The discontinuities of a ridge, defined by the geophysical properties, often coincide with geochemical variations in lava, highlighting the relationship between ridge discontinuity and the underlying magmatic system. This study presents bathymetric, geophysical, and basaltic geochemical data from the Daxi-non transform discontinuity (NTD) and adjacent segments. The Daxi-NTD is a typical micro-NTD, with an offset less than 15 km. Within the NTD, a neo-volcanic ridge has emerged, with an active hydrothermal system suggesting an underlying magmatic system. The study examines mantle composition, melting degree, crystallization pressure, and melt extraction processes beneath Daxi-NTD. Comparative analysis reveals that basalts in the Daxi area undergo extensive differentiation, characterized by higher crystallization pressure and lower melting degree compared to the adjacent segments. We propose that Daxi-NTD hosts an independent magmatic system, where melt migrates vertically through the magmatic system rather than laterally from the adjacent segment center. This approach aids in understanding the magmatism along slow-spreading ridges and provides insights into the geodynamics and tectonic evolution of younger ridge systems.
The interaction between the Izanagi-Pacific ridge and the northeastern Eurasian Plate during the Eocene remains controversial. We focus on oceanic crust-derived adakitic rocks due to their potential for reconstructing the slab window associated with spreading ridges. New and previously published age data suggest that these adakitic rocks can be divided into three main episodes: Early Ypresian (ca. 55 Ma), Lutetian (ca. 46 Ma), and Bartonian (ca. 36–38 Ma). These rocks, which range from andesitic to dacitic in composition, are characterized by pronounced depletions in heavy rare earth elements (HREEs), low Y, high Sr, and high Sr/Y ratios. Variations in Mg, Mg#, Cr, and Ni values indicate partial melting of the subducted slab, followed by interaction with the surrounding mantle during ascent through the mantle wedge. Spatially, the first stage is localized as a ‘spot’ in NE China, suggesting a limited ridge-trench intersection. The subsequent two stages occur in two narrow belts, indicating large-scale ridge-trench intersections subparallel to the NE Eurasian margin. The temporal and spatial variations in adakitic rocks related to slab windows are best explained by changes in the scale of the Pacific-Izanagi ridge Subduction, possibly reflecting the variations in Pacific Plate movement during the Early Eocene.
The rapid accumulation of conglomerates not only preserves tectonic episodes and uplift/denudation histories of the orogenic belt, but also correlates with the coupling process of the basin and the mountains. Two units of conglomerates that belong to the third (Mbr 3) and fourth (Mbr 4) members of the Upper Triassic Xujiahe Formation are distributed along the northern Sichuan Basin. Mbr 4 has an uncomfortable contact on Mbr 3. Mbr 3 is dominated by carbonate gravels forming fan-shaped deposits distributed discontinuously, whereas Mbr 4 consists of massive quartzite gravels that extend eastward continuously. Detrital zircon U-Pb data show the peak age of 227 Ma from the Qinling orogenic belt are widespread in Mbr 3, but occur in only the central part of the northern Sichuan Basin of Mbr 4. However, paleocurrent indicators and sandstone petrologic data reveal both units were sourced from the Qinling Orogen. We interpret the differences in clastic compositions and U-Pb ages as reflecting discrepant uplift and rapid unroofing processes of the Qinling orogenic belt, which underwent continual uplift and southward thrusting. This process controlled the evolution and infilling of the Late Triassic Sichuan foreland basin in the tectonic domains of syn-collision between the South China and North China Blocks.
