Geological Journal最新文献

{"title":"Characterising Depositional-Diagenetic Aspects and Geochemistry for Assessing Source Rock Potential of the Thanetian Lockhart Limestone, Lesser Himalayas, Pakistan (Eastern Tethys)","authors":"Nasar Khan,&nbsp;Ubaid Ullah,&nbsp;Muhammad Awais,&nbsp;Bakht Baidar,&nbsp;Muhammad Ishaq,&nbsp;Sreepat Jain,&nbsp;Muhammad Awais Aziz,&nbsp;Zahra Mohammadi,&nbsp;Mohamed Abioui,&nbsp;Salman Ahmed Khattak,&nbsp;Rudy Swennen","doi":"10.1002/gj.70027","DOIUrl":"https://doi.org/10.1002/gj.70027","url":null,"abstract":"<div>\u0000 \u0000 <p>Depositional and diagenetic processes constrain organic matter characteristics in siliciclastic rocks; however, such controls are elusive in carbonates. To increase oil and gas production and expand exploration opportunities, it is essential to assess the potential of non-traditional source rocks, for example, carbonates. This study investigates the depositional facies and diagenetic constraints on the organic matter (OM) accumulation, preservation and source rock potential of the Palaeocene Lockhart Limestone exposed at the Kala-Chitta Range, Lesser Himalayas, Pakistan. An integrated approach combining conventional methods for source rock evaluation (i.e., sedimentology, petrography, cathodoluminescence, TOC, Rock-Eval pyrolysis, and vitrinite reflectance) with stable isotopes (δ¹³C and δ¹⁵N) analysis is employed. Three microfacies are identified, that is, mudstone (MFT-1), foraminiferal wackestone (MFT-2), and foraminiferal packstone (MFT-3). Carbonate diagenesis revealed the presence of eo-, meso- and telo-diagenetic transformations that affected both microfacies and source rock potential. The δ¹³C_org and δ¹⁵N_org proxies suggest suboxic to anoxic conditions, facilitating OM preservation. Microfacies, OM enrichment, stable isotopes and C/N ratios infer that the Lockhart Limestone was deposited within a shallow marine carbonate-dominated inner (lagoon) to middle ramp setting. The total organic carbon (TOC) content exceeding 0.3 wt.% and S₂ yield &gt; 0.2 mgHC/g rock represent OM enrichment and source rock potential of the formation. Based on OM geochemical analyses, the Lockhart Limestone is dominated by Type-ΙΙΙ kerogen exhibiting over-thermal maturity (<i>T</i>_max &gt; 470°C) and is prone to dry-gas generation. The organic geochemical characteristics elucidate indigenous OM, implying the generation of hydrocarbon during meso-diagenesis. The present data suggest that the studied bituminous limestones are poor to moderate source rocks for potential hydrocarbon generation.</p>\u0000 </div>","PeriodicalId":12784,"journal":{"name":"Geological Journal","volume":"61 4","pages":"1120-1142"},"PeriodicalIF":2.2,"publicationDate":"2026-04-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147708010","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"On the First Occurrence of Chapmanina gassinensis Silvestri, 1904 From the Middle/Late Eocene Gehannam Formation, Nile—Fayoum, Egypt","authors":"A. Khaled,&nbsp;S. Al Menoufy,&nbsp;R. Abul-Nasr,&nbsp;S. Abd El-Aziz","doi":"10.1002/gj.70017","DOIUrl":"https://doi.org/10.1002/gj.70017","url":null,"abstract":"<div>\u0000 \u0000 <p>For the first time, three larger benthonic foraminiferal species (<i>Chapmanina gassinensis</i>, <i>Nummulites incrassatus</i> and <i>Gaziryina pulchellus</i>) were identified from the Gehannam Formation exposed at Girza section located in the area isolating the Nile Valley from the Fayoum Depression (Nile—Fayoum Divide) of the Western Desert, Egypt. The Gehannam Formation at Girza section correlates with the <i>Globigerinatheka semiinvoluta</i> Zone (E14) of (late Bartonian to early Priabonian) age, where the Lower part of the studied formation is marked by the existence of <i>Turborotalia pseudoampliapertura</i> Zone (late Bartonian) and the Upper part characterised by the presence of <i>Globigerinatheka semiinvoluta</i> Zone (early Priabonian). Larger benthic foraminiferal (LBF) zones of the described species from the Gehannam Formation attest to SBZ16/17 (late Bartonian) and SBZ18 (early Priabonian). These zones exhibit correlations with those found in Egypt and other Mediterranean countries. This work provides a detailed