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Application of integrated geophysical exploration technology in the geothermal exploration of northern Jinan
ZHANG Yi, LIU Peng-Lei, WANG Yu-Min, ZHANG Peng-Peng, ZHANG Chao, ZHANG Ning
Geophysical and Geochemical Exploration    2024, 48 (1): 58-66.   DOI: 10.11720/wtyht.2024.1141
Abstract227)   HTML10)    PDF (8896KB)(408)      

Ji'nan possesses highly abundant geothermal resources, which are hosted by Ordovician-Cambrian karst-fissured geothermal reservoirs and Neogene-Paleogene clastic pore-fissure geothermal reservoirs. The geothermal exploration in this study focuses on the Ordovician-Cambrian karst fissured geothermal reservoirs in Daqiao Town in northern Ji'nan. Through geophysical profile measurements, this study aims to identify the distributions of strata and fault structures and the burial depths of geothermal reservoirs, infer the attitudes and spatial morphologies of fault structures associated with heat control and conduction, delineate the target area for geothermal well construction, and conduct drilling verification in the favorable underground water-rich position. Building on the collected data, this study interpreted and inferred the fault structures in the study area and comparatively analyzed the water-bearing properties by employing direct-current sounding, controlled source audio magnetotellurics, and magnetotelluric survey. A geothermal exploration and production combined well was constructed in a favorable position of the geothermal target area, manifesting a completion depth of 1 532.06 m, a static-water burial depth of 13.03 m, a wellhead water temperature of 50.1 ℃, a water yield of 132.998 m3/h, and a dropdown depth of 18.27 m.

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Advancements in research on geochemical exploration methods and technologies for mineral resources in overburden areas
SUN Yue, ZHANG Zhen-Yu, FENG Bin, YANG Shao-Ping, WANG Zhi-Feng
Geophysical and Geochemical Exploration    2023, 47 (6): 1387-1399.   DOI: 10.11720/wtyht.2023.0109
Abstract289)   HTML16)    PDF (2899KB)(385)      

Following China's planning for ore prospecting in overburden areas, China's geochemical exploration researchers have conducted extensive research on the fundamental theories, methods, and technologies of geochemical exploration for overburden areas in the past decade. They achieved significant advances mainly in two aspects: (1) the research on the migration mechanism, occurrence state, and anomaly formation mechanism of elements in overburden areas; (2) advances in methods and technologies, including geoelectrochemistry, active state of elements, geogas, separation of micro-fine-sized soil particles, soil thermomagnetic composition, and integrated gas survey, as well as numerous experimental demonstrations. These advances represent continuous progress in the research on the fundamental theories, methods, and technologies of geochemical exploration for overburden areas, providing new geochemical methods and technologies for ore prospecting breakthroughs in overburden areas.

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Prospecting for concealed skarn iron deposits using the high-precision gravity-magnetic survey method
DONG Jian, LI Xiao-Peng, FU Chao, DANG Zhi-Cai, ZHAO Xiao-Bo, ZENG Qing-Bin, HU Xue-Ping, WANG Jin-Hui
Geophysical and Geochemical Exploration    2024, 48 (1): 31-39.   DOI: 10.11720/wtyht.2024.1047
Abstract223)   HTML8)    PDF (7885KB)(354)      

The Laiwu area in central Shandong Province, situated in the eastern North China Craton, is a significant production area of skarn iron-rich ores. Its ore deposits occur primarily in the contact zone between the mining rock mass and the Middle Ordovician carbonate formation. Based on the latest areal gravity and magnetic survey results, this study thoroughly investigated the characteristics of gravity and magnetic anomalies along the Shijiaquan-Liujiamiao area in the western periphery of the mine rock mass. Then, this study delineated the deep prospecting target combining the characteristics of gravity and magnetic fields of the known iron deposits in the Laiwu area. Large-scale gravity and magnetic profiles were arranged in the favorable mineralization area. With the known boreholes as constraints, the gravity and magnetic anomalies were qualitatively and quantitatively interpreted using the 2.5D gravity-magnetic joint inversion technique. The interpretation results provide a basis for the location and depth of the borehole to be placed, which revealed a 15.8 m-thick iron-rich ore deposit, suggesting remarkable prospecting effects. This study holds critical indicative significance for further exploration of skarn iron ore deposits in this area.

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Geophysical characteristics and deep prospecting prediction of the Dachaigou gold deposit in the eastern Kunlun area
YU Zhong-Hong, YAN Ling-Qin, ZHANG Zhan-Xiong, LI Peng, LI Feng-Ting, FU Jia
Geophysical and Geochemical Exploration    2024, 48 (1): 40-47.   DOI: 10.11720/wtyht.2024.1126
Abstract143)   HTML5)    PDF (7232KB)(306)      

The eastern Kunlun metallogenic belt, as a significant metal metallogenic belt in China, hosts extensive orogenic gold deposits and large-scale Kunlunhe, Gouli, and Wulonggou gold concentration areas. The Dachaigou gold deposit is a large-scale gold deposit newly discovered in the Wulonggou gold field in recent years. Despite its high metallogenic potential, the western extension of its ore belt has not been defined. Hence, this study conducted induced polarization (IP) sounding and wide-field electromagnetic sounding in the deposit. The results show that the known ore belt is situated in the regional gravity anomaly gradient zone, the transition zone of positive and negative weak magnetic anomalies, the edge of IP anomalies, or the electrical gradient zone. The development zone of the regional tectonic belt resides in the large-scale IP anomaly section. The regional tectonic belt is characterized by a wide range of low-resistivity anomaly zones. The IV and III alteration zones of the known ore belt are located in the opening position of the low-resistivity anomaly zone and the shallow electrical anomaly gradient zone, respectively. Based on the above understanding and the electromagnetic anomaly change patterns of several parallel profiles in the western extension segment, it was inferred that the regional ore-controlling structure extends steadily in the W-NWW direction, forming a favorable prospecting space in the western extension segment of the deposit. The results of deep geophysical exploration in the Dachaigou deposit indicate that geophysical methods manifest significant advantages in deep geological prospecting research, providing successful experience for deep prospecting in the eastern Kunlun gold deposit area.

