As a material and energy exchange process between deep fluids and shallow depositional systems, hydrothermal activity exerts a crucial control on depositional environments, diagenesis, and organic matter enrichment, and shows significant spatial-temporal distribution in typical petroliferous basins of China. Based on mineralogical, lithological, and elemental-isotopic evidence, this study systematically summarizes and identifies hydrothermal mineral assemblages (e.g., dolomite, pyrite, and authigenic quartz) and geochemical fingerprints (e.g., enrichment of Fe, Mn, and light rare earth elements, Eu anomalies, and low δ18O values), and further outlines characteristic lithologic associations (e.g., siliceous rock-black shale and carbonate-organic matter interbeds). Within a regional comparative and multi-proxy framework, the geological records and paleoenvironmental changes related to hydrothermal activity in sedimentary basins are synthesized. Hydrothermal fluids alter redox gradients, supply nutrients (N, P, Fe, Si, etc.), and regulate temperature-salinity structures and water column stratification, thereby modifying salinity and local carbon cycling, which indirectly or directly affect primary productivity and organic matter preservation. Overall, hydrothermal activity exerts a dual “promotion-inhibition” effect on organic matter enrichment, with the final outcome controlled by multiple factors including temperature, fluid composition, and tectonic setting. Therefore, exploring the spatial-temporal distribution and environmental impacts of hydrothermal activity can improve our understanding of source rock formation and evolution, and provide a scientific basis for hydrocarbon potential assessment.

Globally, granite buried-hill oil and gas reservoirs have been revealed in 25 basins across 17 countries, with proven reserves exceeding 3 billion tons of oil equivalent. In China’s basins, proven reserves exceed 1.5 billion tons of oil equivalent. Granite has become an important target for oil and gas exploration in China, and rich achievements have been made in reservoir space types, rock physical properties, reservoir distribution patterns and genesis. Studies show that there are 7 categories and 12 types of reservoir spaces, mostly secondary pores and secondary fractures, with a small number of vesicles. The characteristics of reservoir space types vary among different oil and gas reservoirs. Granite buried-hill reservoirs are mainly of low to ultra-low porosity and medium to low permeability. The weathering crust thickness mostly ranges between 40 and 280 meters. The physical properties of granite buried-hill reservoirs decrease with increasing distance from the top of the weathering crust, though in rare cases, high porosity zones also exist at depth. Most oil layers/suspected oil layers/gas layers/oil-bearing water layers/gas-bearing water layers are distributed within about 200 meters to the top of the weathering crust, mostly concentrated within 150 meters. Granite buried-hill reservoirs exhibit zonation: The residual zone and weathering dissolution zone are mainly porous, the weathering fracture zone is mainly porous-fractured, and the bedrock zone is mainly fractured. Structural fractures exhibit a “sweet spot” distribution pattern. Parameters such as uniaxial compressive strength, permeability, and chemical alteration index can be used to establish quantitative relationships for the vertical zonation of the weathering crust. The reservoir formation mechanisms are mainly tectonic activity, weathering, erosion, and burial dissolution. Rock mechanics test results indicate that favorable internal conditions for fracture formation include coarse-grained crystals, high quartz and potassium feldspar content, etc.. Favorable external conditions include rapid cooling processes of the rock, and strong stress transformation during surface exposure. Weathering can form abundant weathering intergranular pores, weathering fractures, mold pores, sieve-like pores, intragranular micropores, and dissolution fractures in the residual zone and weathering dissolution zone. Erosion affects the preservation of the residual zone and weathering dissolution zone. A gentle slope on the top surface of the buried-hill favors the preservation of the residual zone and weathering dissolution zone. Burial dissolution can further expand pre-existing dissolution pores and fractures, promoting the development of inner reservoir zones in the bedrock zone. It is pointed out that inner reservoirs are more developed in the basin subsidence center areas. The porosity evolution of the reservoir at the top of the residual zone and weathering dissolution layer under compaction conditions follows a modified Athy formula. The average particle size and plagioclase content are negatively correlated with the porosity reduction amount while the chemical alteration index is positively correlated with the porosity reduction amount. Differences in rock fabric and the coupling relationship between the buried-hill uplift process and tectonic stress action result in differential fracture effects in buried-hills. In summary, favorable exploration areas for granite buried-hills are identified as regions with coarse grains, high quartz content, high potassium feldspar content, rapid exhumation, gentle slope surface, proximity to the basin subsidence center, and strong late tectonic modification. 

