The artificial source electromagnetic method is an important technique for deep resource exploration. The key challenge is to improve the depth and precision of detection through innovative technology. The detection mode of electromagnetic methods is evolving from far-field to near-field, and the study of near-source electromagnetic methods has become an international research frontier in recent years. Building on the recent advancements in wide-field electromagnetic methods and multi-channel transient electromagnetic methods, the short-offset transient electromagnetic method (SOTEM) has been further developed and proposed. The distinguishing features of SOTEM are its stronger signals and wider bandwidth, which are advantageous for achieving the detection requirements of greater depth and higher precision. This special issue presents eight articles covering the methods, techniques, software, and applications of SOTEM, providing strong support for the growing need for high-resolution subsurface detection.

Soil carbon pools play a significant role in regulating global carbon balance and mitigating greenhouse gases. Hence, estimating soil carbon stocks is critical for assessing the carbon cycle in terrestrial ecosystems. Based on the soil carbon data obtained from the land quality geochemical survey in the study area, this study estimated the stocks of total, organic, and inorganic carbon of various soil layers in Northwest China using the unit soil carbon amount (USCA) method. It analyzed the content characteristics of organic and inorganic carbon in soil under different soil, land use, and topographic types. The results of this study are as follows: (1) All the soil layers at depths ranging from 0 to 2 m in the study area exhibited total carbon of 10 099.4 Mt, including 1 224.8 Mt in the topsoil layer (0~0.2 m), 5 345.9 Mt in the upper soil layer (0~1.0 m), and 4 753.5 Mt in the lower soil layer (1.0~2.0 m). Inorganic carbon predominated in all the soil layers, with its proportion gradually increasing from top to bottom, whereas organic carbon was principally concentrated in the topsoil layer; (2) The high-value areas of inorganic carbon content were primarily distributed in the Huangshui Valley of Qinghai Province, and the Loess Plateau region covering the Longzhong area of Gansu Province, northern Shaanxi Province, and southern Ningxia Province. In contrast, the high-value areas of organic carbon content were chiefly distributed in the Qilian Mountains; (3) The aeolian sandy soil exhibited the lowest organic, inorganic, and total carbon contents in the topsoil and deep soil layers. The dark loessial soil and the loessal soil showed the highest inorganic carbon content in the topsoil layer. The dark felty soil and the dark loessial soil displayed the highest organic carbon contents in the topsoil and deep soil layers, respectively. Additionally, the dark felty soil had the highest total carbon content in the topsoil and deep soil layers; (4) Forests exhibited the highest organic carbon content in the topsoil and deep soil layers, and the highest total carbon content in the topsoil layer. Grasslands showed the highest inorganic and total carbon contents in the topsoil layer. Cultivated land had the highest inorganic carbon content in the deep soil layer. Bare land manifested the lowest inorganic, organic, and total carbon contents; (5) Mountains displayed the highest organic and total carbon contents in the topsoil and deep soil layers. Loess had the highest inorganic carbon content in the topsoil and deep soil layers. Plains showed intermediate carbon contents generally between those of loess and mountains. Besides, high-altitude areas manifested extremely high organic carbon content.

The grounded-source short-offset transient electromagnetic (SOTEM) method involves many parameters in field data acquisition. The selection of these parameters is closely associated with the signal quality and detection sensitivity of measured data. Based on the relevant provisions in the organization standard, Technical specification for grounded-source short-offset transient electromagnetic method (T/CGS 002—2021), issued by the Chinese Geophysical Society, numerical emulations, and practical cases, this study analyzed and expounded the selection criteria of critical parameters like transmitting source length, transmitting fundamental frequency, offset, device type, and observation component. The insights obtained in this study are significant for guiding the field construction of the SOTEM device and leveraging its detection performance.

Black soil layer thicknesses, anessential attribute of black soil,serves as a significant indicator for measuring the fertility and erosion degree of black soil. Their spatial prediction holds critical significance for supporting China's black land conservation and ensuring food security.Considering the diagnostic characteristics of black soil layers in soil system classification, this study regarded soil layers with organic carbon content higher than 6×10^-3 of soil parent materials as black soil layers.Moreover, it derived the calculation formula for the thicknesses of black soil layers relying on the exponential distribution pattern of organic carbon in the vertical soil profile. Based on the 62 896 topsoil and 15 687 deepsoil organic carbon data obtained from the multi-purpose regional geochemical survey, this study conducted detailed spatial prediction of the thicknesses of black soil layers in the Songliao Plain and analyzed their relationship with soil types and climate factors. Key findings are as follows:(1) The thicknesses of black soil layers in the Songliao Plain range from 0 to 165 cm, with a median of 23.33 cm;(2) The spatial distribution of black soil layers exhibits significant heterogeneity, characterized by thin southwestern and thick northeastern portions;(3) The black soil layers of swampy soil and peat soil manifest the largest average thicknesses between 60 and 80 cm, followed by those of typical black soil (average thickness: 56 cm) and those of albic soil and meadow soil (average thickness: 40~50 cm);(4) The spatial distributions of the thicknesses of black soil layers are closely associated with climatic conditions, primarily showing a significant negative correlation with temperature and a positive correlation with rainfall;(5) The mean annual temperature of 0 ℃ is a significant temperature threshold for the development of thick black soil layers.Above this temperature, the average thickness of black soil layers exceeds 80 cm and no longer changes with temperature. With global warming, the southward shift of this 0 ℃ is otherm may significantly influence the thicknesses of black soil layers.

Many cities or urban residential areas in central and western China reside in alluvial plains formed from piedmont alluvial fans. Hence, revealing the stratigraphic architectures and stability of alluvial fans holds critical significance for urban construction planning and rational land use. The alluvial fan in the eastern piedmont of the Liupan Mountains hosts the urban residential areas and villages of Guyuan City, with a dense population. Moreover, the alluvial fan develops several event deposits recording the activity of the alluvial fan under tectonic movements and climatic changes. Through field geological survey, optically stimulated luminescence dating, controlled source audio-frequency magnetotellurics (CSAMT), and conventional radon measurement, this study revealed the stratigraphic architecture of the alluvial fan and its two-phase event deposits (~43.33 ka B.P. and 22.92~20.72 ka B.P) since the Late Pleistocene. As indicated by the CSAMT and conventional radon measurement results, the alluvial fan still exhibits high activity under the influence of the Haiyuan and Qingshuihe faults. The results of this study provide fundamental data for crustal stability assessment, prevention and control of geologic hazards, and engineering construction in the Liupanshan area.