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Research on time-frequency electromagnetic method detection of Wumishan Formation thermal reservoir in deep Xiong’an New Area
Cheng Zheng-Pu, Lian Sheng, Wei Qiang, Hu Wen-Guang, Lei Ming, Li Shu
Geophysical and Geochemical Exploration    2023, 47 (6): 1400-1409.   DOI: 10.11720/wtyht.2023.1611
Abstract149)   HTML8)    PDF (2331KB)(272)      

Xiong’an New Area is one of the areas with the best conditions for the development and utilization of geothermal resources in sedimentary basins of eastern China. Wumishan Formation of Jixian System is the main thermal reservoir, with buried depth of the top boundary varies greatly, which istypical carbonate type thermal reservoir. In order to find out the stratigraphic structure and concealed faults within 6 km of the starting area of Xiong’an New Area, focus on finding out the spatial distribution and structural characteristics of the main deep thermal reservoirs, and predict the favorable geothermal areas, the time-frequency electromagnetic method is applied to the geothermal resources exploration of Xiong’an New Area. Through high-standard data acquisition, refined data processing and resistivity-constrained inversion, the pseudo-seismic imaging technology and borehole data are used to calibrate the resistivity horizon, which effectively improves the reliability of interpretation results. In this work, 8concealed faults were identified, mainly NNE strike normal faults, which controlled the salient-depression pattern and stratigraphic distribution of the study area. The study area is divided into Rongcheng salient, middle sub-depression, Niutuozhen salient and Baxian depression from west to east. The thermal reservoirs of Wumishan Formation is mainly distributed in Niutuozhen salient, Rongcheng salient and middle sub-depression, with buried depth of top interface is about 600~2600m. Vsing the inversion results of the time-frequency electromagnetic method, the three-dimensional geological model of the study area is constructed, and the Niutuozhen salient area is considered to be the optimal geothermal favorable area from the aspects of heat source, channel, reservoir, caprock and fluid, especially near the footwall of F4.

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Research on the application of the integrated gravity-magnetic-radioactive geophysical exploration method in the exploration of rare earth deposit in Weishan, western Shandong
LAN Jun, LI Zhao-Ling, ZHANG Peng, LI Zhi-Min, LI De-Jian, XING Nan, SUN Li, YANG Yun-Tao, XU Hong-Yan, WANG Jian, WANG Qiao-Yun
Geophysical and Geochemical Exploration    2023, 47 (6): 1417-1424.   DOI: 10.11720/wtyht.2023.0189
Abstract149)   HTML8)    PDF (4793KB)(265)      

Since the periphery of the Xishan rare earth deposit in Weishan County, western Shandong is mostly covered by the Quaternary strata, single geophysical exploration methods are ineffective in searching for rare earth elements in this area. To establish a geological-geophysical prospecting model for deep rare earth prospecting in this area, a combination of exploration techniques and methods suitable for the deep exploration of rare earth deposits in this area were selected through multiple geophysical exploration technology experiments on the known geological profiles. The distribution range of the underground Mesozoic Xishan alkaline complex was roughly determined through gravity survey and high-precision magnetic survey. The ore body outcrop was delineated through ground-based gamma spectrometry, and the deep ore body characteristics were revealed through drilling. Finally, this study developed an integrated geophysical exploration method including gravity-magnetic joint delineation of rock masses, radioactive positioning for ore body outcrops, and deep drilling. By using this exploration model, one super-large rare earth deposit was discovered in this area, providing a reference for the exploration of rare earth deposits in the surrounding area.

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Application of audio magnetotellurics in the study of the subsurface water-bearing properties of the Santunhe area, Xinjiang
YANG Ming-Yuan, ZHANG Han-Xiong, MA Chao, YANG Hai-Lei, ZHU Wei
Geophysical and Geochemical Exploration    2023, 47 (6): 1441-1449.   DOI: 10.11720/wtyht.2023.1574
Abstract104)   HTML6)    PDF (5344KB)(262)      

Audio magnetotellurics (AMT) is widely used for energy and mineral explorations because of its high exploration efficiency and high vertical resolution. Using a three-dimensional (3D) inversion algorithm based on data space, this study performed 3D inversion of the AMT data collected from geothermal exploration in the Santunhe area of Xinjiang. As indicated by the inversion results, the 3D inversion avoids the influence of inhomogeneous geobodies on the survey lines in the study area and yielded very rich and intuitive 3D geoelectric anomalies. In combination with the geological data and the 3D inversion results, this study analyzed the subsurface electrical properties of the study area and the formation water-bearing properties related to geothermal reservoirs, and finally inferred several favorable areas for geothermal reservoirs from the geothermal accumulation patterns of the study area.

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A review of thirty years of airborne geophysical surveys in the Qiangtang Basin and future prospect
ZHOU Dao-Qing, XIONG Sheng-Qing, WANG Bao-Di, CAO Bao-Bao, GUO Zhi-Hong, HU Yue, ZHENG Yu-Zhou, ZHAO Rui, WEI Yan-Yan, XIAO Meng-Chu, HU Xia-Wei, YAN Qiao-Juan
Geophysical and Geochemical Exploration    2024, 48 (2): 287-295.   DOI: 10.11720/wtyht.2024.1413
Abstract209)   HTML14)    PDF (7354KB)(258)      

Airborne geophysical surveys, characteristic of being green, economical, efficient, and subjected to less influence by surface factors, serve as the one of most effective means of basic surveys and scientific research on the Qinghai-Tibet Plateau. This study reviewed the progress in the airborne geophysical surveys in the Qiangtang Basin of the Qinghai-Tibet Plateau in the past thirty years, systematically summarizing the progress and geological interpretation results of comprehensive airborne geophysical surveys in the basin. Furthermore, this study presented research progress and understanding of major basic geological issues of the basin, such as the basin's boundaries, central uplift zone, basement properties, deep structures, and cover characteristics, as well as the identification of favorable structural areas for oil and gas exploration. Finally, based on an analysis of the developmental trends of airborne geophysical surveys in the Qiangtang Basin, this study proposed opinions and suggestions for key research directions in the future.