 The helium gas (He) is one of the important strategic scarce resources, and the understanding of depletion mechanisms and resource potential is extremely weak. The Xinchang gas field from the Sichuan basin is taken as an example in this study to analyze the abundance and origin of helium, and the depletion mechanisms and main controlling factors are revealed with the resource potential being further discussed. The study indicates that natural gas from different strata of the Xinchang gas field displays the He content ranging from 0.007 7% to 0.040 0%with a low He content. The R/Ra ratio ranges from 0.010 to 0.050, suggesting a typically crustal source with little contribution by mantle-derived He. The He content displays positive and negative correlations with the N2 content in natural gas and the content of total dissolved solids (TDS) in reservoir water, respectively. The depletion of helium is mainly attributed to the source of helium being the strata themselves rather than the basement rocks due to the underdevelopment of deep faults, the high gas generation intensity of source rocks and charging intensity of natural gas, as well as the small uplift amplitude and weak dissolution effect since the Cretaceous. The Xinchang gas field is a medium helium gas field with a proven helium reserve of 25.45×106 m3. The exploration of high-helium and helium-rich gas resources in the Sichuan basin is suggested to pay attention to the areas with the development of basement faults, medium gas generation intensity of source rocks, and high uplift amplitude after gas accumulation.

 As critical strategic mineral resources, dispersed metals play an irreplaceable role in national economic development, security, and technological innovation. They serve as fundamental supports in cutting-edge fields such as high-tech industries, precision manufacturing, clean energy, and next-generation information technology. Constrained by their geochemical properties, these elements typically occur in a highly dispersed state in nature, seldom forming independent minerals and instead mainly existing as associated components hosted in major metal minerals. Within Pb-Zn deposit systems, sphalerite is widely recognized as a key host mineral for critical dispersed elements such as gallium (Ga), germanium (Ge), cadmium (Cd), and indium (In). This paper systematically reviews recent research advances on the enrichment patterns of dispersed elements in Pb-Zn deposits, with a focus on elucidating their occurrence states and enrichment mechanisms. Studies indicate that elements such as Ga, Ge, Cd, and in primarily occur in an isomorphous form within the crystal lattice of sulfide minerals like sphalerite, while independent minerals are extremely rare and generally negligible in abundance. Specifically, Ga, Ge, and In tend to couple with ions such as Cu+, Ag+, and Fe2+ to jointly replace Zn2+ in sphalerite, whereas Cd, due to its geochemical similarity to Zn, can directly substitute for Zn2+ in the crystal lattice. Consequently, sphalerite becomes the most significant host for these dispersed elements. It is noteworthy that elevated iron content in sphalerite significantly inhibits the isomorphic substitution of Cd, demonstrating the strong influence of crystallochemical conditions on its enrichment behavior. Additionally, Ge can occur isomorphously in silicate minerals such as quartz. From a regional metallogenic perspective, the concentrations of dispersed elements vary considerably among different genetic types of Pb-Zn deposits. Even within deposits of similar geological settings, their spatial distribution often exhibits pronounced heterogeneity. In terms of enrichment environments, Ga, Ge, and Cd are more readily enriched in low-temperature hydrothermal Pb-Zn deposits, whereas In is predominantly concentrated in intermediate- to high-temperature magmatic-hydrothermal systems or tin-bearing polymetallic Pb-Zn deposits. In terms of research methodology, modern microanalytical techniques, particularly electron probe microanalysis (EPMA) and laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS), have played a pivotal role. With their high spatial resolution and in-situ analytical capabilities, these techniques enable precise characterization of the occurrence and spatial distribution of dispersed elements in minerals at the nanoscale, thereby providing indispensable technical support for understanding their geochemical behavior and enrichment mechanisms. Future research should focus on key scientific issues such as identifying the material sources of dispersed elements, understanding their migration forms in ore-forming fluids, clarifying precipitation mechanisms, and deciphering their coupling relationships with the mineralization processes of major metals. Such efforts will deepen the understanding of the super-enrichment mechanisms of dispersed elements and provide theoretical guidance for integrated exploration and efficient utilization.