discussion of the Middle/Upper Eocene (Bartonian/Priabonian) boundary. Paleoecologically, the important environmental parameters for the foraminiferal content used in this study attest that the lower portion of the studied formation at Girza section was deposited in middle to outer continental shelf environments, while the upper part of this formation formed in inner to middle neritic environments. The palaeobiogeographic distribution of <i>Chapmanina gassinensis</i> Silvestri during the Middle/Upper Eocene (Bartonian/Priabonian) boundary shows a broad palaeobiogeographic distribution through the northern Tethys province (NTP), the eastern Tethys province (ETP) and the southern Tethys province (STP).</p>\u0000 </div>","PeriodicalId":12784,"journal":{"name":"Geological Journal","volume":"61 4","pages":"945-966"},"PeriodicalIF":2.2,"publicationDate":"2026-04-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147708132","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Magmatic Response to Closure of the Hegenshan Ocean and Subsequent Post-Orogenic Extension: Insights From Middle Triassic A-Type Granites in the Meilaotewula Ophiolitic Belt, Central Inner Mongolia, China","authors":"Shuai Wang,&nbsp;Yingjie Li,&nbsp;Guochen Dong,&nbsp;Peipei Dong,&nbsp;Xiawei Zhang,&nbsp;Dongfang Zhao,&nbsp;Zhibin Liu,&nbsp;Song Jin,&nbsp;Jinghua Guo","doi":"10.1002/gj.70018","DOIUrl":"https://doi.org/10.1002/gj.70018","url":null,"abstract":"<div>\u0000 \u0000 <p>The timing of closure of the Hegenshan Ocean and the evolution of post-orogenic extension in the southeastern Central Asian Orogenic Belt (CAOB) are debated. To address this, we investigated the petrography, whole-rock geochemistry and zircon U–Pb geochronology and Hf isotopic composition of the Harigentai granites that intrude the Meilaotewula ophiolitic belt in the Hegenshan ophiolite-arc-accretionary complex, central Inner Mongolia. These granites are monzogranites with Middle Triassic ages of 239.3 ± 1.4 and 238.7 ± 1.3 Ma. The monzogranites are weakly peraluminous and highly alkaline, and are enriched in Rb, Th, U, K and Ta, and depleted in Ba, Sr, P and Ti. They have flat chondrite-normalised rare earth element (REE) patterns with negative Eu anomalies (<i>δ</i>Eu = 0.15–0.38) and high Y/Nb ratios (1.42–2.72). They have positive <i>ε</i>_Hf(<i>t</i>) values (7.5–12.0) and young two-stage Hf isotopic model ages (788–500 Ma), with high zircon saturation temperatures (792°C–817°C). These characteristics suggest the monzogranites are A₂-type granites that formed under high-temperature and low-pressure conditions by partial melting of juvenile mafic-intermediate crust. The results of this study, combined with the spatial distribution of Carboniferous-Triassic ophiolites and igneous rocks within the Hegenshan ophiolite-arc-accretionary complex, indicate that the Hegenshan Ocean closed at the end-Permian, followed by a post-orogenic extensional setting during the Triassic.</p>\u0000 </div>","PeriodicalId":12784,"journal":{"name":"Geological Journal","volume":"61 4","pages":"967-983"},"PeriodicalIF":2.2,"publicationDate":"2026-04-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147708276","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Energy Markets, Geopolitical Risks, and Global Trade: A High-Stakes Tug of War","authors":"Seyi Saint Akadiri,&nbsp;Oktay Özkan","doi":"10.1002/gj.70026","DOIUrl":"https://doi.org/10.1002/gj.70026","url":null,"abstract":"<div>\u0000 \u0000 <p>The ever-evolving energy landscape and rising geopolitical tensions are reshaping global trade like never before. Trade stability faces significant threats, with crude oil, coal, and natural gas prices fluctuating wildly alongside growing geopolitical uncertainties. This study examines the intricate relationship between energy market swings and geopolitical risks, captured through geopolitical risk acts and threats, to uncover their quantile-specific impact on global trade dynamics. Using daily data from December 30, 2016, to January 13, 2025, we apply Multivariate Quantile-on-Quantile Regression and Quantile Regression to dissect how these forces influence trade across different levels. Our findings reveal that crude oil remains the