic resonance sounding based on simulated annealing method
CHEN Liang, FU Li-Heng, CAI Dong, LI Fan, LI Zhen-Yu, LU Kai
Geophysical and Geochemical Exploration    2022, 46 (1): 141-149.   DOI: 10.11720/wtyht.2022.1158
Abstract187)   HTML67)    PDF (4080KB)(183)      

When the magnetic resonance sounding (MRS) method is applied in an environment with high electromagnetic noise, the signal-to-noise ratio of the measured data is often reduced due to the interference of electromagnetic noise. As a result, it is difficult to accurately determine the aquifer distribution using the inversion results, thus reducing the application effects of the method. In this paper, aiming at the common problem of multi-source harmonic noise interference in the field data acquisition using the MRS method, this paper derives the grid search simultaneous removal method based on the model denoising and further proposes the more efficient simulated annealing simultaneous removal method. The simulation results show that both methods can effectively suppress multi-source harmonic noise. Compared with the grid search simultaneous removal method, the efficiency of the simulated annealing simultaneous removal method is improved by 2.35 times in the case of double fundamental frequency harmonics, which greatly reduces the time cost of the denoising process. Meanwhile, the simulated annealing simultaneous removal method allows for great denoising effects of multi-source harmonic noise. Finally, the proposed denoising algorithm was applied to a field example. The comparison of the inversion results and borehole data shows that the simulated annealing simultaneous removal method can effectively suppress the multi-source harmonic noise in the measured data obtained using the MRS method and can significantly improve the application effects of the method.

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An edge recognition technique enhanced with interface inversion for potential field data
FENG Xu-Liang, WEI Ze-Kun
Geophysical and Geochemical Exploration    2022, 46 (1): 130-140.   DOI: 10.11720/wtyht.2022.1116
Abstract186)   HTML126)    PDF (11443KB)(352)      

One of the pivotal tasks in energy and resources exploration is identifying geological boundaries such as petroliferous structure, ore-controlling faults, and rock mass boundaries. The edge recognition of gravity and magnetic potential data has unique advantages in the detection of geological boundaries, and has become an indispensable and important means in energy and resources exploration. We have combined interface inversion and normalized vertical derivative of the total horizontal derivative (NVDR_THDR) for potential field data to improve the effect of the potential field edge recognition method for deep small-scale geological bodies. Firstly, we invert the gravity anomaly using density interface inversion method to make the anomaly more prominent of the small-scale geological structures, then the NVDR_THDR technique is used as an edge extraction and enhancement method to deal with the density interface inversion result. The results conducted with rifted basin model and the isolated bodies model show that the proposed method has obvious advantages of edge enhancement and can balance the deep and shallow anomalies to some extent. The real gravity data test of the northern Ordos Basin also show that our method can detect the small-scale faults in the basement of the basin, which indicates that this method can be successfully used in real data processing.

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Research and implementation of key technologies of spectral induced polarization instruments
SHI Jia-Yu, GUO Peng, LI Yong
Geophysical and Geochemical Exploration    2021, 45 (6): 1475-1481.   DOI: 10.11720/wtyht.2021.0443
Abstract185)   HTML2)    PDF (1683KB)(152)      

The measurement of the electrochemical polarization effect of rock (ore) in an AC electric field (i.e., the phase between receiving potential different and transmitting current) using spectral induced polarization (SIP) can provide important information for distinguishing ore from non-ore. Based on the deep research on the key technologies of SIP instruments, this study designs a new synchronous correlation detection technology of weak signals, and accordingly improves the prototype for practical purposes, simplifies the circuit structure, and improves the stability of phase measurement of the SIP instruments. The tests in mining areas show that the improved SIP instrument has lower cost, stronger anti-interference ability, higher practicability, and is suitable for large-scale promotion and application.