 The petrogenetic age and magmatic evolution of large granitic complexes are significant for elucidating petrogenesis and deep-seated dynamic processes. The Huangyangshan pluton in eastern Junggar, Xinjiang Province, a typical granitic complex within the Kalamaili alkali-rich intrusion belt, is featured by accompanying alkaline and aluminous A-type granites and hosting two large crystalline graphite deposit closely associated in its aluminous unit. However, the petrogenetic sequence of its lithofacies and the relationship between magmatic evolution and graphite mineralization remain debated. Based on detailed field geological investigations and previous data, this study conducted SIMS zircon U-Pb dating analyses on different lithofacies of the Huangyangshan pluton, and discussed its evolution sequence, the relationship between magmatic evolution and graphite deposit formation. The results reveal reveal a clear south-to-north progression: Fine-grained biotite alkali-feldspar granite ((312.7±1.4)Ma), medium-coarse-grained biotite alkali-feldspar granite ((313.5±1.5) Ma), medium-fine-grained amphibole alkali-feldspar granite ((302.4±1.9)Ma), medium-grained arfvedsonite granite ((297.7±1.5)Ma), and medium-fine-grained arfvedsonite granite ((297.1±1.5)Ma), all formed in the Late Carboniferous, showing a clear magmatic evolution sequence from early to late stages. The ~15 Ma duration of aluminous A-type magmatism likely controlled the super-large graphite deposit formation within the pluton. The formation of the Huangyangshan pluton initially involved dehydration melting of biotite and amphibole in calc-alkaline rocks in the magma source area to generate the aluminous A-type unit. Subsequent partial melting of hornblende (+ minor biotite) in the pre-existing calc-alkaline rocks, induced by mantle-derived high-temperature magma or alkali-rich fluid metasomatism, ultimately formed the alkaline A-type unit in the northern part of the pluton.

 The accurate reconstruction of the formation and evolution of ancient ocean basins, as represented in the orogenic belts, constitutes an important research content in geotectonics. Focusing on the Meso-Tethys (Bangong-Nujiang suture zone) of northern Tibet, this study systematically examines the characteristics of ocean islands (seamounts) and therir geological significance in understanding paleo-oceanic basin dynamics. Ocean islands (seamounts) within orogenic belts exhibit not only widespread distribution but also remarkable diversity.In addition to the traditional hotspot-type ocean islands (seamounts), they also include slow- and fast-spreading mid-ocean ridge-type ocean islands (seamounts) and intra-oceanic arc-type ocean islands (seamounts). Their common characteristics are the development of ultrabasic-basic magmatic rock assemblages and pelagic colluvial conglomerates. Ocean islands (seamounts) are the main components of “oceanic crust fragments” in orogenic belts and serve as important carriers of information on the formation and evolution of ancient ocean basins. Particularly, they provide critical insights, particularly in revealing the nature of ancient ocean basins, reconstructing their convergence and termination processes, and analyzing the temporal duration of ancient oceanic crust. 

