Geoscience frontiers最新文献

{"title":"Neoarchean-Paleoproterozoic metallogenesis associated with plate tectonics in early Earth: Insights from the North China Craton","authors":"Tao Zeng ,&nbsp;Li Tang ,&nbsp;M. Santosh ,&nbsp;Hanhui Wang","doi":"10.1016/j.gsf.2024.101990","DOIUrl":"10.1016/j.gsf.2024.101990","url":null,"abstract":"<div><div>Precambrian cratons are archives of several precious metallic deposits that significantly contribute to our planet’s resources and habitability and also provide key information on plate tectonics on Earth. The North China Craton (NCC) preserves important records of Neoarchean to Paleoproterozoic tectonic processes and associated episodes of metallogenic pulses that generated five major types of mineral deposits including banded iron formations (BIFs), volcanogenic massive sulfide (VMS) Cu–Pb–Zn deposits, orogenic Au deposits, magmatic sulfide Cu-Ni deposits and porphyry Cu deposits. These deposits are distributed in Neoarchean granite-greenstone belts and Paleoproterozoic orogenic belts, and show dominant mineralization ages of 2.6–2.5 Ga and two subordinate age groups of 2.7–2.6 Ga and 2.3–1.95 Ga. The Neoarchean metallogenic events generated BIFs, VMSs, Au and magmatic sulfide Cu-Ni deposits and the tectonic framework correlates with the microblock amalgamation and plate subduction possibly also aided by mantle plumes. The BIFs representing the dominant mineral deposits in Neoarchean are mainly Algoma-type with few examples of Superior-type. Meta-basaltic rocks associated with the Algoma-type BIF deposits in the granite-greenstone belts of the NCC display highly variable trace element compositions and LREE-depleted and LREE-enriched. The REE distribution patterns and high field-strength element characteristics of <em>meta</em>-basaltic rocks suggest the formation of BIF and VMS deposits in mid-ocean ridge, island arc and back-arc settings. The formation of VMS, Au and magmatic Cu-Ni deposits correspond to plate subduction and collision in a convergent continental margin setting during the late Neoarchean. The Paleoproterozoic deposits are represented by BIFs and porphyry Cu deposits. The Paleoproterozoic BIFs and <em>meta</em>-basaltic rocks correspond to magmatic-hydrothermal activities in passive continental margin or island arc settings, whereas the porphyry Cu deposits were formed in an extensional environment, corresponding to the Paleoproterozoic subduction-rifting events in the Trans-North China Orogen. The variation of <em>δ</em>⁵⁶Fe, Ce anomalies and Y/Ho ratios in BIFs from Neoarchean to Paleoproterozoic indicate the initial increase of oxygen in late Neoarchean and the change of ambient marine environment from anoxic to oxic during the Great Oxidation Event. The multi-stage Neoarchean to Paleoproterozoic metallogenic systems of the NCC were intrinsically linked to the plate subduction along with arc-plume interaction and rifting-subduction-collision activities. The contemporaneous increasing in weathering of exposed continental crust due to plate subduction potentially controlled the atmosphere-hydrosphere oxidation state and formation of BIF deposits in the NCC.</div></div>","PeriodicalId":12711,"journal":{"name":"Geoscience frontiers","volume":"16 2","pages":"Article 101990"},"PeriodicalIF":8.5,"publicationDate":"2024-12-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143145404","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"An insight into seismotectonic scenario of the southwestern part of Delhi-NCR and delineation of new faults: Implications to seismic hazard potential","authors":"Sudipto Bhattacharjee ,&nbsp;Sanjay Kumar Prajapati ,&nbsp;Uma Shankar ,&nbsp;O.P. Mishra","doi":"10.1016/j.gsf.2024.101991","DOIUrl":"10.1016/j.gsf.2024.101991","url":null,"abstract":"<div><div>The southwestern region of the Delhi-National Capital Region (NCR) experiences sporadic micro (M ≤ 3.0) and occasional small (M &gt; 3.0) earthquakes with a seasonal influence. This study integrates remote sensing and seismological data to elucidate the seismotectonic scenario and identify potential unmapped faults. Analysis of DEM data (Cartoset) reveals numerous