Search Results (174)

The Circum-Rhodope Belt fringes the Rhodope and Serbo-Macedonian zones in the Alpine orogen of the northern Aegean region. This belt contains Late Paleozoic and Mesozoic metasedimentary successions that record depositional history along the continental margin of Eurasia. Critical successions of the eastern Circum-Rhodope Belt, such as those exposed in the Fanari and Petrota areas, are studied here, integrating their structure, whole-rock geochemistry and U-Pb LA-ICP-MS zircon geochronological context. The Fanari turbiditic succession contains quartz arenite, while the Petrota succession consists of Fe-rich shale and sandstone, and both successions are distinguished by REE-depleted and REE-enriched characteristics and acidic and intermediate arc-related sedimentary sources, respectively. Detrital U-Pb zircon geochronology reveals a Late Carboniferous–Early Permian maximum depositional age of 301.2 ± 8.4 Ma for Fanari quartz arenite and a Late Jurassic maximum depositional age of 147.0 ± 2.0 Ma for Petrota Fe-shale. The results are interpreted in terms of Late Paleozoic continental slope deposition of the Fanari succession along the Eurasian margin and trench-arc sedimentation of the Petrota succession linked to the development of a Jurassic island arc system pertinent to the eastern Circum-Rhodope Belt. These tectonic settings and depositional environments can be used to restore an overall picture of a Late Paleozoic to Mid-Mesozoic sedimentation at the Rhodope–Serbo-Macedonian continental margin of Eurasia. Structures that developed in greenschist facies conditions and N-directed kinematics of the studied successions unequivocally relate them to other units of the eastern Circum-Rhodope Belt and its Late Jurassic tectonic evolution. Full article

To constrain the Late Paleozoic tectonic evolution of Taiyuan Formation, we conducted detrital zircon U-Pb dating and Hf isotopes analysis. The U-Pb age spectra from ten sandstone samples (taken from both the top and bottom of the formation) display four major age groups of 2.6–2.4 Ga, 2.2–1.8 Ga, 496–421 Ma and 350–270 Ma with highest peaks at ca. 323 Ma and 443 Ma. Moreover, on the basis of the weighted mean age of the five youngest detrital zircons (293.0 ± 4.1 Ma), combined with published results, we propose that the Taiyuan Formation formed during the Early Permian. Comparison of detrital zircon U-Pb age spectra and Hf isotopic compositions with potential source regions indicates that the early Paleozoic zircons were largely derived from the North Qinling orogenic belt, whereas the late Paleozoic zircons originated from the Inner Mongolia uplift. This shift reveals a significant provenance change recorded in the Taiyuan Formation. The uplift of the northern North China Craton (Inner Mongolia uplift) is interpreted as a response to the resubduction of the Paleo-Asian Ocean during the Late Paleozoic. The resulting paleogeographic pattern—higher in the north and lower in the south—redirected sediment supply for the uppermost sandstone and overlying strata of the Taiyuan Formation in the Qinshui Basin from the earlier North Qinling orogenic belt to the Inner Mongolia uplift. Full article

