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As a result of a deep burial depth (> 6.5 km), the depositional history of the Early to Middle Ordovician carbonate platform in the Shuntuoguole Low Uplift (Tarim Basin, NW China) has been difficult to unravel, leading to problems in understanding the controls of the facies distribution, particularly in terms of petroleum exploration. Integrated with geophysical surveys, detailed sedimentological observations document the platform evolution and show that a carbonate ramp system developed in the Shuntuoguole Low Uplift during the Early-Middle Ordovician, with twelve lithofacies types arranged into two facies associations, including peritidal to semi-restricted subtidal and open-marine subtidal facies. Based on the tempo-spatial distribution of lithofacies, seven third-order depositional sequences are identified, each composed of a transgressive lower package and a regressive upper part. Their sequence boundaries are commonly characterised by a transitional zone with no obvious subaerial exposure features. The correlation of relative sea-level (or accommodation space) changes derived from the vertical stacking pattern of facies with the global sea-level curve of Haq and Schutter (2008) and sea-level oscillations of coeval successions worldwide suggests that eustatic sea-level fluctuations were the overriding factor controlling the development and evolution of this carbonate ramp during the Early-Middle Ordovician. Meanwhile, regional or local tectonic subsidence and environmental factors (e.g. palaeoclimate and prevailing wind) also exerted an influence on the depositional processes of the Shuntuoguole Low Uplift over this time interval. [ABSTRACT FROM AUTHOR]

Airborne geophysical surveys serve as an effective tool for litho-structural mapping, providing extensive and high-resolution underground information. They offer vital data support for the interpretation and analysis of lithologies and structures, complementing surface geological mapping. In the study area of the Nanpanjiang-Youjiang metallogenic belt in southeast China, we obtained high-resolution aeromagnetic and gamma-ray spectrometry data covering an area of approximately 27,000 km2, which facilitated the conduct of litho-structural mapping. The total magnetic intensity, reduction to the pole, and directional derivative maps generated from the aeromagnetic data, efficiently identified concealed rocks and faults. Additionally, the total count, potassium, thorium to potassium ratio, and ternary maps generated from the airborne gamma-ray spectrometry data demonstrated advantages in distinguishing carbonate rocks from clastic rocks. They also provided more comprehensive geological information, refining the structural strike and location interpreted by the aeromagnetic data. The litho-structural map produced in this study significantly contributes to our understanding of the structures in the Nanpanjiang area and offers valuable guidance for successful mineral exploration endeavors. [ABSTRACT FROM AUTHOR]

It is normally difficult to identify the ground deformation of potential landslides in highly vegetation-covered areas in terms of field investigation or remote sensing interpretation. In order to explore a methodology to effectively identify potential landslides in highly vegetation-covered areas, this paper established an integrated identification method, including sliding prone area identification based on regional geological environment analysis, target area identification of potential landslides in terms of comprehensive remote sensing methods, and landslide recognition through engineering geological survey. The Miaoyuan catchment in Quzhou City, Zhejiang Province, southeastern China, was taken as an example to validate the identification methods. Particularly, the Shangfang landslide was successfully studied in terms of comprehensive methods, such as geophysical survey, drilling, mineral and chemical composition analysis, and microstructure scanning of the sliding zone. In order to assess the landslide risk, the potential runout of the Shangfang landslide was evaluated in a quantitative simulation. This paper suggests a methodology to identify potential landslides from a large area to a specific slope covered by dense vegetation. [ABSTRACT FROM AUTHOR]

The sub-bottom profiler is a valuable tool for obtaining high-resolution shallow stratigraphic data in marine geological and geophysical surveys. To detect and acquire the structural characteristics of small submarine objects, we developed a data processing method that utilizes 2D data to construct a 3D structural model. We conducted application experiments using sub-bottom profile detection data from Chuanshan Islands, which were explored using China’s most advanced unmanned exploration platform and commercial shallow formation profiling system. To create high-resolution 3D seafloor structure models from recorded 2D sub-bottom profile datasets, an optimized data processing sequence was devised, comprising two stages: 2D data processing and 3D data processing. The 2D data processing stage involved spectrum analysis, band-pass filtering, matching filtering, time-varying gain, and surge correction. The subsequent 3D data processing stage encompassed ping location reallocation, static correction, and extraction of feature layer information. Notably, the final pseudo-3D sub-bottom profile time slice exhibited significant amplitude variations near the target body. This methodology represents an extension of the application of 2D sub-bottom profile data, enhancing the target recognition capabilities of such data. To further improve the precision of target body characterization, we used ArcScene 10.0 to create a 3D sub-bottom profile formation model spatial database. We constructed a submarine 3D formation structure model to show the 3D structural characteristics of the target body in detail and identified a seabed target body measuring 6.4 × 9.2 × 10 m. [ABSTRACT FROM AUTHOR]

Seawater intrusion has been a globally significant environmental issue. This paper comprehensively reviews and highlights the research methods of seawater intrusion in China, recommending the potential application of novel radioactive radium-radon isotopes. Geochemical and geophysical techniques have been extensively utilized in studying seawater intrusion in China, including methods such as hydrochemical analysis, groundwater level observations, geophysical survey techniques, and isotope tracing. The former three methodologies boast a lengthier historical application in seawater intrusion field, while the radium-radon tools in isotope tracing, as newcomers, can specifically indicate crucial scientific questions such as seawater intrusion rates, salt groundwater age, water-rock reactions, and preferential flow dynamics. However, it is imperative to acknowledge the limitations inherent in the utilization of radium-radon tools within the realm of seawater intrusion research, as with any other methodologies. Strategic integration of radium-radon tools with other methodologies will propel advancements in the investigation of seawater intrusion in China. While the primary focus is on research methods in China, insights gained from novel radium-radon tools could have broader value for seawater intrusion research and coastal management globally. [Display omitted] • China's Research methodology for seawater intrusion is comprehensively summarized. • Radium-radon is highly recommended for global seawater intrusion studies. • Comparative study of deepening radium-radon and other methods. • New directions for future seawater intrusion research methods are indicated. [ABSTRACT FROM AUTHOR]

