Search Results (572)

The Donggou Pb-Zn deposit in the Qimantagh region is stratabound, with ore bodies occurring as stratoid and lenticular forms within clastic rocks and andesites of the Qimantagh Group. To constrain the mineralization age, ore genesis, and ore-forming conditions, this study conducted zircon U-Pb dating, sulfur isotope analysis, and LA-ICP-MS trace element analysis of sphalerite. Zircon U-Pb dating of the overlying andesite yields an age of 437.1 ± 1.9 Ma, which provides an upper age constraint for mineralization. Sulfur isotope values (δ³⁴S range from −5.98‰ to +12.01‰) suggest a mixed sulfur source, dominated by magmatic sulfur with a minor seawater contribution. Trace element analysis of sphalerite (Sp1) shows enrichment in Fe, Mn, Co, Cd, and In, and depletion in Ni, Ga, and Ge. The estimated mineralization temperature, based on the sphalerite geothermometer, is approximately 327–344 °C. Volcanic rocks in the deposit are mainly andesite with minor dacite and rhyolite, indicating an island arc setting, and the clastic rocks point to a continental arc provenance and a shallow marine environment. Collectively, these features suggest that the Donggou Pb-Zn deposit is a VMS-type deposit formed during the late subduction stage of the Qimantagh Ocean. This study provides new constraints on the Early Silurian Pb-Zn mineralization in the Qimantagh region and has implications for exploration targeting in similar volcanic-hosted settings. Full article

The Lower Anti-Atlas Supergroup (LAAS) constitutes a major Proterozoic sedimentary archive exposed along the northern margin of the West African Craton (WAC), yet its age, internal stratigraphy, and regional correlations remain controversial. This study integrates detailed sedimentological investigations, lithostratigraphic correlations, petrography, and new LA-ICP-MS U–Pb zircon geochronology from the Igherm Inlier (western Anti-Atlas, Morocco) to refine the evolution of the LAAS. Three representative stratigraphic sections allow subdivision of the succession into five lithostratigraphic units: the Coarse-Grained Quartz Sandstone, Lower Siliciclastic–Carbonate, Quartz Sandstone, Upper Siliciclastic–Carbonate, and Volcanic units. These units are correlated, from base to top, with the Tasserda Formation, Ifrane n’Taghatine Formation, Oumoula (Mimount) Formation, Tizi n’Taghatine Group, and Tachdamt Formation recognized elsewhere in the Anti-Atlas. Sedimentological data indicate deposition within a long-lived shallow-water system that evolved from tide-influenced braided fluvial channels, through mixed tidal-flat and peritidal platform environments, to extensional basaltic volcanism. Newly identified reworked volcanic tuffs from the Lower Siliciclastic–Carbonate Unit yield a maximum depositional age of 1857 ± 33 Ma, providing the first direct temporal constraint for this interval. Additional maximum depositional ages of 1880 ± 30 Ma for the Oumoula Formation and 1970 ± 29 Ma and 1904 ± 41 Ma for the Tizi n’Taghatine Group are consistent with previously published constraints. Detrital zircon populations with predominantly Paleoproterozoic and subordinate Archean dates were likely derived from the WAC. Correlation of zircon age spectra with those of the Taoudeni Basin supports the existence of extensive intracratonic depositional systems that evolved across the WAC during the Nuna and Rodinia supercontinent cycles, culminating in Tonian syn-rift magmatism represented by the ca. 883 Ma Tachdamt Formation. Full article