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2D seismic and high-density resistivity sounding reveal the shallow three-dimensional geological structure characteristics of Xiong'an New Area
LONG Hui, XIE Xing-Long, LI Feng-Zhe, REN Zheng-Wei, WANG Chun-Hui, GUO Shu-Jun
Geophysical and Geochemical Exploration    2022, 46 (4): 808-815.   DOI: 10.11720/wtyht.2022.1319
Abstract181)   HTML10)    PDF (4550KB)(246)      

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

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Denoising of magnetotelluric data based on Hilbert-Huang transform
CHEN Jun, YAN Liang-Jun, ZHOU Lei
Geophysical and Geochemical Exploration    2021, 45 (6): 1462-1468.   DOI: 10.11720/wtyht.2021.0047
Abstract178)   HTML97)    PDF (4159KB)(329)      

Near-field effects are liable to rise in magnetotelluric signals due to noise, which seriously affects the quality of the collected signals. The widely used remote reference method-Robust-still has some shortcomings in suppressing near-field interference. In this paper, after being verified using numerical simulation in terms of denoising effects, the Hilbert-Huang transform (HHT) was applied to a magnetotelluric signal with serious near-field interference, achieving remarkable effects. Meanwhile, the polarization distribution of the electric and magnetic fields was calculated using the distribution function of polarization directions. It was found that the distribution function was closer to a Gaussian distribution function, also verifying the effectiveness of the HHT in suppressing near-field interference.

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Multi-level division method of flow units for accurate permeability assessment of glutenite reservoirs:A case study of reservoir W53 of Paleogene Wenchang Formation in Lufeng oilfield
SHI Lei, GUAN Yao, FENG Jin, GAO Hui, QIU Xin-Wei, QUE Xiao-Ming
Geophysical and Geochemical Exploration    2022, 46 (1): 78-86.   DOI: 10.11720/wtyht.2022.1071
Abstract178)   HTML49)    PDF (5518KB)(158)      

The glutenite reservoirs of the Paleogene Wenchang formation in the Lufeng oilfield in the eastern South China Sea are characterized by complex lithology,low porosity,and strongly heterogeneous pore structure.Since different types of reservoirs show greatly different seepage characteristics,traditional permeability models are difficult to meet the demand for petroleum production and development due to their low calculation precision.Flow units can effectively characterize the internal seepage characteristics of reservoirs.However,the division of flow units based only on flow unit indicators will lead to misclassification.Given the macro and micro hierarchical heterogeneity of reservoirs of the Wenchang Formation,this study establishes a multi-level division method of flow units by combining geological,logging,and core data.Specifically,the first-order flow units are determined according to sedimentary facies.Then the second-order flow units are determined according to the lithology identified by calibrating conventional logging based on core and imaging logging.Finally,the third-order flow units are determined using flow zone indicator (FZI) approaches combined with pore structure.In this manner,a three-level division method of flow units based on sedimentary microfacies-lithology-pore structure is formed.As indicated by application results,this method can effectively avoid the inaccurate classification of flow units and improve the accuracy of permeability calculation,thus having great significance for finding high-quality reservoirs and the efficient development of oil reservoirs.

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The prediction of electrochemical prospecting in Youfang area of the Xiangshan orefield
TANG Rui, OUYANG Fei, LUO Xian-Rong, ZHENG Chao-Jie, TANG Guo-Dong, LIU Pan-Feng, CAI Ye-Lei, YANG Xiao-Xiao
Geophysical and Geochemical Exploration    2021, 45 (6): 1425-1438.   DOI: 10.11720/wtyht.2021.1470
Abstract177)   HTML2)    PDF (15559KB)(214)      