The Alxa Block is located in the middle part of the Central Asian orogenic belt, which is the coupling belt of the North China, Tarim, and Kazakhstan Plates. The east–west-trending deep faults control stratigraphic distribution and magmatic activity in the region. To detect the EW-trending ore-controlling deep structures, a 440 km NS section of magnetotelluric sounding was conducted from Minle to Ejinaqi. The phase tensor and electrical principal axis were analyzed based on the measured data to build the exploration model. The electrical structure model along the section was obtained using nonlinear conjugate gradient (NLCG) 2D inversion. Combined with the geological, geophysical, and deposit distribution characteristics in the area, the comprehensive study of magnetotelluric sounding profile shows that the resistivity presents as zoned along the profile. The Engelwusu ophiolite mélange belt is stacked in clumps with high and low resistivity, indicating that the northern margin of the Engelwusu Belt subducts below the high-resistivity zone, representing the passive continental margin. The southern end of the Engelwusu ophiolite belt is primarily the prospecting potential area for copper–gold deposits, whereas the northern end of the Engelwusu ophiolite belt corresponds to copper polymetallic deposits. [ABSTRACT FROM AUTHOR]

Integrated geophysical surveys using ground penetrating radar (GPR), seismic and electrical resistivity tomography, are carried out to characterize the subsidence, combining with engineering examples in the Glauber's salt mining area in the northwestern region of Gansu Province, China. Because some of the dissolved ore bodies in the Glauber's salt mining area are accompanied by the top and floor, the geophysical response of the floor strata has different physical properties. It is theoretically feasible to use resistivity imaging, GPR and seismic methods to detect. However, it is very necessary to choose an effective geophysical method through experimentation. the limitations of electrical resistivity tomography method and GPR are discussed: in actual work, if the electrical difference between the target body and the surrounding rock is not large enough, the conventional electrical resistivity tomography method cannot be used for fine detection; due to factors such as human noise from the mine's annex, the GPR electromagnetic wave reflection method cannot carry out effective work. Seismic refraction tomography processing is discussed and it was found that the interpretation results of refraction wave tomography can better distinguish the strata in the sub-survey area, which has an excellent effect on the delineation of the range of dissolution and collapse in Glauber's salt mine. Theory and engineering examples prove that seismic refraction wave tomography technology has good applicability in the detection of underground dissolution areas in Glauber's salt mines. [ABSTRACT FROM AUTHOR]

A group of Han dynasty tombs were found in a small town in central eastern China. It is difficult to infer the underground structures of the cemetery based on surface information. Geophysical methods are nonintrusive technology that can be used in archaeological excavations to provide important underground information. Multiple geophysical methods including total magnetic field (TMF), self‐potential (SP), direct‐current resistivity (DCR) and ground‐penetrating radar (GPR) were used to investigate the structure of ancient tombs. Total magnetic anomaly (TMA) and SP data can be used to obtain the projections of anomalous bodies on earth surface. DCR and GPR data can be used to gauge and further determine the spatial locations and depths of the anomalies. The results of the integrated geophysical interpretation were used to optimize the excavation plans and were verified by the subsequent works, such as coffin chambers, dromoi, ancient building foundations and funeral pit. Integrated geophysical survey can effectively reduce the uncertainly of a single method and obtain the targets more accurately. [ABSTRACT FROM AUTHOR]

Hierarchically nested groundwater flow systems have been widely investigated by numerical modeling and laboratory experiments but seldom recognized from in situ observations and testing. Groundwater age and geochemical profiles were obtained by the authors using a packer system along two wellbores drilled in the Ordos Plateau, China. Groundwater age profiles were constructed from 3H, 85Kr, 14C, and 81Kr data, with the apparent age generally increasing with depth, while exhibiting several inflection points. These inflection points were compared with geochemical profiles and numerical modeling results to delineate groundwater flow systems. Inflection points with significant increases in the gradients of age and Cl− concentration versus depth may indicate interfaces among flow systems. A concurrent decrease‐increase turning of groundwater age and Cl− concentration is influenced by a stagnation point. The groundwater age profiles are quite different from previous studies, indicating that the method can greatly reduce the uncertainty in model construction. Plain Language Summary: The provision of renewable groundwater, a crucial source of drinking water worldwide, relies on a circulation path from recharge to discharge zones with a subsurface flow in reservoirs (aquifers). Basin‐scale groundwater circulation is speculated to form hierarchically nested flow systems with differing capabilities for renewal. However, flow systems are invisible and difficult to detect through in situ observations on groundwater. In this study, nested groundwater flow systems were identified from groundwater age and geochemical profiles along wellbores. Inflection points on these profiles provide significant insights into the interfaces and stagnation points among nested groundwater flow systems. Uncertainties could be brought by the aquifer heterogeneity in the hydraulic conductivity and localized soluble salts. This adopted method is expected to be improved by incorporating geophysical survey and high‐resolution geochemical analyses to eliminate uncertainties in model construction. Key Points: Groundwater age and geochemical profiles were obtained to investigate groundwater flow systemsInflection points on profiles are used to infer interfaces or stagnation points among different groundwater flow systemsGroundwater flow models constrained by inflection points greatly reduce the uncertainty of flow system characterization [ABSTRACT FROM AUTHOR]

Mantled karst is characterized by solution processes in underground conditions, where karst evidence can be masked. In mantled karst environments, cover-collapse sinkhole can be considered one of the most hazardous elements. This study seeks to develop a methodological framework utilizing different techniques and approaches to understand cover-collapse sinkhole genesis and its likely evolution. The study area is located in the Conghua district of Guangzhou city, Guangdong Province, in the south-eastern region of China. A mapping procedure was introduced to combine data from aerial photographs and intensive field investigations. In addition, data interpretations from borehole drilling activities and different geophysical approaches were performed to reconstruct the Quaternary deposit features, rock head morphology, and karst features. During these investigations, the detailed typology, morphometry, and chronology inventory of 49 cover-collapse sinkholes were analysed, and three karst fissure zones covered by Quaternary soil were observed. In the study, the hydrogeological data suggested that karst aquifer pumping triggered the drop in groundwater levels. Cover-collapse sinkholes might be ascribed to erosion of the soil layers due to the groundwater level decline. [ABSTRACT FROM AUTHOR]

Old goaf under the overpass becomes serious hidden trouble of subgrade-pavement and bridge engineering. Based on geological survey, geophysical survey and theoretical analysis, this paper studies on formation mechanism and distribution characteristics of the surface residual deformation in old goaf in No.9 Line Overpass across Rapid Rail Transit Line No.3 in Dalian city. A comprehensive analysis and evaluation has been made on the stability of old goaf. Based on the calculation principle of the probability integration method, the conception of ground residual subsidence coefficient and the predicted model of residual deformation are proposed, ground residual deformation of old goaf under the overpass is predicted. According to the zonal principles of ground stability, the stabilities of areas are divided. The results indicated that, new overpass has an important effect on the old goaf overburden rock activation in study area that the surface will be instability uneven settlement and the ground residual deformation values will exceed allowable values. Some treatment should be done to the old goaf because of the poor stability of goaf and non-goaf within influence zone in study area. [ABSTRACT FROM AUTHOR]

