Precambrian Research最新文献

{"title":"The Lac Opasatica igneous complex: An autochthonous Abitibi greenstone basement to the Pontiac Subprovince","authors":"T.A. Ducharme ,&nbsp;C. Guilmette,&nbsp;J. Darveau","doi":"10.1016/j.precamres.2025.108002","DOIUrl":"10.1016/j.precamres.2025.108002","url":null,"abstract":"<div><div>Basement underlying the Archean metasedimentary belts of the Superior Province is rarely exposed, but key to understanding the tectonic provenance of these basins. The Pontiac Subprovince is one such belt dominated by turbiditic clastic rocks and minor volumes of intrusive and extrusive igneous rock. Tectonic models for the Pontiac Subprovince propose that it represents either a paleo-accretionary wedge or an extensional basin host to authigenic volcanism. Both models consider the supracrustal sequence to overlie older tonalite-trondhjemite-granodiorite (TTG) gneisses, the Opasatica Gneiss, classically interpreted as the regional basement. This work presents new zircon U-Pb data and bulk-rock geochemical data for Opasatica TTG gneisses and newly identified felsic volcanites situated structurally above the gneisses. Four felsic volcanic samples record zircon U-Pb ages of 2755 and 2740 Ma, coeval with the oldest volcanism in the adjacent Abitibi Subprovince. Four TTG gneiss samples yield U-Pb ages as young as 2690 Ma, coeval with TTG occurrences elsewhere in the Pontiac and Abitibi. Melanocratic components of the gneiss yield older ages of c. 2745 Ma, implying a composite intrusion history, and trace element systematics resembling those of the felsic volcanics imply these rocks may have been comagmatic. The revised geochronological framework of the Pontiac suggests it shares its magmatic history with the Abitibi Subprovince. We propose that the Pontiac is an integral component of the Abitibi Subprovince, obscured beneath a thick sedimentary cover. This interpretation of the Pontiac, and its record of <em>syn</em>-sedimentary magmatism, are incompatible with deposition of the Pontiac Group in an accretionary wedge environment.</div></div>","PeriodicalId":49674,"journal":{"name":"Precambrian Research","volume":"433 ","pages":"Article 108002"},"PeriodicalIF":3.2,"publicationDate":"2025-12-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145840811","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Revisiting the Fennoscandia–Sarmatia Paleoproterozoic Suture: evidence from the PolandSPAN™ seismic survey and integrated geophysical modelling","authors":"Mateusz Mikołajczak ,&nbsp;Stanisław Mazur ,&nbsp;Piotr Krzywiec","doi":"10.1016/j.precamres.2025.108001","DOIUrl":"10.1016/j.precamres.2025.108001","url":null,"abstract":"<div><div>The East European Craton (EEC) consists of three major Precambrian domains—Fennoscandia, Sarmatia, and Volgo-Uralia—assembled during Paleoproterozoic continent–continent collisions. In eastern Poland, the crystalline basement comprises southwestern Fennoscandia and the adjoining northwestern margin of Sarmatia, separated by the Fennoscandia–Sarmatia Suture (FSS). Although its overall NE–SW orientation is well established, the precise location and internal structure of the FSS remain debated. In this study, we reassess the FSS in the Polish segment of the EEC using deep reflection seismic profiles from the PolandSPAN™ survey, combined with 2-D gravity and magnetic modelling and 3-D geophysical models of basement depth and crustal thickness. The results reveal a 100–120 km wide transitional zone, including of the Belarus–Podlasie Granulite and Okolovo Belts, characterized by anomalously dense and magnetically susceptible lithologies. These are interpreted as remnants of arc-related magmatic complexes, mafic igneous suites, or high-pressure metamorphic rocks, which are diagnostic of collisional sutures. Seismic imaging and geophysical modelling show that these anomalies extend through the entire crust, indicating a deeply rooted Paleoproterozoic collision. We conclude that the FSS does not correspond to a discrete fault but represents a diffuse, cryptic suture zone c. 100–120 km wide, comparable to those recognized in other Precambrian cratons. The northern and southern boundaries of the suture zone align with the margins of the Belarus–Podlasie Granulite and the Osnitsk–Mikashevichi Igneous Belts, respectively. Despite later overprinting, the FSS remains clearly detectable in integrated seismic and potential-field datasets. Its recognition as a wide collisional boundary provides new constraints on the tectonic evolution of the EEC.