multidirectional minor faults, some coincident or conjugate to known major faults. Earthquake epicentres spatially correlate with several of these delineated faults. Fault plane solutions suggest a transition from central normal faulting to peripheral thrust faulting. Moment tensor decomposition indicates dominant double-couple mechanisms with significant non-double-couple components for earthquakes ranging from Mw 2.5 to 4.4. A major variation in principal stress orientation is apparent between the eastern and western regions of the study area. Stress inversion reveals a NW-SE shortening direction and unusual principal axis plunges, suggesting a rare “odd” or “unknown” faulting regime. These findings suggest ongoing rifting in the eastern Alwar basin may be inducing thrusting in the surrounding region along pre-existing Aravalli-Delhi fold belt thrusts. Seismogenesis likely results from a complex interplay of faulting, regional tectonics, and fluid interaction. This study highlights the value of a multidisciplinary approach for unravelling the intricacies of seismotectonic in low-to-moderate seismicity regions, with varying strengths due to diverse structural heterogeneity associated with mapped or unmapped (hidden) faults, which have been delineated in this study, as an additional information for assessing seismic hazard potential for Delhi-NCR.</div></div>","PeriodicalId":12711,"journal":{"name":"Geoscience frontiers","volume":"16 2","pages":"Article 101991"},"PeriodicalIF":8.5,"publicationDate":"2024-12-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143145405","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Black carbon aerosols impact snowfall over the Tibetan Plateau","authors":"Ye Zhou ,&nbsp;Junhua Yang ,&nbsp;Shichang Kang ,&nbsp;Yuling Hu ,&nbsp;Xintong Chen ,&nbsp;Mian Xu ,&nbsp;Mengmeng Ma","doi":"10.1016/j.gsf.2024.101978","DOIUrl":"10.1016/j.gsf.2024.101978","url":null,"abstract":"<div><div>Snowfall is the primary form of cold-season precipitation over the Tibetan Plateau (TP), crucial for the maintenance of glaciers and snow cover, affecting regional climates and water resources availability. Through an integrative analysis of observations, numerical simulations, and statistical analyses, we found that the spatiotemporal distribution of snowfall across the TP is significantly influenced by black carbon (BC) aerosols from South Asia and the TP. BC affects the snowfall process through multiple mechanisms. Specifically, BC significantly raises atmospheric temperature over the TP, thereby reducing snowfall, particularly in the central TP during autumn, with reductions reaching approximately − 9 mm water equivalent month⁻¹. Moreover, BC enhances cold-season moisture transport from the Bay of Bengal, increasing moisture flux in the southeastern TP and thereby augmenting snowfall in that area by up to 5 mm water equivalent month⁻¹. This study elucidates the complex impact of BC on the spatial–temporal snowfall patterns across the TP and provides important insights into the sustainable development of water resources in the region amid ongoing climate change.</div></div>","PeriodicalId":12711,"journal":{"name":"Geoscience frontiers","volume":"16 2","pages":"Article 101978"},"PeriodicalIF":8.5,"publicationDate":"2024-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143145340","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"An unusual lunar origin and chondritic refractory Antarctic micrometeorites","authors":"D. Fernandes,&nbsp;N.G. Rudraswami","doi":"10.1016/j.gsf.2024.101975","DOIUrl":"10.1016/j.gsf.2024.101975","url":null,"abstract":"<div><div>We report unearthing the first silicate-type (S-type) lunar Antarctic micrometeorites (AMM) spherule and another spherule with a refractory chondritic phase. The lunar spherule is made of Augite with minor Ni magnetite (&lt;1 wt.%), in contrast to other known cosmic spherules. The Augite’s minor oxide range in the spherule are as follows: Wo_37-41En_25-27Fs_34-36, Al₂O₃: 0.7–1 wt.%, Cr₂O₃: 0.01–0.06 wt.%, MnO: 0.32–0.39 wt.% and TiO₂: 0.03–0.09 wt.