The Shijia gold deposit, situated in Penglai City, Shandong Province, is distinguished by fracture-filling auriferous quartz-sulfide veins. Studies of fluid inclusions and stable isotopes of hydrogen, oxygen, carbon, and sulfur were conducted on this deposit. The results reveal that the auriferous quartz primarily contains four types of fluid inclusions, including CO2-H2O inclusions, pure CO2 inclusions, two-phase aqueous inclusions, and solid mineral-bearing multiphase inclusions. The ore-forming fluids of Shijia belong to a heterogeneous H2O-CO2-NaCl system, characterized by moderate to high temperatures (187–386 °C), a wide range of salinities (0.2%–41.2% NaCleq), and low densities (0.72–1.07 g/cm3). Evidence suggests that fluid immiscibility and fluid-rock interaction occurred at Shijia, with mineralization depths ranging from 3.3 to 3.9 km. The δD and $\delta^{18}\rm{O}_{\rm{H}_{2}\rm{O}}$ values of auriferous quartz vary from −86.1‰ to −79.1‰ and from 9.4‰ to 10.5‰, respectively, suggesting that the ore-forming fluids are of magmatic origin. Carbon isotope compositions of hydrothermal calcite (−3.31‰ to −0.86‰) indicate the carbon might be related to a mantle source that was contaminated by marine carbonates. The positive δ34S values of sulfides (4.3‰–7.3‰) reflect that the ore-forming materials may be sourced from the metasomatized lithospheric mantle beneath the North China Craton, related to the subduction of the Yangtze Craton in the Triassic. Collectively, geology, fluid inclusion and H-O-C-S isotopes evidence indicate that the Shijia gold deposit is of magmatic-hydrothermal origin and related to the Guojialing granite formed by the mixing of crust- and mantle-derived magmas.
Tourmaline is a common borosilicate mineral in granite and pegmatite, and it is also an important carrier to record the physicochemical evolution information of magmas. However, the genetic relationship between pegmatite-type rare metal mineralization potential and tourmalinebearing pegmatites is not clear, and the tourmaline geochemical indication of the mineralization type of rare metals needs to be supplemented. In the middle Altun region, extensive tourmalinebearing pegmatite dykes are prevalent within and surrounding the Tugeman complex. In this paper, the petrology and geochemical characteristics of tourmaline within the pegmatite of the Tugeman Be-Li deposit have been comprehensively analyzed. The research delves into the genetic evolution and metallogenic potential of the pegmatite, emphasizing the indicative role of tourmaline geochemistry in discerning mineralization types in the Tugeman Be-Li deposit. Major and trace element analysis of tourmaline reveals varying contents of FeO (9.37 wt.%–17.10 wt.%), Al2O3 (28.6 wt.%–35.2 wt.%), and MgO (0.13 wt.%–2.47 wt.%) in the Tugeman Be-Li pegmatite. Li, Zn, and Sn contents range from 204 ppm to 1 590 ppm, 1 143 ppm to 4 089 ppm, and 74.1 ppm to 396 ppm, respectively. The tourmaline analyzed in this study is of magmatic origin and belongs to the schorl series, exhibits substitution relationships, including (Na, Fe2+)(X□, Al)−1, (Fe2+, Fe3+)(Mg, Al)−1, (Al, X□)(R2+, Na)−1, (Na, Mg)(X□ Al)−1 and X□NaR2+−1. The trace element data of tourmaline show that lithium has four enrichment stages in different mineral crystallization phases. Notably, the tendency of tourmaline in the Tugeman Be-Li pegmatite to evolve towards elbaite implies a magmatic evolution sequence from low to high, transitioning through microcline-albite pegmatite, muscovite-microcline-albite pegmatite, albite pegmatite, and microcline pegmatite. Furthermore, we also propose that the Sc content in schorl can serve as an indicator of pegmatite mineralization type, and the Tugeman Be-Li pegmatite has evolved to a beryllium-rich stage and has certain lithium enrichment potential.
Analyzing and integrating evidential layers is essential for mineral prospectivity mapping. Remote sensing data from Landsat 8 and PALSAR-2/ALOS-2 were used to extract information about hydrothermal alterations and lineaments in a vegetation-covered study area. After integrating geological data, five evidential layers were identified, associated with gold mineralization, including lithology, hydrothermal alterations, lineaments, quartz veins, and geochemical anomalies. Based on these layers, prospective maps for mineralization were generated using RF and Fuzzy AHP models, as well as their ensemble. The P-A plot was used to evaluate the capability of model prediction. The results indicated that the three models yielded similar predictions, with areas of high mineralization potential located in the central part of the Daping area. The ensemble model demonstrated superior predictive performance.