dominant driver of global trade, with its influence intensifying at higher trade quantiles. Meanwhile, coal and natural gas exhibit varying impacts and geopolitical risk acts unexpectedly boost trade in high-quantile scenarios, whereas geopolitical risk threats consistently dampen trade flows. These insights shed light on the dual nature of energy markets and geopolitical risks as catalysts and disruptors of global trade. To navigate these turbulent waters, we advocate for energy diversification, proactive geopolitical risk management, and integrating green energy policies to stabilise trade flows and bolster economic resilience amid growing uncertainties.</p>\u0000 </div>","PeriodicalId":12784,"journal":{"name":"Geological Journal","volume":"61 4","pages":"1105-1119"},"PeriodicalIF":2.2,"publicationDate":"2026-04-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147708034","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Provenance of the Carboniferous Clastic Rocks in the Eastern Tibetan Plateau: Insights Into the Palaeogeography and Tectonic Evolution of the Northern Margin of East Gondwana","authors":"Junwei Qiao,&nbsp;Xinru Fu,&nbsp;Xiaochen Zhao,&nbsp;Fangpeng Du,&nbsp;Cheng Yang,&nbsp;Yu Zhang,&nbsp;Jintao Li","doi":"10.1002/gj.70015","DOIUrl":"https://doi.org/10.1002/gj.70015","url":null,"abstract":"<div>\u0000 \u0000 <p>The terranes in the eastern Tibetan Plateau are regarded as the key position in reconstructing the evolutionary history of the Paleo-Tethys Ocean and the break-up of East Gondwana. However, the tectonic affinities of these terranes during the late Palaeozoic, as well as the position of Gondwana's northern margin at that time, remain contentious, owing principally to inadequate investigation of the provenance characteristics and tectonic setting of the constituent strata. The late Palaeozoic strata (especially Lower Carboniferous) exposed in the eastern Tibetan Plateau terranes provide crucial constraints for understanding their tectonic affinities and for more precisely defining Gondwana's northern margin during this time interval. This study presents a systematic provenance analysis of the Carboniferous strata from Kaqiong (Bangda Fm.), Zuogong (Kagong Fm.) and Qamdo (Machala Fm.) terranes in the eastern Tibetan Plateau, via new U–Pb dating of the detrital zircons. The detrital zircon U–Pb age data of Bangda Fm. yielded ages ranging from 336 to 2837 Ma with major age peaks at ~1000 Ma. The detrital zircon U–Pb age data of Kagong and Machala formations revealed obviously different age patterns, featured by predominant late Palaeozoic zircon ages (ca. 320 ~ 380 Ma), which were similar to the timing of synsedimentary magmatic arc activities. The U–Pb age spectra of the Bangda Formation are consistent with those of the lower Carboniferous in the southern Qiangtang, Lhasa and Himalaya blocks to the south. It indicates that the sediments of the Bangda Formation shared the same sources with these blocks. In contrast, the U–Pb age spectra of the Kagong and Machala formations indicate plentiful input of the late Palaeozoic zircons, which were probably derived from arc magmatic rocks distributed in the North Qiangtang, Qamdo terranes along the Longmucuo–Shuanghu–Lancangjiang suture zone. Furthermore, the differences in paleobiogeographic assemblages, stratigraphic sequence and tectonic setting of the lower Carboniferous from the Kaqiong and Zuogong–Qamdo terranes indicate the existence of an ancient ocean along the Longmucuo–Shuanghu suture zone. From this study, we infer that the Kaqiong terrane might have been located at the northern margin of East Gondwana, while Zuogong–Qamdo terranes were located at the southern margin of the Eurasia Blocks.