</div></div>","PeriodicalId":49674,"journal":{"name":"Precambrian Research","volume":"433 ","pages":"Article 108001"},"PeriodicalIF":3.2,"publicationDate":"2025-12-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145840812","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Carbonatite and syenite magmatism at the Archean-Proterozoic boundary in the Western Dharwar Craton, Southern India: Implication for petrogenesis, source characteristics and terrane geodynamics","authors":"Samir Debnath ,&nbsp;Rohit Pandey ,&nbsp;B. Belyatsky ,&nbsp;David Chew ,&nbsp;N.V. Chalapathi Rao ,&nbsp;Mahendra Kumar Singh","doi":"10.1016/j.precamres.2025.107995","DOIUrl":"10.1016/j.precamres.2025.107995","url":null,"abstract":"<div><div>A comprehensive study integrating field data, geochronology, mineral-whole rock geochemistry, and Sr-Nd-Pb-C-O isotope systematics is presented for a newly identified carbonatite-syenite complex from Gundlupete area, near the tectonic boundary between the Western Dharwar Craton and the Granulite Terrain, South India. The syenite, composed of alkali feldspar, albite, clinopyroxene, and biotite, yields a U-Pb titanite crystallisation age of 2590 ± 42 Ma. It displays shoshonitic geochemistry, with enriched LILE-LREE, depletion in Mg, Ni, Cr, HFSEs, and crust-like Th/Nb and Nb/U ratios. Initial εNd values (–1.4 to +1.0) and Nd model ages of 2.8–3.0 Ga indicate derivation from partial melts of Mesoarchean TTG crust, modified by fractional crystallisation. The intrusive carbonatite with a monazite U-Pb age of 2474 ± 27 Ma, is dominated by calcite, apatite, magnetite, monazite, amphibole, and phlogopite, and is enriched in Sr, REEs, and LILEs. Field and petrographic observations reveal distinctive apatite-magnetite-silicate banding within the carbonatite near the syenite contact, a feature inconsistent with simple magmatic differentiation. Instead, metasomatic reactions at the carbonatite-syenite interface likely produced antiskarn assemblages through wall-rock silica contamination. Sr-Nd-Pb isotope data shows time integrated higher Rb-Sr but low Sm/Nd and U/Pb ratios, tapping a chondritic to slightly enriched lithospheric mantle source modified by incorporation of small fractions of ancient subducted sediments into the source region. C–O isotope data show mantle-like δ¹⁸O, and the uniformly low δ¹³C (–10.23 to –9.41 ‰) further points to an organic component in the subducted sediments. Syenite and carbonatite magmatism relates to the Neoarchean amalgamation of the Dharwar Craton and Granulite Terrain, driven by northward subduction of the Dharwar ocean lithosphere. The syenite emplacement at 2.59 Ga is linked to the regional subduction-related magma underplating and crustal anatexis, while carbonatite intrusion at 2.47 Ga suggests a post-collisional magmatic pulse during terminal accretion near the Archean-Proterozoic boundary. The temporal, geochemical, and isotopic evolution recorded in the Gundlupete complex thus provides a robust archive of subduction-driven carbon recycling, mantle metasomatism, and crustal reworking processes at the Archean-Proterozoic transition.</div></div>","PeriodicalId":49674,"journal":{"name":"Precambrian Research","volume":"433 ","pages":"Article 107995"},"PeriodicalIF":3.2,"publicationDate":"2025-12-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145840814","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Distribution and petrogenesis of 1.62 Ga Taishan mafic dyke swarm in the North China Craton: Implications for supercontinental geodynamics","authors":"Chong Wang ,&nbsp;Peng Peng ,&nbsp;Xin Chen ,&nbsp;Xu Liu ,&nbsp;Xinping Wang ,&nbsp;Bisheng Xu ,&nbsp;Binghe Li","doi":"10.1016/j.precamres.2025.107999","DOIUrl":"10.1016/j.precamres.2025.107999","url":null,"abstract":"<div><div>The spatial–temporal distribution of mantle-derived mafic magmatism provides crucial constraints on global/regional geodynamics, particularly rifting to breakup processes. This study investigates the 1.62 Ga Taishan mafic dyke swarm in the North China Craton, extending its recognized distribution through new field identifications in the Western Shandong Province. High-precision SIMS baddeleyite dating constrains the emplacement age to 1604–1617 Ma, confirming widespread magmatic activity during this period. Geochemical analyses reveal the dykes are tholeiitic characterized by SiO₂ (48.1–52.0 wt%), MgO (4.3–7.4 wt%), total Fe₂O₃ (10.9–17.2 wt%), TiO₂ (0.93–1.73 wt%), Al₂O₃ (12.1–17.6 wt%), CaO (2.3–5.4 wt%), and Mg numbers of 45–60. Systematic trends in major elements indicate fractional crystallization dominated by plagioclase and Fe–Ti oxides. The dykes are enriched in light rare earth element and can be divided into two groups based on (La/Yb)<em>_N</em> ratios (2.5–3.4 and 4.8–6.0). Their trace element patterns are characterized by positive K anomalies and depletions in Nb–Ta and P. The ε_Nd(<em>t</em>) values range from –3.6 to +1.6. Geochemically, the Taishan dykes resemble the subalkaline basalts of the coeval Dahongyu Formation