Taohemu deposit is a superlarge silver‐polymetallic deposit discovered in the Great Xing'an Range metallogenic belt of China in recent years. The deposit occurs in the terrestrial volcanic rock sequences of Late Jurassic age. The ore bodies consist mainly of rhyolitic tuffs, brecciated tuffs, and volcanic breccia bearing Ag‐Pb‐Zn mineralization, and are largely conformable with the surrounding layered volcanic and volcaniclastic rocks with a gradual transitional relationship manifesting as strata‐bounded features in general. The mineralization system appears to be generally controlled by a paleo‐volcanic chamber. It is suggested that the late volcanic hydrothermal fluids flowed within the permeable layers of rhyolitic pyroclastics consisting mainly of volcanic breccias and breccia‐bearing tuffs. This resulted in the formation of superlarge Ag‐Pb‐Zn polymetallic ore deposit metasomatism and fracture filling. The majority of the deposit occurs as shallowly dipping concealed ore bodies, as defined by sparsely distributed drill holes. Because of its short discovery history, new mineralization style and low degree of comprehensive research, the boundaries of most ore bodies have not been effectively delineated along vertical and lateral extensions. At present, it is crucial to strengthen the comprehensive studies on the deposit, conduct more detailed geological exploration, and establish the metallogenic and prospecting models. For this reason, we have designed and implemented long sections of magnetotelluric (MT) and controlled‐source audio magnetotelluric (CSAMT) sounding across the Taohemu ore field and obtained a large number of geological structures and valuable underground exploration results that provided reliable geophysical support for promoting deep resource exploration. Plain Language Summary: The geological structures associated with metallogenic system is usually covered by surface vegetation and Quaternary layer. Furthermore, surface mineralization is not relevant to deep ore bodies. To reveal the shape of ore bodies and geoelectrical structures in this study area, we applied geophysical electromagnetic methods to achieve this purpose. The results showed that the ore bodies are largely conformable with the surrounding rocks as strata‐bounded features in general tested by borehole information. The mineralization system appears to be generally controlled by a paleo‐volcanic chamber. Key Points: Underground geoelectric structures are imaged from MT and CSAMT exploration over Taohemu superlarge silver‐polymetallic deposit, Inner MongoliaOre bodies are conformable with surrounding volcanic and volcaniclastic rock with a gradual transitional relationship manifesting as strata‐bounded featuresThe mineralization system appears to be generally controlled by a paleo‐volcanic chamber [ABSTRACT FROM AUTHOR]

Xiaoshan gold–polymetallic concentrated area is located in Henan Province, central China. The area is principally underlain by typical metamorphic core complexes (MCCs), along with essential components of the basins and ranges of western Henan. Mineralization occurs in the regions where the geochemical anomalies of Au and related elements are widely distributed and consist predominantly of mineralized altered rocks and auriferous quartz veins, both of which are hosted within shear zones or fractures of varying sizes and orientations. Several small‐ to medium‐sized gold–polymetallic ore deposits, along with numerous clustered occurrences, have been found in the area in recent years. However, despite the fact that the Xiaoshan District has traditionally been deemed as an excellent geological endowment area with enormous potential for large‐sized deposits, no significant discoveries have been made to date. It is suggested that the main reason responsible for the present exploration situation could be the scarcity of applications of deep‐penetration geophysical prospecting in the area. It is anticipated that integrating geological and geophysical data would be crucial to enhance the successful mineral explorations. In this contribution, a conceptual geological model for the study area was initially reviewed so that the corresponding electromagnetic responses could then be modelled, which would simulate a geophysical type of survey, with appropriate uncertainties added into the analyses. Then, based on such an integrated approach, the required precision of detecting deep‐buried deposits could then be evaluated. In addition, by employing supplementary geophysical data acquired over known deposits, it is possible to gain more instructive insights into the practical geological model. The viabilities of this approach were demonstrated through a case study in which a hidden gold deposit in the studied area was successfully detected. Geophysical surveys were carried out by employing a grounded‐wire short‐offset TEM (SOTEM) technique and revealed two new anomalies (one of which was subsequently tested by drilling). The drilling then confirmed that this anomaly was caused by an ore body 30 m in thickness occurring at about 550 m below surface. [ABSTRACT FROM AUTHOR]

A residential building in Guilin City, China, underwent an up‐and‐down vibration with an amplitude of 2 cm. By eliminating several causes such as earthquake, wind and construction, in combination with the unique karst geological conditions of Guilin, it was inferred that the effect of turbulent karst water is the main contributor to the occurrence of this vibration. Therefore, a geophysical survey was undertaken on the vibration zone and its surroundings. The resutls suggest that the soil in the upper part of the karst grooves shows conspicuous traces of disturbance and the water content has low resistance. A comprehensive analysis indicates that there is a karst strong runoff zone beneath the area. According to the water level and water temperature data collected automatically by the instrument, it can be concluded that the groundwater level had changed significantly twice during this period, so it was determined that the denudation of groundwater strong runoff causes the overlying soil layer to collapse, forming a soil‐water soft‐flow material with mixed phase. Since the building in this area was supported by friction piles, the groundwater‐soil soft‐flow material with mixed phase has intense plasticity, and the up‐and‐down vibration resulted in the change of the friction piles, which caused the up‐and‐down vibration of the building structure. [ABSTRACT FROM AUTHOR]

A subsurface landslide is the key problem to a large affordable home program in the southern Qinshui Basin, China. A geophysical survey integrated with seismic refraction tomography (SRT), seismic scattered wave imaging (SSI), and electrical resistivity tomography (ERT) was performed along five profiles over the landslide body. The bedrock surface was a crucial interface, represented by a relatively high velocity, high density, and high resistivity in contrast to the unconsolidated soil and landslide material above it. Based on the most comparable geophysical features, several problems were uncovered such as a ''sandwich velocity structure'' in the SRT results, velocity trap in the SSI results, and rapid variations in the local topography in all three methods. Aiming to improve the comprehensive interpretation of the ERT, SRT, SSI data, the vertical gradient extremum in the ERT and SRT data and tracing the target wave group according to the velocity sensitivity in the SSI data were analyzed. Moreover, a joint interpretation of the three geophysical survey datasets as well as 32 geological wells and 73 geotechnical boreholes helped to determine one undulating bedrock surface, delineate two types of failure surface geometry (landslide surface and collapse surface), and identify three external shapes in the ex situ body (ancient river channel, landslide body and collapse body). The results showed that the integrated geophysical survey not only provided detailed evidence for the existing of landslide but also presented meaningful evidence for the sliding mechanism. These results were difficult to fully describe and to apply to understanding landslide processes. Furthermore, for near-surface landslide events, the joint interpretation of geologic, geotechnical and geophysical data was necessary to reduce problems with any single geophysical survey. [ABSTRACT FROM AUTHOR]