Western Guangxi is one of the principal bauxite-producing regions in China; however, its metallogenic model remains unclear. Building on previous studies, this paper systematically examines the ore-forming materials, sedimentary setting, ore genesis, mineral assemblages, diaspore formation, and pisoid (ooid) development of sedimentary bauxite deposits in western Guangxi. Based on this synthesis, a comprehensive metallogenic model is proposed to clarify the formation processes of these deposits. Metallogenic evolution is interpreted to involve five successive stages: weathering, leaching and alteration, deposition, post-depositional modification, and capping–sealing. Ore-forming materials are derived from volcanic ash supplied by the Emeishan Large Igneous Province and the Permian magmatic arc of the Paleo-Tethys. These materials are transported to isolated carbonate platforms and subsequently subjected to intense chemical weathering. During the early stages of ore formation, bauxite undergoes leaching and alteration, and variations in leaching intensity lead to the development of distinct ore types. Future work should focus on the genesis of diaspores, the formation of pisoids (ooids), and ore-forming mechanisms, while also addressing the coupling relationships among deep-time paleoclimate, major geological events, and sedimentary bauxite formation. Such efforts are essential for advancing a comprehensive metallogenic framework for sedimentary bauxites. Full article

The Arteni volcanic complex (Armenia) represents a distinctive volcanic landscape characterized by well-preserved pyroclastic deposits, rhyolitic domes, extensive obsidian flows, and significant archaeological evidence. This study aims to evaluate the geoheritage value of the complex and to develop a scientifically grounded geotouristic trail model based on the targeted selection of representative sites. Field-based investigations were integrated with a simplified semi-quantitative assessment of selected sites and Geographic Information System (GIS)-supported spatial analysis, including topographic, viewshed, and accessibility analyses. The results allowed for the selection of nine representative sites, effectively representing the principal stages of volcanic evolution, including explosive eruptions, lava flow emplacement, and dome formation. Spatial analysis demonstrates that the selected sites enable the development of a coherent, accessible, and scientifically meaningful geotouristic route while balancing scientific representativeness with visitor accessibility and safety. In addition, the widespread occurrence of obsidian and associated archaeological artifacts highlights the combined geological and cultural significance of the area. The proposed approach provides a transferable framework for the development of geotourism in volcanic regions and contributes to geoheritage conservation, geoeducation, and sustainable regional development. Full article

Sandstone-type uranium deposits are the main source of uranium in China. The Ordos Basin, one of the most typical Mesozoic intracontinental sedimentary basins in northern China, is a major uranium-bearing basin in China. The Hangjinqi area is a significant uranium-bearing region in the northern Ordos Basin, with favorable geological conditions and promising exploration prospects for mineralization, and the Lower Cretaceous Huanhe Formation is one of the uranium-bearing strata in this area. This study focuses on the Huanhe Formation in the Hangjinqi area to investigate the governing factors of uranium enrichment and mineralization in this stratum. U-Pb dating of detrital zircons from sandstones of the Huanhe Formation reveals dominant peak ages of 2370–2585 Ma, 214–320 Ma, and 1805–2325 Ma, and secondary peak ages of 340–506 Ma, 1598–1797 Ma, and 110–150 Ma. The age results of the selected detrital zircons indicate that the provenance of the Huanhe Formation is mainly derived from three sources: (1) the 2.6–2.5 Ga TTG gneisses and granulites in the Yinshan Block; (2) the Paleoproterozoic (2500–1800 Ma) khondalites and granitic gneisses in the Daqingshan–Wulashan–Jining area, as well as granites in the Yinshan area; and (3) large-scale intermediate–acidic intrusive rocks and volcanic rocks of the Yinshan orogenic belt, whose ages range from 110.9 to 505.9 Ma (predominantly Paleozoic). These source rocks may have provided a potential uranium source. The paleoclimate proxies, including Sr/Cu, Sr/Ba, V/Cr, Ni/Co, and Fe²⁺/Fe³⁺ ratios, combined with the Chemical Index of Alteration (CIA) and the Index of Compositional Variability (ICV), suggest that the Huanhe Formation was formed in a relatively arid and oxidized environment with a low degree of chemical weathering, which facilitated the migration of uranium-bearing ore-forming fluids. The sedimentary environment, provenance, and paleoclimate created favorable geological conditions for uranium enrichment in the Huanhe Formation of the northern Ordos Basin. Full article