Modern oceanographic studies demonstrate that marginal seas and semi-restricted marine environments, including epicontinental seas and carbonate platforms, are highly sensitive to changes in circulation, freshwater input, stratification, and redox conditions, allowing climatic perturbations to be recorded with high fidelity. Understanding the behavior of such systems under icehouse conditions is therefore important for interpreting climate variability in both ancient and modern oceans. The Late Paleozoic Ice Age was a prolonged icehouse interval characterized by repeated glacial and interglacial oscillations, yet its climate dynamics are still mainly constrained by Gondwanan glacigenic records and low-latitude carbonate successions. High-resolution climate information from mid-latitude regions remains limited. The purpose of this study is to obtain high-resolution mid-latitude geochemical constraints on climate variability during the Late Paleozoic Ice Age using a semi-restricted marine carbonate succession. Specifically, this study aims to (1) establish high-resolution carbon and oxygen isotope records from well-preserved carbonate samples spanning the Visean to Asselian interval; (2) identify and characterize major glacial to interglacial cycles recorded in the succession; (3) evaluate the extent to which semi-restricted paleogeography amplifies isotopic responses relative to coeval low-latitude open-marine settings and (4) assess the climatic significance of a short-lived negative carbon isotope excursion during the middle Bashkirian. Here we present high-resolution carbon and oxygen isotope records from a Visean to Asselian marine carbonate succession deposited in a semi-restricted basin. Stable isotope analyses of well-preserved carbonate samples document temporal variations in carbonate carbon and oxygen isotopes. The records resolve at least three major glacial to interglacial cycles, with isotope shifts substantially larger than those reported from coeval low-latitude open-marine settings. Carbon isotope variations reach up to 7.7‰, while oxygen isotope variations reach up to 9.2‰. These pronounced responses are attributed to semi-restricted paleogeography, facies heterogeneity, and the sensitivity of marine carbonate systems to stratification, redox variability, and organic carbon cycling. A short-lived negative carbon isotope excursion during the middle Bashkirian may record a Northern Hemisphere deglaciation event superimposed on the broader Gondwanan icehouse background, a signal that is not clearly expressed in other regions. Overall, this study describes new mid-latitude geochemical constraints on Late Paleozoic climate variability and offers valuable analogs for understanding climate responses in modern marginal marine systems. Full article

The Tawenchahanxi mining area, situated in the southeastern Qimantagh region of the East Kunlun Orogenic Belt, hosts a skarn-type Fe–polymetallic deposit associated with acidic granitic intrusions. Laser ablation–inductively coupled plasma–mass spectrometry zircon U–Pb dating yields ages of 233.3 ± 1.2 to 234.3 ± 1.1 Ma for a granodiorite and 397.7 ± 1.4 Ma for a quartz porphyry, indicating two magmatic intrusive events during the Early Devonian and Late Triassic. The Early Devonian quartz porphyry is characterized by high ${\mathrm{S}\mathrm{i}\mathrm{O}}_2$ (72.39%–74.04%), high total alkalis (7.81%–7.83%), high TFeO (>1.0%) and high crystallization temperatures (~865 °C), together with low CaO (1.64%–1.70%) and MgO (0.61–0.65%), which are all consistent with A-type granite affinity. The granodiorite exhibits aluminum saturation index (A/CNK) values of 0.67–1.07 (metaluminous to weakly peraluminous) and belongs to the high-K calc-alkaline series. It exhibits moderate negative Eu anomalies (δEu = 0.71–0.83), and zircon saturation temperatures of ~748 °C, collectively indicative of I-type granite affinity. Both rock suites display depletion in Nb, Ta, and Sr and enrichment in Rb and LREEs. Zircon Hf isotopic data show εHf(t) values of −0.64 to 0.57 for the quartz porphyry and −4.37 to −1.06 for the granodiorite, indicating derivation primarily from partial melting of ancient crust with variable mantle contributions. These intrusions formed during post-collisional extensional (Early Paleozoic) and collisional to post-collisional (Late Paleozoic–Early Mesozoic) stages, respectively, associated with mantle magma underplating and crust–mantle mixing. Such processes formed the material basis for the polymetallic mineralization in the Tawenchahanxi district by providing Fe–Cu–Pb–Zn and other ore-forming elements from deeper crust. Full article

“Placoderm” and sarcopterygian fishes dominated Devonian waters. Following the end-Devonian crisis, actinopterygians rapidly became major contributors to vertebrate diversity. This transition constitutes the first major diversification event of actinopterygians. Here, we investigate the morphological diversification of Devonian and Carboniferous actinopterygians by quantifying disparity using two-dimensional (2D) geometric morphometrics, which estimates disparity from continuous data and brings geometric information related to the shape changes in several morphological features. In total, 13 landmarks and 203 semi-landmarks were digitized on the body shape reconstructions of 84 species, and 18 landmarks and 50 semi-landmarks were digitized on the reconstructions of the lateral view of the skulls of 86 species. When compared to variations in taxonomic diversity over time, the pattern of body shape variations is congruent, reaching a maximum during the Viséan, but the pattern of skull disparity is not entirely congruent, presenting a first increase during the Late Devonian. Changes in body shape are associated with locomotory properties, while changes in skull shape are associated with functional properties of the feeding apparatus. This pattern strongly suggests the diversification of actinopterygians to be driven by divergence in trophic strategies. This evolutionary radiation seems to be the result of an adaptive response to new ecological opportunities, triggered by big environmental changes in mid-Paleozoic oceans. Full article