</p>\u0000 </div>","PeriodicalId":12784,"journal":{"name":"Geological Journal","volume":"61 4","pages":"912-928"},"PeriodicalIF":2.2,"publicationDate":"2026-04-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147708273","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Geochemical Characteristics and Timing of Sn Mineralization From Yunling Tin Deposits, SW China: Insights for Ore-Forming Processes","authors":"Si-Ying Li,&nbsp;Nai Wang,&nbsp;Zi-Hao Wen","doi":"10.1002/gj.70012","DOIUrl":"https://doi.org/10.1002/gj.70012","url":null,"abstract":"<div>\u0000 \u0000 <p>The tin (Sn) deposits in western Yunnan, constituting a vital component of the Southeast Asian Metallogenic Belt, exhibit inadequately constrained genetic mechanisms underlying Cenozoic Sn mineralization. This study integrates U–Pb geochronology, in situ trace element geochemistry, and oxygen isotopic analysis of cassiterite from the Yunling tin deposit. Tera-Wasserburg lower-intercept ages for samples ULC-1 (17.5 ± 1.9) Ma and ULC-3 (23.44 ± 0.82 Ma) demonstrate temporal coincidence with the regional strike-slip shear belt activation during the Early Miocene. Cassiterite oxygen isotopes yielded δ¹⁸O_fluid values of 7.37‰–9.22‰, suggesting that the parent magma was mainly derived from a crustal magma source. The characteristics of trace element concentrations of cassiterite indicate skarn-type affinities. The integrated evidence demonstrates that Sn enrichment initiated through syn-exhumation decompression melting during crustal thickening, coupled with synkinematic asthenospheric upwelling. These synergistic processes established high-temperature reducing conditions promoting biotite-dehydration-driven anatexis, liberating Sn into fractionated melts that underwent distal migration to generate concealed Sn-mineralized granitic plutons, with subsequent ore precipitation localised within crustal-scale fault systems through fluid–rock interaction. We propose that the Yunling Sn mineralization is temporally and genetically linked to ~20 Ma magmatism associated with regional shear zones. Consequently, concealed granitic intrusions and shear zone developed areas are potential targets for Sn prospecting in the Baoshan Block.</p>\u0000 </div>","PeriodicalId":12784,"journal":{"name":"Geological Journal","volume":"61 3","pages":"832-847"},"PeriodicalIF":2.2,"publicationDate":"2026-03-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147563211","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"GIS-Based Landslide Susceptibility Mapping of Almora District in India: A Comparison of Different Techniques","authors":"Sandeep Panchal,&nbsp;Amit Kr. Srivastava","doi":"10.1002/gj.70002","DOIUrl":"https://doi.org/10.1002/gj.70002","url":null,"abstract":"<div>\u0000 \u0000 <p>Landslide susceptibility maps at the regional scale are a very efficient tool for landslide planning and management. The Himalayan region in India is highly prone to the occurrence of landslides that lead to huge losses. In this paper, we prepared the landslide susceptibility maps for the Almora district in Uttarakhand, India using different techniques. A landslide inventory was prepared using the available historical data of landslides in the region. Eight factors including slope, aspect, curvature, relative relief, distance from lineament, drainage density, geology, and distance from faults are designated as causative factors of landslides. The contribution of the causative factors and sub-factors is modelled using different techniques. In this study, frequency ratio, statistical index, analytic hierarchy process, and landslide numerical risk factor are applied for calculating the weightage of causative factors. A hybrid method by combining the landslide numerical risk factor and analytic hierarchy process termed as AHP-LNRF method is also proposed. Five landslide susceptibility maps of the study area were prepared in a GIS environment. The landslide susceptibility maps are divided into five categories according to the susceptibility of different zones to the occurrence of landslides. The accuracy of the output of the study is predicted by receiver operating characteristics (ROC) curve technique. It is observed that the statistical index technique had the highest prediction rate (0.789) whilst frequency ratio showed a prediction rate of 0.764. Landslide numerical risk factor technique showed the least accuracy with a prediction rate of 0.719 which is improved to 0.738 in the AHP-LNRF technique. The AHP technique had a prediction rate of 0.735. The models and their output can be improved by improving the landslide inventory and optimising the causative factors of landslides. The results of the study can be used by the planner, managers, and researchers for landslide risk planning and management.