The Mangling ore concentration area with intense magmatic activity has become a focal area for deep prospecting in the North Qinling tectonic belt in recent years. The formation of molybdenum deposits in this area is closely related to small Late Jurassic acidic intrusions. To achieve breakthroughs in deep ore prospection within this area, this study conducted the wide-field electromagnetic sounding over the concealed Yaozhuang intrusion delineated based on gravity anomalies. The results indicate the presence of pronounced high-resistivity anomalies at depth, and it is inferred that the protruding part of the anomalies corresponds to the concealed Yaozhuang intrusion. The resistivity inversion results roughly delineated the variations in the top surface of the intrusion, with the elevations and N-S width of the top surface estimated at -300~620 m and 1300~1600 m, respectively. Drilling in the most favorable deep mineralized part confirmed the presence of the concealed intrusion and concealed molybdenum ore bodies. The results of this study demonstrate that the wide-field electromagnetic sounding method exhibits great sounding depths and high resolutions, serving as an effective method for deep ore prospecting in the Mangling ore concentration area.

Recommendation system algorithms, having recently garnered significant attention in the field of digital Earth science, are expected to be widely applied in metallogenic prediction. Traditional metallogenic prediction studies fail to fully mine the various types of semantic information in massive geoscience data. The deep interest evolution network (DIEN), as a recommendation system algorithm, can fully mine semantic information to predict user preferences. Therefore, this study employed the DIEN model as the prediction model and the semantic information extracted from bedrock interpretation as the ore-controlling elements according to the database provided by the Western Australian government. The model was trained to perform metallogenic prediction for the study area. The prediction results indicate that 92.95% of uranium ore occurrences fell within the medium-high probability zone in the prediction map, with some unknown zones also showing high prediction probabilities. After removing known uranium ore occurrences in some zones, the retrained model still yielded medium-high prediction probabilities in these zones. The results suggest that the DIEN can effectively mine semantic information in metallogenic prediction studies, and the DIEN model exhibits strong predictive capacity for the study area, providing a novel approach for metallogenic prediction studies.

In response to the increasing demand for large-scale field seismic acquisition, this study developed a low-cost multifunctional nodal rotational seismometer (RBWL) with a micro-electro-mechanical system (MEMS) sensor, considering the functionality, economic feasibility, and the ease of arrangement. The RBWL employs a low-cost and low-power MEMS sensor to acquire seismic signals, involving three-component translational motions (T_x,T_y,T_z) and three-component rotational motions (R_x,R_y,R_z). To reduce the impacts of environmental factors on measurements, the system of the RBWL automatically records real-time information including temperature and attitude while performing compensation correction on the measurement results. For real-time monitoring and data transmission at acquisition nodes, the system establishes a data transmission link integrating 4G, cloud, and client, with the measured maximum data transmission rate up to 100 Mbps. The testing of H/V spectral ratios verifies the system functions and principal performance parameters of the RBWL and its effectiveness in engineering physical exploration.

The Mianning-Dechang area in western Sichuan serves as the most important metallogenic belt of light rare earth elements (LREEs) in China. To make breakthroughs in the exploration of rare earth resources in the Dechang area, a 1:50 000 stream sediment survey was conducted in this study. The analysis of test data characteristics and the extraction of geochemical anomalies reveal that the total rare-earth oxides (REOs) in the area exhibit a pronounced enrichment pattern and that element anomalies largely overlap the spatial distribution of related geological bodies. Through comprehensive analysis using the cumulative frequency method and iterative method, this study determined the lower limits of anomalies and, accordingly, plotted element anomaly maps, with five main anomaly areas being delineated. The comprehensive evaluation of anomalies revealed four prospecting target areas: Huangjiaba, Jiaobacun, Yibasan, and Huajiaoyuan. The analysis of metallogenic geological conditions and the anomaly verification based on drilling in the Gannan area led to the discovery of three light rare earth deposits in the Huangjiaba prospecting target area, two heavy rare earth deposits in the Jiaobacun prospecting target area, two heavy rare earth deposits in the Yibasan prospecting target area, and two heavy rare earth deposits in the Huajiaoyuan prospecting target area. This study posits that the Triassic biotite moyite and biotite monzogranite in the study area are the metallogenic parent rocks of ion adsorption-type rare earth resources, with REEs primarily undergoing enrichment and mineralization in completely weathered layers. Therefore, a simple and effective prospecting pattern for "endogenous and exogenous" ion adsorption-type rare earth deposits in the Dechang area consists of analyzing the geochemical characteristics of the total REOs based on a 1:50 000 stream sediment survey, delineating metallogenic prospect areas that indicate parent rocks for REE enrichment, and selecting sections favorable for the formation and preservation of weathered crusts based on the hypergenic conditions of the enrichment areas, thus achieving the quick delineation of the prospecting target areas.

Unfavorable geobodies such as Karsts, weak soil, and water-rich areas are extensively distributed in China. Under heavy rainfall, they are prone to geologic hazards like collapse. A severe geological collapse occurred in Xiacun Town, Yushui District, Xinyu City, near the Shanghai-Kunming high-speed railway. The space around the collapsed foundation pit was limited, with many interference sources like underground pipelines. With early signals subjected to the mutual inductance effects of receiver and transmitter coils, the conventional transient electromagnetic method exhibited low detection accuracy and anti-interference ability, encountering significant shallow blind zones. To locate unfavorable geobodies in the study area and provide suggestions for the prevention and control of geologic hazards, this study innovatively applied the opposing-coils transient electromagnetic method (OCTEM), supplemented by borehole-based verification. The results show that: (1) The OCTEM exhibited high accuracy, as demonstrated by the high consistency between the geophysical exploration results and the drilling results of the study area; (2) The low-resistivity zone spread across the study area, and the low-resistivity anomalies revealed by geophysical exploration were caused by groundwater according to borehole-based verification; (3) The strata from top to bottom were composed of soft plastic silty clay, hard plastic silty clay, soft plastic silty clay, and moderately weathered limestones; (4) The subsurface micro-confined water in the collapse area surged upward, gradually eroding the soft plastic silty clay layer around the area. The static water level in the collapsed foundation pit manifested an elevation of 55.60 m, located approximately 1.4 m below the surface; (5) A groundwater channel existed under the collapse area, with soil caves formed in the limestone layer under the prolonged erosion effect of water flow; (6) Long-term groundwater extraction may expand the underground seepage zone; (7) The administrative department in charge must promptly contain groundwater in the collapse area to prevent it from further eroding the surrounding unconsolidated soil layer.