The Hatu region in the Western Junggar, Xinjiang, is one of the most significant gold metallogenic concentration areas in China. Gold mineralization is primarily controlled by several parallel NE-trending strike-slip faults and Late Paleozoic granitic plutons, accompanied by multiple stages of hydrothermal activity. To enhance the objectivity and accuracy of mineral prospecting prediction, this study develops an integrated forecasting framework that combines multi-source remote sensing datasets with machine learning techniques. Alteration anomalies related to iron staining and hydroxyl-bearing minerals are extracted from ASTER data, alteration mineral mapping is performed using GF-5 hyperspectral imagery, and Landsat-9 data is used for structural interpretation to refine the regional metallogenic framework. On this basis, these multi-source remote sensing products are then integrated to delineate five prospective metallogenic areas (T1–T5). Subsequently, a Random Forest (RF) model optimized by the Grey Wolf Optimizer (GWO) algorithm is employed to quantitatively integrate key evidence layers, including alteration, structure, and geochemistry, for estimating mineralization probability. The results show that the GWO-RF model effectively concentrates anomalous areas and identifies two high-confidence targets, Y1 and Y2, both with mineralization probabilities exceeding 0.8. Among them, the Y1 target is associated with the Bieluagaxi pluton and exhibits strong montmorillonitization, chloritization, and iron-staining alteration, typical for magmatic–hydrothermal controlled mineralization. In contrast, the Y2 target is strictly controlled by the Anqi Fault and its subsidiary faults, primarily characterized by linear chloritization and iron-staining anomalies indicative of structure–hydrothermal mineralization. Field verification confirms the significant metallogenic potential of both Y1 and Y2, demonstrating the effectiveness of integrating multi-source remote sensing and machine learning for predicting orogenic gold systems. This approach not only deepens the understanding of the diverse gold mineralization processes in the Western Junggar but also provides a transferable methodology and case study for improving regional mineral exploration accuracy. Full article

Insect pollination, a critical ecological process, pre-dates the emergence of angiosperms by nearly 200 million years, with fossil evidence indicating pollination interactions between insects and non-angiosperm seed plants during the Late Paleozoic. This review examines the symbiotic relationships between insects and gymnosperms in pre-angiosperm ecosystems, highlighting the complexity of these interactions. Fossil records suggest that the mutualistic relationships between insects and gymnosperms, which facilitated plant reproduction, were as intricate and diverse as the modern interactions between angiosperms and their pollinators, particularly bees. These early pollination systems likely involved specialized behaviors and plant adaptations, reflecting a sophisticated evolutionary dynamic long before the advent of flowering plants. The Anthropocene presents a dichotomy: while climate change and anthropogenic pressures threaten insect biodiversity and risk disrupting angiosperm reproduction, such upheaval may simultaneously generate opportunities for novel plant–insect interactions as ecological niches are vacated. Understanding the deep evolutionary history of pollination offers critical insight into the mechanisms underlying the resilience and adaptability of these mutualisms. The evolutionary trajectory of bees—originating from predatory wasps, diversifying alongside angiosperms, and reorganizing after mass extinctions—exemplifies this dynamic, demonstrating how pollination networks persist and reorganize under environmental stress and underscoring the enduring health, resilience, and adaptability of these essential ecological systems. Full article