Since goaf water can cause water inrush, collapse or other severe geological hazards in coal mining, its detection has become a significant issue. As the grounded electrical source airborne transient electromagnetic (GREATEM) system can provide considerable prospecting depth, lateral resolution, and high detection efficiency, the method may be suitable for goaf water detection. To verify the feasibility, a field electromagnetic survey over Qinshui coal mine (Shanxi province, China) was conducted, and the system was used to detect the geoelectric characteristics of goaf water. After data acquisition, data processing, and apparent resistivity calculation, the resistivity profile of survey area is clearly presented, which is consistent with the information provided by Shanxi Coal Geology Geophysical Surveying Exploration Institute, China. The result shows that the application of GREATEM system is an effective technique for resistivity detection of goaf water, and can reduce the risks in coal mining. [ABSTRACT FROM AUTHOR]

• The Lushan earthquake occurred at the boundary zone between the high- and low-resistivity bodies. • The crustal structure of the southern Longmen Shan thrust belt matches the multiunit combination seismogenic model. • The seismogenic potential of the southern segment of Longmen Shan is weaker than that of the central segment. Since the Ms 7.0 earthquake occurred in Lushan on April 20, 2013, five years after the Wenchuan Ms 8.0 earthquake, the seismogenic potential of southern Longmen Shan has been a considerable concern. Comparative studies of active faults and deep structures of the Lushan and Wenchuan earthquakes are important to evaluate Longmen Shan potential. Terrace measurements, geophysical surveys and borehole drilling reveal that late Quaternary fault activity in the southern segment of the Longmen Shan thrust belt is weaker than that along the central segment. Magnetotelluric data across the southern segment of the Longmen Shan thrust belt show that the central fault and the front-range fault are the electrical boundaries of the crust and that the Longmen Shan thrust belt is a high-resistivity body. The Lushan earthquake occurred at the boundary zone between the high- and low-resistivity bodies, and the crustal structure of the southern Longmen Shan thrust belt matches the multiunit combination seismogenic model, indicating a potential large earthquake in Longmen Shan. Compared to conditions along the central segment, the low-resistivity layer of the upper and lower crust on the western side of the Songpan-Ganzi block develops along the Xianshuihe fault, which may reduce the strain accumulated from the Songpan-Ganzi block to the southern Longmen Shan thrust belt. This interpretation suggests that the main crustal shortening is accommodated by foreland thin fold structures, whereas the structural deformation accommodated by the thrust belt accounts for only a small proportion; thus, the seismogenic potential of southern Longmen Shan is weaker than that of the central segment. [ABSTRACT FROM AUTHOR]

The Changbaishan volcano is an active and considerably hazardous volcano located on the border of China and North Korea. This paper summarizes a series of geophysical surveys as well as seismological and volcano-observational networks around the Changbaishan volcanic area. We characterize deep structures related to the Changbaishan volcanic area. The prominent low-velocity anomalies and low-resistance bodies associated with the magma system under the Changbaishan volcano were detected in the crust and upper mantle, and high-velocity anomalies were imaged within the mantle transition zone, suggesting that the origin of the Changbaishan volcano is related to the subducted Pacific slab. However, there exist a few major obstacles for comprehensively elucidating the deep structure of the Changbaishan volcano as well as for the preparedness for and response toward future volcanic unrest and activity. It is essential to collect data from both China and Korean Peninsula to image the deep structure beneath the Changbaishan volcanic area. A multi-disciplinary approach comprising seismological investigations, deformation information from GNSS and InSar, and gravity and magnetotelluric surveying is a reliable manner for imaging high-resolution structures and fluid movement for the spatial distribution and variation of the volcanic magma chamber. An effective volcano-monitoring network system is considerably important to improve hazard assessments and characterize the potential future eruption of the Changbaishan volcano. [ABSTRACT FROM AUTHOR]

The Antarctic Ice Sheet plays a critical role in global climate and sea level change resulting in it being the focus of international scientific exploration. Airborne platforms have been applied to study large geographical regions of Antarctica that are logistically difficult to reach by other means. For 30 years Chinese Antarctic expeditions, have widely applied ground based platforms in Antarctica. During the 32nd Chinese National Antarctic Research Expedition (years 2015/16), the first fixed-wing aircraft (Snow Eagle 601) was deployed by Polar Research Institute of China with special modifications for polar operation and airborne geophysical investigation of ice sheets. Here, the airframe of the aircraft and modifications for science operation in Polar Regions, as well as scientific instrumentation, system integration and its first application in Antarctica are introduced in detail. [ABSTRACT FROM AUTHOR]

The Yangyi geothermal field in southern Tibet has enormous potential for geothermal energy development. It is the high-temperature geothermal field at the highest elevation in the world, and the second largest high-temperature geothermal field in China. The total planned installed capacity of the geothermal power station is 32 MW. At present, no detailed three-dimensional (3D) geophysical survey has been carried out in the Yangyi geothermal field, and in-depth research is urgently needed. The main goal of our geophysical exploration is to study the geothermal structure of this region. In this study, the audio magnetotelluric (AMT) data of 85 stations were collected in the Yangyi geothermal field. The average distance between the stations was about 500 m, and the dimensions of the exploration area were 6 × 7 km. First, we analyzed the magnetotelluric data using the phase tensor method to qualitatively estimate the dimensionality of the subsurface resistivity structure. Then, by performing 3D inversion of 85 AMT data with relatively high quality, the 3D resistivity model from the surface to a depth of 2 km was determined, the high-temperature hydrothermal system under the Yangyi geothermal field was displayed for the first time. In addition, the main characteristics of the geothermal system were identified, and the genetic mechanism of the geothermal system was discussed based on the geological information and borehole data. • Yangyi is the magma-type high-temperature geothermal field at the highest elevation in the world. • Yangyi is the second largest high-temperature geothermal field in China. • For the first time, the three-dimensional resistivity structure of the Yangyi geothermal field was obtained. • The Yangyi high temperature hydrothermal system was imaged for the first time, and the main features of the geothermal system were identified. [ABSTRACT FROM AUTHOR]

