Search Results (149)

Al-Musk Lake, an artificial waterbody of 2.9 km² formed by illegal dumping of 9.5 million cubic meters of raw sewage near Jeddah, Saudi Arabia, remains a significant subsurface environmental hazard after drainage activities in 2010. The current research employs a multidisciplinary approach, integrating geological mapping, aeromagnetic and electromagnetic surveys, Landsat imagery, and chemical analyses, to investigate contamination migration and accumulation. The objective is to delineate subsurface contamination pathways and assess their impact on soil and groundwater quality. Frequency-domain electromagnetic (FDEM) surveys identified areas of high apparent conductivity (up to 200 mS/m at 2000 kHz), indicative of deep contamination saturation. Chemical analysis of water and soil samples revealed distressing levels of heavy metals, Na⁺ up to 2400 mg/L, Ca²⁺ up to 3648 mg/L, and Fe up to 4150 mg/L, far exceeding irrigation safe standards. Findings locate two at-risk areas several kilometers from the lake, where contaminants accumulate through basement depressions controlled by faults. These pose immediate risks to adjacent residential areas and expanding agricultural belts. In short, subsurface contamination continues to spread westward. Short-term remedies include halting agricultural activities, treating in-storage water, and paving infiltration zones. A larger-scale geophysical survey, along with denser geochemical sampling and analysis, is necessary to guide long-term remediation and to protect public health. Full article

The Jaboi geothermal field, located on Weh Island in western Indonesia, has a potential output of approximately 55 MWe. Previous geophysical surveys have not sufficiently identified the components of the geothermal system. The success of drilling in identifying a geothermal system depends heavily on the accuracy of the conceptual model. Consequently, developing a more precise subsurface model is crucial to minimizing drilling failures. This study aims to map the resistivity structure of the Jaboi geothermal field using the magnetotelluric method. In our research, we used 16 magnetotelluric sites that recorded data for 7 to 8 h. We successfully estimated the cap rock area with resistivity < 10 Ωm distributed across Jaboi Volcano to depths of 500 m and identified an intense resistive anomaly starting at depths of 1–2 km with resistivity > 5000 Ωm. This anomaly is probably due to a block of crystalline basement being uplifted by upwelling magmatic intrusions. The reservoir zone was estimated to be located directly below the cap rock area. The resistivity structure also reveals a fluid pathway zone in the upflow and outflow zone that connects the reservoir to the surface manifestations influenced by the Ceunohot Fault and Jaboi Fault. The resistivity structure confirmed the boundary of the Jaboi geothermal system along the coastline and in the southeastern part. This study successfully identifies key components of geothermal systems, including cap rock, reservoir zones, and fluid migration pathways. Full article

The Datangpo-type Mn ore deposits in northeastern Guizhou (southern China) are a relatively newly discovered type of sedimentary exhalative manganese ore deposit. Previous three-dimensional geological modeling has revealed an NW-trending trough-like depression that obliquely intersects the ENE-trending Nanhua Rift within the Nanhua System in this area. This depression likely represents a paleorift that was present before the metallogenetic period; its intersection with the Nanhua Rift corresponds precisely with the area in which a series of super-large and large new-type Mn ore deposits are located. Here, we used remote sensing image processing techniques, along with hierarchical spatial data fusion and mining methods adopted for exploration, to investigate this paleorift. Specifically, Bouguer gravity data were used to obtain middle–lower-crust structural information; aeromagnetic ΔT data were used to obtain middle–upper-crust structural information; and remote sensing and outcrop data coupled with regional geological survey, mineral exploration, and geochemical exploration data were used to obtain near-surface structural information. Combining these data, we determined the control that different deep tectonic frameworks exert on the formation and distribution of Mn ore deposits within the study area. This study proposes a new conceptual method and technical protocol permitting an improved understanding of the material source and mineralization pattern of Mn ore deposits within the study area, while verifying the existence of the NW-trending Tongren Paleorift. Full article