This study focuses on the mineralogy and mineral chemistry of the accessory minerals occurring in the Kastoria pluton situated in NW Greece, which intrudes the Pelagonian nappe having crystallized during the Late Paleozoic (~300 Ma). The pluton consists of porphyritic granite (GR) that hosts mafic microgranular enclaves (MME) of monzonitic composition. Both lithologies contain quartz, microcline, plagioclase, biotite, secondary white mica, hornblende, and actinolite along with accessory minerals including titanite, epidote, allanite, apatite, zircon, and magnetite. Compared to the granite, the enclaves are richer in biotite, amphibole, and plagioclase but poorer in quartz and microcline. Mineral chemistry indicates a calc–alkaline affinity, consistent with the observed magmatic trends. Crystallization pressure, estimated at 3 kbar from Al in a hornblende barometer, suggests emplacement at mid-crustal levels. During the Alpine deformation, the pluton underwent low-grade greenschist to amphibolite-facies metamorphism, which partially overprinted the primary mineral assemblages. Magmatic titanite and allanite crystals are well preserved, showing only recrystallization features. Metamorphism produced tiny titanite needles and epidote replacing primary minerals (plagioclase, amphibole, and biotite). Later, hydrothermal alteration produced another generation of secondary epidote. Only a couple of epidote crystals preserve potential magmatic relict characteristics (euhedral habit, zircon inclusions, positive Eu anomaly, and sharp contact with primary minerals). These results provide insights into both the primary magmatic features and the subsequent metamorphic modification of the I-type Kastoria pluton within the Pelagonian domain. Full article

There exists an east–west trending albitite (breccia) zone, approximately 400 km in length, closely related to gold mineralization, in Devonian strata in the South Qinling tectonic belt. The genesis and formation age of these albitite (breccia) are of great significance for understanding gold enrichment mechanisms and guiding future exploration. Past studies have mainly focused on the Fengxian–Taibai area in the western segment of the albitite (breccia) zone, whereas the eastern segment remains significantly understudied. In this study, a systematic field investigation, as well as petrology, geochemistry, and accessory-mineral geochronology studies were conducted on albitites and albitite breccias in the Shangnan area, the eastern segment of the albitite (breccia) zone. The results show that the albitites are interlayered with or occur as lenses within Devonian clastic rocks. The albitite breccias are mostly enclosed in albitite and Devonian strata, and the clasts within are subangular, uniform in type, and exhibit minimal displacement. Both albitites and albitite breccias exhibit similar trace-element characteristics and detrital zircon age spectra to those of Devonian clastic rocks. Abundant hydrothermal monazites with U–Pb ages ranging from 260 to 252 Ma are present in both albitites and albitite breccias but absent in Devonian clastic rocks. Collectively, these results indicate that the albitites in the Shangnan area are of hydrothermal metasomatic origin, while the albitite breccias record hydraulic fracturing and cementation, and both are products of the same fluid activity event in the Late Permian. We propose that albitite (breccia) zones in the South Qinling tectonic belt were formed under distinct tectonic settings during different evolution stages of the Late Paleozoic Mianlüe Ocean. Specifically, the albitites (breccias) in the Shangnan area are products of thorough metasomatism, local fracturing, and cementation of Devonian clastic rocks by mixed fluids, which ascended along the Fengzhen–Shanyang Fault coeval with the emplacement of magmatic rocks related to subduction of the Mianlüe Ocean. In contrast, the albitite breccias in the Fengxian–Taibai area are the result of fluid activity during the transition from regional compression to extension after the closure of the Mianlüe Ocean. Full article

