Search Results (1,052)

Uranium exploration in southeastern Mongolia remains constrained by fragmented Soviet-era datasets and limited modern synthesis. This study addresses the problem of integrating historical geological records with contemporary exploration methods to evaluate uranium mineralization potential. A comprehensive GIS-based database was compiled from Soviet reports legally acquired from the Mineral Resources Authority of Mongolia and expanded with geological, geophysical, and drilling data collected between 2006 and 2011. Methodological advances included remote sensing detection of anomalous radioactivity in arid environments, stratigraphic modeling, and hydrogeochemical surveys. The dataset encompasses more than 1100 radioactive anomalies and approximately 300 mineralized zones, with emphasis on the Han Bogd granite massif, Ail Bayan coal deposit, Suujin Tal structural system, Zuunbayan depression, and Naarst structural complex. Results indicate that most anomalous zones are sub-economic, commonly associated with organic-rich facies such as coal seams, while the continuity of mineralized bodies remains uncertain. Nevertheless, the dual consideration of granitic source terrains and coal-bearing sedimentary traps provides new insights into uranium mobility and deposition. The significance of this work lies in its systematic integration of historical and modern data, offering a refined geological framework and highlighting key areas for future investigation, thereby contributing to ongoing discussions on sedimentary uranium resources in Mongolia. Results indicate that most anomalous zones are sub-economic, commonly associated with organic-rich facies such as coal seams, while the continuity of mineralized bodies remains uncertain. Importantly, the study highlights granitic intrusions and volcanic complexes as the primary uranium sources, with coal-bearing and sedimentary basins acting as secondary depositional environments. The dual consideration of source terrains and depositional traps provides new insights into uranium mobility and deposition. Full article

The hornblende gabbro investigated in this study crops out in northwestern Elazığ, eastern Türkiye, within the Southeastern Anatolian Orogenic Belt (SAOB), where Late Cretaceous ophiolitic, volcanic, plutonic, and metamorphic units are widely exposed. This study examines the petrology, whole-rock geochemistry, Sr–Nd isotopic composition, mineral chemistry, and crystallisation conditions of these gabbroic bodies to constrain their petrogenesis and tectonomagmatic significance. Field observations show that the rock occurs as rounded to sub-rounded blocks with fresh inner cores and altered outer rims. Petrographic and XRD data indicate that the fresh gabbro mainly consists of plagioclase and amphibole, whereas the altered outer rims contain quartz and minor secondary phases. Whole-rock geochemical data classify the samples as low- to medium-K, tholeiitic, and predominantly metaluminous gabbro. Primitive mantle-normalised trace-element patterns display enrichment in large-ion lithophile elements and depletion in high-field-strength elements, whereas chondrite-normalised REE patterns show slight LREE enrichment, relatively flat HREE patterns, and weak Eu anomalies. Sr–Nd isotopic compositions are characterised by positive εNd_(T) values (+4.4 to +5.3) and moderately radiogenic initial ⁸⁷Sr/⁸⁶Sr ratios (0.704792–0.705344), indicating a predominantly mantle-derived magma source affected by subduction-related modification, with limited crustal contribution. Mineral chemistry data show that amphiboles belong to the calcic amphibole group and plot in the magnesio-hornblende field. Amphibole thermobarometric calculations yielded temperatures of 873–991 °C and pressures of 1.49–3.26 kbar, corresponding to crystallisation depths of 5.1–15.3 km. Overall, the results indicate that the hornblende gabbro was derived from a mafic magma generated from a spinel lherzolite mantle source and crystallised in a subduction-related tectonomagmatic setting. Full article

This study reports on the first Mesozoic turtle remains from Cambodia. The material, consisting of shell fragments, was collected at Koh Moul, an island in the Gulf of Thailand. These turtle remains are assigned to Trionychoidae indet. and have strong similarities with the Early Cretaceous basal trionychoid Basilochelys macrobios from the Khorat Group, NE Thailand. The discovery suggests an Early Cretaceous age for the fossil-bearing strata. Full article