Several thermal springs associated with tectonic activity occur along the Chuhe fault zone. Except for the Bantang thermal spring at the southern end, other springs along the fault zone exhibit unideal utilization of thermal energy. This affects the development of local industries. Therefore, it is necessary to delve into the geochemical characteristics and formation mechanism of typical thermal springs along the Chuhe fault zone. The purpose is to provide scientific evidence for the rational utilization and exploration methods of geothermal resources in the thermal spring groups in the future. Therefore, this study investigated thermal springs in the Bantang, Zhaoguan, and Xiangquan areas along the Chuhe fault zone, where nine samples of thermal spring water, cold well water, and surface water were collected individually. For these samples, the composition tests of 25 indices, including anions, cations, and major and trace elements, were tested, and the hydrogen and oxygen isotope values were determined. The analyses of the 25 measured indices, along with the investigation of the geothermal water source and controlling factors through hydrogen and oxygen isotope tracing, indicate that the thermal spring water in the three areas tends to be of the CaSO₄ type and is all closely related to the interactions between groundwater and surrounding rocks. The thermal spring water, cold well water, and surface water in Bantang and Zhaoguan show consanguinity, with geothermal water being directly recharged with local precipitation and surface water. In contrast, the thermal spring water, surface water, and cold well water in the Xiangquan area show weaker consanguinity, indicating different sources for the underground cold water runoff and geothermal water. This should be noted when determining the primary factors controlling the thermal spring in this area. The temperatures calculated using a chalcedony geothermometer were close to the temperatures of the hot water recovered on the surface. In contrast, the temperatures calculated using a quartz geothermometer approached the temperatures of deep geothermal reservoirs. The results of this study preliminarily reveal the geochemical characteristics, recharge relationships, and water-rock interactions of thermal spring water in the Chuhe fault zone and propose effective geochemical geothermometers for the study area. These contribute to deeper insights into the mechanisms and controlling factors of the thermal springs along the fault zone, as well as providing practical value and a methodological model for enhancing thermal spring functionality and geothermal resource exploitation and utilization in the future.

The extended spatial autocorrelation (ESPAC)-based microtremor exploration(natural-source surface wave exploration) technology has been extensively used in shallow formation exploration owing to its simplicity,efficiency,and accuracy.However,the imaging effect of dispersion energy extracted based on the ESPAC method is unsatisfactory in practical applications.In particular,different observation array arrangements influence the extraction of dispersion curves from collected data.By investigating the imaging principle of the ESPAC method,this study conducted the simulation experiment of natural-source microtremor recording through ambient noise simulation.It compared the differences in dispersion energy under various dominant frequency distributions of wavelets.Moreover,it quantitatively analyzed the influence of different station arrangements and acquisition durations on the imaging quality of dispersion energy.The comparative study reveals the imaging patterns of the ESPAC method in shallow surface exploration.The ESPAC method can maximize the imaging quality of dispersion energy in the fundamental mode while considering both efficiency and exploration costs.The results of this study were applied to engineering application cases to further verify the simulation results.

Tight sandstones serve as significant oil and gas reservoirs.Their lithofacies identification can assist in further understanding the developmental characteristics of reservoirs.Combining core observations with log data processing,this study analyzed the lithofacies and sedimentary microfacies characteristics of tight sandstones in the Xinchang area and the internal relationships between lithofacies and sedimentary microfacies.Moreover,it constructed a random forest classification model with geological implications through data mining of sedimentary microfacies characteristics.The results show that:(1)Tight sandstones in the Xinchang area can be classified into seven typical lithofacies,including mudstone,siltstone with ripple lamination,massive fine sandstone,fine sandstone with parallel bedding,massive medium- to coarse-grained sandstone,and medium- to coarse-grained sandstone with parallel/cross bedding;(2)The sedimentary microfacies in the Xinchang area consist primarily of subaqueous distributary channel,subaqueous distributary bay,river-mouth bar,and prodeltaic mud,which are closely associated with the sedimentation of lithofacies;(3)In the classification model,the relative centroid(RM),root mean square deviation(GS),average median(AM),and average slope(M) of the gamma ray(GR) curve can be used as the characteristic parameters of sedimentary microfacies to increase the number of characteristics in the dataset;(4)Considering the characteristics of sedimentary microfacies,especially the energy and turbulence of water bodies,can significantly enhance the performance of the random forest classification model.Overall,the results of this study provide a novel approach for lithofacies identification using machine learning methods and a significant reference for oil and gas exploration in tight sandstones.

Underground research laboratories (URLs) for the geological disposal of high-level radioactive waste serve as critical facilities for verifying the safety and suitability of the sites of potential disposal repositories and for developing disposal technologies. URLs are irreplaceable in many aspects such as the siting and system design of potential disposal repositories, the development of the theories and technologies for disposal engineering, the safety and characteristic assessments, full-scale field tests, and on-site demonstration. This study highlights the definition, classification, and functions of URLs and categorizes existing primary URLs both in China and abroad. URLs are generally categorized into general URLs (first generation) and site-specific URLs (second generation). The construction of disposal repositories in China has progressed from national, regional, and site screening to site evaluation and to URL construction. The authors of this study proposed the concepts of "site-specific URLs" and "third-generation URLs" in 2010 and 2014, respectively. Furthermore, the Beishan URL-the world's first site-specific URL for the geological disposal of high-level radioactive waste-has been built. This study introduces the siting process, planning, positioning, and functions of the Beishan URL, as well as the functions of primary scientific experiments and main field experiments conducted during its construction. The results of this study serve as a guide for future siting and R&D of disposal repositories.

Over recent years, large-scale geochemical surveys on a scale of 1:25,000 have been conducted in the eastern Kunlun region for geological prospecting. These surveys, characterized by the rapid and accurate location of anomaly sources, have been widely applied in mineral explorations, yielding encouraging mineral prospecting results. Using 1:25,000-scale stream sediment surveys, this study delineated 12 geochemical integrated anomalies of the element associations of Cu, Co, and Ni in the Hedong area, Mangya City, eastern Kunlun. These anomalies include one integrated anomaly dominated by Co, where various element anomalies exhibit high-degree overlap, relatively large scales, high intensity, and distinct concentration zoning. The Co anomaly is closely associated with the Ordovician Qimantag Group, demonstrating a high degree of spatial consistency. The subsequent anomaly verification reveals four cobalt mineralized zones within anomalies GA16, GA26, GA11, and GA39, with three ore bodies and multiple mineralized bodies of cobalt being identified within the mineralized zones. The comprehensive analysis indicates that the eastern Kunlun region enjoys excellent metallogenic geological conditions and favorable geochemical characteristics, with promising prospecting results having been achieved. Therefore, this region has the prospecting potential of medium to large-scale cobalt deposits.

The telecontrol electrode array is a new type of electrode array for power supply and observations that utilizes the carrier waves of the power-supply and measurement wires used in conventional electrical prospecting to transmit signals. By remotely controlling a series of coded electrode switches between various wires and their connections, this array allows for orderly power supply and measurements. This array enables flexible spacings between electrodes and the gradual expansion of the distances between power supply electrodes via remote control, thus achieving a gradient-based sounding array. The borrowing-line remote controller can be used combined with single-channel, multi-channel, and high-density resistivity instruments, and the combined arrays can perform 2D/3D electrical prospecting more effectively. Followed by the brief introduction of the principle of the borrowed-line telecontrol electrode array, this study discusses the applications and examples of this array and several combined arrays in the resistivity method and induced polarization (IP).