%. The lunar spherule’s chemical characteristics indicate that it originated from very low Ti lunar basalt (VLT) mare basalts. Chondritic diopside (Wo_46-47En_50-47Fs_5-6, Al₂O₃: 1.7–1.6 wt.%, Cr₂O₃: 0.6–0.63 wt.%, MnO: 0.2–0.4 wt.%, and TiO₂: 0.0–0.02 wt.%) makes up the refractory phase in the second spherule. The chemical composition of diopside is indistinct from those of calcium aluminium inclusion (CAIs) found in both ordinary and carbonaceous chondrites. Our finding reveals that micron-sized lunar impact debris can potentially reach the Earth’s surface, similar to the earliest formed nebulae solid component.</div></div>","PeriodicalId":12711,"journal":{"name":"Geoscience frontiers","volume":"16 2","pages":"Article 101975"},"PeriodicalIF":8.5,"publicationDate":"2024-11-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143145403","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Satellite gravity fields and the identification of accreted microplates","authors":"C. Braitenberg ,&nbsp;G. Maurizio ,&nbsp;T. Pivetta ,&nbsp;A. Pastorutti ,&nbsp;W. Cavazza","doi":"10.1016/j.gsf.2024.101976","DOIUrl":"10.1016/j.gsf.2024.101976","url":null,"abstract":"<div><div>Small-scale lithospheric terranes (microplates) are important building-blocks of continental accretion but their presence is often obscured by subsequent plate-margin deformation events and by younger volcano-sedimentary covers. The geological fabric of the eastern Anatolian-Caucasian region results from the sequential accretion of lithospheric terranes against the southwestern continental margin of the Eurasian plate. Widespread sedimentary and volcanic covers conceal some of the principal tectonic boundaries in the region, and major uncertainties persist as to the number and extent of the various terranes.</div><div>We determine whether the topographic height fits the expectance from crustal thickness, complying to the isostatic equilibrium. The input data of the study are the topography, the satellite derived gravity field, the geologic knowledge defining magmatic intrusions and tectonic terranes, arcs and sedimentary basins, the seismic Moho depth, and a seismic tomography model. We accomplish a topography-gravity regression analysis controlled by a seismic Moho model, which produces well defined positive and negative anomalies. Allowing for varying density contrast in lower crust, the topography is greatly in isostatic equilibrium and controlled by the crustal thickness, that is topographic uplift has evolved proportionally to crustal thickening. The average density contrast in lower crust is between 200 and 300 kg/m³ for the orogenic belt, with local exceptions.</div><div>The inversion of the prominent positive linear anomalies of the regional gravity field defines discrete crustal density inhomogeneities, which can be interpreted as related to specific tectonic events, thus placing cogent constraints on the accretionary history and the overall anatomy of the eastern Anatolian-Caucasian lithospheric agglomerate. Three linear belts of intracrustal increased density are found along (i) the Greater Caucasus, (ii) the Lesser Caucasus, and (iii) a previously unidentified parallel belt ca. 80 km south of the Lesser Caucasus. The latter gravity anomaly clearly delineates for the first time the southwestern margin of the South Armenian Block, a lithospheric element (microplate) whose existence has long been a matter of debate.</div></div>","PeriodicalId":12711,"journal":{"name":"Geoscience frontiers","volume":"16 2","pages":"Article 101976"},"PeriodicalIF":8.5,"publicationDate":"2024-11-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143145342","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Timing of syn-orogenic extension in the Western Alps revealed by calcite U-Pb and hematite (U-Th)/He dating","authors":"Antonin Bilau ,&nbsp;Yann Rolland ,&nbsp;Stéphane Schwartz ,&nbsp;Cécile Gautheron ,&nbsp;Thierry Dumont ,&nbsp;Dorian Bienveignant ,&nbsp;Benjamin Brigaud ,&nbsp;Nicolas Godeau ,&nbsp;Abel Guihou ,&nbsp;Pierre Deschamps ,&nbsp;Xavier Mangenot ,&nbsp;Marianna Corre ,&nbsp;Rosella Pinna-Jamme ,&nbsp;Nathaniel Findling","doi":"10.1016/j.gsf.2024.101969","DOIUrl":"10.1016/j.gsf.2024.101969","url":null,"abstract":"<div><div>Understanding