A rifted margin can be regarded, in the first place, as a crustal thinning taper framed by “box-shaped” continental and oceanic crusts whose top basement and Moho are parallel. Attempts to understand the relationship between lithosphere extension, crustal thinning and strain localization have been addressed in part by characterizing and modeling rift modes. However, a weakness of models stems from their using generalized physical parameters and initial conditions, while each system is unique in terms of its geological complexity. In this study, we develop a new approach to investigate the relation between crustal shape, the nature of the top basement and the accommodation space to reveal the link between extension, strain localization and crustal thinning in the northern South China Sea (N-SCS). Our results show the following: (1) box-shaped crusts may indicate no or minor extension, or extension compensated by crustal flow and/or magmatic additions; (2) crustal thinning and strain localization occurred through extensional detachment faults coevally during the rifting of the N-SCS; (3) strain localization was triggered or enhanced by magmatic weakening, and the weak crustal rheology at the onset of the rifting favored the formation of detachment faults; and (4) the inherited composition of the crust (magmatic rocks in the arc and meta-sediments in the forearc) controls the distribution of crustal thinning. We propose that the different initial conditions, changes in extension rates and the presence/absence of subduction dynamics account for the different rift evolutions observed in the SCS and Atlantic-type rift systems. Full article

The formation of fractures in urban areas is typically related to construction processes, natural ground settlement, and material quality. In valleys, the distribution of ground fissures is associated with aquifer overexploitation and basement faulting. However, where the soil layer is only a few meters thick or absent, the influence of basement structures remains poorly understood. We hypothesize that urban fractures develop parallel to major basement faults. To test this, we applied a simple structural geology technique to systematically measure extension axes, from street fractures, throughout the town of Las Pilas. These axis orientations were then compared with those calculated for normal faults of Las Pilas Complex. Street fractures are generally about 1 cm thick, with lengths ranging from 0.51 to 1 m and occasionally reaching up to 3 m. They occur within streets 2 to 4 m wide, typically appearing as a single fracture within a 1–2 m wide fracture zone. Based on these characteristics, the fractures do not represent a significant hazard. Measurement results indicate that urban fractures primarily extend in an NE-SW direction. This is consistent with the orientation of the minimum principal stress axis (3) of the regional San Luis-Tepehuanes fault system, thereby supporting our hypothesis. Full article

High-precision gravity surveys are effective in detecting concealed geological structures and mineral deposits with density contrasts. In this study, 754 dense gravity measurements (average accuracy: 0.0043 mGal, or 4.3 × 10⁻⁸ m/s²) were deployed in Dingzhai Township, northeastern Zhejiang, China, to investigate concealed ore bodies and structural controls on mineralization. Using the mean-field method for source-field separation of Bouguer anomalies, combined with density inversion and edge detection, we delineated subsurface density distributions and fault systems. A newly identified “tongue-shaped” high-density anomaly near Xiashadi is interpreted as resulting from local upward intrusion of intermediate-acid porphyry from the Chencai Group basement, indicating significant exploration potential. Beneath Quaternary cover, a previously unrecognized east–west-trending concealed fault was detected, which may have controlled the structural evolution of mineralization at the Daqi’ao Ag deposit and Miaowan Cu deposit. Gravity profile inversion reveals a deep high-density anomaly beneath Xie’ao–Xi’ao’an, possibly representing the deep extension of the Hengtang Cu–Mo deposit. Low-density anomalies near Chenxi and Dongli villages are attributed to Early Cretaceous low-density intrusions (e.g., monzogranite) and multi-phase volcanism in the Shangshawan caldera. This work provides robust geophysical constraints for deep mineral exploration and advance understanding of the metallogenic tectonic evolution in northeastern Zhejiang. Full article

The Nezamabad Fault System (NFS) in the Fars area of the Zagros Fold–Thrust Belt represents a persistent, basement-rooted transverse shear zone that fundamentally controls the regional hydrocarbon system. This study integrates seismicity distribution, isopach analysis, and tectono-stratigraphic modeling from the Triassic to the Cenozoic to unravel how recurrent basement reactivation governs trap evolution. Isopach maps reveal a pronounced southwest-thickening asymmetry, with Triassic successions exceeding 1400 m, indicating long-term differential subsidence during four key phases: (1) Triassic syn-rift salt accumulation (Dashtak Formation) forming the primary detachment; (2) Jurassic–Early Cretaceous passive subsidence promoting source rock deposition; (3) Mid-Cretaceous transpression enhancing reservoir dolomitization; and (4) Late Cretaceous–Cenozoic inversion generating hybrid traps. Seismicity analysis of over 240 events confirms the 256-km-long NFS is a crustal-scale structure, with most foci at 10–33 km depth and others extending to 150 km, implying lithospheric stress transfer. This deep-crustal activity has periodically reorganized stress, enhanced fracture permeability, and rejuvenated traps through seismic pumping and cross-scale mechanical coupling. The results demonstrate that hydrocarbons in the Fars area are not a passive outcome of folding but a dynamic expression of lithospheric coupling. The findings establish a predictive framework for identifying analogous basement-influenced petroleum systems in other foreland fold–thrust belts worldwide. Full article