The Precambrian Ukrainian Shield is known for its enormous mineral endowment. Mineral deposits are a part of the overall geological and tectonic setting, including the deep energy source, the mineral source, the fluid channels, and the deposition mechanisms. All these aspects can be accompanied by associated geological and geophysical manifestations from the surface to the mid-lower crust. The network of 279 long-period magnetovariational data within the periods 100–900 s allowed us to investigate the geoelectrical structure in the northwestern Ukrainian Shield, bounded by coordinates 48.5°–51.7° N and 26°–30° E. 3D inversion of magnetic components of the natural electromagnetic field led to the construction of regional-scale spatial geoelectric models of the area. The character and position of the conductors indicate their link to recently active faults, their intersections, and to mineralization. The Precambrian history of crystalline rocks primarily suggests a sulphite-graphite origin of the conductivity anomalies, but their depth, vertical extent and association with reactivated fault systems may indicate the origin of mineral deposits in fluid upwelling from depth. The obtained results in correlation with geothermal models contribute to the idea of the depth structure, tectonic processes and the link between geoelectrical characteristics of the Earth’s crust and upper mantle with fault systems and mineralization.
Shale has strong compositional and structural heterogeneity, and its molecular structure model accuracy is a bottleneck which limited the molecular simulation results. To improve reproducibility of three-dimensional (3D) intact shale model and enhance the reliability of molecular simulation results. The chemical composition of the carbon skeleton, functional groups, and chemical bonds in organic matter (OM) were quantitatively characterized through a combination of methods including 13C nuclear magnetic resonance (NMR), Fourier transform infrared spectroscopy (FT-IR), and X-ray photoelectron spectroscopy (XPS). The two-dimensional (2D) OM structure was reconstructed according to above experimental results in software ACD/C + H NMR, until the iterative validation of 13C NMR profiles was successfully obtained. Then, the 3D OM structure was reconstructed in software Material Studio (MS) based on the reconstructed 2D structure after geometric optimization and anneal. It is a 3.23 × 3.23 × 3.23 nm (α = β = γ = 90°) cell with a molecular formula of C1900H1340O240N100 and relative molecular mass of 29 380. Density and porosity of experimental and calculated results were compared to validate its precision, the results exhibit low relative errors of 2.0% and 1.6%, respectively. Finally, the 3D intact shale structure was reconstructed based on the total organic matter content (TOC) and mineralogical composition data, with the fractions of 936 quartz, 73 illite, 19 kaolinite, five chlorite, and two 2D OM structures, respectively. Its cell size is 6.21 × 6.21 × 6.21 nm (α = β = γ = 90°). The 3D intact shale structure was also validated by experimental and calculated results on porosity and density, with relative errors of 2.8% and 1.3%, respectively. The density deviation is mainly caused by the density differences in quartz and other brittle minerals, whereas the porosity deviation is influenced by both mineralogical composition and different calculation models of the experiments and probe detection. The excellent compatibility of the real shale sample and the reconstructed structure confirms the reproducibility and reliability of this 3D intact shale model, and the effectiveness and feasibility of this construction method. These findings fill the knowledge gap of a systemic 3D construction method for intact shale and provide a highly reproducible 3D structure model for the Longmaxi shale gas reservoir.
Gas content and geochemical composition of shale gas are routinely employed for resource potential assessment and production optimization strategies. Shale gas is conventionally collected from horizontal wells after hydraulic fracturing. In the early exploration stage, gas can also be collected by canister desorption of freshly drilled shale cores in the field. However, for the same shale layer, little attention has been paid to the geochemical compositional differences between hydraulic fracturing-produced shale gas (HFS gas) and canister desorption-derived shale gas (CDS gas), and the influence on gas production evaluation. In this study, the CDS gas and HFS gas from the Wufeng-Longmaxi shale of the Yiye 2 well, Middle Yangtze region (South China) were analyzed to evaluate the genetic origin and the influence of desorption on gas compositional and isotopic compositional shifts. The HFS gas is an over-mature dry gas, dominated by methane (94.06% to 96.44%) with a small amount of ethane and nitrogen, averaging 1.17% and 2.38%, respectively. The isotopic composition indicates thermogenic, oil-prone cracked gases. The CDS gas has relatively low hydrocarbon content and high N2 content. Carbon isotopic patterns of HFS gas are characterized by partial isotopic reversal, i.e., δ13C1 > δ13C3 > δ13C2. In contrast, the CDS gas displays larger isotopic variation and different isotopic reversal patterns, i.e., δ13C3 > δ13C1 > δ13C2. The differences in shale gas components and isotopic compositions between HFS gas and CDS gas are probably caused by successive gas diffusion. Gas diffusion of the CDS gas caused decreased concentrations of light carbon molecules in shale reservoirs and increased concentrations of heavy molecules. Isotopic fractionation during degassing results from molecular mobility differences, which are influenced by molecular adsorption/diffusion. The amplitude of δ13C variation during desorption is related to shale pore structure. Isotopic fractionation is weak in mesopores, macropores and fractures with good interconnectivity after hydraulic fracturing, resulting in a slightly restricted diffusion for the HFS gas. The 13C-depleted CH4 in the CDS gas resulted from preferential diffusion of light molecules in matrix-related nanopores resulting in more efficient “molecular sieves” and enhanced isotopic fractionation. Secondary alteration, including gas diffusion, can be identified using the cross plots of ln (C1/C2) value versus δ13C1-δ13C2. Considering the variation in geochemical compositions of the two different collecting gases, any deviations in molecular composition will alter the isotopic fractionation.