</p>\u0000 </div>","PeriodicalId":12784,"journal":{"name":"Geological Journal","volume":"61 3","pages":"671-687"},"PeriodicalIF":2.2,"publicationDate":"2026-03-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147564949","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Coal Accumulation in Marine to Continental Transitional Sequence During Late Carboniferous—Early Permian in the Southeastern Ordos Basin, China","authors":"Zixiao Peng,&nbsp;Jianhua Qu,&nbsp;Chunqiang Chen,&nbsp;Hehua Wang,&nbsp;Dancheng Zhu,&nbsp;Zhongrong Mi,&nbsp;En Xie,&nbsp;Zhenghong Zhang,&nbsp;Xinghe Yu,&nbsp;He Wang","doi":"10.1002/gj.5247","DOIUrl":"https://doi.org/10.1002/gj.5247","url":null,"abstract":"<div>\u0000 \u0000 <p>Thick coal-bearing strata developed in different environments in the Upper Palaeozoic Ordos Basin, providing high-quality source rocks and reservoirs for coalbed methane fields. However, accurate prediction of coal occurrence and geometry requires a better understanding of coal seam characteristics within a marine-to-continental transitional sequence framework. Sequence stratigraphy, coal-accumulating environment and coal distribution in SE Ordos Basin are analysed by integrating analysis of cores, well logs and seismic interpretation. Four types of depositional systems are developed in four fourth-order sequences: barrier-lagoon of SQ1, carbonate platform of SQ2, meandering river delta of SQ3 and braided river delta of SQ4. A complete transition from nearshore to terrestrial sequence occurred during the late Carboniferous to early Permian, shifting from high accommodation to low accommodation. SQ1 and SQ3 are dominant coal-accumulating sequences, and the lagoon and distributary bay provide favourable environments for coal formation, forming regionally thick and thick-thin continuous coal, respectively. SQ2 and SQ4 contain no to weak coal accumulation, with locally thin coal and carbonaceous mudstone. The differences in the accommodation of each sequence and the relative sea-level changes within a sequence individually exert primary and direct control over coal accumulation. The thickest and most continuous coals were developed in the late highstand of the high accommodation sequence and the early highstand of the low accommodation sequence. The results of this study are important for predicting favourable areas for coal distribution in paralic settings worldwide and could be further applied to the exploration and development of unconventional resources in the Ordos Basin.</p>\u0000 </div>","PeriodicalId":12784,"journal":{"name":"Geological Journal","volume":"61 3","pages":"549-565"},"PeriodicalIF":2.2,"publicationDate":"2026-03-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147566541","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Incisor Enamel Microstructure of the Late Miocene Siwalik Rodents From Dunera, Punjab State, North India: Functional and Ecological Implications","authors":"Ningthoujam Premjit Singh,&nbsp;Abhishek Pratap Singh,&nbsp;Ramesh Kumar Sehgal,&nbsp;K. Milankumar Sharma","doi":"10.1002/gj.5250","DOIUrl":"https://doi.org/10.1002/gj.5250","url":null,"abstract":"<div>\u0000 \u0000 <p>Fossil rodent teeth are well known from the Neogene Siwalik Group of sediments and can provide insights into the evolution, taxonomy, diets and adaptations to various ecological niches. However, data on the microstructure of rodent incisors from the Indian Neogene Siwalik sediments is sparse compared to that on molars. We herein provide an analysis of enamel microstructures (in both transverse and longitudinal sections) of a selected few rodent incisors from the late Miocene (~10–11 Ma) Siwalik sediments at Dunera, Punjab State, north India. Based on the microstructure analysis, the rodent incisors are identified as cf. <i>Progonomys</i> (murids), cf. <i>Democricetodon</i> (cricetids), cf. <i>Sayimys</i> (ctenodactylids) and cf. <i>Tamias</i> (sciurids). The identified cf. <i>Progonomys</i>, cf. <i>Democricetodon</i> and cf. <i>Tamias</i> are represented by uniserial Hunter-Schreger Bands, whereas cf. <i>Sayimys</i> shows multiserial Hunter-Schreger Bands. Besides