Accurately identifying faults is crucial for the exploration and exploitation of oil and gas fields,and further fault extraction based on this holds critical significance for later comprehensive research.At present,the commonly used fault extraction techniques primarily include automatic fault tracking,fault slice interpretation,and manual interpretation.However,these fault extraction techniques and their application in practical exploration and exploitation often face the following challenges.Automatic fault tracking based on an attribute volume often extracts faults with low accuracy and poor continuity,whereas fault slice interpretation and conventional manual interpretation require long work cycles.Hence,this study proposed a fault extraction technique based on structure-oriented filtering.First,the original poststack seismic data were processed through structure-oriented filtering to improve the quality of fundamental data and enhance the fault boundary features.Then,a relative isochronous model was established based on the filtered data volume,with sensitive attributes that can characterize faults extracted.Finally,based on the analysis of fault combination relationships,a comprehensive interpretation method combining plane and profile views was employed to extract faults.The technique proposed in this study has been successfully applied to a certain block of SB.As indicated by the application results,the proposed technique exhibits higher reliability,accuracy,and efficiency compared to the three commonly used fault extraction techniques, thus demonstrating high applicability.

The Salt Lake geothermal field in Yuncheng City, Shanxi Province, China lies beneath a densely populated urban area, posing significant challenges to further geothermal exploration and extraction. Based on the distribution of geothermal gradients in the geothermal field, which are higher in the southwest and lower in the northeast, a NE-trending microtremor survey profile was arranged in the southern part of Yuncheng City, aimed at investigating the deep geothermal reservoir structure and NW-trending structures in the geothermal field. The 2D velocity structure profile reveals a pronounced low-velocity anomaly in the eastern part, which is supposed to be induced by the fault fracture zone formed by multiple NW-striking tensional faults. Spatially, this concealed fault zone roughly corresponds to the low-geothermal gradient anomaly in the northeastern Salt Lake geothermal field, suggesting that this fault fracture zone might facilitate the rapid infiltration of cold surface water, thereby lowering the temperature of deep rocks in the northeastern part, leading to the formation of a large-scale low-temperature anomaly zone. Additionally, the faults identified by the microtremor survey can be traceable and confirmed in a controlled source reflection seismic profile in the study area, demonstrating the complementary nature of the two methods. This study further reveals the deep geothermal structures of the Salt Lake geothermal field based on previous efforts. This study provides more valuable bases and guidance for future exploration and resource evaluation of geothermal fields in the region while also demonstrating the effectiveness and superiority of the microtremor survey method in research on urban geothermal resources.

In practical detection operations using ground-penetrating radar (GPR), factors such as environmental noise and instrument errors frequently cause signals to be mixed with substantial noise, seriously reducing signal quality and the reliability of analytical results. To address this issue, this study proposed a time-frequency peak filtering method combined with minimum mean cross-entropy (TFPF-MMCE) for denoising GPR signals. This method combined time-frequency peak filtering with the cross-entropy function, enabling effective noise suppression and precise preservation of valid signals through precise optimization of the time-frequency representation, thereby significantly improving the quality of GPR signals. Numerical simulation and field GPR experiments validated that the TFPF-MMCE method exhibited a high noise removal capability and, thus, can effectively eliminate random noise while significantly improving signal clarity and reliability. Compared to traditional denoising methods, TFPF-MMCE shows significant advantages in denoising effectiveness and noise resistance stability, suggesting promising application potential and practical value in the field of GPR signal processing.

In the past two decades, high-sensitivity ring laser gyroscopes have demonstrated the potential of rotational observation data in global seismology. Commercial fiber-optic three-component rotational seismometers have heralded a new development phase of rotational seismography. Field experiments for high-sensitivity portable fiber-optic rotational seismometers in China remain in the initial stage, whereas their relevant data analysis results have been obtained internationally. This study elucidated the co-located observation experiments on six components (6C, including three components of translational motions and three components of rotational motions) of an active source and a natural earthquake, involving experimental schemes, implementation steps, and subsequent data analysis. Moreover, this study revealed the primary factors influencing the experiment results by comparatively analyzing the similarities and differences of experiments. Fiber-optic rotational and conventional seismometers need to be fixed on the same rigid panel to ensure the consistency of received signals. Besides, proper ground coupling and burial processing contribute to high-quality experimental data. The experimental results indicate that water bodies will affect surface wave manifestation and P-wave clarity. These findings, enriching the practical experience in seismic rotational observation experiments, serve as a reference for the design of subsequent rotational observation experiments, thereby assisting in completing the experiments and obtaining higher-quality data. In terms of data application, this study optimized and substantiated the feasibility of the preprocessing scheme, with the backazimuth calculation accuracy improved by 58.8° and 50° at the two active-source measuring points, and by 24.1° and 29.4° at the two passive-source measuring points. The application of six-component seismic data from a single seismic station suggests that additional observation of rotational components can acquire more seismic wavefield information, thus the observation of rotational components can be employed to enhance the utilization of China's massive seismic observation data. Overall, fiber-optic rotational seismometers broaden the boundary of seismic monitoring technology, boost seismology research, and create new possibilities for future earthquake research.

The geomagnetic field is a vector field in space. However, traditional marine magnetic surveys focus on geomagnetic field intensity, failing to fully acquire and utilize rich information about the geomagnetic vector field. Given this, this study developed a towed marine geomagnetic vector measurement system. This system was designed to operate in dynamic marine conditions and ultimately acquire geomagnetic vector field data within the geographical coordinate system. Through sea trials of the system, grid line and repeat line measurements were obtained. After preprocessing the collected data, the measurement accuracy of repeat lines and crosspoints was better than 6.7 nT and 6 nT, respectively. The results of the sea test indicate that the measurement system has the preliminary ability to measure the geomagnetic vector field at sea, and it can be applied to geomagnetic field measurement tasks near or far sea, obtaining richer geomagnetic field information.

To evaluate the resource potential of the Jinchanshan mining area, this study conducted analysis and tests of metal element content in soil samples from two geochemical profiles using the electro-adsorption method. By combining the geological conditions of the mining area, this study revealed pronounced positive geochemical anomalies of Au, Ag, Cu, Pb, and Zn above the known gold deposits. The anomalous areas corresponded well with deposits, confirming the effectiveness and feasibility of the electro-adsorption method in the study area. The study identified geochemical anomalies Ⅰ and Ⅱ to the west of the Guaibanggou-Yangpo-Xiaoxigou mineralization zone in the first geochemical profile. Along the second profile, located between the Guaibanggou-Yangpo-Xiaoxigou and Nandawa-Limazigou-Loufengmao mineralization zones, anomalies Ⅲ and Ⅳ were observed at the westernmost end. The comprehensive geological analysis of the mining area indicates that the Ⅰ and Ⅲ anomaly zones exhibit favorable geological conditions for mineralization, serving as play fairways. The play fairway prediction conducted in this study provides targets for future exploration in the mining area.