The Rzhanski granitoid pluton and Ignatitsa diorite porphyry bodies are considered Late Paleozoic in age, belonging to the Western Balkan Zone (WBZ) in Northwestern Bulgaria. Here, we provide U-Pb zircon geochronology of these magmatic bodies, together with their geochemistry complemented by the geochemistry of the overlying volcanic rocks. Geochemical data indicate that the intermediate to acid magmatic rocks are mostly peraluminous, calc-alkaline diorite/andesite to granite, that have an origin in a continental magmatic arc tectonic environment. All plutonic, subvolcanic and volcanic rocks exhibit uniform LILE- and LREE-enriched characteristics of an arc-related igneous suite. Zircons in the Ignatitsa diorite porphyry yield a magmatic crystallization age of 315 Ma, while the zircons in the Rzhanski aplitic metagranite pluton crystallize at 294 Ma. The record of the Variscan intrusive magmatism encompasses a region-wide, well-defined time interval 332–294 Ma in the WBZ, which coincides with those of the Central Balkan Zone and the adjacent Sredna Gora Zone. The age of the Variscan greenschist facies metamorphism using the metagranite and host greenschists relationships is limited between 294 Ma and the unpublished depositional age of 268 Ma for the overlying clastic formation in the studied part of the WBZ. Full article

As a tectonically stable and extensively superimposed basin situated in the North China Craton, the Ordos Basin hosts abundant reserves of oil, natural gas, and coal within its Paleozoic strata, rendering it a focal area in energy-related geological research. The basin’s evolutionary history provides a comprehensive record of key geological transitions—from an Early Paleozoic carbonate platform to Late Paleozoic marine–continental transitional deposits and ultimately to continental clastic sedimentation—largely governed by the regional tectonic dynamics associated with the North China Plate. This study presents a systematic review of the sedimentary and tectonic evolution of the Paleozoic sequence in the basin. Findings indicate that during the Early Paleozoic, the basin developed under a passive continental margin setting, characterized by widespread epicontinental marine carbonate deposition. By the Late Ordovician, subduction of the Qinqi Ocean triggered the Caledonian orogeny, resulting in regional uplift across the basin, widespread erosion, and a significant hiatus in Middle to Late Ordovician sedimentation, which facilitated the formation of paleo-weathered crust karst reservoirs. In the Late Paleozoic, the basin evolved into an intracratonic depression. From the Late Carboniferous to the Early Permian, the Hercynian tectonic event influenced the transformation from isolated rift basins to a broad epicontinental sea, leading to the deposition of critical coal-bearing strata within marine–continental transitional facies. Starting in the Middle Permian, the closure of surrounding oceanic domains induced widespread tectonic uplift, shifting the depositional environment to a terrestrial fluvial-lacustrine system and marking the termination of marine sedimentation in the region. Based on the comprehensive research findings, this study underscores that the superposition, inheritance, and interaction of multiple tectonic events are the primary controls on the paleogeographic architecture and sedimentary. Full article

Currently, the formation and evolution processes of overpressure in the Upper Paleozoic tight sandstones of the Ordos Basin are not clearly understood. Taking the Shan 1 Member of the Shanxi Formation in the Yanchang area, southeastern Ordos Basin, as an example, we adopted a numerical simulation method considering pressurization effects (e.g., hydrocarbon generation and disequilibrium compaction) to quantitatively reconstruct the paleo-overpressure evolution history of target sandstone and shale layers before the end of the Early Cretaceous. We calculated two types of formation pressure changes since the Late Cretaceous tectonic uplift: the pressure reduction induced by pore rebound, temperature decrease and pressure release from potential brittle fracturing of overpressured shales, and the pressure increase in tight sandstones caused by overpressure transmission, thus clarifying the abnormal pressure evolution process of the Upper Paleozoic Shanxi Formation tight sandstones in the study area. The results show that at the end of the Early Cretaceous, the formation pressures of the target shale and sandstone layers in the study area reached their peaks, with the formation pressure coefficients of shale and sandstone being 1.41–1.59 and 1.10, respectively. During tectonic uplift since the early Late Cretaceous, temperature decrease and brittle fracture-induced pressure release caused significant declines in shale formation pressure, by 12.95–17.75 MPa and 20.00–25.24 MPa, respectively, resulting in the current shale formation pressure coefficients of 1.00–1.06. In this stage, temperature decrease and pore rebound caused sandstone formation pressure to decrease by 12.07–13.85 MPa and 16.93–17.41 MPa, respectively. Meanwhile, the overpressure transfer from two phases of hydrocarbon charging during the Late Triassic–Early Cretaceous and pressure release from shale brittle fracture during the Late Cretaceous tectonic uplift induced an increase in adjacent sandstone formation pressure, with a total pressure increase of 7.32–8.58 MPa. The combined effects of these three factors have led to the evolution of the target sandstone layer from abnormally high pressure in the late Early Cretaceous to the current abnormally low pressure. This study contributes to a deeper understanding of the formation process of underpressured gas reservoir in the Upper Paleozoic of the Ordos Basin. Full article