taxonomy, the functional and ecological significance of these rodents have been studied using enamel crystallite patterns because the microstructural change(s) in incisor enamel are generally linked to the variety of diets consumed by these mammals. In our analysis, the absence of modified radial enamel in the incisors of cf. <i>Progonomys</i>, cf. <i>Democricetodon</i>, and cf. <i>Sayimys</i> suggests that these rodents plausibly consumed a soft diet comprising of leaves, flowers, seeds, fleshy roots and insects, while the presence of specialised three-layered Schmelzmuster in the incisors of cf. <i>Tamias</i> suggests that the rodents may have preferred a diet composed of relatively harder parts such as acorns, walnuts, and hazelnuts.</p>\u0000 </div>","PeriodicalId":12784,"journal":{"name":"Geological Journal","volume":"61 3","pages":"609-624"},"PeriodicalIF":2.2,"publicationDate":"2026-03-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147570075","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Neoarchean Arc Magmatism and Crust Recycling in the Northern Marginal Zone of the Limpopo Complex, Zimbabwe: New Insights From Zircon U-Pb-Hf Isotopes of a Charnockite Suite","authors":"Toshiaki Tsunogae,&nbsp;Md. Sazzadur Rahman,&nbsp;Gao Pin,&nbsp;M. Santosh,&nbsp;Wataru Fujisaki,&nbsp;Sam Uthup,&nbsp;Prince Mandingaisa","doi":"10.1002/gj.5248","DOIUrl":"https://doi.org/10.1002/gj.5248","url":null,"abstract":"<p>Charnockite is one of the conspicuous lithologies in Precambrian granulite terranes, and isotope studies on them can help better understand regional tectonics. Here, we present new petrological, geochemical, and zircon U-Pb and Lu-Hf isotopic data for charnockite and associated felsic/mafic orthogneisses from the Northern Marginal Zone (NMZ) of the Limpopo Complex, a Neoarchean orogen regarded to have been formed by the collision of the Zimbabwe and the Kaapvaal Cratons in southern Africa. The REE and trace element patterns reveal volcanic arc affinity for the charnockites. Oscillatory-zoned and near-concordant zircons from the charnockites yielded weighted-mean ²⁰⁷Pb/²⁰⁶Pb and concordia intercept ages of 2691 ± 6 to 2640 ± 16 and 2607 ± 55 Ma, respectively. The age of felsic orthogneiss (2628 ± 16 Ma) is nearly consistent with those of the charnockites. Zircons from the mafic granulite, which occurs as a layer parallel to the foliation of the 2607 Ma charnockite and shows arc-magmatic geochemical signatures such as Nb, P, and Zr depletion, yielded a weighted-mean age of 2607 ± 16 Ma. As both charnockite and the protolith of the mafic granulite from the same locality show consistent magmatic crystallisation ages, bimodal magmatism under a magmatic-arc setting is inferred. Zircons from a Chilimanzi Suite Granite (Zimbabwe Granite) of the Zimbabwe Craton adjacent to the NMZ show a weighted-mean ²⁰⁷Pb/²⁰⁶Pb age of 2607 ± 35 Ma and a concordia-intercept age of 2627 ± 36 Ma, which is comparable with the age range of charnockite. Therefore, the charnockite probably corresponds to the lower-crustal equivalent of the Chilimanzi Suite Granite. The syn- to post-tectonic Razi Granite from the NMZ-Zimbabwe Craton boundary yielded a weighted-mean age of 2542 ± 16 Ma, which marks the youngest intrusion event in this region. Lu-Hf isotopic data of magmatic zircon cores from the Neoarchean charnockite, felsic orthogneiss, Zimbabwe Granite, and Razi Granite samples all show negative εHf(<i>t</i>) values (−11.18 to −2.20) with T_DM^C ages of 3699–3158 Ma, suggesting their protolith formation by crustal recycling in an arc setting through partial melting of Eo- to Paleoarchean crustal components such as the Tokwe Segment of the Zimbabwe Craton. Our new data thus support northward subduction of the oceanic plate underneath the proto-Zimbabwe Craton, and the southern margin of the proto-Zimbabwe Craton corresponds to a continental arc.</p>","PeriodicalId":12784,"journal":{"name":"Geological Journal","volume":"61 3","pages":"566-592"},"PeriodicalIF":2.2,"publicationDate":"2026-03-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/gj.5248","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147570174","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}