Earthquake-induced landslides represent a critical threat to transportation infrastructure in tectonically active mountainous regions, particularly in tropical volcanic settings where weak, highly weathered geomaterials dominate. This study develops an integrated framework that directly links physically based seismic threshold modelling with real-time landslide monitoring and operational early warning. The approach is demonstrated in the Cugenang area of Cianjur Regency, West Java, Indonesia, which was severely impacted by the moment magnitude (Mw) 5.6 earthquake in 2022. Slopes composed of highly weathered pyroclastic deposits [Plasticity Index (PI) = 54–68%; porosity > 60%] exhibit low shear strength and high sensitivity to seismic loading. Limit equilibrium analysis using the Morgenstern–Price method that combines the influence of seismic loading and groundwater conditions suggests that a horizontal seismic coefficient (kh) of approximately 0.06, corresponding to a Peak Ground Acceleration (PGA) of about 0.12 gravitational acceleration (g), is a critical threshold for initial landsliding. This comparatively low threshold challenges commonly reported values and demonstrates that slope failure in tropical volcanic terrains can occur under moderate ground shaking, reinforcing the need for site-specific hazard characterisation. The derived thresholds are operationalised within a multi-sensor early warning system integrating Micro-Electro-Mechanical Systems (MEMS) accelerometers and inclinometer measurements. Three hazard levels—Normal (<0.06 g), Alert (0.06–0.12 g), and Emergency (≥0.12 g)are combined with deformation thresholds [<10 milimeter (mm), 10–30 mm, >30 mm] to capture progressive failure processes and minimise false alarms. By coupling geotechnical modelling and real-time monitoring, this study provides a transferable and scalable framework for enhancing infrastructure resilience in landslide-prone regions. Full article

The discovery of a super-large sandstone-hosted uranium ore field in the eolian sandstones of the Pengyang area (Ordos Basin, North China) represents a major breakthrough, yet the relationship between chlorite alteration and uranium mineralization in this deposit type remains unclear. This study conducted detailed mineralogical and geochemical analyses of chlorite using SEM, TEM, and EPMA. Five distinct types of chlorite were identified from mineralized and non-mineralized sandstones from the Luohe Formation in the Pengyang area from the southwestern Ordos Basin. This study addresses the formation temperatures, material sources, and possible formation mechanisms of those chlorites. The chlorites closely associated with uranium minerals formed at temperatures ranging from 130 to 170 °C, which represent the true formation temperature of the uranium minerals in the Pengyang uranium deposit. Comparing chlorite from uranium deposits related to granitic and volcanic rocks hosted uranium deposits in South China and sandstone-hosted uranium deposits in northern Ordos, North China, it is revealed that the chlorites from the eolian sandstone depositional area of the Pengyang experienced multiple episodes of fluid alteration. In addition, the chlorites closely related to uranium mineralization were formed by relatively low-temperature and oxidizing fluids, which may indicate that the uranium-bearing oxidative fluids in this region were primarily derived from interlayer infiltration. Full article

In the northern Sichuan Basin, distant from the main body of the Emeishan Large Igneous Province (ELIP), marine deposits of the Wujiaping Formation from the Permian period contain widely distributed tuffs of varying thicknesses. To clarify the genesis of these tuffs and their relationship with the ELIP, this study conducted field measurements and sample collection at the Daliang Section, Wangcang County, and the Qiaoting Section, Nanjiang County, of the northern Sichuan Basin and compared them with basalts and tuffs from Well DY1 in a minor basaltic eruption zone in the northern Sichuan Basin. The results indicate that tuffs from the Daliang and Qiaoting Sections of the northern Sichuan Basin exhibit high Al₂O₃/TiO₂ ratios (23.65–39.55) and significant depletion of Eu, Ba, and Sr elements. These characteristics suggest that their origin is linked to multiphase felsic volcanic activity within the ELIP and formation in an intraplate extensional setting. The basalts and tuffs developed at Well DY1 share the same low Al₂O₃/TiO₂ ratios (4.02–4.97), similar to the Emeishan basalts. In the Zr-Ti, Zr/Sc-Th/Sc, Nb/Y-Zr/TiO₂, and Zr/TiO₂-SiO₂ diagram plots, they fall within the basalt range, indicating that the tuffs at Well DY1 originated from the mid-ELIP eruption of basic basalt. In contrast to the felsic nature of the tuffs at Well DY1, the northern Sichuan Basin lacks records of such basic–alkaline igneous eruptions, suggesting that the influence of basalt eruptions in the northeastern Sichuan Basin is limited and does not affect the Wujiaping Formation in the northern Sichuan Basin. There is a positive correlation between volcanic activity and the total organic carbon (TOC) content of black siliceous rocks and siliceous shales in the Wujiaping Formation of northern Sichuan. The acid volcanic eruptions from Emeishan likely also played a key role in the formation of high-quality hydrocarbon source rocks in the deep-water continental shelf areas of the Wujiaping Formation in the northern Sichuan Basin. Full article