in the Yanliao rift, which are spatially associated with ∼ 1625 Ma OIB-type alkaline volcanics. We interpret that these magmatic suits originated from a common plume-related event, where: (a) the tholeiitic dykes and subalkaline basalts were derived from higher-degree melting of metasomatized subcontinental lithospheric mantle, and (b) alkaline volcanics formed by lower-degree melting of an asthenosphere or plume source. Globally, the contemporaneous Melville Bugt mafic dyke swarm (Greenland) and Biryusa mafic sills (Siberia) share notable petrological and geochemical characteristics with the Taishan swarm, supporting a possible geodynamic linkage among these cratons within the supercontinent Columbia/Nuna framework.</div></div>","PeriodicalId":49674,"journal":{"name":"Precambrian Research","volume":"433 ","pages":"Article 107999"},"PeriodicalIF":3.2,"publicationDate":"2025-12-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145840813","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Possible dickinsoniomorphs from the latest Ediacaran Nama Group, southern Namibia","authors":"Brandt M. Gibson ,&nbsp;Joshua H.F.L. Davies ,&nbsp;Simon A.F. Darroch ,&nbsp;Ajani Bissick ,&nbsp;Andrea Boscaini ,&nbsp;Galen P. Halverson ,&nbsp;Frederick J. Hilgen ,&nbsp;Peter R. Liberty ,&nbsp;Johnathan A. Sorrentino ,&nbsp;Bianca R. Spiering ,&nbsp;Patricia Vickers-Rich ,&nbsp;Marc Laflamme","doi":"10.1016/j.precamres.2025.107981","DOIUrl":"10.1016/j.precamres.2025.107981","url":null,"abstract":"<div><div>The late Neoproterozoic Ediacaran Period is marked by one or more pulses of biotic turnover thought to represent intervals of global extinction, and which removed several enigmatic groups of Precambrian metazoans over a ∼10-million-year interval in the lead-up to the Cambrian. Here, we report the discovery of putative dickinsoniomorph ‘survivors’ from the Nama Group of southern Namibia, including specimens preserved in place directly above an ash bed dated in this study at 538.97 ± 0.21 Ma, and thus within error of the currently defined Ediacaran-Cambrian boundary. Some key features are poorly preserved and thus identification at this point is not definitive; however, following comparisons with a wide variety of other Ediacaran taxa and abiotic structures, we argue that interpretation as dickinsonimorph body fossils is most parsimonious. More material is undoubtedly required; however, if supported these fossils would represent the youngest dickinsoniomorph fossils found anywhere in the world, showing that this group survived the first pulse of Ediacaran extinction at ∼550 Ma, and necessitating a re-evaluation of hypothesized drivers of late Ediacaran biotic turnover events. We suggest that these new fossil discoveries are consistent with recent models of selective extinction driven by pulses of ecological stress, reinforcing the inference that environmental perturbations were likely a crucial influence on patterns of early animal evolution prior to the main phase of the Cambrian explosion.</div></div>","PeriodicalId":49674,"journal":{"name":"Precambrian Research","volume":"433 ","pages":"Article 107981"},"PeriodicalIF":3.2,"publicationDate":"2025-12-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145840810","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"South China in the Rodinia-Gondwana transition: Constrains from the Ediacaran Doushantuo Formation of the north Yangtze Block","authors":"Lisha Hu ,&nbsp;Jie Yang ,&nbsp;Yuansheng Du ,&nbsp;Zuozhen Han ,&nbsp;Hongwei Kuang ,&nbsp;Yongqing Liu ,&nbsp;Chao Han ,&nbsp;Yi Zhang ,&nbsp;Wei Jin ,&nbsp;Le Wan","doi":"10.1016/j.precamres.2025.107996","DOIUrl":"10.1016/j.precamres.2025.107996","url":null,"abstract":"<div><div>The paleogeographic position of South China and its tectonic affinity with other continental blocks during the Rodinia-Gondwana transition remain not well established. This study reports new zircon U-Pb ages and Lu-Hf isotopic data from the Ediacaran Doushantuo Formation in the Chengkou-Zhenba area on the northern margin of the Yangtze Block. Detrital zircons yield concordant ages ranging from 2654 to 596 Ma, with 95 % of the grains clustering in the range of 1066 and 596 Ma. The age spectrum exhibits two major peaks at 633 Ma and 609 Ma, along with three minor peaks at 893 Ma, 851 Ma, and 749 Ma. The ε_Hf(t) values are predominantly positive, with 92 % of the analyses ranging from + 1.1 to + 13.6. The detrital zircon age distribution of the Doushantuo Formation is largely consistent with that of magmatic rocks from the Panxi-Hannan belt, supplemented by an additional Pan-African age population (ca. 630–600 Ma). Integrated U-Pb–Hf isotopic provenance analysis of Neoproterozoic rocks from the north Yangtze Block suggests that, aside from the ca. 630–600 Ma detritus, most detrital zircons were likely derived from nearby magmatic rocks in the Panxi-Hannan belt of the north Yangtze Block. Qualitative comparisons of detrital zircon age distributions between our samples and contemporaneous Ediacaran sedimentary strata in South China and other continental blocks indicate that the ca. 630–600 Ma detritus likely originated from Pan-African orogens in northern Gondwana, particularly the East African Orogen in southern India. These findings support a close paleogeographic and tectonic connection between South China and India during the Rodinia–Gondwana transition.