fault activity over time provides valuable insights for reconstructing the tectonic history of an orogen, assessing seismological risks and understanding mineralization processes. In the Western Alps, one of the main controversies in existing tectonic models is the understanding of <em>syn</em>-orogenic extension. Seismological evidence shows widespread extensional deformation related to the reactivation of major lithospheric structures, such as the Penninic Frontal Thrust (PFT). However, the onset age and origin of extension are still debated due to the lack of suitable geochronological data. Fault hematite and calcite geochronology as well as clumped isotope data can be used to relate fluid regimes to fault activity. The analysis of calcite brecciae from extensional faults above the PFT shows that two distinct fluid regimes were present. The first regime, occurring before 2 Ma is associated with upwelling of deep fluids and is recorded by fault calcite at a temperature &gt; 110°C. The second fluid regime is characterized by a meteoric signature and temperatures around 36 °C, representing crystallization since 2 Ma. This study presents a new model for the Miocene tectonic history of the Western Alps that combines (U-Th)/He and U-Pb geochronology on fault hematite (13.3 ± 0.8 to &lt; 0.8 Ma) and calcite (5.3 ± 0.6 Ma). Results demonstrate a progression of extensional fault activity from east to west, from the Middle Miocene (ca. 13 Ma) to the Quaternary. The onset of extension in the inner part of the belt coincides with the development of the fold and thrust belt in the western Alpine foreland. Our new model proposes that extension occurs in the hanging wall of a large top-to-the-west thrust, known as the Alpine Frontal Thrust. This thrust, located to the west of the External Crystalline Massifs gives rise to their uplifting and extension at the rear.</div></div>","PeriodicalId":12711,"journal":{"name":"Geoscience frontiers","volume":"16 2","pages":"Article 101969"},"PeriodicalIF":8.5,"publicationDate":"2024-11-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143145401","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"High-resolution astronomical records of shale strata in faulted lake basins and implications for the sedimentary process of laminated sediments","authors":"Xianzheng Zhao ,&nbsp;Xiaoping Liu ,&nbsp;Huan Liu ,&nbsp;Fengming Jin ,&nbsp;Xiugang Pu ,&nbsp;Biao Sun ,&nbsp;Zhannan Shi","doi":"10.1016/j.gsf.2024.101974","DOIUrl":"10.1016/j.gsf.2024.101974","url":null,"abstract":"<div><div>Lamina structure, a typical feature of shale, has significant implications for hydrocarbon generation, shale oil and gas reservoir evaluation, and palaeoenvironmental studies. In this study, we conducted a high-resolution astronomical analysis of shale strata from the Kongdian Formation in the Cangdong Sag, Bohai Bay Basin, China, and performed macroscopic and microscopic textural characterization of core samples. The time series analysis of the G108-8 Well indicates that stratigraphic cycles of 113.2–25.3 m, 12.7–7.8 m, 4.7–2.7 m, and 2.3–1.3 m are controlled by long eccentricity, short eccentricity, obliquity, and precession, respectively. The sedimentary accumulation rate (SAR) is estimated to be approximately 20.3 cm/kyr. The core description reveals that Ek₂ primarily consists of laminated shale with individual laminae less than 1 cm in thickness. Using a polarizing microscope, the average thickness of a single lamina is approximately 250 μm, with most laminae being less than 400 μm. We constructed a time-depth model for lacustrine laminated sediments and compared it with other ancient lacustrine strata and modern lakes. The sediment accumulation rate of ancient lacustrine strata ranges from 1.3 to 20.3 cm/kyr. The sedimentation rate of shale and the thickness distribution of individual laminae provide evidence for the annual nature of the lamina couplets. Finally, we propose a simplified model to illustrate the sedimentation process, emphasizing the record of laminated sediments in semi-deep to deep facies. Our results contribute to the understanding of lacustrine sedimentary processes, laminated sedimentary records, organic matter enrichment processes, palaeoenvironments, and their potential relationships.