With the application of high-precision,high-density 3D seismic technology and significant improvements in acquisition efficiency,the volume of data from nodal seismic data acquisition has expanded sharply.This leads to growing demands for the quality monitoring of nodal seismic acquisition.Especially,the lag in the synthesis of common shot gather data in node data has affected the quality monitoring and processing efficiency of seismic data.Therefore,the demand for quality control technology has become increasingly prominent in nodal seismic data acquisition.By delving into technologies including the visual monitoring of pre-acquisition node states,node data synthesis,and seismic data quality monitoring,this study independently developed a quality monitoring platform for nodal seismic data acquisition,enabling quality control for the whole nodal seismic data acquisition,involving equipment status,data synthesis,and data quality control.This platform has achieved satisfactory application results in a practical seismic data acquisition project.

A variogram serves as a crucial tool for quantifying spatial correlations. However, existing variogram fitting methods often yield unstable results. This study proposed an automatic variogram fitting method based on deep learning, aiming to enhance the precision and stability of automatic fitting. The fitting of the experimental variogram is essentially a nonlinear optimization problem, which involves optimizing the matching between the experimental and theoretical variograms. The proposed method generated substantial training datasets using several sets of theoretical variograms with varying parameter values for training and learning in deep neural networks. The trained model was then used for the automatic fitting of the experimental variogram. Multiple sets of experimental results demonstrate that based on the robust fitting capability of deep neural networks, the proposed method manifested superior fitting stability and computational efficiency compared to the least squares method, providing a novel approach for automatic variogram fitting in geostatistics.

This study performed forward modeling for the short-offset transient electromagnetic (SOTEM) responses of a three-dimensional geoelectric model using the three-dimensional finite-difference time-domain method. The results reveal that: (1) The attenuation curves of the E_x responses from the electric field above the goaf or collapse column were above the background response curve at early times but below it at later times; (2) A shorter offset corresponded to a higher relative anomaly of ∂B_z/∂t response signals. Increasing the length of the transmitting source could enhance the signal intensity while slightly decreasing the relative anomaly; (3) In the case of survey lines close to the transmitting source, the overall ∂B_z/∂t responses of the goaf or collapse column were weaker than the background responses. For survey lines away from the transmitting source, the overall ∂B_z/∂t responses of the goaf or collapse column were stronger than the background responses. In summary, the calculation results demonstrate significant implications for understanding the ability of the SOTEM method to detect typical water-rich bodies in coal mines, laying a theoretical foundation for the parameter selection of SOTEM devices and their generalized application in the coal sector.

Within a coal mine in Peixian County, Xuzhou City, brick-red Paleogene and Neogene strata were deposited in the faulted basin during the Cenozoic, with extensive Quaternary strata overlying various strata. The Quaternary, Jurassic, and Cretaceous strata exhibit thick overburden, up to over 500 m. This study explored the coal mine using the short-offset transient electromagnetic (SOTEM) method. Based on geoelectric conditions, reasonable observation parameters were designed to obtain the subterranean electric structure within a burial depth of 1500 m. Goafs were detected at a burial depth of 900 m, with their delineated boundaries aligning with the mining situation of the coal mine. The results of this study serve as a reference for detecting goafs with thick overburden in North China-type coalfields.

Non-destructive testing of the internal structural characteristics of ancient buildings is the key to preserving cultural relics.To determine the structures and internal defects of the ancient Great Wall in Linhai City,this study performed non-destructive testing of the wall structures in different orientations using a ground-penetrating radar (GPR) combining 100 MHz and 270 MHz antennas.The testing results show significant structural stratification in the ancient Great Wall.The GPR signal-reflected images reveal clear internal wall defects like pores,cracks,voids,and other hidden dangers.This study demonstrates the reliability of the GPR in detecting structures and defects of ancient walls,there by providing technical support for the structural protection of the ancient Great Wall.

Due to dense buildings and structures and insufficient drilling surveys, the construction of shield tunnels passing through urban karst formations that host dense buildings faces significant risks of surface fracturing and subsidence caused by karst development. Hence, this study employed the microtremor survey technology with strong anti-interference capability in complex environments to address this challenge. Based on the technology, it analyzed the structural characteristics of wave velocities in underground rock formations through the inversion of the apparent shear-wave velocity profile. Combined with geological drilling data, it inferred the bedrock interface, highly weathered unconsolidated formations, and karst cave anomaly zones. Key findings are as follows: (1) The apparent shear-wave velocities in the study area gradually increased from the shallow to deep formations. Formations with wave velocities above and below 300 m/s were inferred to be limestone and Quaternary formations, respectively, with the rock-soil interface at depths approximately between 10~15 m; (2) Seven low-value anomaly zones of apparent shear-wave velocities ranging from 150~240 m/s were interpreted. They were presumed to be unconsolidated formations or karst caves at depths ranging from 8~30 m. Relying on strong anti-interference and high accuracy, the microtremor survey technology can accurately identify the shear-wave velocity structures of underground profiles, lithologic interfaces of formations, unconsolidated formations, and karst cave anomalies. Therefore, the technology is effective in the geological exploration of urban dense building areas with karst development.

The transform from transient electromagnetic (TEM) field to pseudo wavefield is the basis for using the imaging technique. The TEM field follows the diffusion equation, while the pseudo wavefield follows the wave equation. These two can be transformed into each other via the Q-transform. As the integral transformation from TEM field to pseudo wavefield is ill-posed, numerical method is used to get the desired pseudo wavefield. As a result, it is often the case that the methods and parameters are need to be optimized to get a optimal pseudo wavefield. Therefore, here in this paper, we derived the analytical solution of the pseudo wavefield from the TEM field. We start from the analytical formula of TEM field, and utilize the Laplace transform to establish the analytical solution pairs. The pairs can be used to test the accuracy and stability of the numerical method, as well as examining the features of the pseudo wavefield to get an effective imaging method.

In shallow engineering investigations, the small-loop transient electromagnetic (TEM) system is challenged by limitations such as overweight equipment, significant transmitter-receiver mutual inductance, and high manpower requirements. Hence, this study introduced an improved system. Based on the opposing-coils transient electromagnetic (OCTEM) theory, this study calculated the magnetic field distribution of the generalized opposing-coils antenna device. Furthermore, it designed and developed efficient portable antennas and the supporting system (collectively referred to as the portable OCTEM system). Subsequent field experiments demonstrate that while ensuring exploration accuracy, the portable OCTEM system can enhance the investigation efficiency by effectively mitigating the transmitter-receiver mutual inductance and significantly reducing manpower requirements. This study preliminarily verifies the feasibility of the portable OCTEM system, providing a novel technology route for developing downsized shallow exploration equipment.