 To address the theoretical and technological bottlenecks in drilling and extraction under complex utilization, and to enhance China’s competitiveness in fields such as strategic resource development, new energy and extreme environment exploration, this study defines the concept of complex conditions, and separates it into four dimensions, namely, complex geological conditions, complex surface environments, complex resource resource conditions, and complex environmental protection requirements. It systematically reviews core literature, typical engineering practice cases, and achievements in key technological breakthroughs in the field of drilling and extraction under complex conditions at home and abroad. From five perspectives such as deep drilling technology and equipment, polar scientific drilling technology, unconventional energy and mineral drilling and extraction technology, bionic drilling and extraction theory and technology, and multi-process percussion-rotary drilling technology, the study conducts an in-depth analysis of the technological bottlenecks in this field. Aligning with major national strategic demands in the deep earth, deep sea, deep space, and polar regions, breakthrough pathways are proposed to shift from “passive response to complexity” to “proactive mastery of extremes”, based on four dimensions of deep earth extreme geology, cross-border extreme environments, low-quality and hard-to-extract resources, and stringent environmental constraints. This research provides a systematic technological framework and decision-making support for safeguarding national resource security, facilitating the transformation and upgrading of the energy structure, and implementing the strategy of building China into a leading science and technology nation.

 In cold region engineering, the shear performance of frozen soil-structure interface is a key factor influencing the long-term service stability of facilities. However, the existing studies lack systematic characterization of the interface damage mechanism under the action of multi-physical field interactions. In order to reveal the mechanical behavior of frozen soil-structure interface by adjusting the ice-water phase transition process under the disturbance of thermodynamic conditions, this study systematically reviews the research progress of shear properties of frozen soil-structure interface from three aspects such as experimental methods, influencing factors and constitutive models. Firstly, by summarizing the methods of direct shear test, in-situ test and model pile test, the influence pathways of various factors on the mechanical behavior of the interface under the multi-field coupling condition of heat-water-salt-force are clarified. Furthermore, the mechanism of temperature, moisture, freeze-thaw cycle and salt on the interfacial shear performance by regulating the ice-water phase transition process was analyzed. Finally, the applicability and limitations of the existing constitutive model of frozen soil-structure interface are evaluated. The results show that the temperature gradient and water migration change the interfacial shear performance by regulating the ice cementation strength and the thickness of the unfrozen water film during the ice-water phase transition process. The pore reconstruction and ice crystal differentiation caused by freeze-thaw cycles lead to the deterioration of interface strength. Salt affects the interface space composition by changing the phase transition temperature threshold and salt crystallization expansion effect. The existing models have obvious deficiencies in ice-water phase transition, long-term freeze-thaw and multi-field coupling characterization. It is suggested that future work focus on developing a thermo-hyforr-salt-mechanical coupled interface model based on a “test-observation-model” framework integrated  with cross-scale observation technology, thereby providing a design basis and research direction for frost-heave prevention and disaster mitigation in cold regions.

 In Southwestern China, soil-rock mixtures characterized by loose structure, high porosity, and low strength are widely distributed. Tunneling through such strata often leads to, challenges such as poor stability, excavation collapse, and structural failure,posing serious risks to construction and operation. Based on a metro tunnel section in Chongqing, this study investigates the mechanical responses during tunnel excavation using physical model tests. It reveals the evolution of surrounding rock displacement, stress distribution, and surface settlement, and compares the effects of three excavation methods such as full-face, top-and-bottom heading, and core-soil-reserved methods. The displacement of the surrounding rock during excavation progresses through four stages, namely, undisturbed, slow deformation, abrupt change, and stable equilibrium. Deformation is most significant at the tunnel crown, where vertical displacement at 0.2 times the tunnel diameter above the crown is 1.96 times the horizontal displacement at the same distance from the haunch. Radial stress variations exhibit a zigzag trend. Stress-relief influence weakens from crown to shoulder to haunch, while stress-drop magnitude ranks shoulder, haunch, crown. Surface settlement also follows a four-stage pattern: insensitive, slow deformation, accelerated deformation, and stabilization. The curvature of surface monitoring points along the tunnel axis increases gradually as the excavation face approaches the monitoring section. The influence of different excavation methods on the disturbance of surrounding rock is decreased in the order of full section method, upper and lower bench method and reserved core soil method. The reserved core soil method can effectively reduce the deformation of surrounding rock, surface settlement and surface influence range.