This study explores the timing and processes of hydrocarbon evolution in the Sichuan Basin, focusing on pyrobitumen and sphalerite from the Dengying Formation. By utilizing Re-Os geochronology, we aim to refine the precise timing of hydrocarbon generation, migration, and alteration in this area, with particular attention to the effect of hydrothermal fluids. The Re-Os study of pyrobitumen provided isochron ages of 166 ± 26 and 183 ± 39 Ma, which are interpreted as representing the pyrolysis of ancient hydrocarbon reservoirs and subsequent pyrobitumen generation, potentially associated with thermochemical sulfate reduction (TSR). These findings correspond to the timing of large-scale mineralization events in the Sichuan-Yunnan-Guizhou region, reinforcing the value of Re-Os geochronology in high thermal maturity bitumen. Additionally, the study underscores the impact of hydrothermal alteration on the Re-Os system, as sphalerite samples showed lower Re-Os concentrations than bitumen. This suggests that the Re-Os isotope composition of petroleum may reflect inputs from both source rocks and hydrothermal fluid interactions. The research emphasizes the necessity for precise sampling and understanding of isotopic systematics to minimize variability in data and ensure reliable geochronological interpretations. Overall, this study enhances our understanding of hydrocarbon system evolution and provides key insights into the time-frame of critical events in hydrocarbon systems.
The Xinzhou geothermal field, situated within the Xinzhou Basin of northern China, represents a classic hydrothermal system with substantial development and utilization potential. To characterize the distribution of the geothermal system in this region, we deployed an integrated electromagnetic survey network comprising 98 Magnetotelluric (MT) stations and 226 Controlled-Source Electromagnetic (CSEM) stations. Through the application of three-dimensional MT inversion techniques and two-dimensional CSEM inversion methodologies, we constructed a comprehensive electrical conductivity model of the region, revealing the distinctive electrical characteristics of the deep subsurface structures. The crustal structure within the study area can be vertically subdivided into three primary stratigraphic units. The uppermost unit (C1), composed of Quaternary and Neogene sedimentary sequences, presents as a low-resistivity layer with thickness varying from 20 to 360 m. Within this layer, anomalous conductive zones associated with clay alteration zones have been identified. The intermediate unit, predominantly consisting of Archaean metamorphic rocks, manifests as a high-resistivity layer (R1), which contains three distinct low-resistivity anomalies (C2–C4). These anomalous bodies, characterized by resistivity values below 40 Ω·m, are interpreted as geothermal reservoirs located at depths ranging from 0.5–3 km. The basal unit comprises an extensive low-resistivity layer (C5), primarily situated at depths between 6–12 km. This layer is interpreted as an indirect heat source for the geothermal field, with estimated temperatures ranging from 195 to 420 °C. The formation of this heat source is likely attributed to crust-mantle thermal conduction processes. Distinct thermal conduits exist between the heat source and the geothermal reservoirs, characterized by relatively low resistivity features that are closely associated with concealed fault systems in the region. These conduits facilitate heat transfer within the system. This comprehensive investigation not only delineates the spatial distribution of the Xinzhou geothermal system but also provides crucial technical support for the sustainable development and utilization of geothermal resources in the region.