The Triassic strata in the Lunnan area of the Tarim Basin represent a continental deltaic sedimentary system,with sedimentary subfacies including deltaic plain,deltaic front,and prodelta.The rapid phase transition of reservoirs and the high-frequency sand-mudstone alternating deposition create thin,highly heterogeneous reservoirs,rendering high-precision reservoir prediction extremely challenging.Under the guidance of sedimentary petrology and seismic sequence stratigraphy,this study conducted comprehensive seismic and geological research.Then,based on isochronous sequence interpretation,as well as seismic facies analytical results,this study established a lithofacies model.By constraining the pre-stack geostatistical inversion process,this study determined the spatial distribution of sand bodies.The practical application demonstrates that the proposed method enhances the vertical resolution of heterogeneous,thin reservoirs while significantly reducing lateral uncertainty.The predicted results align with actual drilling and production performance data and thus can provide valuable support for the efficient exploitation of hydrocarbon reservoirs.

Seismic data processing reveals that internal multiples exhibit highly complex formation mechanisms,making their accurate identification and effective suppression a persistent challenge in geophysical exploration.Traditional methods for internal multiple suppression frequently require manual identification of subsurface reflection interfaces,making them difficult to apply to complex underground medium structures.Moreover,these methods are not only computationally cumbersome but also typically ensure only temporal and positional consistency when predicting internal multiples.The amplitude often deviates from observed values,requiring adaptive matching subtraction algorithms for effective suppression.This study developed an internal multiple suppression method based on Marchenko theory.Specifically,the wavefield relationships between the focusing function and Green’s function were constructed using the convolution and correlation reciprocity theorem of the Green’s function during data processing.The Green’s function was then solved using the focusing function,yielding either multiples or primaries constructed from the Green’s function.This method requires only the background velocity or the original data as operators during the iterative multidimensional correlation and convolution process,rendering it simple and computationally efficient. This study constructed an expression for the primary wave field using the Green’s function and the Marchenko equation.The tests using the SMAART model and actual data from the Gulf of Mexico demonstrate that the Marchenko method can effectively suppress internal multiples under the conditions of complex subsurface media.The iterative process requires no velocity information,providing significant advantages over conventional methods and great potential for application in complex underground environments where layers are difficult to distinguish.

The method of structural superimposed halo to find blind ore is a new method to find blind ore, which is based on the study of the theory of primary halo to find blind ore-the axial zoning of primary halo, and puts forward two new theories of ‘primary superimposed halo theory’ and ‘structural superimposed halo theory’. The accuracy of blind ore prediction by superimposed halo of structure is determined by the correctness of prediction marks and indexes. Based on the summary of seven common signs of structural superimposed halos in the prediction of deep blind ore deposits in more than 100 hydrothermal deposits, four important quantitative qualitative prediction signs are upgraded to quantitative prediction indicators. The structural superimposed halo prediction signs and indicators of 17 different combinations of accurate prediction of blind ore and discrimination of ore body denudation degree in the deep and periphery of the mining area are described in detail, and a practical ideal model of structural superimposed halo for predicting blind ore and discriminating ore body denudation degree is established. The common prediction signs and indicators of the model have important guiding significance for the prediction of deep blind ore in typical hydrothermal deposits, and have achieved remarkable prospecting results in more than 100 mine applications.

The successful operation of geothermal wells on the eastern margin of the Yinchuan Basin suggests a new geothermal exploration orientation around the Huanghe fault and its secondary faults. To further investigate the controlling effect of the Huanghe fault on geothermal resources in the study area and pinpoint the exploration target, this study arranged four magnetotelluric (MT) lines, obtaining 71 survey points.The preprocessing and two-dimensional inversion of MT data yielded a two-dimensional electrical structure of the study area within a depth of 10 km.Based on the previous geological, gravity, microtremor, and controllable source audio magnetotellurics(CSAMT) data in the study area, this study further interpreted the strata and fault structures of the study area.It posited that the relatively-low-resistivity zone within the high-resistivity zone of the Ordovician basement reflected by the MT lines may be the secondary-fault development site at the rear edge of the Huanghe fault, which is caused by the fragmentation and water filling of Ordovician strata, showing certain exploration potential for geothermal resources.

The Autonomous Underwater Vehicle (AUV) equipped with a magnetometer conducts underwater magnetic anomaly detection, enabling long-duration and large-scale continuous sampling. It offers advantages such as concealment, high efficiency, high practicality, wide application range, strong maneuverability, and robust endurance. To improve measurement accuracy, synchronous seabed magnetic field data is needed as a reference to counteract environmental magnetic noise. To address this, a submarine optically pumped magnetometer was developed to provide a reference for processing AUV magnetic anomaly detection data.The submarine optically pumped magnetometer consists of a magnetic field measurement unit and an acoustic release unit, capable of high-precision autonomous acquisition of the total magnetic field on the seabed, as well as underwater acoustic release and recovery. The magnetic field measurement unit includes an optical pumping probe, electronic unit, counter, battery pack, and nylon pressure chamber. The acoustic release unit includes an acoustic transducer, acoustic communication board, electro-corrosion decoupler, cement block, buoyancy block, and frame. This design addresses key technical challenges such as miniaturization, autonomous acquisition, and underwater acoustic communication.In 2022, a magnetic anomaly detection test was conducted in the offshore waters of Qingdao. The test results verified the autonomous seabed magnetic field acquisition and the release and recovery functions of the submarine optically pumped magnetometer, providing effective reference data for underwater target detection.

The Galinge iron deposit in Qinghai is overlain by deposits measuring greater than 150 m in thickness. The great burial depths of ore bodies lead to gentle magnetic anomaly morphology, making it difficult to characterize the spatial distribution of ore bodies. Therefore, this study employed three-dimensional magnetic anomaly inversion to determine the three-dimensional distribution characteristics of subsurface magnetic intensity in the study area. Given the prior information of non-magnetic surrounding rocks, the three-dimensional magnetic intensity model clearly presented the spatial distribution of the ore bodies and reflected the presence of intense magnetic bodies at depths of less than 500 m in existing boreholes. Accordingly, it can be inferred that there exist concealed ore bodies at depths exceeding 500 m in the study area. The results of this study suggest that three-dimensional magnetic anomaly inversion can effectively improve target identification, providing clear information on the horizontal positions, depths, and scales of magnetic ore bodies. The proposed inversion method can offer strong support for drilling design and reserve estimation, warranting promotion in detailed exploration of solid minerals.

Marine controlled-source electromagnetics (MCSEM) is used to explore resources such as oil and gas hydrates, as well as deep geological structures, by revealing resistivity differences below the seabed. Different excitation frequencies correspond to varying detection depths. To enhance the resistivity imaging of targets beneath the seabed, this study investigated the MCSEM-based technology for generating arbitrary-frequency waveforms to flexibly alter the excitation frequency and improve the exploration effectiveness and efficiency. Using the direct digital frequency synthesis (DDS) chip AD9833 and the joint control of a microcontroller and a complex programmable logic device (CPLD), this study achieved the generation of arbitrary-frequency waveforms with limited precision. The test results indicate that this technology can effectively enhance the spectral adaptability and flexibility of MCSEM.