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Design and implementation of key technologies for real-time three-dimensional ground-penetrating radar
YIN Da, XIN Guo-Liang, SUN Xue-Chao, ZHANG You-Yuan, ZHANG Qi-Dao
Geophysical and Geochemical Exploration    2024, 48 (1): 194-200.   DOI: 10.11720/wtyht.2024.1030
Abstract162)   HTML0)    PDF (3013KB)(243)      

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

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Improvement in active-source surface wave acquisition device and its application in subway construction exploration
QIN Chang-Chun, WANG Guo-Shun, LI Jing
Geophysical and Geochemical Exploration    2024, 48 (1): 264-271.   DOI: 10.11720/wtyht.2024.1132
Abstract85)   HTML1)    PDF (8905KB)(240)      

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

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Application of comprehensive geophysical prospecting in exploration of the Duhu copper deposit in Xinxing County
HE Jun-Fei
Geophysical and Geochemical Exploration    2024, 48 (2): 375-381.   DOI: 10.11720/wtyht.2024.1101
Abstract188)   HTML11)    PDF (5778KB)(238)      

Since individual geophysical exploration methods suffer the multiplicity of solutions, comprehensive geophysical prospecting has been extensively applied in deep ore prospecting presently. This study conducted the geological exploration of the Duhu porphyry copper deposit in Xinxing County using multiple geophysical methods such as high-precision magnetic survey and controlled source audio-frequency magnetotellurics (CSAMT). It was inferred that the CSAMT-derived medium-low resistivity anomalies and the low-gentle anomalies derived from the high-precision magnetic survey serve as significant prospecting indicators. Satisfactory results were achieved in follow-up verification of the anomalies. Specifically, copper, molybdenum, silver, and gold mineralized bodies with a cumulative thickness of 178.2 m were identified in a 1 000 m deep borehole, with the highest copper grade of 1.45%. The application of comprehensive geophysical prospecting holds great significance in guiding the exploration of porphyry copper deposits in western Guangdong.

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Fine-scale prospecting targets of skarn iron deposits in the Pandian gravity-magnetic anomaly zone of northwestern Shandong Province: Insights from deep prospecting using the wide-field electromagnetic method
GUO Guo-Qiang, LI Ya-Dong, WANG Yang, YU Jia-Bin, WANG Run-Sheng, GAO Xiao-Feng, ZHANG Da-Ming, HU Dong-Ning, FANG Lei, GUO Wei-Fang
Geophysical and Geochemical Exploration    2024, 48 (2): 327-333.   DOI: 10.11720/wtyht.2024.1157
Abstract133)   HTML4)    PDF (4258KB)(237)      

Significant aeromagnetic and gravity anomalies were found in the ultra-deep coverage zone of the Pandian area in the northwestern Shandong Province. Through systematic verification of gravity and magnetic anomalies, a breakthrough in prospecting for deep skarn iron deposits has been achieved through several boreholes around the Pandian gravity-magnetic anomaly zone. However, the gravity-magnetic anomaly zone spreads extensively and its characteristics cannot directly indicate the prospecting target, thus some boreholes failed to find ores or revealed poor ore-finding conditions. Hence, to accurately delineate the ore-forming location in the gravity-magnetic anomaly zone and achieve a further breakthrough in ore prospecting, this study conducted the wide-field electromagnetic (WFEM) sounding in the verified Pandian gravity-magnetic anomaly zone. Combining the drilling verification, this study delineated the deep ore-forming interval of skarn iron deposits in the deep coverage zone and the favorable structural plane for ore-forming, suggesting the deep fine-scale prospecting targets.

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Advances in research on the distributed optical fiber acoustic sensing system in the field of geophysical exploration
ZHOU Shao-Yu, BAO Qian-Zong, SHI Wei
Geophysical and Geochemical Exploration    2024, 48 (2): 411-427.   DOI: 10.11720/wtyht.2024.1304
Abstract205)   HTML5)    PDF (7793KB)(234)      

Distributed acoustic sensing (DAS) technology, one of the most advanced sound field detection technologies, can achieve distributed, long-distance, and high-precision real-time detection of the ambient vibration and sound field information interacting with optical fiber. The optical fiber exploration system of the DAS technology solves the problems of high cost and deployment difficulty of conventional geophones in complex geological environments. In recent years, the DAS technology has experienced rapid development, especially in monitoring application scenarios that require long-term and large-scale deployment. However, its systematic understanding is insufficient due to divergent research results. To further understand the research advances of the DAS technology in geophysical exploration for more effective subsequent research, this study systematically classified and summarized the development history of the DAS technology and its recent research results in geophysical exploration based on the oil and gas, marine, and environmental engineering application scenarios through literature research. This study focused on the development process of the DAS technology in different directions, the research advances in data processing, and relevant literature with specific results. Finally, this study generalized the development trend and urgent problems of the DAS acquisition system, analyzing the DAS development prospect.

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Chronology and geochemical characteristics of trachytes in the Tiaojishan Formation, Xuanhua Basin, northwestern Hebei Province, and their geological implications
YANG Ji-Yuan, HU Xin-Zhuo, ZHOU Jing, QI Peng-Chao, LI Ze-Yang, MENG Jia-Bao, XU Fan, ZHANG Hui-Bin, QI Hui-Yun
Geophysical and Geochemical Exploration    2024, 48 (1): 1-14.   DOI: 10.11720/wtyht.2024.2503
Abstract197)   HTML14)    PDF (8237KB)(221)      

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

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Application of high-density electrical resistivity tomography and audio magnetotellurics for groundwater exploration in the karst area in southwestern China
XIA Shi-Bin, LIAO Guo-Zhong, DENG Guo-Shi, YANG Jian, LI Fu
Geophysical and Geochemical Exploration    2024, 48 (3): 651-659.   DOI: 10.11720/wtyht.2024.1237
Abstract165)   HTML5)    PDF (5894KB)(221)      

Huize County of Yunnan Province is situated in the karst area in southwestern China, where karst groundwater is its primary water source. To conquer local difficulties in drinking water, this study constructed a conceptual model of groundwater occurrence by fully investigating the hydrogeological conditions of the Huize area. Moreover, this study evaluated the applicability and optimal combination of geophysical methods based on the measurement results of petrophysical properties. According to the actual local needs, this study deployed a comprehensive profile combining high-density electrical resistivity tomography (HDERT) and audio magnetotellurics (AMT) in Tuogu Village, Huize County. The groundwater enrichment site was delineated relying on resistivity anomalies, effectively guiding the layout of boreholes. The boreholes achieved the maximum single-borehole water yield of 20.76 m3/d, thus effectively alleviating the local drinking water problem. The HDERT-AMT combined exploration method proves to be optimal for prospecting for groundwater in carbonate rock areas. HDERT can accurately characterize weathered layer thicknesses, bedrock boundaries, fissure evolutionary degrees, and water-bearing properties of strata, constraining groundwater recharge channels, thus counteracting AMT's defects for identification of near-surface stratigraphic structures. AMT can accurately reflect the spatial structures of fracture zones and the macrostructures of strata, limiting the boundary conditions (aquicludes) of water-bearing structures, thus making up for the defects of insufficient detection depths of HDERT in high-resistivity stratigraphic regions. HDERT and AMT, which are complementary to each other in terms of accuracy and depth, can be applied to identify and constrain the spatial occurrence conditions of groundwater migration, storage, and enrichment.