Drought resilience is essential for reducing the economic impacts of drought, yet its role has been underutilized in drought loss models. This study develops a novel drought loss function that, for the first time, explicitly incorporates drought resilience into direct economic loss estimations and quantifies its impact. By employing a drought resilience index (DRI) constructed from 56 indicators across six domains, this study quantifies the impact of resilience across China from 1994 to 2020. The results showed significant improvements in the accuracy of drought loss simulations, with errors reduced to a range of 6.34%–37.63% for 2015–2020. This contrasts sharply with errors exceeding 70% when drought resilience factors were not considered. The DRI also captured regional disparities in coping capacities and filled gaps in recorded drought loss data, with economically developed regions benefiting the most. These findings highlight the importance of drought resilience in enhancing the accuracy of drought loss simulations, and emphasize the need for continued investment in infrastructure, technology, and ecological restoration to strengthen resilience, particularly in regions most vulnerable to droughts in a warming climate.
Diverse river channel types in alluvial rivers hold great significance in river dynamics and fish protection. How fish habitat suitability of meandering and braided river channels varies under complex flow scenarios remains partially unexplored. This research employed an eco-hydraulic model to assess the habitat suitability of seven alluvial river types for Schizothorax prenanti and Schizothorax davidi under normal discharges, short-term flood flush and long-term flush in the Yangtze River source. The seven designed rivers included a straight river channel, three types of meandering rivers, and three types of braided rivers. The results indicated that both species exhibited considerable habitat suitability in meandering and braided rivers under discharge corresponding to the 3/4 elevation of each channel. Flood flush had an adverse impact on fish habitat suitability. Long-term flush had little effect on the habitat suitability of meandering rivers but decreased that of braided rivers. Furthermore, increasing sinuosity of meandering rivers was not always beneficial for improving habitat suitability, and regular sandbar shape in braided rivers brought more habitat benefits. Under all flow scenarios, the habitat suitability of meandering rivers was generally higher than that of braided rivers, and the habitat suitability of seven river channels for Schizothorax prenanti was generally higher than that for Schizothorax davidi. The results can provide references for developing fish habitat assessments in river management and fish conservation.
Tectonic activity shapes geothermal systems, yet its influence on microbial biogeography remains poorly resolved. Here, we investigate how tectonic activity influences geothermal systems and their microbial communities by comparing hot springs situated along convergent (Yunnan-Tibet) and divergent (Baikal Rift) margins. The results show that hydrochemistry and microbial community in these two tectonically different regions exhibit pronounced differences: Yunnan-Tibet hot springs, shaped by deep crustal interactions, show high concentrations of Na+, K+, and Cl− ions and are dominated by thermophilic microbes such as Acetothermia, Anaerolineae, Bacteroidia, Chloroflexia, and Deinococci. These microbial groups exhibit correlations with environmental factors like temperature and ion concentrations. Conversely, Baikal Rift hot springs, associated with shallower rift-related processes, are primarily inhabited by Gammaproteobacteria and Cyanobacteria, which are negatively correlated with temperature and ion levels but positively associated with higher pH. Multivariate statistical analyses confirm that the tectonic setting is an important factor driving hydrochemical diversity, which in turn shapes microbial community structure. Despite localized geochemical variability, microbial assemblages tend to cluster strongly according to their tectonic origin, highlighting the fundamental influence of plate dynamics on the assembly of geothermal microbial ecosystems. These results provide evidence that tectonic processes exert a significant influence on the composition and diversity of microbial communities in extreme environments.
While phosphorus (P) enrichment is a well-recognized driver of eutrophication in freshwater ecosystems, the effect of phosphorus enrichment on viral communities and functions remains poorly understood. Here we conducted microcosm experiments manipulating P availability using water from an oligotrophic plateau lake, integrating amplicon sequencing/viromics and direct experimentation. The results reveal that P enrichment induces niche partitioning in prokaryotic communities, favoring copiotrophic taxa such as Cyanobacteria while maintaining α-diversity. Concurrently, viral communities exhibited β-diversity shifts, with specific lineages (e.g., Tequatrovirus, Lambdavirus) enriched and several P-related auxiliary metabolic genes (AMGs, purL, phnO and pyrE) involved in purine/pyrimidine metabolism and phosphonate utilization were identified bioinformatically in P-enriched viral metagenomes. Furthermore, viral-host interaction networks structure was changed, with cyanobacteria and Alphaproteobacteria emerging as crucial taxa. Notably, viral AMGs may accelerate P turnover rates, driven by viral-mediated production of labile organic phosphorus compounds. These findings bridge viral ecology and eutrophication science by demonstrating that viral AMGs act as metabolic catalysts, amplifying P cycling under nutrient stress. This work underscores the necessity of integrating viral processes into predictive models of eutrophication and identifies viral AMGs as potential early-warning indicators for mitigating P-driven cyanobacterial blooms and restoring ecosystem balance.