The latest Cretaceous saw the final diversification of dinosaurs before the K/Pg extinction. Discussions of end-Cretaceous dinosaur diversity have focused on well-sampled faunas from Laurasia; far less is known about dinosaurian faunas of the Southern Hemisphere, especially Africa. The late Maastrichtian Phosphates of Morocco provide a rare window into African dinosaur diversity. Abelisaurids, lambeosaurines, and titanosaurian sauropods are known. However, no diagnostic titanosaur remains have been recovered, leaving the affinities of these sauropods unclear. We describe Phosphatotitan khouribgaensis gen. et sp. nov., a new titanosaur from the Maastrichtian of Sidi Chennane, Khouribga Province. Phosphatotitan is represented by dorsal, sacral, and caudal vertebrae, and the pelvis. The new species differs from titanosaurs described from the Cretaceous of Africa and Europe but resembles South American Lognkosauria, and especially Patagotitan, in having short dorsal and caudal centra, expanded dorsal and caudal neural spines, and a broad pubis. Its small size relative to other Lognkosauria (3.5–4 tonnes) suggests a lineage selected for small size. The close relationships of Morocco’s titanosaurs and abelisaurids to South American species may reflect a wide distribution of these clades prior to the opening of the South Atlantic and the separation of Africa and South America ~100 Ma, while a complex pattern of oceanic dispersal may explain the presence of distinct saltasauroid lineages worldwide. The latest Cretaceous Gondwanan dinosaur faunas were highly endemic due to a combination of continental fragmentation, extinction, and dispersal, creating high endemism in southern continents and within Africa, suggesting that Maastrichtian dinosaur diversity is underestimated. Full article

The Qingshankou Formation shales in the southeastern uplift of the Songliao Basin provide an ideal archive for constraining the controls of paleoenvironment on organic matter enrichment. Taking the shale succession at the Niaohexiang section of Binxian as the study object, we combined field sampling with TOC measurements, whole-rock X-ray diffraction, and major, trace, and rare earth element analyses. The strata are dominated by black shale and dark gray mudstone, with mineral assemblages composed mainly of clay, felsic, and carbonate minerals; argillaceous shale exceeds 60%. Normal alkanes display a post-peak distribution with C₂₇ as the dominant peak, low Pr/Ph ratios, and gammacerane index values of 0.18–0.26. Regular steranes are generally V-shaped, whereas some samples show high C₂₉ sterane contents and a reversed L-shaped pattern. Major elements are dominated by SiO₂ and Al₂O₃, trace elements such as Sr and Ba are relatively enriched, and rare earth elements show light REE enrichment with a pronounced negative Eu anomaly. These signatures indicate an upper-crustal felsic provenance and a continental island arc tectonic setting. Organic matter contents are low and derived mainly from terrestrial higher plants with minor aquatic input. Paleoenvironmental reconstruction suggests deposition in a freshwater to slightly brackish, semi-arid, anoxic-reducing shallow lacustrine setting with relatively low productivity, whereas dolostone formed under more saline, arid, and more productive conditions. Climatic fluctuations, salinity variations, and alternating redox states jointly controlled organic matter enrichment, and late-stage lacustrine salinization and anoxia associated with dolostone horizons enhanced organic matter preservation. Full article

Sandstone of the Lower Cretaceous Luohe Formation is the main water inrush source in the Binchang Mining Area in the southwestern Ordos Basin. Its sedimentary environment and provenance features are critical for local coal development and safe mining. The Luohe Formation at Xiaozhuang Coal Mine comprises three vertical members: the lower member dominated by coarse- to medium-grained sandstones, the middle member mainly composed of fine-grained sandstones, and the upper member characterized by interbedded fine- to medium-grained sandstones and sandy conglomerates. This subdivision newly identifies a complete hydrodynamic evolutionary cycle of depositional environments from high-energy to low-energy and back to high-energy conditions. Integrated petrographic observations and analyses of major and rare earth elements first confirm that the tectonic affinity of the Luohe Formation progressively shifted from a passive continental margin to an active continental margin, accompanied by a corresponding transition in sediment provenance from the North China Craton to a magmatic arc source region. Trace element compositions precisely indicate that the Luohe Formation was deposited in a fluvial freshwater environment under hot, arid, and oxidizing conditions, thus providing new constraints on the paleoenvironmental evolution of the region. Full article