</div></div>","PeriodicalId":12711,"journal":{"name":"Geoscience frontiers","volume":"16 2","pages":"Article 101974"},"PeriodicalIF":8.5,"publicationDate":"2024-11-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143145343","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Provenance of a Stenian succession in the eastern Jiangnan (Sibao) Orogen, South China: Implications on tectonic affinity and pre-Neoproterozoic crustal evolution","authors":"Kai Wang ,&nbsp;Shuan-Hong Zhang ,&nbsp;Shuwen Dong ,&nbsp;Qiqi Zhang ,&nbsp;Tianyu Zhao","doi":"10.1016/j.gsf.2024.101973","DOIUrl":"10.1016/j.gsf.2024.101973","url":null,"abstract":"<div><div>The Lower Tieshajie Subgroup at the conjunction zone of the Yangzte and Cathaysia blocks represents the only Stenian sedimentary succession in the eastern Jiangnan (Sibao) Orogen of South China, bearing important clues on plate boundary and pre-Neoproterozoic crustal evolution. We report the first U-Pb and Hf isotopic data of detrital zircons from this succession to investigate the age and provenance characteristics. Age and Hf isotopic compositions of detrital zircons from the lower and upper parts of the metamorphosed Lower Tieshajie Subgroup are similar. They are exclusively of magmatic origins, showing youngest age peaks at ca. 1.17 Ga and ca. 1.15 Ga, respectively, but both with a rarity of 1.12–1.10 Ga ages from the nearby magmatic rocks. This constrains protolith deposition of the Lower Tieshajie Subgroup to be mainly at 1.17–1.12 Ga, while the timing of metamorphism is bracketed by the intruding unmetamorphosed granites to be 1.10–0.84 Ga, that is, related to Grenville-aged orogenesis at the Jiangnan Orogen. The detrital zircons yielded a broad age range of 3.28–1.03 Ga, dominated by a 1.20–1.10 Ga population interpreted to be sourced from coeval magmatic rocks within the Tieshajie Complex itself. The abundant Archean and Paleoproterozoic detrital zircons are well-matched with magmatic records from the Eastern Yangtze Block, suggesting a Yangtze Block affinity of the Lower Tieshajie Subgroup. This implies that the surface boundary between the Yangtze and Cathaysia blocks is located to the south of the Lower Tieshajie Subgroup, probably in between the two parts of the Tieshajie Group. Age peaks of detrital zircons at 2.85–2.78 Ga, 2.68 Ga, and 2.50 Ga, combined with regional data, suggest episodic magmatism involved both crustal growth and reworking during the late Archean in the Jiangnan Orogen and adjacent areas of the Eastern Yangtze Block, while the 2.10–1.80 Ga peak corresponds to significant reworking of pre-existing crust related to the early assembly of the Nuna (Columbia) Supercontinent. Regional correlations based on detrital zircon age spectra and tectono-magmatic histories show similarities between the Yangtze Block and North India, suggesting the two continents were likely in spatial proximity at least during the late Mesoproterozoic to Neoproterozoic time.</div></div>","PeriodicalId":12711,"journal":{"name":"Geoscience frontiers","volume":"16 2","pages":"Article 101973"},"PeriodicalIF":8.5,"publicationDate":"2024-11-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143145339","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Middle Cambrian convergence at the southwestern Baltica margin, Holy Cross Mts., Poland, and its significance for reconstructions of early Gondwana","authors":"Riccardo Callegari ,&nbsp;Stanisław Mazur ,&nbsp;William C. McClelland ,&nbsp;Christopher J. Barnes ,&nbsp;Grzegorz Ziemniak ,&nbsp;Karolina Kośmińska ,&nbsp;Jarosław Majka","doi":"10.1016/j.gsf.2024.101972","DOIUrl":"10.1016/j.gsf.2024.101972","url":null,"abstract":"<div><div>The western periphery of Baltica has traditionally been viewed as a passive continental margin formed during the fragmentation of Rodinia and the opening of the Iapetus and Tornquist Oceans. This view is supported by the Volyn Large Igneous Province (VLIP) of Ediacaran age in Eastern Europe, which may be associated with break-up and evolution of the Tornquist