Nitrogen pollution is a major cause of lake eutrophication, garnering global concern for its detrimental impact on lake water quality. However, the intricate interplay between lakes and groundwater in the accumulation and release of nitrogen remains largely overlooked. Using Honghu Lake as a case study, a large lake in the Yangtze River Basin long plagued by nitrogen pollution, this study analyzed the temporal shifts in its water area from 1990 to 2021 using remote-sensing image classification algorithms. From 1990 to 2005, the natural water area of Hong Lake decreased by 72%. The transformation of much of this area into aquaculture zones and agricultural lands has led to a substantial influx of pollutants, culminating in the degradation of water quality. Despite efforts to restore the natural water area after the ban on aquaculture activities, the water quality of the lake remains compromised, indicating other pollution sources menacing the ecosystem of the lake. Field investigations conducted in 2011 and 2019 unvealed significantly higher concentrations of NH4-N and NO3-N in groundwater compared to lake water, with a discernible upward trajectory in pollutant levels over time. The 18O mass-balance model was employed to assess groundwater flow dynamics, revealing an estimated lacustrine groundwater discharge of 0.71 × 106 m3/d, underscoring the substantial annual influx of pollutants into the lake via groundwater pathways. Through a comprehensive analysis of surface water and groundwater quality trends within the study area, this research provides novel evidence implicating groundwater as a formidable contributor to the persistent nitrogen pollution afflicting Honghu Lake.
The Guanzhong Basin, located in Shaanxi Province, China, has abundant geothermal resources in its hinterland. Focusing on typical thermal reservoir structural units, namely the Xianli fault-step (XL) and Xi’an depression (XA), this study reveals the genesis of geothermal water by combining hydrochemistry and environmental isotopes. The geothermal waters of XL uniformly correspond to the Na-Cl type with high contents of major ions, while the geothermal water of XA has complex hydrochemical types. The quartz geothermometer (with maximum steam loss) and the Na-K-Ca geothermometer are recommended for XL and the quartz geothermometer (with no and maximum steam loss) and the Na-K geothermometer for XA. Their temperature ranges are 99–159 and 93–146 °C, respectively. The circulation depth of geofluids in the XL and XA ranges from 2 579 to 4 766 m and from 2 541 to 4 330 m, with mean apparent ages of 21 543 and 20 345 yr B.P., respectively. The geothermal water in XL originates from a mixture of sedimentary water and ancient infiltration water, and its formation mode is vertical heat conduction with a cooling process. In contrast, the geothermal water in XA originates from the dual process of cooling and mixing, with the process being dominated by ancient infiltration water and supplemented by modern infiltration water.
The lack of detailed information on Valencia’s subsurface configuration poses significant challenges for civil engineering and urban planning projects. To date, most studies have focused on geotechnical aspects or shallow sedimentology, providing only a limited understanding of the horizontal and lateral variability of sedimentary facies characteristic of alluvial environments. This study presents a high-resolution model of the first 50 m of the Holocene subsurface in central Valencia, providing new insights into its geological architecture and shallow aquifer system. The methodology integrates geological and geotechnical data with direct drilling, offering detailed lithological information. Sedimentological, stratigraphic, and paleoenvironmental analyses enabled stratigraphic correlation and a 3D subsurface reconstruction. Four detrital sedimentary facies were identified: silts and clays, sands, gravels, and pebbles, subdivided into channel and lobe facies. The paleoenvironmental model suggests a coastal fan system (fan-delta) with occasional marine reworking at its front. This study reconstructs the geometry of the Holocene stratigraphic framework, illustrating the depth distribution and lateral variability of deposits. Additionally, it provides a fundamental framework for improving the understanding of Valencia’s subsurface, serving as a valuable tool for future planning and development projects in the region.