Roman theatres were designed to host spoken drama and musical performances, relying on typical semicircular architectural form and stone materials to achieve favourable acoustic conditions. This study investigates the acoustic behaviour of the Roman theatres of Herculaneum and Cales, two sites characterized by markedly different states of preservation and historical reconstruction challenges. The theatre of Herculaneum remains largely buried beneath volcanic deposits, requiring a hypothetical reconstruction based on archaeological documentation and historical sources, while the theatre of Cales is partially preserved and directly accessible for geometric surveys. Virtual acoustic models of both theatres were developed to analyses their sound field characteristics under unoccupied and occupied conditions. Key acoustic parameters relevant to music, including reverberation time, clarity, strength, and ITDG, were evaluated through numerical simulations. Particular attention was given to the influence of original surface materials, such as stone and wood, on sound propagation and spatial distribution. The comparative analysis highlights how differences in architectural layout, scale, and reconstruction assumptions affect the resulting acoustic performance. Despite these differences, both theatres exhibit acoustic conditions consistent with their intended use, demonstrating the effectiveness of Roman design principles. The results contribute to a better understanding of ancient performance spaces and provide insights into the acoustic restitution of Roman theatres. Full article

Volcanic ash preserves critical information on eruption dynamics, magma evolution, and fragmentation processes, yet its small size and fragile structure pose challenges for conventional analytical methods. Advances in SEM-based automated mineralogy combined with X-ray mapping (GXMAP) provide high-resolution characterization of ash textures, particle morphology, and mineral assemblages, offering a more robust basis for interpreting pyroclastic deposits. This study applies an integrated GXMAP workflow alongside sieve-based granulometry to the Early Pleistocene trachyandesite to rhyolitic pyroclastic sequences at the Kurtan quarry (Kechut Volcanic Province, Armenia), a key regional stratigraphic marker associated with early human occupation. GXMAP-based granulometry minimizes preparation-induced fragmentation and yields more consistent and reliable grain-size and morphological data for fine ash deposits than dry sieving. The three stratigraphic units at Kurtan display distinct combinations of grain size, mineral assemblages, and particle morphologies, reflecting contrasting magma evolution, fragmentation conditions, and depositional regimes. Shape-parameter fields derived from BSE images reveal clear differences between the highly irregular, concave compound fragments dominating TP-13-1 and the smoother, more compact particles characteristic of TP-13-2 and TP-13-3. Most particles fall within the ductile domain of established shape-morphology diagrams, indicating that ductile deformation of bubble walls was a major component of fragmentation, accompanied by heterogeneous brittle breakage. These results demonstrate the effectiveness of the combined SEM-based automated mineralogy and GXMAP approach for resolving primary fragmentation, sorting characteristics, and depositional processes in fragile pyroclastic deposits. The Kurtan sequence provides new constraints on explosive volcanism in the Lesser Caucasus Mts. region. At the same time, the methodological framework offers broad applicability to tephra studies worldwide and underscores the potential of imaging-based techniques in volcanology. Full article