In the Missan oilfields, the linkage among basement faults, halokinesis, and hydrocarbon accumulation, and their control on structural-trap geometry and seal effectiveness, remains insufficiently constrained, especially the timing/drivers of salt piercing and its coupling with regional folding. To address this, we integrate 3D seismic, well, and surface data to quantify these interactions across adjacent fields. Results show a clear correspondence between surface topographic highs and subsurface salt-related deformation. Buzurgan exhibits limited fault reactivation with persistent folding until the Late Miocene, whereas Fauqi and Abu Ghirab record Pliocene reactivation and intense salt deformation that generate disharmonic syncline-over-anticline geometries. The listric–conjugate faults are structurally linked to deep-seated basement faults and display clear spatial alignment with their orientations, enhancing halokinesis and accommodating differential shortening. At the same time, hydrocarbon charge pathways are primarily governed by the intensity of deep-seated faulting and the effectiveness of salt sealing. Critically, the study integrates disparate geological processes—fault reactivation, salt tectonics, and hydrocarbon migration—into a single coherent, field-validated model for the region and provides a practical method to anticipate subsurface complexity. The results show that variations in fault intensity across three adjacent fields (Buzurgan, Fauqi, Abu Ghirab) correspond to distinct reservoir outcomes: minimal faulting in Buzurgan confines charge to deeper Mishrif reservoirs; moderate faulting in Fauqi permits entrapment in Mishrif and Kirkuk; and intense faulting in Abu Ghirab facilitates vertical leakage to shallow Kirkuk. Collectively, the work moves beyond isolated case descriptions to provide a unified, exploitable framework for predicting how basement-involved faulting and salt mobility jointly control deformation style and hydrocarbon distribution in foreland basins. Full article

While 3D seismic reflection is well established in hydrocarbon exploration at the kilometer scale in relatively simple offshore settings, its application to shallow faulting in continental basins is rare, owing to difficulties in adapting acquisition and processing to rugged terrains and complex near-surface conditions. We present the first high-resolution 3D seismic study of a seismogenic fault in a structurally complex intramontane basin at depths < 200 m. The survey focuses on the Pantano–Ripa Rossa Fault, ruptured during the 1980 Mw 6.9 Irpinia earthquake, the largest Italian event of the past century. This fault cuts across the Pantano di San Gregorio Magno, a small basin filled with Quaternary sediments and showing modest cumulative displacement. Our results demonstrate that in such environments, where morphotectonic analysis and 2D geophysics provide limited constraints, high-resolution 3D seismic imaging is crucial to resolve fault geometry and to assess surface-faulting hazard. The 3D volume reveals a ~35–40 m wide intra-basin deformation zone beneath the 1980 rupture, composed of synthetic and antithetic splays, and highlights lateral variations in fault geometry and stratigraphy. Deformation is distributed and complex, with fault-controlled depocenters, variable sedimentary architectures, and rapid basement-depth changes—features unresolved by 2D data. We infer that the Pantano–Ripa Rossa Fault is relatively young, active since the late Middle Pleistocene, and developed in the hanging wall of the NE-dipping southern basin-bounding fault, challenging previous models that located the master fault along the northern basin margin. Full article