Ocean. However, in western Ukraine, the sedimentary succession overlying the VLIP contains latest Ediacaran to early Cambrian detrital zircon with mixed <em>ε</em>_Hf(<em>t</em>) values that can be interpreted to reflect deposition in a convergent margin setting with input from a continental volcanic arc. To investigate the potential convergent tectonic setting along SW Baltica during the Ediacaran to Cambrian transition, we conducted research in the Holy Cross Mts. (HCM), Poland. Here, tightly folded, and low-grade metamorphosed slates are unconformably overlain by Lower Ordovician (Tremadocian) sedimentary rocks. We applied ⁴⁰Ar/³⁹Ar geochronology on white mica defining cleavage in lower Cambrian rocks and U-Pb geochronology on detrital zircons to constrain the timing of the deformation. Our samples show similar populations of detrital zircons, with affinities to regions within or on the outskirts of Baltica. For all Cambrian samples, the calculated maximum depositional age is close to their stratigraphic age, suggesting rapid deposition in an active tectonic setting. The <em>ε</em>_Hf(<em>t</em>) values range from −18 to +12, indicating significant mixing of mantle-derived magmas with mature crustal material typical of continental magmatic arc systems. Single-grain fusion ⁴⁰Ar/³⁹Ar geochronology on white mica yielded two populations of weighted average ages of 537 ± 1 Ma and 510 ± 4.4 Ma, interpreted as a detrital white mica population and the maximum approximation of the age of post-depositional early to middle Cambrian deformation, respectively. The similarities in zircon populations and isotopic compositions between Cambrian sediments of the HCM and those from Ukraine, suggest that both areas were sourced from a continental arc on the Baltica margin, above a subduction zone consuming Neoproterozoic Mirovoi Ocean crust. This arc is likely an equivalent to the Cadomian Arc on the opposite side of the ocean.</div></div>","PeriodicalId":12711,"journal":{"name":"Geoscience frontiers","volume":"16 2","pages":"Article 101972"},"PeriodicalIF":8.5,"publicationDate":"2024-11-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143145341","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Change in the direction of Early Cretaceous tectonic extension in eastern North China Craton as the result of Paleo-Pacific/Eurasian plate interaction","authors":"Lei Ji ,&nbsp;Jun Deng ,&nbsp;Junlai Liu ,&nbsp;Xiaoyu Chen ,&nbsp;Xuefei Liu ,&nbsp;Xinmin Yang ,&nbsp;Jinlong Ni ,&nbsp;Liangliang Zhang ,&nbsp;Yu An ,&nbsp;Pengfei Tian","doi":"10.1016/j.gsf.2024.101965","DOIUrl":"10.1016/j.gsf.2024.101965","url":null,"abstract":"<div><div>How the subduction direction of the Paleo-Pacific plate beneath the Eurasian plate changes in the Early Cretaceous remains highly controversial due to the disappearance of the subducted oceanic plate. Intraplate deformation structures in the east Asian continent, however, provide excellent opportunities for reconstructing paleostress fields in continental interior in relation to the Paleo-Pacific/Eurasian plate interaction. Anisotropy of magnetic susceptibility (AMS), geological, and geochronological analyses of post-kinematic mafic dykes intruding the detachment fault zone of the Wulian metamorphic core complex (WL MCC) in Jiaodong Peninsula exemplify emplacement of mantle-sourced dykes in a WNW–ESE (301°–121°) oriented tectonic extensional setting at ca. 120 Ma. In combination with the results from our previous kinematic analysis of the MCC, a ca. 21° clockwise change in the direction of intraplate extension is obtained for early (135–122 Ma) extensional exhumation of the MCC to late (122–108 Ma) emplacement of the dykes. Such a change is suggested to be related to the variation in subduction direction of the Paleo-Pacific plate beneath the Eurasian plate, from westward (pre-122 Ma) to west-northwestward (post-122 Ma).</div></div>","PeriodicalId":12711,"journal":{"name":"Geoscience frontiers","volume":"16 1","pages":"Article 101965"},"PeriodicalIF":8.5,"publicationDate":"2024-11-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142746988","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}