The Nam Xan gold deposit is located in the central Truong Son Fold Belt of Laos. It is a newly identified distal intrusion-related gold system (IRGS) in a continental arc setting. This study uses whole-rock geochemistry, Pb and S isotope systematics, and mineral-scale analyses to trace magmatic evolution and ore-forming processes. Whole-rock data indicate that the associated intrusive suite is a calc-alkaline volcanic-arc granite (VAG) series, derived from a subduction-modified mantle source with notable crustal contributions. Pb isotopes reveal mixing arrays rather than true isochrons. Monte Carlo modeling shows binary mantle–crust mixing for igneous rocks and ternary mixing with an additional radiogenic component in ore samples, indicating enhanced fluid–rock interaction during mineralization. Sulfur isotope data show a shift from magmatic sulfur (δ³⁴S ≈ −5‰) in early skarn-stage pyrite to heavier values (δ³⁴S ≈ +6‰) in gold-bearing stages, reflecting fluid evolution driven by cooling and redox changes. Mineral chemistry data demonstrate that gold is present both as invisible gold within arsenian pyrite and as free gold in late-stage fractures. Strong correlations between Au and As, along with elevated Co/Ni ratios and enrichments in Bi, W, and F, collectively support a magmatic-hydrothermal origin. These findings define a three-stage mineralization process: an initial phase involving high-temperature magmatic fluids, a main stage characterized by sulfidation and gold deposition, and a final stage marked by polymetallic overprinting. The Nam Xan deposit is therefore interpreted as the distal manifestation of a Permian arc-related magmatic system in which magmatic fluids migrated along structural conduits and precipitated gold through interaction with carbonate host rocks. The identification of these intrusions in the distal IRGS at Nam Xan informs regional exploration models in the Truong Son Fold Belt, demonstrating the potential of carbonate platforms near Permian intrusions for future mineral exploration. Full article

Seabed studies are a valuable tool in the investigation of active continental margins, both in volcanic and sedimentary settings. Being an example of a slope-confined sedimentary basin, the “Ammontatura” slope basin has been discussed using multibeam bathymetry and seismo-stratigraphic data matched with previously available cores. Being a significant tectonically controlled slope bounded by the Capri-Sorrento regional fault, the southern slope of the Sorrento Peninsula has been explored employing a dense network of bathymetric profiles. The data have shown the underwater extension of the mainland drainage system, comprising a dense network of submarine gullies, reflecting the onshore drainage system. The northern Ischia debris avalanche deposits have been studied through seismo-stratigraphic data, previously unpublished, whose geologic evolution has been placed within the Quaternary stratigraphic framework of Ischia. This research revealed how several geological events, such as the tectonic phases, the emplacement of erosional and depositional domains, the volcanic eruptions, and the reworking of volcanic deposits, interacted in controlling the sedimentary structure of slope basins. In the Ammontatura slope basin, the tectonic setting has probably controlled its emplacement along a NE–SW trending regional fault, resulting from the submarine prolongation of the Sarno-Sebeto normal fault, while intense reworking of volcaniclastic deposits acted as the main control factor in slope settings. Full article

The deposition of volcanic ash in areas affected by erupting volcanoes can contaminate the soil with heavy metals, thereby jeopardizing food security and public health. This study focused on the use of compost for the bioremediation of this type of contaminated soil and on evaluating the effectiveness of this remediation technique in a horticultural crop. To this end, composts made from organic waste generated in the areas with volcanic-ash-affected soil, such as crop residues, cow manure, and cheese whey, were used. The design and optimization of the composting process for these wastes were described using three piles with the same proportion of crop residues and cow manure but different doses of whey (pile 1: without whey, pile 2: whey diluted with water (1:2 (v:v)); and pile 3: with undiluted whey) and by monitoring the evolution of physicochemical and biological parameters throughout the compositing process. The effectiveness of the composts obtained for soil remediation was evaluated by assessing the physiological response of a lettuce crop in pots. Five treatments were used: control soil without fertilization, inorganic fertilization, and the three composts obtained. The main agronomic properties of the soil and heavy metal availability were measured, along with the physiological and chemical parameters of the lettuce, including growth and macronutrient and heavy metal content. The results obtained in the composting experiment showed that the addition of cheese whey only affected the rate of organic matter degradation and the salt content of the final composts, without negatively affecting the stability and humification of their organic matter or their plant nutrient content. In the pot experiment, all composts improved soil fertility and reduced the availability of Ni, As, Cd, and Pb, but this did not consistently reduce uptake into lettuce, except in the case of Pb. Therefore, it is advisable to adjust the compost application rate and optimize crop selection to minimize the impact of heavy metals on the food chain, thereby ensuring safe production. Full article