The Eastern Sag of the Liaohe Depression, situated in the Bohai Bay Basin, represents a key area for hydrocarbon exploration in northeastern China. Despite decades of research, the mechanisms governing its complex structural evolution remain unclear, largely due to multiple tectonic reactivations associated with the Tan–Lu Fault Zone. In this study, newly acquired deep seismic reflection data were used to interpret representative structural profiles across the sag. Complementary sandbox modeling experiments were conducted to reconstruct the basin’s prototype and to verify the structural kinematics inferred from the seismic data. Integration of seismic interpretation, physical modeling, and thin-section microstructural observations of fault-related cores allowed us to establish a comprehensive Cenozoic evolutionary model of the sag. The results reveal three main tectonic evolution stages: (1) an extensional fault-depression stage during the Shahejie period, (2) a strike-slip modification phase during the Dongying period, and (3) a subsequent thermal-subsidence stage in the Guantao period. Pre-existing basement faults exerted a significant control on fault geometry, subsidence patterns, and the segmentation of four sub-sags. Moreover, transtensional and transpressional deformation during the late stages reshaped the basin architecture and fault linkage systems. These findings provide new insights into the structural evolution and controlling mechanisms of the Eastern Sag, offering valuable guidance for deep hydrocarbon exploration in the Bohai Bay Basin. Full article

The Variscan and Mesozoic basement are covered by Neogene and Quaternary sediments belonging to the Guadalquivir foreland Basin (southern Spain). This study explores the subsurface of the northern margin of its westernmost sector using the HVSR method, recording seismic noise at 334 stations between the mouths of the Guadiana and the Guadalquivir rivers, near Doñana National Park. Fundamental frequency and basement measurements enabled the estimation of an empirical formula for basement depth: h = 80.16·f₀^−1.48. Five distinct HVSR responses were obtained: (a) low-frequency peaks, indicating deep substratum; (b) high-frequency peaks, shallow bedrock; (c) broad peaks, potential critical zones (3D-2D effects, suggesting faults); (d) double peaks (marshlands); and (e) no peaks, near-outcropping bedrock. The soil fundamental frequencies range from 0.23 to 18 Hz, with bedrock depth ranges from 1 to 5 m in the northwest to over 600 m in the southeast. Borehole data correlate strongly with HVSR-derived results, with typical discrepancies of only a few tens of meters, likely due to the presence of non-geological basement acting as a mechanical basement. Although the possibility of ancient fluvial terraces of the Guadalquivir River contributing to abrupt slope changes is considered, H/V spectra with broad peaks suggest tectonic origins. This study presents the first regional three-dimensional model of the basin basement over an area exceeding 2300 km², revealing a horst-and-graben system formed by foreland deformation linked to the westward advance of the Rif-Betic orogenic front. Full article

The Diaoyu Islands Folded-Uplift Belt consists of metamorphic basement, magmatic rocks and Paleogene series in the Eastern Depression Zone of the East China Sea Basin which was deformed and uplifted by magma emplacement. The emplacement of the magma resulted in an unclear understanding of the Paleogene geomorphy in the paleo-uplift, further affecting the analysis of the eastern boundary and the sedimentary environment of Paleogene prototype basin in the Eastern Depression Zone. To explore the Paleogene geomorphy and magma emplacement process of the Diaoyu Islands Folded-Uplift Belt, we conducted a detailed interpretation of 2-D seismic profiles and identified nearshore subaqueous fans and fan deltas within the deformed strata. The development scale of them helps to determine the approximate location of the Paleogene eastern boundary of the Eastern Depression Zone. We integrated the boundary location with gravity, magnetic, and well data to obtain the Paleogene geomorphy of the Diaoyu Islands Folded-Uplift Belt. Our results indicate that the subduction direction of the Pacific Plate was almost perpendicular to the Eurasian Plate during the late Eocene, leading to the development of numerous left-lateral strike-slip faults within the East China Sea Basin, further forming channels within the paleo-uplift, which connected the Eastern Depression Zone and the ocean. In the Early Oligocene, the subduction rate of the Pacific Plate abruptly increased, resulting in large-scale and significant exhumation of the paleo-uplift, and the Eastern Depression Zone had transformed into a lacustrine sedimentary environment. Furthermore, due to the continuous retreat of the Pacific Plate, the extension center of the back-arc basin moved to the eastern margin of the Eastern Depression Zone in the late Oligocene. This work provides a method for recovering the geomorphology of complex tectonic units in back-arc basins based on fine seismic interpretation, solving the key problem that constrained the recovery of boundaries and sedimentary environment of the prototype basin. Full article