 This review aims to elucidate the synergistic mechanisms, influential factors, and remediation potential of combined biochar-microbially induced carbonate precipitation (MICP) technology for addressing complex contamination in farmland soils. Recent studies were systematically analyzed to compare the physicochemical properties of biochar and the microbial mineralization pathways of MICP, assess their respective stabilization mechanisms for pollutants, and evaluate the performance and environmental implications of their combined application under different contamination scenarios. Biochar immobilizes pollutants via adsorption, complexation, and pH regulation, but its long-term stability is constrained by environmental aging. MICP achieves durable heavy-metal stabilization through carbonate precipitation and lattice incorporation, yet suffers from slow reaction rates and environmental sensitivity. Their combination produces notable synergistic effects: biochar serves as a microbial carrier and pollutant enrichment matrix to enhance urease activity and carbonate formation, while MICP-generated mineral layers reinforce biochar stability. The joint system reduces pollutant mobility and improves soil microbial diversity and enzymatic activity. However, issues such as ammonia accumulation, pore clogging, and uncertain long-term ecological impacts remain unresolved. The biochar-MICP combined approach integrates rapid adsorption with durable mineral stabilization, offering a promising strategy for farmland soil remediation. Future research should focus on microbial engineering, cost-effective calcium sources, targeted biochar modification, multi-process collaborative remediation systems, and long-term ecological risk assessment.

 The Songliao basin, a vital energy and industrial base in China, has substantial CO2 emissions and abundant underground saline water, possessing potential for CO2 geological sequestration. To enable the scientific selection of sites for CO2 geological storage in saline aquifer and to systematically evaluate the storage suitability of this region, this study focuses on the Central depression of Southern Songliao basin, analyzing the engineering geological conditions, sequestration potential, and socioeconomic conditions with a geographic information system (GIS) based multi-criteria decision analysis (MCDA) approach. Firstly, an evaluation indicator system comprising 3 primary indicators and 31 secondary indicators was established. Secondly, GIS was used to generate a 1 km-resolution raster layer of the data for each evaluation indicator. Then, reclassify the raster data according to the classification criteria. Finally, the raster layers for each indicator were overlaid with weighted values based on the weights determined by the analytic hierarchy process (AHP) and generate a  suitability map for CO2 geological storage in saline aquifers in the Central depression area of the southern Songliao basin. The results indicate that suitable areas are mainly located in the northern portion of the Honggang terrace and the southwestern part of the Changling depression, accounting for approximately 24.0% of the total regional area. Unsuitable areas are concentrated in the Fuxin uplift, accounting for only 6.8% of the total regional area. In total, nearly 56.0% of the area is suitable or relatively suitable for CO2 geological sequestration in saline aquifers. More than half of the areas within the Central depression in the southern Songliao basin meet the fundamental requirements for CO2 geological storage in saline aquifers. Further optimization and engineering deployment can proceed.

 To construct a comprehensive anti-pollution system in mining areas, ensure the safety of soil and groundwater, and safeguard public health, it is of great scientific and practical value to investigate the release and migration patterns of heavy metals in mining areas and developing corresponding pollution assessment and numerical simulation methods. Based on sorting out existing research results, this review systematically summarizes the common experimental methods and kinetic models for studying heavy metal release from tailings and waste rocks, concludes the influence mechanisms of internal mineralogical characteristics and external environmental factors on heavy metal release behavior, and reveals the key roles of heavy metal occurrence forms, physical and chemical properties, and soil physical and chemical properties in their migration process. Meanwhile, this paper systematically reviews the common assessment methods and numerical simulation software currently used in the field of groundwater heavy metal pollution, conducts a comparative analysis of the applicable conditions and limitations of various methods and tools, and discusses the emerging application progress of machine learning technology in this field. Research shows that although existing achievements have made important progress in revealing the release and migration laws of heavy metals in the groundwater environment of mining areas and in pollution assessment and prediction, challenges still exist in comprehensively explaining the release and migration mechanisms under the coupling effect of multiple factors and realizing long-term dynamic and accurate prediction. Future studies should strengthen the combination of laboratory mechanism research and on-site monitoring, promote the in-depth integration of interdisciplinary collaboration and data-driven technologies, thereby providing more solid scientific basis and technical support for the prevention and control of heavy metal groundwater pollution and ecological environment protection in mining areas.