This study fills a knowledge gap in the distribution of the Upper Cretaceous dinosaur tracks in central China by examining two newly discovered tracksites near Xiakou village (Nanzhang County) and Jiuxian town (Yuan’an County), Hubei Province. Eleven Isolated tracks were analyzed to identify the ichnofauna assemblage. Morphometric analysis indicates the presence of tridactyl and rounded morphologies. The tridactyl tracks are consistent with a small-sized theropod and ornithischian ichnofauna, whereas the rounded shape remains ichnotaxonomically indeterminate. These tracks are the first reported dinosaur ichnite from central China at this age. Despite limited preservation, this research highlights how extromorphological factors influence track morphology, a key issue in ichnological studies. Overall, it contributes new data on the presence of dinosaur ichnofauna in China during the late Mesozoic. Full article

The northern part of the Great Xing’an Range in China hosts a prominent Au mineralization belt, where Mesozoic clastic rock-hosted Au deposits represent the mineralization type. A study of the Baoxinggou Au deposit in this region might provide new perspectives on the mineralization mechanisms of these Mesozoic clastic-rock-hosted Au deposits. This study investigated the age of mineralization, origins and evolution of the ore-forming fluids, and sources of the ore-forming materials in this deposit. Rubidium–Sr dating of sulfides yielded a mineralization age of 119 ± 2 Ma. Fluid inclusion analyses revealed that the ore precipitated from fluids with temperatures of 105–415 °C and salinities of 4.3–8.8 wt.% NaCl equivalent. Hydrogen and O isotopic data show that the ore-forming fluids were of magmatic origin and, during mineralization, the proportion of meteoric waters increased gradually and eventually dominated the late mineralization stage. Fluid mixing was the primary ore-forming mechanism. Sulfur isotopic data for pyrite and chalcopyrite (δ³⁴S_V–CDT = −4.35‰ to −0.91‰) and Pb isotopic ratios (²⁰⁶Pb/²⁰⁴Pb = 18.429–18.477; ²⁰⁷Pb/²⁰⁴Pb = 15.581–15.591) indicate the ore-forming materials were magmatic in origin, with a similar source as an Early Cretaceous diorite and mixed crust–mantle materials. The results indicate the Baoxinggou Au deposit is a magmatic–hydrothermal deposit. Full article

The Rio Grande Rise (RGR) is the largest oceanic plateau in the South Atlantic and represents a key natural laboratory for understanding oceanic plateau formation, deep-sea circulation, ecosystem functioning, and ferromanganese crust development. This study presents a critical synthesis of current scientific knowledge on the RGR, integrating geological, geophysical, oceanographic, biological, and geochemical evidence published over the last two decades. Geophysical data reveal a complex tectono-magmatic evolution involving Late Cretaceous plume-related volcanism, crustal thickening, rifting, and subsequent subsidence. The structural framework of the plateau is dominated by the Cruzeiro do Sul Rift, which plays a central role in controlling sedimentation, magmatism, and seawater circulation. Oceanographic studies demonstrate that the interaction between the southern branch of the South Equatorial Current and the complex topography of the RGR generates intense internal tides and bottom currents, strongly influencing sediment transport and benthic habitats. Biological investigations indicate that the RGR hosts diverse deep-sea communities, including sponge grounds, cold-water corals, and associated fauna, whose distribution is tightly linked to geomorphology and hydrodynamics. Ferromanganese crusts occurring on the plateau preserve valuable geochemical records of oceanographic and redox conditions, although their spatial distribution, thickness, and metal budgets remain incompletely constrained. Despite major advances, significant knowledge gaps persist regarding crustal structure, sedimentary evolution, ecosystem functioning, and mineral formation processes. This review highlights these uncertainties and outlines research priorities necessary to improve understanding of oceanic plateaus and deep-sea systems in the South Atlantic. Full article