This study presents the first integrated, basin-scale analysis of helium distribution and its geological controls within the Ordos Basin, one of China’s most prospective cratonic gas provinces. Through comprehensive sampling and experimental analysis of the helium content in natural gas, combined with high-resolution gravity and magnetic data processed using the normalized vertical derivative of the total horizontal derivative (NVDR-THDR) method, we reveal significant spatial heterogeneity in helium enrichment. The results show that helium concentrations are generally higher along the basin margins and structurally complex zones, while central areas are relatively depleted. Helium primarily originates from the radioactive decay of uranium (U) and thorium (Th) within metamorphic and magmatic basement rocks. Fault systems act as efficient vertical migration pathways, enabling deep-sourced helium to accumulate in structurally and stratigraphically favorable traps. This study proposes a new enrichment mode, “basement-sourced helium generation, fault-mediated migration, and caprock-controlled preservation”, which highlights the synergistic roles of basement lithology, deep-seated faults, and sealing capacity in controlling helium distribution. This model is supported by the observed alignment of high helium concentrations with zones of strong basement magnetism and major fault intersections. These findings advance our understanding of helium accumulation mechanisms in stable cratonic settings and provide a predictive framework for helium exploration in similar geological contexts worldwide. Full article

The Chating Cu-Au and Magushan Cu-Mo deposits in Anhui province are two representative deposits within the recently defined Nanling-Xuancheng ore concentration area in the Middle and Lower Yangtze River Metallogenic Belt (MLYB). Magmatism and mineralization for the area are not well known at present due to a lack of in-depth studies on the petrogenesis of ore-bearing intrusive rocks and their relationship with deposits. Here, the ore-bearing intrusive rocks of the two deposits are investigated through analyses of whole-rock geochemistry and Sr-Nd isotopes, zircon U-Pb ages, and zircon Hf isotopes. The results reflect the two intrusions, both formed in the Early Cretaceous (138.9 ± 0.8 Ma and 132.2 ± 1.3 Ma). They belong to the sub-alkaline high-K calc-alkaline series, while trace elements are enriched in LILEs and LREE and depleted in HFSEs. However, the intrusions of the Chating deposit (I_sr = 0.7064–0.7068; ε_Nd(t) = −8.5–−7.3; ε_Hf(t) = −11.9–−7.0) have obviously different Sr-Nd-Hf isotopic compositions from the intrusions of the Magushan deposit (I_sr = 0.7079–0.7081; ε_Nd(t) = −5.7–−5.4; ε_Hf(t) = −5.4–−3.6). The characteristics indicate that the two intrusions were formed in the same diagenetic ages and tectonic settings and derived from a crust–mantle mixture with predominant mantle-derived materials. But the crust materials of sources are different, which further leads to different metallogenic elements, showing that the Chating deposit is enriched in Cu and Au, while the Magushan deposit is enriched in Mo. Moreover, the characteristics and magma sources of two intrusions and metallogenic elements correspond respectively to the Tongling Cu-Au polymetallic ore concentration area in the MLYB and the southern Anhui Mo polymetallic ore concentration area in the Jiangnan orogen. The correlation implies differences in magmatism and mineralization between the northwestern and southeastern parts of the Nanling-Xuancheng ore concentration area, demarcated by the Jiangnan Deep Fault. These variations were mainly controlled by the Pre-Sinian crustal basement. Full article

Our understanding of foreland basin subsurface structures relies heavily on seismic reflection data. The seismic profile across the eastern Rioni foreland basin in western Georgia is critical for characterizing its deformation structural style. We applied fault-related folding and thrust wedge theories to interpret the seismic profile and construction structural cross-section, which reveals that compressional structures are controlled by multiple detachment levels. Both thin-skinned and thick-skinned structures are identified. The seismic profile and structural cross-section reveal the presence of normal faults, reverse faults, thrust faults, duplexes, triangle zone, and crustal-scale duplexes. The deep-level detachment within the basement is responsible for the development of the crustal-scale duplexes. These structures appear to have formed through the reactivation of pre-existing normal faults during compressive deformation. Based on our interpretation, the imaged duplex system likely represents the western subsurface continuation of the Dzirula Massif. Full article