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Practices and future research directions of geophysical exploration for normal-pressure shale gas in complex structural areas,southeastern Chongqing
HE Xi-Peng, LIU Ming, XUE Ye, LI Yan-Jing, HE Gui-Song, MENG Qing-Li, ZHANG Yong, LIU Hao-Juan, LAN Jia-Da, YANG Fan
Geophysical and Geochemical Exploration    2024, 48 (2): 314-326.   DOI: 10.11720/wtyht.2024.1202
Abstract106)   HTML7)    PDF (7986KB)(214)      

Southern China boasts great potential for normal-pressure shale gas resources,with distribution areas primarily including the peripheral complex structural areas and the extrabasinal fold belts of the Sichuan Basin.These areas exhibit intricate surface and subsurface geological conditions,leading to poor seismic acquisition quality,low imaging accuracy,and unclear varying patterns of sweet spot parameters.This study systematically summarized the research achievements and technical advances in the seismic acquisition,image processing,and reservoir prediction for normal-pressure shale gas in southeastern Chongqing,including:①The development of variable-density 3D observation system design technique and the seismic excitation and reception technique for complex mountains with limestone surfaces,ensuring sufficient sampling of the reflected wave field in complex subsurface structures and improving data quality and construction efficiency;②The optimization of prestack seismic preprocessing technique for complex mountains,imaging techniques for complex structures in basin-margin transition zones, and imaging techniques for synclinal structures in extrabasinal fold belts,achieving resulting profiles with high signal-to-noise ratios,wide effective frequency bands,and high structural imaging accuracy;③The quantitative prediction of the thickness,formation pressure coefficient,and brittleness of high-quality shales based on research on petrophysical characteristics;the quantitative prediction of the organic carbon content,gas content,and porosity of shales based on statistical petrophysics;the quantitative prediction of fractures formed due to the superimposed effect of multi-stage structural modifications based on the paleo-stress field evolution revealed using the finite element simulation technique;and the ascertainment of the distribution patterns of the current in-situ stress field using the current stress field prediction technique developed using the combined spring model.The above breakthroughs have effectively guided the sweet spot prediction,exploration,and production of normal-pressure shale gas,providing a basis for the discovery of the Nanchuan normal-pressure shale gas field.Subsequent research should focus on more scientific and reasonable seismic acquisition techniques based on seismic reception using 5G wireless nodes,high-precision automatic image processing technologies for high-steep structures in complex mountains,and integrated geology-engineering-economy seismic evaluation methods for sweet spots.

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Exploring geological conditions for tunnel construction in hydropower engineering using a 3D resistivity method
HUANG Yao
Geophysical and Geochemical Exploration    2024, 48 (1): 281-286.   DOI: 10.11720/wtyht.2024.2602
Abstract88)   HTML1)    PDF (2923KB)(214)      

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

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Exploring electromagnetic noise suppression technologies for magnetotelluric sounding in high-interference ore districts
HAO She-Feng, TIAN Shao-Bing, MEI Rong, PENG Rong-Hua, LI Zhao-Ling
Geophysical and Geochemical Exploration    2024, 48 (1): 162-174.   DOI: 10.11720/wtyht.2024.1140
Abstract104)   HTML3)    PDF (9636KB)(213)      

Magnetotelluric sounding (MT) has been extensively applied in mineral resource exploration. However, strong anthropogenic electromagnetic interference severely constrains the acquisition of high-quality original MT data. This study provided a detailed summary of the common types of electromagnetic noise sources in China and analyzed the characteristics of electromagnetic noise they produced. By comparing the methods for MT electromagnetic noise reduction at home and abroad, this study developed a rapid and effective construction and processing technology for MT data denoising in high-interference ore districts based on actual production demands. The results indicate that Robust processing, remote reference technique, and manual selection are effective and necessary in enhancing MT data quality. Besides, theoretical calculations suggest that the distance between the remote reference stations should be set at 3.56-fold skin depth or above, as verified by the MT experiments in the ore district of the Hongze salt basin, Jiangsu Province.

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Joint inversion of geophysical data under the guidance of petrophysical properties
LIAN Sheng, CHENG Zheng-Pu, LUO Xuan, LI Jing-Jie, TIAN Pu-Yuan
Geophysical and Geochemical Exploration    2023, 47 (6): 1580-1587.   DOI: 10.11720/wtyht.2023.0032
Abstract95)   HTML2)    PDF (4905KB)(213)      

The joint processing and integrated interpretation of multi-source geophysical exploration data are indispensable to the exploration evaluation of deep geothermal resources. Joint inversion and post-inversion geological differentiation are two major hot research topics in deep resource exploration. To integrate the multi-source geophysical field information and reduce the inversion multiplicity of single geophysical fields, this study built a structural model using the stratigraphic structure information from seismic interpretation, with the prior information of petrophysical properties as a guide. This study constrained the stratigraphic geophysical parameters using the Gaussian mixture model and conducted regularized joint inversion of gravity, magnetic, and magnetotelluric data, thus achieving the coupling of multiple physical structures. Finally, this study developed the software for the joint inversion of gravity, magnetic, magnetotelluric, and seismic data. Based on the joint inversion results and electrical resistivity, this study predicted the temperature field at typical hot dry rock sites using the Arrhenius law. The forward modeling results of the theoretical model for cubic anomalies were used for the joint inversion. Compared with individual inversion, the joint inversion performs well in the spatial characterization of anomalies and the recovery of physical property values. Furthermore, the joint inversion can fully integrate multiple data on geology, petrophysical properties, and geophysics, thus well conforming to the actual conditions.