 Under low hydraulic gradients, low-permeability media often exhibit low-velocity flow. Investigating the mechanisms of low-velocity seepage is crucial for groundwater environmental protection research. Fluid flow in low-permeability porous media is influenced by a combination of multiple factors. This study systematically investigates the effects and mechanisms of low-velocity seepage in different types of cohesive soils at varying temperatures through laboratory constant-head permeability tests and nuclear magnetic resonance (NMR) experiments. The results indicate: 1) Temperature elevation significantly enhances the hydraulic conductivity of clayey soils. Within the 5-30 ℃ range, increasing temperature raised the hydraulic conductivity of white clay, loess, and silty clay by 289.9%, 210.4%, and 156.2%, respectively, while simultaneously decreasing the critical hydraulic gradient from approximately 10 to around 4. 2) Temperature elevation promotes the conversion of weakly bound water to free water. When temperature increased from 5 ℃ to 30 ℃, the bound water mass fraction of white clay, loess, and silty clay decreased by 23.1%, 22.8%, and 25.6%, respectively. Reduced bound water mass fraction increases effective pore space and lowers flow resistance, thereby enhancing hydraulic conductivity and decreasing the critical hydraulic gradient. 3) Temperature regulation of permeability coefficients exhibits a viscosity-bound water coupling effect, but bound water dominates permeability influence. Within the 5-30 ℃range, the contribution of bound water to hydraulic conductivity coefficients in cohesive soils increases with rising temperature. At constant temperatures, white clay soil exhibits the strongest influence of bound water on hydraulic conductivity, followed by loess, with silty clay showing the weakest effect.

 Through ongoing exploration efforts, the distributions of mineral resources within the upper 500 m have been largely mapped across most regions. However, over two-thirds of China’s territory is covered by complex terrain such as marshes, forests, deserts, and medium-to-high mountain ranges. Mineral exploration in these challenging terrains has reached a critical juncture requiring urgent breakthroughs. The airborne-ground-borehole gravity-magnetic multi-parameter detection technology   (encompassing raw field, component field, and gradient field measurements) forms a rapid breakthrough chain of ‘rapid delineation-detailed verification-precise targeting’. This constitutes an effective approach for the rapid and accurate exploration of mineral resources within complex terrain areas. This paper, guided by the exploration requirements for mineral resources in complex terrain areas, systematically outlines research advances in  principles, equipment, data calibration and processing, platform technologies, and inversion methods of  airborne-ground-borehole multi-parameter gravity-magnetic detection. We clarify the complementary hierarchical structure of aerial, ground-based, and downhole detection within the three-dimensional exploration technology system, elucidating its practical application logic and future development trends towards miniaturisation and intelligent operation. This provides technical reference for the upcoming strategic initiatives aimed at achieving breakthroughs in mineral exploration.

 Adjusting the derivative order of fractional-order magnetic gradient (FMG) can tune the resolution of magnetic materials at different depths. However, direct FMG measurement methods remain lacking. Therefore, this article focuses on the research of fractional-order magnetic gradient measurement method. This article uses the external source terms of the Laplace equation solved in a spherical coordinate system as the model of the magnetic field inside the sphere, calculates the fractional-order derivatives in the corresponding directions of the model, and achieves FMG measurement. We evaluate sensitivity to measurement position error and field-measurement error through simulation, showing that the normalized root mean square error  increases monotonically with the derivative order. An experiment is conducted to verify the measurement method, and the relative error between the experimental results and the theoretical values does not exceed 6.00%, verifying the correctness of the measurement method.