In order to make a breakthrough in prospecting in the Youfang area of the Xiangshan ore field, the authors carried out geoelectric extraction and surveying in this area for deep prospecting prediction. It is found that the anomalies are obviously controlled by the faults, and are mainly distributed along the ore-controlling faults and the intersection of the faults. Cluster analysis and factor analysis reveal that there is a significant correlation between the trace elements, thus forming the corresponding element combinations: F1 factor (Ti、V、Mo、Th、U), F2 factor (As、Pb、Sb), and F3 factor (Co、Ni). The spatial distribution of uranium-thorium ratios shows a significant positive correlation with the estimated base depth of AMT, controlled by volcanic rock thickness. The authors synthesized the abnormal features of geoelectrically extracted elements and the mineralization regularity of the Xiangshan ore field, established a comprehensive geological-geoelectrochemical prospecting model, and delineated two corresponding targets in the study area, of which No.1 target area has good prospecting prospect.

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Gas-bearing property prediction of Leikoupo Formation in the northwest Sichuan Basin based on the theory of two-phase media
ZHANG Hao, XIN Yong-Guang, TIAN Han
Geophysical and Geochemical Exploration    2021, 45 (6): 1386-1393.   DOI: 10.11720/wtyht.2021.1340
Abstract176)   HTML40)    PDF (6737KB)(278)      

The Leikoupo Formation in northwest Sichuan Basin has great potential in exploration,quite a few wells demonstrate active oil and gas showings during drilling,and good gas-bearing property and reservoir development are interpreted from well logging.Aiming at tackling the unclear distribution of favorable gas-bearing zones of Leikoupo Formation and based on the combination of seismic geological conditions and well logging data,the authors conducted Empirical Mode Decomposition processing to compensate high-frequency energy while preserving the low-frequency energy,which laid the data basis for subsequent bi-media hydrocarbon detection technique.Then amplitude spectrums at different well locations were compared and analyzed,the low-frequency energy enhancement and high-frequency energy attenuation were found where reservoir contained gas.With the optimized frequency range,hydrocarbon detection based on two-phase media theory was implemented on the seismic data of the study area.The results of hydrocarbon detection are well consistent with the data from drilling wells and the geological law,which confirms the validity of proposed techniques and provides the directions for expanding oil and gas exploration range and area of Leikoupo Formation in northwest Sichuan Basin.

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3DVSP channel gather cutting technique based on tensile ratio and its application
ZHANG Jie
Geophysical and Geochemical Exploration    2022, 46 (1): 169-174.   DOI: 10.11720/wtyht.2022.2325
Abstract176)   HTML58)    PDF (8319KB)(144)      

3DVSP common detection point gathers produce different tensile distortion effects at different offsets after conventional processing,especially at the shallow layer and large offset,which affects the imaging quality of the superimposed section.In view of such a situation,the author analyzed the stretch effect reason,deduced the stretch rate formula,and proposed a trace-set cutting method based on stretch rate:to calculate the stretch rate of each point in the trace set of common detection points point by point,determine the range of effective stretch rate,and cut the points with excessive stretch rate.The results of model analysis and actual data processing show that the method is correct and effective.

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Forward modeling of well-ground direct current resistivity method for undulating terrain based on Gmsh
ZHANG Yu-Zhe, MENG Lin, WANG Zhi
Geophysical and Geochemical Exploration    2022, 46 (1): 182-190.   DOI: 10.11720/wtyht.2022.1232
Abstract175)   HTML53)    PDF (6358KB)(155)      

This paper focuses on the forward modeling of the direct current resistivity method. To this end, the Gmsh software-a 3D finite element grid generator-was used to model the anomalous bodies under undulating terrain and conduct relevant irregular grid division. Then partial grid data generated by Gmsh were applied to a 2.5D finite element forward modeling program, and the forward calculation results were analyzed using the well-ground joint observation method. The analytical results show that good effects can be obtained by using irregular grids to fit the undulating terrain and using the well-ground joint observation method to explore the geological conditions under the undulating terrain. The effects of the valley terrain on the anomalous response below using different observation devices were also studied. The results achieved are practically significant and they also prove that the Gmsh software has great application value in the forward modeling and meshing based on the finite element method.

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