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Critical processing techniques for ocean bottom node data of the diapir fuzzy zone of the Dongfang 1-1 structure and their application
ZHANG Min, DENG Dun, LI San-Fu, SHI Wen-Ying, ZHANG Xing-Yan, ZHI Ling
Geophysical and Geochemical Exploration    2023, 47 (6): 1456-1466.   DOI: 10.11720/wtyht.2023.0006
Abstract135)   HTML3)    PDF (13508KB)(212)      

The Dongfang 1-1 structure is situated in the northern part of the central mud diapir tectonic belt of the Yinggehai Basin on the northern continental shelf of the South China Sea.The Dongfang 1-1 gas field is the first uncompartmentalized shallow gas field discovered in the Yinggehai Basin.Despite abundant oil and gas reserves in this region, the imaging of the diapir fuzzy zone has been a critical factor restricting oil and gas exploration in this region.The original streamer-based seismic data,through multiple rounds of multi-company reprocessing,still failed to effectively image the diapir fuzzy zone.Therefore,the second acquisition of three-dimensional ocean bottom node(OBN) seismic data was conducted in this region.According to the geological conditions and the characteristics of OBN data in this region,this study proposed several critical processing techniques,including OBN preprocessing,multi-component joint shear-wave noise suppression,wavelet-domain dual-sensor summation,and full-waveform-inversion(FWI) high-precision velocity modeling.These techniques effectively improved the imaging of shallow fault structures and middle and deep diapir fuzzy zones,thus providing reliable fundamental data for the subsequent target evaluation.

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Comprehensive geogas anomalies in the Hongling area of Hami, Xinjiang: Characteristics and implications for prospecting
HAN Ruo-Pu, ZHOU Si-Chun, WANG Deng-Hong, LIU Xiao-Hui, CHEN Shou-Bo, WU Jian-Xin
Geophysical and Geochemical Exploration    2023, 47 (6): 1657-1664.   DOI: 10.11720/wtyht.2023.0297
Abstract72)   HTML3)    PDF (4499KB)(203)      

In recent years, several pegmatite veins have been discovered in the Hongling area of Hami, Xinjiang, suggesting a promising prospect for pegmatite-type rare metal deposits. In this study, two long profiles crossing the main pegmatite veins were deployed in the area, and the integrated geogas prospecting technology was applied to evaluate the ore-bearing properties of the main pegmatite veins. Rapid soil X-ray fluorescence measurements performed by a handheld X-ray fluorescence instrument were used to evaluate the ore-bearing properties of the top or exposed parts of the pegmatite veins. The dynamic geogas prospecting method was employed to obtain the deep mineralization information of the pegmatite veins for evaluating their deep ore-bearing properties. The results show that many pegmatite veins in the Hongling area exhibit mineralization manifestations on their surfaces and in deep parts. Therefore, they are worthy of further prospecting work.

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Design and implementation of a geochemical field sampling system based on mobile GIS
ZHOU Yi-Ning, GAO Yan-Fang, CHANG Chan, ZHANG Bi-Min
Geophysical and Geochemical Exploration    2024, 48 (1): 201-209.   DOI: 10.11720/wtyht.2024.2410
Abstract112)   HTML1)    PDF (4751KB)(201)      

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

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Evaluation of the primary soil fertility indices for the agricultural area of Yongqing County, Hebei Province
HU Qing-Hai, LI Jun-Hua, WANG Xue-Qiu, YI Ming-Xuan, WU Hui, TIAN Mi
Geophysical and Geochemical Exploration    2023, 47 (6): 1611-1619.   DOI: 10.11720/wtyht.2023.1589
Abstract81)   HTML3)    PDF (2213KB)(201)      

Yongqing County, as a pivotal pollution-free vegetable production base in the Beijing-Tianjin-Hebei region, has made significant contributions to ensuring the food safety of this region. However, there has been no systematic and comprehensive evaluation of Yongqing County's soil fertility, hindering the sustainable development of its green food industry. This study collected 338 soil samples from the arable layer (depth: 0~20 cm) throughout the county, including 155 from dry land, 84 from vegetable plots, and 99 from garden plots. Four soil nutrient elements including organic matter, total nitrogen, available phosphorus and potassium were determined using these samples. The results show that: The average contents of organic matter, total nitrogen, available phosphorus, and rapidly available potassium in the soil samples from Yongqing County's arable layer were 5.29×10-3, 0.78×10-3, 41.8×10-6, and 197×10-6, respectively. The soil fertility generally exhibited deficient organic matter and total nitrogen and abundant available phosphorus and potassium. In addition, the soil fertility of Yongqing County was graded and evaluated according to China's agricultural standard Green food-Environmental quality for production area (NY/T 391—2021). For land-use types like dry land, vegetable and garden plots, their organic matter and total nitrogen contents were mostly at level Ⅲ, and available phosphorus and potassium contents were primarily at level Ⅰ. The soil nutrient contents differed significantly in spatial distributions. Specifically, Longhuzhuang, Liujie, and Yangmazhuang townships in the southwest generally had higher soil nutrient contents than Caojiawu Township, Hancun and Lilancheng towns in the northeast. To efficiently develop the green food industry, Yongqing County needs to apply fertilizers scientifically and properly according to land-use types and actual planting situations and considering the soil texture and natural geographical factors. The specific measures are as follows: increasing the organic matter and total nitrogen contents in the soil by applying more organic and nitrogen fertilizers; applying more phosphate and potassium fertilizers to soil lacking available phosphorus and potassium, otherwise, the application of such fertilizers should be controlled.

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Critical factors in microtremor-based exploration at a depth of thousands of meters
QI Juan-Juan
Geophysical and Geochemical Exploration    2024, 48 (3): 777-785.   DOI: 10.11720/wtyht.2024.1358
Abstract171)   HTML3)    PDF (6323KB)(201)      

To explore the critical factors influencing the results of microtremor-based exploration at a depth of thousands of meters,this study conducted experiments using triangular arrays based on spatial autocorrelation(SPAC) and extended SPAC(ESPAC).Focusing on factors such as array size,acquisition unit frequency,and acquisition duration,this study explored the frequency band ranges corresponding to different array sizes,the arrangement of arrays in kilometer-depth exploration for obtaining both deep and shallow data,and the improvement in deep resolution.Based on the analysis and discussion results,this study established a parameter-setting system to improve the accuracy of exploration at a depth of thousands of meters.

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Technical methods for integrated geogas survey and their applications in the exploration of pegmatite-type rare metal deposits
ZHOU Si-Chun, WANG Deng-Hong, LIU Xiao-Hui, WANG Ya-Dong, WEN Chun-Hua, HU Bo, WANG Guang-Xi
Geophysical and Geochemical Exploration    2023, 47 (6): 1627-1634.   DOI: 10.11720/wtyht.2023.0293
Abstract77)   HTML2)    PDF (4268KB)(196)      

The integrated geogas survey is a prospecting technology that integrates geogas survey and X-ray fluorescence measurement for exploring concealed ores based on the prospecting needs of pegmatite-type rare metal deposits. This technology utilizes handheld X-ray fluorescence instruments for rapid measurement to capture secondary or primary halos on the surface, enabling the evaluation of the occurrence positions, strikes, and extension lengths of ore-hosting pegmatite veins on the surface. Moreover, it employs a dynamic geogas survey to capture deep mineralization information for evaluating the deep ore-bearing potential and extension depths of the pegmatite veins. This study demonstrated the main technical methods of the integrated prospecting technology and the application cases of ore prospecting supported by relevant projects in different geochemical landscape environments, in order to provide reference for the extension and application of this method and subsequent prospecting word in similar landscape areas.