Soil fertility is a significant indicator that measures the ability of soil to provide various nutrients required by vegetation and reflects the crop producing power of soil. To ascertain the soil fertility of different forest stand types in the Nanshan forest farm of Jiyuan City, this study investigated the soil of four forest stand types: Platycladus orientalis, Robinia pseudoacacia, Quercus variabilis, and walnut trees. It analyzed the soil nutrients of the forest stand types by determining the pH, organic matter, total nutrients (TN,TP,TK), and available nutrients (AN,AP,AK) of soil at different depths (0~40 cm). Moreover, it assessed the comprehensive soil fertility using the improved Nemerow comprehensive index method. The results show that: (1) Except pH, the physicochemical factors of the soil of the forest stand types in the study area exhibited moderate variations, and the soil TP, TK, AP, AK, and pH manifested significant differences; (2) With an increase in soil depth, the soil in the study area showed increased pH and bulk density, decreased organic matter, TN, and available nutrients, and almost unchanged TP and TK; (3) The assessment of soil nutrient abundance indicated that the TN, TP, and available nutrients were relatively poor in the soil of the study area; (4) Based on a comprehensive assessment, the soil fertility of four forest stand types at different depths decreased in the order of Robinia pseudoacacia, Quercus variabilis, Platycladus orientalis, and walnut trees. Their soil fertility was generally at an average level, with low values observed at depths ranging from 20 to 40 cm. The comprehensive analysis indicates that TN, TP, and available nutrients are deficient in the study area. Therefore, applying appropriate organic fertilizers, nitrogen, and phosphorus is recommended for the study area.

This study investigated data from a 1:50,000 stream sediment survey in the Juxian-Wulian area, Shandong Province using factor analysis. By extracting eight representative factors, this study identified element assemblage types. Then, this study performed geochemical zoning based on the factor scores and discussed the relationships between various sub-zones and their geological background. Based on the geochemical zoning results, as well as geological conditions for mineralization, this study determined favorable geological bodies and prospecting targets and discovered new prospecting clues.The most significant mineralization combination in this area is Au-Cu-Ag-Mo-Bi, followed by Pb-Zn; The V-Ti-Co-Mn combination and Ni-Cr combination can serve as exploration elements, indicating that there may be favorable mineralization mechanisms in the center and deep parts of the combination anomaly zone. Finding volcanic craters and hidden explosive breccia tubes in the distribution areas of volcanic rocks in this region or area is an important direction for mineral exploration; In the area of Shichang Fangzi Village in the eastern part of the research area, there is a comprehensive zoning with a F₂-F₄-F₁ three factor combination model. The Mesozoic Buliu sequence and Weideshan sequence rock bodies are favorable geological bodies for mineralization, and the NE trending structural belt is a favorable place for mineralization, indicating the direction of prospecting.

Surface-related multiple elimination(SRME) is vital in processing seismic data.At present,the SRME method most commonly used for processing marine data can effectively predict surface-related multiple models,achieving multiple elimination through matching and subtraction.However,this method requires full wave field information,thus placing higher demands on observation systems.The irregular land data acquisition makes it difficult to apply this method for processing land data.Hence,this study presented an improved SRME method,which performs moveout correction on adjacent channels for multiple prediction by constructing the minimum error constraint function,thus enhancing the adaptability to complex observation systems.The improved SRME method was applied to process the actual seismic data of land.Its effectiveness was validated by comparing the gathers,velocity spectra,prestack time migration profiles,and synthetic seismograms before and after SRME.

This study aims to improve the seismic exploration effects in the Upper Paleozoic strata of the Yin'e Basin.With the Juyanhai depression in the western Yin'e Basin as an experimental area,it investigated the previous seismic acquisition characteristics and current data processing techniques of the area.Through field seismic acquisition experiments and data processing research in the laboratory,it explored and summarized the seismic exploration techniques for the Upper Paleozoic strata in the Yin'e Basin.Key findings are as follows:(1)The combination of shot holes and seismic vibrators is recommended for seismic excitation in the area according to local conditions;(2)The receiving array length takes precedence over the receiving density;(3)Targeted processing techniques including anisotropy processing,spectral-constrained deconvolution,and wedge transform adaptive denoising can effectively improve the quality of deep seismic imaging.This study provides a reference for relevant research in similar areas.

Tunnel detection in complex environments requires fine-scale detection of small unfavorable geobodies like karst caves and fissures. Hence, this study designed a tunnel construction model with a small karst cave in front of the tunnel face. A borehole was drilled at the center point of the tunnel face towards the construction direction, and then an electrical source was put into the borehole for excitation. Array data acquisition was conducted on the tunnel face. The 3D forward modeling based on transient electromagnetic data was performed using the time-domain finite element method. As indicated by the results, the electromagnetic sounding of the target was achieved through the movement of the electrical source, and the planar position of the unfavorable geobody was determined based on the distribution patterns of the electromagnetic field on the tunnel face. Therefore, electrical source excitation in a borehole can enhance the detection ability of the transient electromagnetic method on small karst caves, serving as a feasible method for improving the accuracy of tunnel seismic prediction.

The exploration and exploitation practices in the Sichuan Basin in recent years indicate that breakthroughs have been achieved in the Jurassic continental tight sandstones.Nevertheless,due to the low porosity and permeability of tight sandstone,conventional post-stack inversion frequently exhibits limited resolution,failing to meet the accuracy requirements for the prediction of actual exploration reservoirs.This necessitates pre-stack inversion for detailed characterization of tight sandstones,while S-wave velocity is crucial to pre-stack inversion.Based on continental exploration wells drilled in the southeastern Sichuan Basin in recent years,this study developed a petrophysical modeling technique for dense sandstones in this region.Specifically,given the low permeability of tight sandstones and the uneven mixing of fluids in the pore space,the Domenico model was preferentially employed to calculate the pore fluid modulus.Although fluid modulus and density are inevitably variable under the actual subsurface conditions,previous studies typically use constant values to conduct petrophysical modeling for tight sandstones.In this study,depth-dependent values were applied.Tight sandstones in the southeastern Sichuan Basin generally exhibit a porosity of less than 10%.Therefore,calculations using the Nur and the Krief models will yield high errors.Given this,this study preferred using the Lee-Pride model to calculate the skeleton modulus and controlled the relationship between the rock matrix and the skeleton by introducing the value of the cementation parameter.The application of the established petrophysical model of tight sandstone to an actual survey area indicates high agreement with data from actual wells.Additionally,based on log statistics,Poisson's ratio,the most sensitive parameter is used for high-precision pre-stack inversion in the proposed technique,enabling detailed characterization and prediction of the internal structure of channel sandstones.