This study reports physical models of clay smear formation along faults. The main factors influencing clay smear are the competence and thickness of the clay layer, and fault throw. Although previous experimental studies acknowledge the impact of competence, to manipulate competence, these studies altered the clay layer instead of the sand layer, leaving the influence of sand unknown. We investigated the competence of shear clay smear in normal faults through water-saturated sandbox analogue modeling experiments, aiming to identify factors influencing the structural evolution of clay smear in normal faults. We used Particle Image Velocimetry (PIV) to track deformation as it offers non-invasive, full-field measurements with high spatial resolution, enabling comprehensive analysis of deformation patterns. In experiments with more competent (stronger) sand layers, steeper branch faults developed as fault throw increased. The resulting clay smear is concentrated along the main fault plane, which was inclined at 60°. In experiments with less competent (weak) sand layers, two extensional overlapping fault segments interact and deform progressively, leading to the formation of continuous clay smear. Clay smear continuity increases as the competence of the sand layer decreases under otherwise identical conditions. Shear clay smear in normal faults is also influenced by the thickness of the clay layer and fault throw. During early stages of faulting, the clay layer undergoes gentle rotation without notable thinning, as the shear stress remains below the threshold required to initiate fault slip. However, during the middle and late stages, continuous clay smear forms through shear localization of faults as distribution becomes more concentrated. In cases with constant clay layer competence and varying sand layer competence, an increasing difference in competence between sand and clay leads to lower continuity of shear clay smear. Therefore, to accurately assess clay smear continuity in normal faults, It is essential to account for the competence contrast between sand and clay layers. Our results show that greater differences in competence reduce the likelihood of continuous smear formation, whereas weaker sand layers facilitate the development of broad, connected clay smear zones.
Monitoring deformation is of critical importance for tunnel boring projects. This importance is further amplified for the metro construction project that involves boring beneath or near susceptible civil infrastructures. Here, we present a case study that uses a robotic total station to perform automated deformation monitoring inside a tunnel during excavation. Further, enabled with the Internet of Things technology, the monitoring data are streamlined through wireless internet access points and processed by a remote control center. A complete suite of software is deployed that can: (1) automatically process monitoring data; (2) set differentiated triggering thresholds corresponding to hazardous incidents of varying levels; (3) store data for subsequent analysis, which includes data visualization, overall risk level quantification, and predictive modelling. Built upon this automated system, a triage of risk response protocol is established that performs reactive treatment according to the levels of reported hazards. A de-risk process, involving third party review, is also established. Overall, this report demonstrates our effort in monitoring the tunnel’s deformation with an automated system to save cost and reduce human-induced errors. This report can be a useful reference for other engineers performing metro tunneling tasks.
Seismic hazards threaten underground structures and subsequently affect surface buildings, making effective vibration reduction measures crucial in shallow underground spaces. This paper proposes a multi-layer shielding pile based on the seismic wave attenuation theory of refraction dispersion and diffraction loss as a new vibration reduction method. By using the dynamic wave interaction between the unique multi-layer structure of the shielding pile and the seismic wave, a shielding area with significant attenuation of the ground motion is formed to achieve the purpose of vibration reduction. The spectral element method (SEM) with high-order source time function and convolution perfect matching layer (PML) is used to simulate the numerical models of shielding piles with different parameters (including background models and excavation models), and the characteristics of ground motion and site effect near shielding piles in various models are analyzed. The study reveals the control effect and regulation of the material, size, and shape of the shielding pile on its vibration reduction effect, and determines the shielding pile parameters with the best vibration reduction effect. Shielding piles enrich the vibration reduction measures for structures in shallow underground spaces, and provide a new method for preventing seismic hazards under dynamic load.
The implementation of deep storage technology for high-salinity water in coal mines offers significant potential for reducing the costs of wastewater treatment, thus expanding its practical application. However, the lack of rapid and reliable monitoring techniques presents a challenge in verifying the distribution of high-salinity mine water after sequestration, which in turn hinders further sealing operations. To address this limitation, this study investigates the use of the Wide-Field Electromagnetic Method (WFEM) for assessing the sequestration of high-salinity water in the Dongsheng Coalfield (Ordos). By leveraging the underground electrical structures identified by WFEM, and integrating petrological analysis with the Archie equation, we monitored the diffusion range of the high-salinity water. The correlation between the low-resistivity range and the high-salinity water volume is validated. Our results demonstrate that WFEM is effective in detecting low-resistivity zones, and the estimated water volume (555 000 to 645 000 m3) closely aligns with the actual sequestration volume. This approach provides a robust method for evaluating the effectiveness of geological sequestration, offering valuable insights for the management of high-salinity water storage.