Rhyolites serve as unconventional hydrocarbon-water reservoirs and also as high-quality volcanic reservoirs. Well BZ8-3S-B exhibits maximum productivity in vertical wells. Drilling results reveal significant mega-scale heterogeneity among different wells within the same rhyolitic volcanic edifice, as well as between different intervals within single wells. To clarify the mega-scale heterogeneity characteristics of rhyolitic reservoirs, this study investigates Block BZ8-3S in the Bozhong Depression, Bohai Bay Basin, China. Based on sidewall cores, logging data and seismic datasets, comprehensive research methods including petrographic/mineralogical analysis, image processing, porosity–permeability testing, mercury capillary pressure measurements, logging facies interpretation and seismic facies analyses were employed. The study establishes correlations between volcanic edifice architecture, stratigraphic boundaries, depositional units and their relationships with reservoir space composition/permeability characteristics, aiming to identify principal controlling factors of mega-scale heterogeneity through systematic stratigraphic architecture analysis. The key findings are summarized as follows: (i) The volcanic edifices in Block BZ8-3S exhibit massive-pseudostratified structural characteristics. (ii) Wells A and B belong to the same volcanic edifice system but occupy distinct facies belts. Well A is located in the crater-near crater belt, while Well B lies in the proximal belt. (iii) Eruptive interval unconformity boundaries (EIUBs) are identified at 1 and 4 depths in Wells A and B, respectively. The EIUBs control the vertical heterogeneity of depositional-unit reservoirs. Reservoir porosity exhibits inverse correlation with burial depth below EIUBs, indicating stratigraphic boundary control on reservoir development. Mega-scale heterogeneity of rhyolitic reservoirs is primarily controlled by the number of stratigraphic boundaries and depositional unit types. From an exploration perspective, lava dome deposited units within crater-near crater belt should be avoided, while priority should be given to proximal belt targets featuring thick sequences with high proportions of lava flow units. This study provides critical insights for optimizing exploration strategies and enhancing development efficiency of rhyolite volcanic edifices. Full article

The distribution and concentrations of gold and other trace elements in numerous pyrite-bearing ore samples from volcanic-hosted massive sulfide (VHMS) deposits were obtained using LA-ICPMS imaging techniques. Pyrite in VHMS deposits is characterized by low Co and Ni (generally less than 100 ppm Co and Ni, but rarely above 1000 ppm in either element). On the other hand, Cu, As, Ag, Au, Sb, Mn, Tl, and Pb are commonly elevated above background and appear to be deposited in multiple forms, including solid solution as well as nano- and micro-inclusions of other mineral phases. Gold is predominantly present in solid solution within the crystal lattice. Such trace element signatures in pyrite are indicative of moderate- to high-temperature hydrothermal fluids varying in pH from moderately to strongly acidic. Pyrite from VHMS-style mineralization is distinguishable from pyrite in other deposit types by its relatively low abundance of Co and Ni. For example, pyrite from IOCG-type mineralization is nearly always enriched in Co at or above the weight-percent level, with lower but still elevated concentrations of Ni. In addition, IOCG pyrites do not contain elements such as Sb, Tl, or Pb in solid solution. Pyrite from porphyry-style Cu-Au-Mo mineralization likewise contains higher average Co and Ni than VHMS pyrite and lacks solid solution deportment of Sb, Tl, Pb, and other associated elements. This study underscores the effectiveness of trace element imaging via LA-ICPMS for the discrimination of pyrite from different mineral systems and for detailed paragenetic information. Full article