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Application of geophysical exploration technologies for channel at sea
TIAN Pei-Xian, CHEN Wei-Jian, LIN Qi-Hui, ZHOU Wei-Bin
Geophysical and Geochemical Exploration    2023, 47 (6): 1450-1455.   DOI: 10.11720/wtyht.2023.0175
Abstract76)   HTML5)    PDF (1980KB)(195)      

Prior to the construction of an offshore channel, it is necessary to acquire data on the water depth and seabed sediments within the channel, aiming to determine appropriate dredging equipment and processes. Based on the mutual verification of data from existing tidal stations, offshore boreholes, and different exploration technologies, this study determined accurate water depth, seabed topography, and the thicknesses and distributions of sediments in both soft and hard oil layers utilizing the multibeam sounding and sub-bottom profiling techniques. Accordingly, this study summarized the technical measures, as well as the inversion characteristics of soft and hard soil layers of sediments, for offshore channel exploration. The obtained results are beneficial for the economical and efficient offshore channel exploration in sea areas with large waves using the multibeam sounding and sub-bottom profiling techniques. Furthermore, these results can be promoted to the exploration of subsea sediments containing toxic substances.

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A short offset transient electromagnetic method for long-distance exploration of boreholes
LI Hao-Jin, MAO Yu-Rong, ZHOU Lei, XIE Xing-Bing, GUO Qin-Ming, LIU Can, KE Xiang-Bin, HE Yi-Fei
Geophysical and Geochemical Exploration    2023, 47 (6): 1563-1572.   DOI: 10.11720/wtyht.2023.1548
Abstract76)   HTML2)    PDF (4588KB)(195)      

With an increase in the difficulty with the exploration of oil, gas, and mineral resources, conventional log and seismic methods fail to accurately evaluate the geological structures and transverse reservoir distribution far from boreholes. Therefore, this study proposed a transient electromagnetic (TEM) method for long-distance exploration of boreholes. Specifically, this study investigated the influence of key parameters of TEM devices for boreholes on the exploration distance. Based on the finite element analysis, this study calculated the responses of low- and high-resistivity geobodies under different receiver-transmitter distances, coil parameters, and exploration distances. The results showed that receiver-transmitter distances had little effect on the distance of electromagnetic exploration in the temporal domain. However, the results indicated that coil parameters had significant effects on the near-well detection distances. Under the transmitter coil parameters of 200 turns and 2A current, the TEM method for boreholes was more sensitive to low-resistivity geobodies, with near-well exploration distances reaching 40~50 m and 30 m for low- and high-resistivity geobodies, respectively. Therefore, it is feasible to conduct short-offset near-well long-distance exploration using TEM detectors with short transmitter coils for boreholes.

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Application of geogas prospecting in the prediction of deep ore-bearing properties in the Chakabeishan exploration area for lithium-beryllium deposits
Liu Xiao-Hui, Zhou Si-Chun, Wang Ya-Dong, Han Ruo-Pu, Fan Xin-Sheng
Geophysical and Geochemical Exploration    2023, 47 (6): 1643-1648.   DOI: 10.11720/wtyht.2023.0295
Abstract67)   HTML1)    PDF (4126KB)(192)      

To provide deep prospecting support for the exploration of lithium-beryllium deposits in the Chakabeishan area, two geogas prospecting profiles each with a length of 800 m were laid out in the exploration area, obtaining the content information of over 30 elements such as Li, Be, Cs, Nb, Rb, Ti, and rare earth elements in the geogas samples from 162 measuring points. Combined with the existing exploration results, the characteristics of local geogas anomalies were investigated in this study. The results are as follows: (1) Significant geogas anomalies of various elements can be detected above the concealed sections of pegmatite veins and beryllium ore bodies; (2) The combined anomalies of elements Li, Rb, Th, Cs, Pb, Nb, Ti, La, and Ce in geogas can indicate pegmatite veins, while the combined anomalies of elements Be, Rb, Nb, Cs, Pb, Ti, and Cu can directly indicate concealed beryllium ore bodies; (3) Be anomalies can indicate beryllium ore bodies within a burial depth of 480 m. This study demonstrates that geogas prospecting can be used to predict the ore-bearing properties of concealed pegmatite veins in the Quaternary coverage area.

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Application of convolution neural networks in gold exploration and prediction in Shandong Province
ZHENG Xiao-Cheng, ZHANG Ming-Hua, REN-Wei
Geophysical and Geochemical Exploration    2023, 47 (6): 1433-1440.   DOI: 10.11720/wtyht.2023.1613
Abstract99)   HTML3)    PDF (5261KB)(191)      

Rapid progress has been made in the application of big data and artificial intelligence technology in the prediction of mineral resources. However, the application of machine learning technology based on convolutional neural networks remains in the exploration and experimental stages, with few practical examples and accomplishments achieved in the exploration and prediction of mineral resources in China. This study proposed applying convolutional neural networks to the exploration of gold deposits. Specifically, a neural network was trained for 2000 rounds using measured geological, mineral, geophysical, and geochemical data collected from a mineralization region covering an area of 3×104 km2 in a gold deposit in Shandong Province. Consequently, a 1D convolutional neural network model with accuracy of 0.95 and a loss rate of 0.11 was obtained. This model was employed to predict the distribution locations of gold deposits (exploration target areas) in other unknown areas in Shandong Province, yielding encouraging outcomes.