Investigation of deposystems, sediment routing, and basin architecture during Gondwana breakup refines understanding of Permian–Cretaceous landscape evolution in the central Andes. New chronostratigraphic and provenance constraints from the Eastern Cordillera and Subandean Zone of Bolivia (19–22°S) are based on U-Pb geochronology of detrital and volcanic zircons and ⁴⁰Ar/³⁹Ar dating of interbedded basalts. A discontinuous <2 km-thick Permian–Cretaceous succession records deposition in fluvial, lacustrine, alluvial fan, eolian, and shallow marine environments. Stratigraphic correlations indicate alternations between isolated half-graben subbasins and regional, non-compartmentalized basins. Detrital zircon age spectra from 18 sandstones document sediment recycling from western orogenic and magmatic arc sources and eastern cratonic basement. Synextensional successions of Early Triassic, Early Jurassic, and mid-Cretaceous age were sourced mainly from the west, including Carboniferous and Devonian rocks, while post-extensional fluvial and eolian systems were derived chiefly from the eastern craton. Variations in thickness, facies, and mafic magmatism reflect alternating extensional and neutral tectonic regimes, with localized synextensional subsidence potentially linked to extensional collapse, mantle plume activity, and South Atlantic opening. Comparison with Andean regions in Peru and Argentina indicates that episodic extension and post-extensional thermal subsidence accompanied subduction along the western margin of South America during Gondwana-Pangea breakup. Full article

Grasping appendages in representatives of the group Insecta are usually of the sub-chelate (jackknifing) type. Only rarely do chelate appendages occur: Carcinothrips (Thysanoptera), Dryinidae (Hymenoptera), and Carcinocorini (Heteroptera). Here, we report a new find from about 100 million-year-old Kachin amber, representing, to our knowledge, the first case of a fossil of the group Insecta with a chelate type of appendage. This find is only the fourth case of an independent or convergent evolution of such a structure. A quantitative morphological comparison of over 2000 grasping structures reveals that the proximal part of the chela (in this case, the femur) has a unique shape in the fossil, unparalleled in the fossil and modern fauna. Moreover, some other new fossils reported do not possess such a shape. The mouthparts, forming a distinct beak, allow us to identify the new fossil with the distinct chela as a representative of Heteroptera. Its short beak, together with some other characteristics, indicates that it most likely is a representative of Nepomorpha. Many other details of the fossil are not well preserved, but the overall appearance shows similarities to extant and fossil representatives of Gelastocoridae, a group of terrestrial predators. Full article

This study investigates the heterogeneity of pore structures in lacustrine shale gas reservoirs, with a specific focus on shales from the Lower Cretaceous Shahezi Formation in the Lishu Fault Sag of the Songliao Basin. By integrating multi-scale characterization techniques—including high-pressure mercury intrusion, N₂/CO₂ adsorption, and nuclear magnetic resonance (NMR)—we examined the pore networks across five identified lithofacies: organic-rich clayey shale, organic-rich mixed shale, organic-rich siliceous shale, organic clayey shale, and organic mixed shale. The results indicate that mesopores (2–50 nm) constitute the dominant fraction of pore volume (31.7%–56.6%), followed by micropores (<2 nm) and macropores (>10 μm). Notable lithofacies-dependent variations were observed: organic-rich clayey shale exhibits abundant organic pores, clay interlayer pores, and intragranular dissolution pores with favorable connectivity; organic-rich siliceous shale is mainly dominated by inorganic pores with limited organic porosity; mixed shales are characterized by clay mineral contraction fractures and intergranular pores. The key controlling factors are mineral composition and organic matter abundance: clay content shows a positive correlation with pore volume and surface area in organic-rich clayey shale, but a negative correlation in organic mixed shale. Brittle minerals (quartz and feldspar) generally reduce porosity through compaction. Total organic carbon (TOC) displays a weak positive correlation with mesopore volume, while thermal maturity (Ro = 1.2%–1.73%) exerts influences that vary by lithofacies. In contrast to marine shales—which are dominated by high-maturity (Ro > 2.0%) organic pores and quartz-supported frameworks—terrestrial shales primarily rely on inorganic pores derived from clay minerals (e.g., illite). This study clarifies the relationships among lithofacies, pore structure, and controlling factors, thereby providing a basis for evaluating the gas potential of terrestrial shales. Full article