 The disturbance signals generated by ferromagnetic objects in a magnetic field provide a non-contact and passive means for target localization and tracking. However, traditional magnetic vector localization methods based on physical modeling suffer from degraded accuracy and limited robustness in complex environments. In this paper, we propose a magnetic anomaly tracking convolutional neural network (MagTrack-CNN) for high-precision spatial dynamic localization of ferromagnetic objects. The proposed method employs a dual-layer magnetic vector observation architecture to enhance localization sensitivity along the depth direction by incorporating vertical gradient information. A dual-branch independent prediction network is designed to mitigate gradient competition among spatial components, while a multi-scale feature extraction framework is constructed to effectively capture magnetic anomaly patterns at different spatial scales. Experimental results in stable magnetic field regions for localization scenarios involving a single uniformly magnetized target demonstrate that MagTrack-CNN achieves an overall positioning accuracy of 1.98 cm on the test set, and exhibits superior accuracy in z-axis localization. In dynamic localization tests across different trajectory types, the method consistently produces correct dynamic positioning. Meanwhile, noise sensitivity experiments show that under measurement noise levels of 0.5%-3.0%, the model maintains low errors (the mean absolute error  increases from 0.42 cm to 0.46 cm). Furthermore, the per-sample inference time remains within 2.3 ms, highlighting its promising potential for practical applications.

 With the depletion of shallow resources, refined exploration of deep metal deposits has become a key focus in geophysical prospecting. Underground electromagnetic (EM) methods demonstrate distinctive potential in deep mineral exploration owing to their proximity to target bodies, strong anti-interference capability, and high-resolution imaging. Internationally, these methods have been established as core technologies for exploring deep (>500 m) massive sulfide and disseminated deposits. This paper systematically reviews recent advances in borehole, crosswell, and borehole-to-surface EM methods both domestically and internationally, analyzing the developments of high-power transmitters, high-sensitivity receivers, and multicomponent observation systems, and summarizing numerical modeling, inversion algorithms, and intelligent data processing under complex well conditions. Within the workflow of deep mineral exploration, application strategies of underground EM techniques at different stages are summarized, including constraining metallogenic background, guiding metallogenic models, supporting target prediction, and locating ore bodies. Results indicate that underground EM methods are evolving toward multi-source integration and multi-parameter fusion, forming deep-exploration frameworks of “multi-parameter cascading with near-far integration” and “strong-source close-receiving with dense irradiation and wide-area coverage”, providing technical support for deep mineral exploration.

 Currently, the exploration potential for mineral resources in China’s plains and gently undulating hilly areas is relatively limited. Future prospective areas for mineral exploration are mainly distributed in the deeply incised, high-altitude regions of western China. These areas are characterized by rugged topography, challenging accessibility, and sensitive ecosystems, which impose significant constraints on the implementation of traditional ground-based geophysical exploration methods. As an efficient geophysical detection technique, the time-domain airborne electromagnetic (TDEM) method holds great application value for mineral exploration in deeply incised complex terrain. This study conducts three-dimensional forward modeling research for TDEM surveys based on the finite volume method and octree mesh technology. The correctness of the forward algorithm is first verified using a half-space model. Ridge and valley terrain models are constructed to compare and analyze the differences in electromagnetic responses under different flight modes. Furthermore, by embedding low-resistivity anomalous bodies beneath undulating terrain, the coupling mechanism between topographic effects and ore body responses is investigated. Finally, the method is performed to forward modeling based on an actual geological profile from the Xiarihamu area. The research demonstrates that in areas with steep terrain such as ridges and valleys, the early-time responses are generally enhanced, while the late-time responses significantly decrease at ridge tops and increase markedly at valley bottoms, revealing characteristic terrain-induced distortions. Additionally, topography causes complex multi-faceted distortions in the responses of mineralized anomalous bodies: early-time and late-time responses may be obscured by terrain-induced distortions, but the variations caused by the anomalous bodies remain identifiable during the mid-time response stage. Lastly, the modeling results from the real geological profile verify the practicality of this method in deeply incised terrain and complex geological conditions, providing reliable theoretical support for three-dimensional inversion of TDEM data.