Heifangtai terrace is famous in China for its irrigation-induced loess landslides. The frequently recurring loess flowslides initiated along the platform margin of the irrigated Heifangtai terrace have caused 42 fatalities and significant economic losses due to their long-runout and high-speed mobility. Yet it is still unclear if the recurring loess flowslides almost always initiate in the same places, and their initiated conditions and subsequent mobility behaviors have not been fully evaluated. To better understand such under-researched questions, we selected three typically recurring loess flowslides on the Heifangtai irrigated area. We performed multiple geophysical surveys using electrical resistivity tomography (ERT) and multichannel analysis of surface waves (MASW). We tested water content, density, and strength of loess using in-situ profile sampling. In addition, we examined the steady-state shear behaviors of saturated loess utilizing a ring shear apparatus under undrained conditions. The geophysical signatures and in-situ loess property profiles showed that hydrogeological conditions are crucial to initiating the recurring loess flowslides. The results also demonstrated that the shear liquefaction behavior of saturated loess controls the mobility after the failure of the loess flowslides. Liquefaction potential was assessed based on a chart showing the liquidity and plasticity index, pore pressure ratio, and steady-state line, which were developed as new criteria of liquefaction susceptibility assessment. The novel criteria essentially contain general information about fine-grained soil's nature, state, and behavior. These findings provide a better understanding of the dynamic mechanisms of the loess flowslides and their implications for landslide hazard mitigation. • The groundwater regime is key for the initiation of the recurring loess flowslides. • The liquefied loess is vital to the mobility of the recurring loess flowslides. • The new criteria afford a novel framework to loess liquefaction assessment. [ABSTRACT FROM AUTHOR]

Controlled source audio-frequency magnetotelluric (CSAMT) is one of the frequently used geophysical methods in various exploration problems such as fault mapping and groundwater exploration around 1 km depth. CSAMT is commonly used in combination with other geophysical methods to emphasize underground structures. Although it seems to be a good alternative, such a survey is expensive and requires more logistics which is not profitable for companies with low operating budgets. In addition, despite the combination of the CSAMT method with other geophysical methods, several boreholes drilled for groundwater exploration have failed due to the inaccurate locations to emphasize the fractures zones. Therefore, we developed the Python toolbox for CSAMT to solve this problem. The toolbox encompasses all the standard data processing as well as the modeling and implements a novel approach called pseudostratigraphic to forecast the strata log at each station. The advantage of this technique is twofold. First, it predicts the strata log at each station by demarcating the fracture zone, and secondly, it estimates the layer thicknesses with less margin error useful before the drilling operations. The approach was tested in the Xingning area, Hunan province, China. As a result, the model predicted with the proposed approach is similar to the mechanical borehole drilled after the geophysical survey with thickness errors of less than six meters. Furthermore, the technique would reduce the rate of unsuccessful drilling and be beneficial for geophysical and drilling companies to save money. • pyCSAMT is a Python toolbox for analyzing CSAMT, geological, and borehole data. • The toolbox forecasts the stratigraphy log. • It reduces the rate of unsuccessful drilling. [ABSTRACT FROM AUTHOR]

Urban and suburban areas of large cities impose great challenges to geophysical surveys because of high-level ambient noise. This is particularly true for controlled source audio-frequency magnetotellurics (CSAMT) because the frequency range of the method overlaps those of many civil and industrial noises. Among the different types of noise sources, perhaps the most noticeable one is the 50-Hz power grid. We have successfully applied the CSAMT method for groundwater exploration in a suburban Beijing area where the ambient noise level is about three times as high as would normally be encountered. Several steps were taken in assuring quality use of the method, including careful survey design, adequate frequency range selection, and large transmitter dipole length and transmitter-receiver spacing. The next step was static effect removal through low-pass filtering and topography correction to remove any nonhorizontal component in the electric field measurement. Finally, a 1D inversion method was applied to construct an (apparent) resistivity cross section. The survey revealed a low-resistivity, waterbearing layer sandwiched between a surface cover layer and the bedrock. The available well data suggested that the depth of the bedrock was accurately mapped, to within about 2 m, at a depth level of 150-165 m. [ABSTRACT FROM AUTHOR]

Archaeological survey in the Chengdu Plain of Sichuan Province has revealed settlement patterns surrounding Late Neolithic walled sites, including large numbers of small settlements from the Neolithic, Bronze Age, and Han Dynasty eras. Here geophysical survey and excavation at one of these small-scale sites dating to the Middle Bronze Age are reported, showing for the first time the value of high-resolution geophysics for evaluating site size and integrity in the Chengdu region. [ABSTRACT FROM AUTHOR]

Abstract: The Wuda coal mining area in Inner Mongolia Autonomous Region, China, is one of the largest coal fire areas world-wide. At the same time it is also one of the most extensively researched ones. The sub-surface coal fires raging in the underground coal seams of the syncline are located directly west of the town of Wuda. The fires have been mapped in situ, based on remote sensing data, as well as based on geo-physical survey all throughout the years 2001 to 2005. Numerous publications depict the situation during that time. In the present study we assess the current situation in Wuda coal field five years after the last field campaigns, under nowadays on-going and accelerating extinguishing activities. We present the results of coal fire dynamics assessment based on in situ mappings between 2004 and 2010, the analyses of changes in mining infrastructure between 2005 and 2012, as well as land cover change in the area from 2005 to 2012. Newest high resolution multispectral and panchromatic Quickbird data, as well as time series of Quickbird data supported this endeavor. We furthermore present the result of semi-structured interviews undertaken with members of the local mine directorate of the Wuda syncline. All jointly analyzed data indicate that the Wuda coal fires tend to move eastwards within the syncline, meaning that they move along the dip of the coal seams to greater depths. Furthermore, mining related infrastructure is clearly moving from the West to the East as well. Despite large funds spent on fire extinguishing, only few fires remain permanently extinct, while other fire areas increase in size. The former land cover structure in the arid syncline does not exist anymore — extinguishing activities have led to a complete ‘turn-over’ of all material in the region. The coal fire problem in Wuda area remains a pressing one. [Copyright &y& Elsevier]

The Tan–Lu fault is a well-known active fault belt in eastern China that has been the focus of geologic studies over the past 40 years. Since the late 1990s, numerous geophysical and geological investigations of this dislocation zone have been carried out by Chinese oil companies, as well as by universities. However, its deep structure, active periods of slip, and fault mechanism remain obscure. This study focuses on the deep structures within the Jiashan–Lujiang segment of the Tan–Lu fault belt, using high-precision geophysical tools, including magnetotelluric and magnetic sounding, and artificial seismic exploration using active source methods. Our results suggest that this segment is composed of several sub-faults. The southern part of the Tan–Lu fault belt, along the Jiashan–Lujiang sub-fault, can be divided into two parts on the basis of contrasting geological features. The Chihe–Taihu sub-fault is taken as the boundary between the two. The region east of the Chihe–Taihu sub-fault is dominated by strike–slip activity along several sub-faults. Only the Jiashan–Lujiang sub-fault is exposed at the surface, forming a large, positive flower structure, the result of late Middle Jurassic to early Late Jurassic strike–slip movement along the dislocation zone. Three sub-faults are present in Dingyuan County, two of which disappear in the southern Hefei Basin. Only the Chihe–Taihu sub-fault extends to the eastern edge of this basin, creating a half-graben depression that formed during the Early Cretaceous. Our results indicate that the present-day deep structure of the southern portion of the Tan–Lu fault zone is the result of a combination of strike–slip and extensional tectonics. [ABSTRACT FROM AUTHOR]