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Geochemical characteristics and source analysis of elements from dry and wet atmospheric deposition in the middle-high mountain and hilly region of Central Yunnan
XU Lei, LI Jun, QU Qiang, WEN Fang-Ping, ZHAO Meng-Sheng, CHENG Yan-Xun, Xu Jie, WANG Hao-Yu
Geophysical and Geochemical Exploration    2023, 47 (6): 1602-1610.   DOI: 10.11720/wtyht.2023.1593
Abstract63)   HTML1)    PDF (5040KB)(189)      

Dry and wet atmospheric deposition is an essential input pathway for surface soil elements. To explore the geochemical characteristics and sources of elements from atmospheric deposition in the middle-high mountain and hilly region of Central Yunnan, this study investigated 35 dry and wet atmospheric deposition samples from three counties in Central Yunnan. The results show that nutrient elements exhibited high annual depositional fluxes, while heavy metal elements manifested low annual depositional fluxes, with their ranking as follows: TOC>Ca>K>I>F>Zn>B>Pb>Cr>Cu>As>Mo>Cd>Se>Ge>Hg. As revealed by the enrichment factors, principal components, and spatial distribution characteristics, Ca, Mo, B, As, and F originated primarily from soil dust; Cu, Cd, Pb, Cr, and Ge were mostly from anthropogenic sources, such as mining activities and coal dust; TOC, K, Se, and I came from both coal dust and soil dust, and Se was also affected by mining activities; and Hg stemmed from coal dust. Coal and copper-dominated polymetallic mineral resources spread extensively across the study area and are subjected to certain mining activities, which are intimately connected with the contents of heavy metals in the atmosphere. Therefore, targeted atmospheric monitoring should be conducted to ensure atmospheric quality and no pollution to soil.

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Application of logging-resistivity joint exploration to 3D geological modeling for environmental investigation of a certain landfill site
SONG Tao, BAO Yi, ZHAO Song, WU Jian-Feng, XU Yuan-Shun, TU Hai-Feng
Geophysical and Geochemical Exploration    2024, 48 (1): 272-280.   DOI: 10.11720/wtyht.2024.1100
Abstract67)   HTML4)    PDF (5420KB)(186)      

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

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Airborne gravity-magnetic anomalies in the Baiyunhu sag,Qiangtang Basin:Characteristics and implications for oil and gas exploration
LIU Zhong-Rong, HU Yue, FAN Zhi-Wei, HE Hong-Bing, ZHOU Dao-Qing, GUO Zhi-Hong, CAO Bao-Bao, WEI Yan-Yan
Geophysical and Geochemical Exploration    2024, 48 (1): 48-57.   DOI: 10.11720/wtyht.2024.1339
Abstract85)   HTML1)    PDF (10307KB)(183)      

Airborne gravity-magnetic data are effective in revealing the deep structures of a basin.Based on the latest airborne gravity-magnetic data,combined with field-measured physical property data,this study expounded the characteristics and geological origin of airborne gravity-magnetic anomalies present in the Baiyunhu sag.Using the airborne gravity-magnetic data,this study identified the distribution of faults and magmatic rocks in the Baiyunhu sag.Furthermore,it calculated the burial depth of the magnetic basement and the structural morphologies of the Mesozoic basement in the sag using the artificial tangent method, power spectrum analysis method,and Parker-Oldenburg iterative inversion algorithm.Additionally,this study verified the structural stratification results through the integrated interpretations of gravity and magnetism in target sections.The findings suggest that the undulations of the Mesozoic and Paleozoic sediments in the Baiyunhu sag are the primary cause of gravity anomalies,while the regional airborne magnetic anomaly primarily reflects the distribution features of the Precambrian basement.The deeply buried basement of the Baiyunhu sag,featuring continuously distributed,thick Mesozoic strata and the lack of regional faulting and magmatic activity,is scarcely affected by tectonic movements and possesses great potential for oil and gas exploration.

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Application of airborne time-domain electromagnetic method in investigation of permafrost
YU Xue-Zhong, XIE Ru-Kuan, SHAN Xi-Peng, HE Yi-Yuan, SUN Si-Yuan, LI Shi-Jun
Geophysical and Geochemical Exploration    2024, 48 (2): 342-347.   DOI: 10.11720/wtyht.2024.1246
Abstract90)   HTML2)    PDF (2651KB)(182)      

Investigating the spatial distribution of permafrost is critical for cryosphere research. At present, China's investigation concerning the spatial distribution of permafrost generally employs the detection method of ground geophysical exploration combined with logs to obtain local point or line data. Alternatively, different remote sensing models can be used to simulate and estimate the thickness of regional permafrost. This study inferred the spatial distribution of permafrost based on airborne time-domain electromagnetic (TDAEM) data and resistivity calculation results. The comparative analysis of the inference results and the known drilling data reveals an average error of 18.5% between the permafrost thickness inferred from the inversion results of TDAEM data and the result determined by borehole temperature measurements. This suggests that the TDAEM method exhibits high effectiveness and accuracy in permafrost thickness investigation. With technical advantages like high efficiency and minor topographic influence, the TDAEM method can be applied to the large-scale, rapid, and quantitative permafrost investigation in the Qinghai-Tibet Plateau and the Greater Khingan Range in northeast China. Therefore, this study provides a new and effective technical solution for a comprehensive investigation of the spatial distribution of permafrost and its influence on ecological environment changes.

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Research on the detection of underground pedestrian passage by high precision gravity exploration
YANG Min, XU Xin-Qiang, CHEN Ming, Ji Xiao-Lin, WANG Wan-Yin, ZHAO Dong-Ming, ZHOU Wei, ZHANG Yi-Mi
Geophysical and Geochemical Exploration    2024, 48 (3): 876-883.   DOI: 10.11720/wtyht.2024.0047
Abstract133)   HTML9)    PDF (3819KB)(182)      

Underground cavities with shallow burial and small scale are difficult to detect. With the development of gravity sensing technology, the accurate and rapid acquisition of micro-gravity variations brings new opportunities for detecting underground cavities, and it has wide research and practical value for the detection of small-scale underground cavities. This paper systematically analyzes and studies underground cavities from three aspects: gravity basic theory, gravity detection technology, and gravity data processing and inversion. Under given body size and gravity data accuracy, the maximum burial depth of gravity detection is calculated using the bisection method. High-density acquisition and high-precision gravity detection methods are applied to the actual detection of an underground pedestrian tunnel in a certain area of a passenger station. A set of high-precision gravity grid data is obtained. The theoretical research and measurement results indicate that existing gravity instruments have the ability to detect underground cavities. By using the minimum curvature potential field separation method, 2.5D interactive inversion and the target area recognition three-dimensional physical property fast inversion method, the approximate SN distribution and burial depth of the underground pedestrian tunnel are obtained, which is approximately 2.5~5 m, consistent with the actual situation. This study has developed a complete gravity exploration process for detecting underground cavities, and it has certain reference value.