The SE Baltic area, the former Eastern Prussia, is renowned for complex natural history. Over the past millions of years, the area experienced major geological events and geomorphic landscape transformations, resulting in the present relief configuration. Past climates and environments gave rise to the specific life-forms that proliferated in the Paleozoic and Mesozoic–Early Cenozoic shallow sea/lacustrine basins, and the Late Cenozoic riverine and continental settings. During the Paleogene, forested sub-tropical lands and deltaic settings of coastal sea lagoons gave rise to the famed amber formations (Blue Ground) hosting inclusions of resin-sealed insect and other small invertebrates that offer an unprecedented look into the 35–34 million-year habitats. Ferruginous sandstones, formed in shallow waters incorporating remains of thermophilous fauna—bivalves and gastropods, bryozoans, and sea urchins, among others—lie above the amber-bearing deposits. Oligocene–Miocene continental (riverine, lacustrine, and palustrine) conditions relate to the “Brown Coal Formation”, embedding a variety of fossil plants. Finally, the Quaternary Period brought dramatic geo-environmental shifts, with cyclic interstadial sea transgressions and massive glacial erosion events delivering fossiliferous erratics with an array of primitive Paleozoic and later Mesozoic life-forms. Overall, the extraordinary paleontology of the SE Baltic area adds, within its geological context, to the European geoheritage and the world natural heritage. Full article

The Hongche Fault Zone in the Junggar Basin exhibits significant spatiotemporal variations in the relationship between fault systems and hydrocarbon accumulation across different structural belts. Two key factors contribute to this phenomenon: frequent tectonic activities and well-developed Paleozoic fault systems. To date, no detailed studies have been conducted on the fault systems in the Paleozoic strata of the Hongche Fault Zone. In this study, the fault systems in the Paleozoic strata of the Hongche Fault Zone were systematically sorted out for the first time. Furthermore, the controlling effects of active faults in different geological periods on hydrocarbon charging were clarified. Firstly, basing on the 3D seismic and well-log data, the structural framework and fault activity, fault systems, source-contacting faults were characterized. Vertically, the Hongche Fault Zone experienced three major thrusting episodes followed by one weak extensional subsidence Stage, forming four principal tectonic layers: Permian (Thrusting Episode I), Triassic (Thrusting Episode II), Jurassic (Thrusting Episode III), and Cretaceous–Quaternary (Post-Thrusting Subsidence). Laterally, six fault systems are identified: Middle Permian (Stage I), Late Triassic (Stage II), Jurassic (Stage III), post-Cretaceous (Stage IV), as well as composite systems from Middle Permian–Jurassic (Stages I–III) and Late Triassic–Jurassic (Stages II–III). These reveal multi-stage, multi-directional composite structural characteristics in the study area. According to the oil–source correlation, the Carboniferous reservoir is primarily sourced by Permian Fengcheng Formation source rocks in the Shawan Sag. Hydrocarbon migration tracing shows that oil migrates along faults, progressively charging from depression zones to thrust belts and uplifted areas. In this process, fault systems exert hierarchical controls on accumulation: Stage I faults dominate trap formation, Stages II and III faults regulate hydrocarbon migration, accumulation, and adjustment, while Stage IV faults influence hydrocarbon conduction in Mesozoic–Cenozoic reservoirs. By clarifying the fault-controlled hydrocarbon accumulation mechanisms in the Hongche Fault Zone, this study provides theoretical guidance for two key aspects of the Carboniferous reservoirs in the study area: the optimization of favorable exploration zones and the development of reserves. Full article