The Late Jurassic–Early Cretaceous Oloy complex was formed in the setting of convergence between the Chukotka microcontinent and the Kolyma–Omolon margin. Its evolution reflects the closure of the South Anyui Ocean, with controversial timing estimates. This study emphasizes the integration of lithological data with magmatic and metallogenic information to reconstruct geodynamic processes. The article presents the results of detailed petrographic and geochemical studies, Sm-Nd isotope analyses, and U-Pb dating of detrital zircons from Kimmeridgian–Lower Hauterivian volcaniclastic and epiclastic sandstones. Petrographic studies and U-Pb dating of detrital zircons identified the main sources at different stages and the amount of synchronous pyroclastic material. Isotope-geochemical investigations suggest a young undifferentiated arc provenance for Kimmeridgian deposits, whereas Tithonian–Valanginian sediments accumulated due to the erosion of more differentiated igneous rocks and input of clastic material from the continent. New data on changes in sedimentation environments and provenance enabled the tracing of the evolution of the Oloy arc. In the Kimmeridgian, the Oloy island arc existed on a heterogeneous basement, with south-dipping subduction towards the Kolyma–Omolon margin. During the Late Tithonian, the arc accreted and magmatic activity continued in the active margin setting. Collision initiated in the latter half of the Berriasian, reaching its active phase in the Valanginian time. Full article

Cranial crests have evolved multiple times in the evolutionary history of vertebrates, serving primarily for visual display. In duck-billed lambeosaurines, one of the most successful dinosaur clades of the Late Cretaceous, the cranial crest became hollow along the paired premaxillae and nasals, and was secondarily selected as a resonating structure atop the skull roof, facilitating acoustic signaling. Here we report the first instance of a hollow supracranial crest in a non-lambeosaurine ornithopod dinosaur, the early-branching hadrosauroid Qianjiangsaurus changshengi, where the paired accessory endonasal cavities just above the nasal cavity proper occur following the dorsoventral thickening of the nasals. This novel nasal cavity configuration is associated with the helmet-like hollow supracranial crest solely formed by the nasals. Comparative resonance modeling suggests that the nasal cavity of Q. changshengi could amplify low-frequency vocalizations similar to those of late-branching lambeosaurines. Seven analogous skull features (including the hollow supracranial crest) and similar low-frequency acoustic capabilities of nasal cavities between Q. changshengi and late-branching lambeosaurines reveal a striking morphological and functional convergence that would likely facilitate safer, more efficient social communication among hadrosauroids. This convergence can be explained by adaptive evolution under similar selection pressures, combined with developmental constraints due to gene pleiotropy. Full article

Mesozoic tree ferns related to the extant Loxsomopsis, a relict and taxonomically isolated genus endemic to tropical South America, are exceedingly rare, making it difficult to trace its origin and evolution. Here, we describe a mid-Cretaceous fossil attributable to Loxsomopsis, Loxsomopsis minor sp. nov., based on two fertile pinnules preserved in Myanmar amber. The new species is assigned to the extant genus based on a suite of diagnostic features, including pinnate fertile segments with short lobes, marginal paraphysate sori, narrowly cyathiform to urceolate indusia, columnar and exserted receptacles, oblique sporangial annuli, and trilete spores. This discovery extends the fossil record of Loxsomopsis back to the Albian–Cenomanian and provides new evidence that the lineage—now restricted to tropical South America—was once more widespread. The occurrence of Loxsomopsis in the Myanmar amber biota is consistent with a Gondwanan affinity for this mid-Cretaceous forest ecosystem and suggests that the genus may have likely originated prior to the breakup of Pangaea. Full article