The 26 November 2005 Jiujiang-Ruichang, Jiangxi, Ms 5.7 earthquake occurred in a seismotectonic setting of moderate earthquake. The northwest-trending Xiangfan-Guangji fault (XFG) does not enter into the epicenter vicinity, but the northeast-trending Ruichang-Wuning fault (RWF) as a regional fault extends to the epicenter nearby, appearing as the Ruichang basin and its marginal faults. Tilting of the Ruichang Basin (RCB) in the Quaternary was controlled by the RCB southeast-marginal, buried fault (RSMBF). Shallow geophysical survey reveals that the RSMBF caused an offset of the reflection layers. Drill hole columnar section demonstrates that there are about 10-12 m displacement in the lower section of the middle-Pleistocene Series along the RSMBF, but no disruption is found in the upper section of the middle-Pleistocene Series. The RSMBF not only has activity in the Quaternary, but also coincides with the nodal plane I from the focal mechanism of the Jiujiang-Ruichang Ms 5.7 earthquake. This evidence, including aftershock distribution and isoseismic lines, strongly suggests that the RSMBF might be the seismogenic tectonics. The RWF is discontinuous at the surface, and consists of three en echelon Quaternary basins, which are the Ruichang, Fanzhen and Wuning basins. Three moderate earthquakes, the Fanzhen ML 4.9 earthquake, the Yejiapu ML 4.1 earthquake and the Jiujiang-Ruichang Ms 5.7 earthquake, have happened in the basins since 1995. The seismogenic tectonics of the Jiujiang-Ruichang Ms 5.7 earthquake is not isolated, but may be controlled by the RWF at depth, the slip of which causes the accumulation of energy for earthquake occurrence. [ABSTRACT FROM AUTHOR]

To identify problematic geological structures which would be encountered when driving tunnels in the high mountainous area of South West China, a joint geophysical and engineering geological study was made. The tunnels will form part of a project to divert water from the Yangtze to the Yellow Rivers. A controlled source audio-frequency magnetotelluric method (CSAMT) was carried out in 2004 between the Ma-ke and Jia-qu rivers in high, steep terrain. The paper discusses the method of data collection, processing, and analysis for the West route. The faults/fractures identified will need to be taken into account in the design and construction of the tunnel. [ABSTRACT FROM AUTHOR]

The effect of contamination by crude oil has been assessed using samples from hand dug trial pits in the Hai-gang region of the Yellow River Delta. In addition to electrical resistivity and in situ penetration tests, grain size analysis, Atterberg limits, compaction, direct shear test and a micro-structure scan were undertaken. The results show that contamination was in the shape of a plume and non-uniform to a depth of 1 m. The more heavily polluted soil had a higher clay particle content, liquid and plastic limit and compression coefficient. However, no notable correlations were found between oil contamination and shear strength parameters. [ABSTRACT FROM AUTHOR]

A geophysical survey was carried out for Taihu Lake, one of the largest shallow lakes in China. The StrataBox™ Marine Geo-physical Instrument was applied for the first time to obtain high-resolution seismic data (in the form of vectorgraphs) of the lake sediment. Data were then interpreted by SonarWiz.Map acoustics software. Data were correlated with core stratigraphy from the lake as well as an outcrop on the northern side of the lake at Yao Bay. Results show that the upper 10 m sediment (beneath the interface of the sediment and the overlying lake water) is characterized by laminated sediments, which can be classified into two stratal types, i.e. lacustrine sediment stratum (U1) and underlying hard loess stratum (U2). The contact of these two lithologies is not continuous, and part of it is absent in the lake basin. Unequally spread over the lake basin, the lacustrine sediment (mainly consisting of sludge and muddy-clay) is found in areas along the western bank, to the northwest of the Xishan Mountains and along the northwestern side of the lake. In the rest of the lake basin, the hard loess stratum is exposed in outcrops. The depth of the lacustrine sediment ranges from 1 to 2 m, while the depth of the sludge (closely related to the modern lacustrine environment) varies from 0.03 to 1.0 m. The spatial distribution of lacustrine sediments in Taihu Lake is primarily influenced by transportation and sedimentation of riverine materials, as well as the hydrodynamics of lake currents. [ABSTRACT FROM AUTHOR]

The article discusses the combination of multiple geophysical datasets in order to determine the earthquake source parameters in China. Topics include the challenges of studying earthquake source parameters, advancements of geodetic procedures for earthquake research, and expectation of studies about earthquake source parameters.

Using the cross-correlation or cross-coherence method to extract the traveltime information of surface waves between two stations from the ambient noise seismic data has become a popular method, which is widely utilized in shallow, regional, and global-scale geophysical surveys. Different from the common-used narrow-band filter (NBF), we adopt the continuous wavelet transform (CWT) as an alternative method to measure the phase velocity from the interstation cross-correlation function (CCF). On account of the distribution of urban noisy sources it is hard to satisfy the requirement of random, stable, uncorrelated, and uniform, which usually makes the measured phase-velocity uncertain. For those surveys with an ultra-short recording time of noise, the adverse effect would be more severe. Hence, we propose to adopt the plane-wave-based beamforming (PWBB) to scan the incoming direction of surface waves based on the hypothesis of plane-wave propagation. To suppress the incoherent components during the stack of CCFs, the phase-weighted stack (PWS) technique is also included in the proposed workflow. Several synthetic tests have verified the good performance of the new method. Especially when only a few seismic sensors are arranged in the research area, the advantages of our method would be more obvious. Then, the workflow is applied to the analysis of the field noise data, which were collected at Fengman hydropower station, Jilin province, China. The beamforming result indicates that the main component of the signals is produced by the effects of river scouring under the reservoir gate. Finally, the S-wave velocity tomogram of the research area and its geological interpretation are given. All data tests demonstrate that the proposed CWT with PWBB can achieve the stable dispersion measurement from the recorded seismic data of two station. • Adopt the CWT to measure the phase velocity of passive surface waves. • The incoming angle of the noise sources is significant. • The PWBB can give better estimation of the incoming angle of noise sources. [ABSTRACT FROM AUTHOR]