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Application of supervised descent method for 2D magnetotelluric inversion and its application
FU Xing, TAN Han-Dong, DONG Yan, WANG Mao
Geophysical and Geochemical Exploration    2024, 48 (1): 175-184.   DOI: 10.11720/wtyht.2024.1417
Abstract113)   HTML1)    PDF (5394KB)(180)      

Traditional two-dimensional inversion methods of magnetotelluric are mature, but there are still some problems, such as reliance on the initial model, reliance on regularization parameter selection, and easy to fall into local minimum. In order to solve the above problems, this paper adopts the supervised descent method to improve the effect of two-dimensional inversion of magnetotelluric. The supervised descent method is a machine learning algorithm that learns the average descending direction to predict the residual of data. Based on the theory of supervised descent method, this paper develops the two-dimensional inversion algorithm of magnetotelluric, designs the theoretical model synthesis example to verify the correctness of the algorithm, and inverts the measured data on the Tibet Plateau to test the practicability of the supervised descent method. The inversion results of the theoretical model synthesis data and the measured data show that, compared with the traditional nonlinear conjugate gradient inversion, the inversion based on the supervised descent method has the characteristics of fast convergence speed, good inversion effect, and strong anti-noise ability.

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The application of an integrated geogas prospecting for exploring rare metal deposits in the periphery of the Renli mining area, southern Hunan Province
GAN Xue-Jun, ZHOU Si-Chun, LIU Xiao-Hui, WANG Deng-Hong, WEN Chun-Hua
Geophysical and Geochemical Exploration    2023, 47 (6): 1649-1656.   DOI: 10.11720/wtyht.2023.0296
Abstract97)   HTML1)    PDF (4319KB)(178)      

In this study, six survey lines were deployed in the Huangbaishan survey area in the periphery of the Renli mining area in southern Hunan Province. An integrated geogas prospecting was applied to explore granite pegmatite-type rare metal deposits in the study area. Based on the characteristics of soil X-ray fluorescence and geogas anomalies above the known pegmatite veins in the mining area, this study captured five soil X-ray fluorescence anomaly zones aligning with the formation trend, with the (Nb+Ta+Rb) cumulative value obtained from X-ray fluorescence measurements as the primary prospecting indicator. The Nos. 1~4 anomaly zones exhibit consistent spatial positions with the known pegmatite veins. Accordingly, this study inferred the positions, trends, and lengths of possible pegmatite veins, and a possibility of extension for the known veins based on the anomaly length. The No. 5 anomaly zone discovered on the south side of the survey area, with a length exceeding 1 000 m, serves as a new prospecting target. Geogas prospecting was conducted along the No. 11 survey line in the middle of the No. 4 anomaly zone with a length of over 1 500 m, capturing the geogas anomalies of elements Li, Be, and Nb that reflect the deep mineralization information of pegmatite veins. This confirms that pegmatite veins in the survey area have significant extensions towards the deep part.

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Application of time-varying frequency-division deconvolution in improving the prediction accuracy of thin sand bodies
ZHAO Ze-Xi, CHENG Li-Fang, FAN Dian-Zuo
Geophysical and Geochemical Exploration    2023, 47 (6): 1588-1594.   DOI: 10.11720/wtyht.2023.0009
Abstract71)   HTML2)    PDF (6233KB)(177)      

The resolution of seismic data directly influences the characterization accuracy of oil reservoirs. To improve the resolution for effective sand body prediction, this study established a frequency enhancement technology process based on time-varying frequency-division deconvolution for thin oil-bearing sand bodies occurring in complex fault blocks. First, seismic signals were separated into different time windows, in which seismic wavelets were computed to obtain their amplitude spectra. Then, the corresponding seismic wavelets were deconvoluted within each time window to obtain the reflection coefficients. Finally, high-resolution broadband seismic signals were attained by integrating the reflection coefficients of the entire seismic data and convolving high-and low-frequency wavelets. This technology process was employed to process the actual 3D seismic data from the Wennan area of the Zhongyuan Oilfield. As indicated by the results, this technology process had a significantly elevated capacity to depict a single sand body by expanding the high-frequency effective information in acquired 3D post-stack seismic data, thus yielding high-quality data for the identification of thin sand bodies. Moreover, the prediction results were highly consistent with the actual drilling results. Therefore, the time-varying frequency-division deconvolution has great potential for application in complex fault blocks.

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Investigation and suitability study of pre-selected sites for geological disposal of high level radioactive waste
LUO Hui, CHENG Wei-Ming, ZHOU Zhi-Chao, LIU Jian, LI Ya-Wei, TIAN Xiao, YUN Long
Geophysical and Geochemical Exploration    2023, 47 (6): 1479-1489.   DOI: 10.11720/wtyht.2023.0455
Abstract67)   HTML2)    PDF (3694KB)(177)      

Based on the requirement of safe disposal of high-level radioactive waste, this study aims at the pre-selection area of the preferred pre-selection area of China's high-level radioactive waste disposal bank (Beishan pre-selection area). The data and materials of geology, hydrogeology, future natural change, geochemistry, construction and engineering, environmental protection and social economy were obtained by using the methods of geology, geophysics, hydrogeology and geochemistry. The constructability of preselected rock mass is demonstrated from the perspectives of engineering construction and engineering safety. The acceptability of the preselected rock mass in transport condition, land use, social economy and humanity was confirmed. On this basis, a relatively perfect site investigation and suitability comprehensive analysis method for the disposal warehouse is established, and a candidate site for the granite disposal warehouse is selected from the computational sub-section through the comprehensive analysis of site suitability and the comprehensive comparison of site identification and safety in the lot. The research results will directly serve the site screening and site characteristics evaluation of China's high-level radioactive waste geological disposal repository, and have important practical significance to ensure the safe management of nuclear waste and the sustainable development of nuclear energy in China.

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A key seismic processing technique for deep geothermal exploration in igneous province in southern China
ZHENG Hao, CUI Yue, XU Lu, QI Peng
Geophysical and Geochemical Exploration    2024, 48 (1): 88-97.   DOI: 10.11720/wtyht.2024.1084
Abstract103)   HTML4)    PDF (15267KB)(177)      

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

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Delineation of areas with high geological background values of heavy metals in soils in Yunnan Province, China based on geological big data technology
XIAO Gao-Qiang, ZHAO Juan, CHEN Zi-Wan, SONG Xu-Feng, ZHU Neng-Gang
Geophysical and Geochemical Exploration    2024, 48 (1): 216-227.   DOI: 10.11720/wtyht.2024.1129
Abstract139)   HTML3)    PDF (4168KB)(176)      

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

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