The topography of the Earth is a crucial component for investigating dynamic topography and lithosphere-upper mantle dynamics. Dynamic topography, caused by geodynamic processes, significantly shapes Earth’s current surface. Residual topography serves as an indicator of this dynamic topography. To determine residual topography, one must first obtain isostatic topography. In this study, we propose a new calculation method for isostatic topography based on the Airy-Heis-kanen lithospheric isostasy model. The method is applied to obtain the residual topography map of the East Asian Continent (EAC) using the global relief model ETOPO1, the latest global crustal model ECM1, and the global seismic tomography model SL2013sv. The short-wavelength components of residual topography provide more detailed information about non-isostatic topography caused by lithospheric tectonic movements as compared to the long-wavelength components. The isostatic gravity anomaly based on the proposed lithospheric isostasy model presents some new insights into the dynamic characteristics of the lithosphere in the EAC.
Storm surges occurring over short periods can cause abrupt changes in ocean mass near the coast, leading to transient crustal subsidence known as Non-Tidal Ocean Loading (NTOL). Existing NTOL products provided by various institutions are typically derived from oceanic gravity or fluid dynamic models combined with Earth’s elastic response theory. However, these model-based products lack validation against in-situ observations, raising concerns about their reliability under extreme conditions. In contrast, geodetic Global Navigation Satellite Systems (GNSS) observations offer high accuracy, high spatiotemporal resolution, and near real-time availability. In this study, we analyze sub-daily GNSS vertical displacements from 12 stations in Hong Kong during a storm surge in October 2021 and compare them with NTOL predictions from three global models (GFZ, IMLS, and GGFC) to assess their consistency in a complex coastal environment. Results show that the IMLS and GGFC NTOL products are more reliable than the GFZ product for detecting sub-daily loading deformations in a small region. The GFZ product suffers from spurious NTOL displacement signals (max ≈ 15 mm) during the peak storm surge period. Among the correlation coefficients between 3-h GNSS vertical displacements and the three NTOL products, the IMLS product achieves the highest correlation (max = 0.67), followed by the GGFC product, while the GFZ product exhibits the lowest correlation. Extending the GNSS solution time span (from 3-h to 6-h or 9-h) improves its correlation with NTOL. However, since storm surge effects typically last only tens of minutes to a few hours, a 6-h or 9-h GNSS solution may not capture the full details of the storm surge-induced deformation. Our work demonstrates that sub-daily GNSS observations can detect the transient NTOL-induced subsidence caused by storm surges, thereby validating the accuracy and applicability of these NTOL models and filling the gap left by the lack of observational support in previous model-based studies.
Paleozoic epicratonic formations in Iran, like many similar deposits globally, have traditionally been interpreted as fully marine based on lithology and facies, but recently developed bulk-sediment elemental proxies (B/Ga, excess boron (Bxs), and Sr/Ba) have shown that such inferences may overlook low-salinity conditions and/or salinity variability. Here, we test these proxies against established lithology- and facies-based salinity interpretations in five well-studied formations: the Uppermost Ordovician–Lower Silurian Sarchahan Formation (Fm) (Zagros, S-C Iran), the Upper Devonian Geirud Fm (Alborz, N-C Iran) and Shishto Fm (Tabas, NE Iran), and the Lower Carboniferous Mobarak and Dozdehband Fms (Alborz, N-C Iran). The study formations are variably carbonate-rich, making the Sr/Ba proxy generally unsuitable for salinity analysis, and constraining the utility of the B/Ga proxy to samples with > 2% Al content; Bxs proved to be the most generally applicable proxy to the study units. Our results show freshwater to brackish conditions in shales and marls of the Dozdehband Fm, brackish to marine conditions in limestones of the Geirud, Shishto, and Mobarak Fms, and fully marine conditions in marls of the Sarchahan Fm. These salinity interpretations mostly support existing paleoenvironmental inferences based on sediment lithology and facies analysis, affirming the reliability of elemental paleosalinity proxies, but they yield more detailed assessments of secular changes in salinity than previously achieved, and they provide more nuanced insights into basin-specific patterns of salinity variation (e.g., episodic brackish events linked to restricted seawater inflow into a marginal-marine basin during deposition of the Dozdehband Fm). Our findings underscore the value of a lithology-calibrated multi-proxy approach for paleosalinity reconstruction and validate the utility of salinity data in assessing paleo-environmental conditions in ancient epicratonic basins.