The intracontinental response to plate-boundary and mantle processes, such as subduction or continental collisions, is an important topic in the Earth Sciences. Cretaceous to Cenozoic extension across East China is related to the interaction between the Asian continental lithosphere and western Pacific oceanic subduction system, and the associated intra-plate structures and basins provide robust temporal and spatial records of regional continental deformation. Although extension may primarily be driven by slab rollback and/or back-arc opening, mid-ocean-ridge subduction may have played a significant role in this process. To explore how the western Pacific subduction system impacts intracontinental deformation across East China, we use onshore-offshore geological records, geophysical survey observations, and time-dependent Pacific plate models to document the temporal and spatial variation of continental deformation in the Lower Yangtze region adjacent to the Yellow Sea. Based on our compilation, we argue that mantle-wedge convection, with coupled subduction of the trench-parallel Izanagi (Paleo-Pacific)-Pacific mid-ocean ridge, exerts a first-order control on extensional deformation in East China. Beneath eastern China, the mantle wedge history consists of two phases: (1) initial development of the mantle wedge as the Cretaceous Izanagi slab transitioned from flat-slab to steep subduction; and (2) mature mantle wedge convection during Cenozoic subduction of the Pacific plate. Relatively steep subduction of the progressively younging Izanagi plate during the Late Cretaceous-Paleocene resulted in strong mantle convection and coupled upper plate extension in eastern China. The collision of the Izanagi-Pacific plate ridge system with the trench resulted in a magmatic gap and short-lived uplift of eastern China. Following this, subduction of the rapidly aging Pacific plate resulted in a larger, but relatively weaker, mantle convection cell that drove weaker upper plate extension. The vigor of wedge mantle convection was modulated by the age of the Pacific subducting slab, which directly influenced the formation and evolution of intracontinental extension and sedimentary basins across eastern China. The pre-existing Triassic Tan-Lu fault zone has reactivated since the Late Eocene (ca. 40 Ma) due to westward subduction of the Pacific slab to partition strain between extensional dextral faulting in the Bohai Bay and Lower Yangtze basins, thereby diversifying Cenozoic lithospheric extensional deformation in eastern China. Several major Cenozoic extensional basins spatially correlate with the Triassic Sulu orogenic belt, which we interpret to suggest that these basins are underlain by the older and fragmented orogenic basement that acted as mechanically weak zones for localized high-magnitude extension. We present a comprehensive tectonic model that relates intracontinental deformation to subduction zone dynamics, particularly emphasizing the importance of the age of the subducting slab, thus providing a coherent geologic process to explain the deformation kinematics in eastern China and the diversity of observed Mesozoic-Cenozoic basin formation. [ABSTRACT FROM AUTHOR]

Accurate inversion of sound velocity in a Holocene stratum and a Quaternary stratum was achieved based on rich high-resolution sub-bottom profiles and boreholes in the Jinzhou Bay, Bohai Sea of China. The average value of the sound velocity is 1540.2 m/s in the Holocene stratum and 1764.7 m/s in the Quaternary stratum. The fitting analysis shows that there is an obvious positive linear correlation between the sound velocity and the burial depth of the stratum, with a gradient of 4.5 s−1. The method involving the solution of over-determined equations was innovatively put forward to explore the sound velocity characteristics of different types of sediments. The eigenvalues of the sound velocities of seven types of sediments and weathered rock in the study area are solved: the sound velocities of mud, muddy sand, muddy silty clay, muddy clay, silty clay, clay, silty sand, and strongly weathered rock are 1513.7 m/s, 1484.3 m/s, 1532.0 m/s, 1511.3 m/s, 1693.9 m/s, 1602.7 m/s, 1599.4 m/s, and 2137.7 m/s, respectively. And statistical analysis shows that the sound velocity of the sediment in the study area has obvious quadratic correlations with the void ratio and compressibility. • Based on sub-bottom profiles and boreholes datasets, this paper develops a method of acoustic inversion of seabed sediment. • Innovatively establishing over-determined equations to solve sound velocities of different types of sediments. • Findings can provide important reference values to the geophysical survey and the development of seabed geoacoustics. [ABSTRACT FROM AUTHOR]

Geophysical electromagnetic (EM) surveys for imaging the subsurface structure under lakes, rivers, or other water bodies have attracted increasing attention. Based on forward modeling and field experiments, a boat-towed audio-frequency magnetotelluric (AMT) multi-channel observation system for shallow fresh water was developed preliminarily. Through the development of water electrodes and the streamer cable, a boat-towed multi-channel data acquisition cable was developed. We carried out a variety of different comparative experiments, such as water- and land-AMT experiments, different polar-distances, and acquisition time-length experiments, and observation experiments at different time, in ditches or rivers around the Qilihai Wetland, Tianjin, China. We also carried out profile detection experiments using this system in southern Baiyang Lake, Xiongan New Area, China. The experimental results demonstrate that the proposed water–AMT system can be utilized to characterize subsurface structure underneath shallow water areas, advancing the potential of geophysical surveys on rivers or lakes. • A boat-towed audio-frequency magnetotelluric multi-channel system is developed. • Water–land, polar-distance, and time-length experiments are carried out. • Field experiment results show the system is feasible and effective. [ABSTRACT FROM AUTHOR]

The evaluation of seismic site amplification and its relationship with geological structures play a vital role in earthquake engineering and hazard assessment. This study presents an analysis of topographic and geologic site amplification effects observed in the Qiaozhuang region, Sichuan Province, China. Seismic recordings at several monitoring stations installed on two slopes located at a distance of about 1 km in the study area after the 2008 Wenchuan earthquake provide evidence of strong and variable amplifications. To assess the combined effect of topographic and geological controls in slope response to seismic motions, we built 2D and 3D dynamic numerical models using monitoring data as inputs. Four layers with different P-wave velocities, based on geophysical survey in the study area, are considered in the numerical models. Models that only consider topography give an amplification factor of <3, which is much lower than the amplification factor of 5–6 from the monitoring data, while those models that considered both the topographic variation and four layers agree well with the monitoring data. The 3D modeling results show that the subsurface amplification factor is less than that on the slope surface even at the same elevation. This is also consistent with the monitoring data and further indicates that the combined topographic and geological amplification effect on the slope surface is more significant than the sole geological amplification effect inside the slope. Our numerical simulation results suggest that it is important to consider the combined topographic and geological amplification effects in the hazard assessment of seismically induced slope failures. • This study presents long-term monitoring data of slope seismic response. • Homogeneous numerical models show that topography alone only produces low amplification effects. • The results from three-layer heterogenous 3D model indicat the importance of geological amplification effect. [ABSTRACT FROM AUTHOR]