 Most seismic data processing techniques have been designed to solve specific practical geophysical problems, with limited focus on the fundamental properties of seismic data. Seismic data vary simultaneously in time, space, and frequency, making conventional signal classification methods inadequate. Currently, there is no clear definition of the essential attributes of seismic data, which limits the development of advanced processing techniques. Here, we propose a new definition of nonstationarity tailored to seismic data, based on the unique ordering relationships of data in seismic acquisition systems and the presence of practical nondeterministic factors. Under this framework, we identify six representative nonstationary features, including statistical properties of random seismic noise, and amplitude compression, energy spectrum predictability, time-frequency spectral attenuation, waveform similarity and amplitude periodicity of effective signals. To address these features, we review the recent advances in seven corresponding processing strategies, including median filtering, sparse transformation, predictive filtering, time-frequency analysis, inverse Q-filtering with Q (quality factor) estimation, similarity analysis, and chaotic system modeling. These methods support the emerging of “two-wide and one-high” integrated acquisition schemes for massive datasets collected in “three-complex” environments—complex near-surface conditions, structural complexity, and heterogeneous lithologies—and target the “three-high and one-fast” processing goals: high signal-to-noise ratio, high resolution, high fidelity, and fast computation. This work lays the theoretical and technical groundwork for high-precision seismic exploration.

 The microtremor horizontal-to-vertical spectral ratio (HVSR) method is an efficient and non-invasive geophysical technique widely used in urban geological surveys and engineering investigations. However, transient interferences caused by pedestrians and vehicles can distort the shapes of HVSR curves. Existing transient interference elimination methods have limitations: the STA/LTA (short-term-average over long-term-average) method is prone to misjudgment and requires complex parameter tuning; The manual rejection method is inefficient; And the frequency-window based rejection algorithm considers only peak-frequency information. To address these issues, this study proposes a machine-learning-based interference suppression method for microtremor HVSR data. First, curve-shape features are extracted to train a curve-rejection model for identifying and removing HVSR curves that significantly deviate from the mean trend. Then, peak-related features are extracted to train a peak-identification model for recognizing valid resonance peaks within the  curves. Finally, a density-based spatial clustering of applications with noise (DBSCAN) algorithm is applied to cluster and further eliminate curves containing peaks with abnormal frequencies or amplitudes. The curve-rejection and peak-identification models achieve F1 scores of 0.967 and 0.985 on the test set, respectively, demonstrating excellent classification performance. Case studies show that the proposed method exhibits higher stability and accuracy in eliminating abnormal curves than the STA/LTA and frequency-window based rejection methods. The processed HVSR curves display more concentrated spectral distributions, more convergent standard-deviation curves, and clearer, more stable peaks. Moreover, the proposed method achieves efficient automatic processing while maintaining strong consistency with manual rejection results.

 To improve the quality of marine exploration signals, this paper investigates the stability control problem of a marine vibrator system with uncertain disturbances. Firstly, for the external and internal disturbances caused by the complex working environment in the ocean, an optimal fast finite-time extended state observer (FFTESO) is designed to observe the lumped disturbances of the system. Meanwhile, the observer can estimate the state variables of the system. Secondly, to improve the stability of the vibrator output waveform, a fractional-order finite-time sliding mode surface control scheme is designed to reduce displacement error and output chattering of the controller. Thirdly, the designed control system is proved to be fast finite-time stable via the Lyapunov’s integer and fractional order theorems. Finally, the simulation results verify the effectiveness and feasibility of the proposed control system combining a FFTESO with a fractional order finite time sliding mode control (FOFTSMC). The results show that the maximum relative error of the observer is reduced by 29.5%, and the peak-to-peak chattering value of the controller decreased by 25%.