Currently,velocity spectrum analysis methods widely used for ground-penetrating radar(GPR) signals mostly construct velocity spectra by superposing the amplitude energy of coherent signals to estimate electromagnetic wave velocities in subsurface media.In the case of multiple peaks and troughs in signal wavelets,velocity spectra constructed using these amplitude-based methods display multiple energy clusters,adversely affecting the identification,picking,and velocity estimation of subsequent energy peaks.Hence,this study proposed a method for estimating electromagnetic wave velocities in subsurface media based on common-offset GPR signal envelope and 3D velocity spectrum analysis.By scanning the signal envelope of hyperbolic diffracted waves in the GPR profile,the proposed method constructed the 3D velocity spectra of superimposed energy varying with zero-offset two-way travel time,test velocity,and measuring point position.Moreover,it extracted the slices of 2D velocity spectra according to the positions of hyperbolic vertices in the 3D velocity spectra.On this basis,the test velocities corresponding to the energy peaks in the slices of 2D velocity spectra were picked as the electromagnetic wave velocities in subsurface media.The numerical test results show that compared to the amplitude-based methods,the signal envelope-based 3D velocity spectrum analysis method obtained velocity spectra characterized by fewer continuous energy clusters,more concentrated energy,and minor velocity estimation errors,thus more effectively constructing the velocity model with inverse-time migration.

Over the past century, electromagnetic exploration technology has evolved from direct current resistivity and induced polarization methods to a comprehensive geophysical system. Yet, in China's new mineral exploration phase, challenges like deep-mining needs, cultural noise, and weak 3D interpretation limit traditional methods. High-power-ultrahigh-power electromagnetic technology, by boosting transmission current, combats these issues. It enhances detection depth, enables 3D exploration, and drives technological and application innovation. This paper reviews the development of high-power-ultrahigh-power electromagnetic instruments and current research. It emphasizes that technologies like true 3D full-waveform IP collection and inversion, tensor CSAMT collection and inversion, and multi-parameter joint inversion of time-and frequency-domain EM methods can strengthen deep-target detection. Future research should tackle anisotropic 3D inversion, full-domain inversion with a field source, and extracting polarization and magnetization rates under complex constraints. These advances will propel electromagnetic methods toward greater depth, precision, and intelligence, supporting China's renewed mineral exploration efforts.

This study investigated the Panxi area as an example to delineate faults and determine their current activity levels using aeromagnetic data and precise relocation results of small earthquakes. A total of 42 faults were delineated in the study area. Among them, 21 faults were inferred to be active currently, including 10 newly inferred active faults. This study examined the three-dimensional structural characteristics of some local sections of major faults in the study area. The results indicate that precise relocation results of small earthquakes can identify highly active faults and characterize their deep structures. Additionally, based on the delineation of basement faults using aeromagnetic data, the locations of active faults were constrained, and concealed active faults within the sedimentary cover were also determined. The proposed method holds certain practical significance for promoting research on the spatial distribution and activity of fault structures using aeromagnetic data.

As a semi-airbone transient electromagnetic (TEM) platform, drones inherently generate electromagnetic signals that may interfere with the collected transient electromagnetic data. This study investigated the impacts of drone noise on the collected data. Through outdoor experiments and systematic performance testing, this study analyzed the impacts of drone noise under varying rotor speeds, suspension lengths, flight height, and flight speeds. Accordingly, this study proposed methods for suppressing drone noise, such as determining the optimal suspension length and incorporating shielding layers. The study was conducted using the KWT-X8L-25 octocopter drones, but the research methodology and philosophy are also applicable to other drone models, thus serving as a reference for the selection of semi-airborne TEM platforms.

In response to the need for large-scale exploration of radioactive minerals in high-relief areas, this study developed an airborne gamma-ray spectrometer based on small-sized NaI (Tl) crystals, which was integrated with the F-120 unmanned aerial vehicle (UAV) to form an airborne gamma-ray spectrometry (AGRS) system. The UAV-AGRS system was applied to the follow-up geochemical survey of uranium deposits in a certain area of South China. The survey results show roughly consistent locations and morphologies for high-anomaly zones with the ground gamma-ray spectrometry results. Moreover, the results of this study exhibit more detailed anomaly morphologies, and more significant responses of uranium content-related uranium channel data to known uranium occurrences in the study area, suggesting superior data. Therefore, the UAV-AGRS system shows promising potential as an effective alternative to ground gamma-ray spectrometry for the follow-up geochemical survey of uranium deposits in high-relief areas.

The gold ore zone in the Daduhe area of Shimian County, Sichuan Province, is located in the rare metal-precious metal-nonferrous polymetal metallogenic belt in the southern segment of the Songpan-Ganzi orogenic belt. It exhibits complex structures and steep terrains, severely restricting prospecting and exploration. Based on the geological settings, conditions, and geophysical characteristics for regional mineralization, this study investigated the typical Luoluoping gold deposit in Shimian by conducting deep geophysical exploration centered on audio-frequency magnetotellurics (AMT). Three low-resistivity anomalies (M1, M2, and M3) were identified, corresponding to the mineralized alteration zone I, the gold mineralization zone III, and the gold-copper ore body, respectively, demonstrating the effectiveness and applicability of geophysical methods for deep prospecting. Combined with geological understanding and engineering verification, this study summarized geological and geophysical prospecting markers for the typical gold deposit, establishing the geological-geophysical prospecting model for the gold ore zone in the study area. Therefore, this study provides technical support for deep prospecting in the study area.

The Zhangye Basin in Gansu Province serves as a national modern agriculture demonstration area in China. The 1990s was the only period that witnessed both agricultural soil surveys and regional geochemical surveys in the area. This study aims to provide data support for investigating the evolution of the regional soil environment in the area. It gathered geochemical survey data of rocks, deep topsoil, and stream sediments, which were sampled by Gansu geophysical and geochemical exploration teams in the Zhangye Basin and its surrounding mountains in the 1990s. Using these data, this study calculated the background values of elements in various geological units as per the Pauta criterion and sampling media. Focusing on heavy metals, it compared their regional background values in deep topsoil with the nationalsoil background values and the coetaneous averages of farming soil elements surveyed by the agricultural sector, as well as the soil background values of Quaternary sediments with the regional background values. Moreover, it combined geochemical hybrid models with geographical factors. Finally, it explored the distribution characteristics and material sources of heavy metals in deep topsoil of the Zhangye Basin in the 1990s. Compared to the national soil background values, the deep topsoil was enriched in Cu and Cd but depleted in Zn. Contrasting with contemporaneous farming soil, the deep topsoil was significantly enriched in Cr but prominently depleted in Cu, Zn, Pb, and As. In terms of sources, heavy metals Zn, Cd, and As were principally derived from the northern Qilian Mountains, Pb originated from the Longshou Mountains, and Hg and Cr might be primarily associated with human activities. The abnormal H3 potential ecological risk index of the deep topsoil resulted from the combined effect of northwest and southeast winds. The enrichment of heavy metals in deep topsoil was positively correlated with human activity intensity but negatively correlated with neotectonic movement intensity.