Debris landslides are one of the most common types of landslides in the Wenchuan earthquake area. The characteristics of the hydrogeological structure are the basis for landslide stability evaluation and protection treatment. The preferred seepage paths developed in debris landslides control the flow of groundwater and have a direct impact on the soil instability and sliding surface instability. Therefore, it is particularly important to understand the groundwater seepage system. Recently, many joint geophysical surveys have been used to detect the hydrogeological structure of landslides. However, these joint surveys aim to detect structures on a large scale and do not focus on the seepage path systems in debris landslides. It is difficult to detect the 3D structure of the seepage path system in detail, taking into account the portability, penetration, and resolution while meeting the practical needs of landslide prevention. To date, no one method has been identified as the best detection method for characterizing complex 3D hydrogeological structures. To reveal the complex seepage paths efficiently, we investigated a debris landslide in Xishan village, Sichuan Province, China, by using the transient electromagnetic method (TEM), which is a fast and portable method. Additionally, we proposed an effective quasi-3D inversion strategy with kdTree to determine the geoelectric structure and to make a geological interpretation. The interpretation was verified with field engineering surveys, other geophysical surveys, and remote sensing data. The results suggest that the complex 3D structure in this debris landslide is characterized by a dendritic pipe network-like seepage drainage system. In addition, this work assessed the ability to detect different parts of the landslide based on the given resolution. Furthermore, the resolution and detection efficiency of the TEM were compared with those of other geophysical methods. The assessment and comparison demonstrated that the TEM can be used as the main survey method to fulfill the real-world demands of detecting seepage path systems in a debris landslide. • 3D complex seepage paths of a huge debris landslide has been revealed efficiently. • We proposed an effective quasi-3D inversion strategy with kdTree to get the geological structure. • We have assessed the ability to detect different parts in the landslide using the resolution. • The resolution and detection efficiency of the TEM were compared with other geophysical methods. [ABSTRACT FROM AUTHOR]

• Seismic reflection data were acquired and analyzed for investigating deep-seated ore-controlling structures. • Joint modeling of potential field and seismic data images Datong graben and identifies three buried granitic intrusions. • Hongniangyu district has high potential of hosting porphyry-type Mo deposits. Since the discovery of several large porphyry Mo deposits (>0.1 Mt Mo) in the Jining region of Inner Mongolia, China, during the past decades, the area has been receiving wide interest for mining activities. However, mineral exploration in this area is challenging because most of it is thickly covered by Cenozoic sediments. Geophysical surveys, especially the seismic method, are becoming increasingly important for investigating deep-seated ore-controlling structures (e.g., porphyry granites, faults and even orebodies), supporting the discovery of buried ore deposits. Recently, potential field data and seismic reflection data have been acquired for the Hongniangyu area, south of Jining region. In this study, we mainly use seismic reflection and potential field data to obtain subsurface geological model in support of mineral exploration targeting. Gravity and magnetic data were firstly used for spatial analysis of mineral system by mapping the distribution of the faults, concealed granites, and the sedimentary basin (through wavelet analysis, tilt angle, and Euler deconvolution). To address the common problem of low signal-to-noise ratio of seismic reflection data obtained in hard-rock terranes, we applied a sophisticated workflow including refraction static correction, noise filtering, surface-consistent deconvolution, and velocity analysis. The obtained post-stack migrated seismic profile clearly imaged the geometry of the concealed graben located at the north end of the Datong Basin, and the South-East dipping Kouquan normal fault controls the depression of the graben and offsets Cenozoic sediments by several hectometers up to ~500 m. Joint modeling of seismic, gravity and magnetic data further provided evidence of the three buried belts of granites. Intriguingly, one of the concealed granitic belts located in the north of Hongniangyu area was found to have both significant chargeability and Mo geochemical anomalies, indicating a high potential of hosting porphyry-type Mo ore deposits. As expected, Mo and W mineralized cores were discovered in this target area but limited to only one deep drilling hole. The presented results provide the geological framework of Hongniangyu district and guidelines for delineating new potential Mo mineralization in the Jining region. [ABSTRACT FROM AUTHOR]

• FDCSEM has high signal-to-noise ratio and greatly improved exploration resolution. • Detectibility of the ore-forming rock masses is realized by 3D forward modeling. • The inversion results are coincided with the borehole results. • The research idea points out a new prospecting direction for sulfide deposits. Several magmatic Ni-Cu deposits associated with Permian-Triassic mafic-ultramafic intrusions have been discovered during the last three decades in the southern part of the Central Asian Orogenic Belt, the northeastern margin of Tarim, and the margin of the North China Craton. The accurate delineations of the large resistive rock masses are crucial for locating potential ore bodies when they are located beneath rock masse. The controlled-source electromagnetic method (CSEM) is an important tool for investigating resistivity contrast in earth subsurface. In this study, we present a comprehensive example of using frequency domain CSEM survey to delineate the resistive rock masses that are related to the forming of orebody. The horizontal electric field, which is more sensitive to resistive target than the other components, is used in our study. We first built a geophysical model of the survey area based on prior confirmed geophysical and geological information. Then, both forward and inverse modeling were performed in order to assess the detectability of the resistive ore-forming rock masses in the model. Finally, this study acquired field data in the Kalatongke Ni-Cu Deposit, which is located in the Kalatongke District of the southern section of the Central Asian Orogenic Belt, and is specifically part of China's southern Altai Orogenic Belt. The resistive ore-forming rock masses were successfully identified during the survey process and further verified by the drilling results. It was observed that both the synthetic and field examples indicated that the adopted frequency domain CSEM method successfully measured the electrical fields, and could be utilized to explore deeply buried resistive targets in future prospecting activities. [ABSTRACT FROM AUTHOR]

The Liaodong area which lies in the Liaoji Belt of northeastern China is rich in geothermal resources, but locating the resources is challenging. Here non-seismic geophysical data, existing geological data and the physical properties of rocks are examined to locate and characterise potential geothermal resources. High-precision gravity, aeromagnetic and magnetotelluric data are analysed to determine the characteristics of the hidden faults in the region and map the spatial distribution of the subsurface rock mass and its properties. The distribution of hidden faults and the basic characteristics of the rock mass were determined via Euler deconvolution of the gravity and aeromagnetic data. The subsurface extension of concealed faults, the spatial distribution of intrusive rocks, and the specific locations of underground thermal storage structures were determined from magnetotelluric data analysis, thereby enabling geothermal energy targets to be identified. The results highlight four potential sites of geothermal energy development in the study area, which indicate that non-seismic geophysical data can provide reliable clues to the geothermal energy potential in a given region. [ABSTRACT FROM AUTHOR]