</div></div>","PeriodicalId":49674,"journal":{"name":"Precambrian Research","volume":"433 ","pages":"Article 107996"},"PeriodicalIF":3.2,"publicationDate":"2025-12-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145798580","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Tonian intra-oceanic subduction initiation at the northwestern Yangtze Block: Evidence from forearc ophiolite fragments in the Bikou microblock","authors":"Li Qin ,&nbsp;Xianzhi Pei ,&nbsp;Ruibao Li ,&nbsp;Lei Pei ,&nbsp;Chengjun Liu ,&nbsp;Zuochen Li ,&nbsp;Shaowei Zhao ,&nbsp;Feng Gao","doi":"10.1016/j.precamres.2025.107997","DOIUrl":"10.1016/j.precamres.2025.107997","url":null,"abstract":"<div><div>The Bikou Group, situated in the southern part of the Bikou microblock along the northwestern Yangtze Block, preserves extensive remnants of Tonian volcanic magmatism. However, the timing of its formation and its tectonic setting remain debated. In this study, we report a newly identified geological record of subduction initiation from the Heimulin forearc ophiolite in the Bikou microblock. The Heimulin ophiolite comprises Tonian forearc peridotites, forearc basalts (diabases), boninites, high-Mg andesites and dacites, resembling the forearc igneous sequences observed in the Izu-Bonin-Mariana (IBM) subduction zone. Forearc basalts (diabase) with zircon U-Pb ages of 841 Ma exhibit geochemical signatures similar to normal mid-ocean ridge basalts (N-MORB) but lower Ti/V ratios indicate slightly higher concentrations of fluid-mobile elements than N-MORB. In contrast, the ∼ 834 Ma boninite displays more pronounced depletion in high field strength elements (HFSEs) and Heavy rare earth elements (HREEs) compared to the FABs. The high-Mg andesites (HMAs) and dacites yield zircon U-Pb ages of 833 Ma and 825 Ma, respectively. The HMAs were derived from partial melting of a mantle wedge metasomatized by melts/fluids released from a subducting oceanic slab, whereas the dacites were produced in a mature intra-oceanic arc setting through dehydration melting of mafic rocks in the middle to lower crust. The Heimulin forearc ophiolites record a magmatic evolution from less to more HFSE-depleted and LILE-enriched, similar to the magmatic evolution of the IBM forearc, reflecting progressive subduction of the oceanic slab. Inherited zircons and negative Hf isotopes indicate the presence of ribbon-like continental fragments in the Heimulin intra-oceanic arc, which may have facilitated the initiation of Tonian intra-oceanic subduction in the Heimulin Ocean. Integrated with previously published reliable data, our study provides further evidence that the northwestern Yangtze Block experienced continuous subduction-accretion processes during the Tonian, with the Yangtze Block (South China Block) likely situated on the margin of the Rodinia supercontinent.</div></div>","PeriodicalId":49674,"journal":{"name":"Precambrian Research","volume":"433 ","pages":"Article 107997"},"PeriodicalIF":3.2,"publicationDate":"2025-12-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145798579","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A shallow, subduction-modified continental lithospheric mantle source for the Palaeoproterozoic Hart Dolerite, Western Australia","authors":"Alex E. Eves ,&nbsp;Rob R. Ramsay ,&nbsp;Anthony I.S. Kemp ,&nbsp;Roland Maas ,&nbsp;Laure Martin ,&nbsp;Marco L. Fiorentini","doi":"10.1016/j.precamres.2025.107978","DOIUrl":"10.1016/j.precamres.2025.107978","url":null,"abstract":"<div><div>Petrogenetic models for continental mafic provinces typically invoke either plume-derived asthenospheric melting or subduction-related enrichment of the continental lithospheric mantle (CLM). Which of these models applies for the ca. 1793 Ma Hart Dolerite of the Kimberley Block (North Australian Craton), a sill-dominated and regionally extensive suite, has long been debated. To test these competing models, the petrogenesis of the Hart Dolerite is evaluated with new field observations, drill-core logging, whole-rock geochemistry, and Sr–Nd–Pb–O isotopes. Samples with liquid-like bulk compositions define transitional tholeiitic–calc-alkaline trends with arc-like HFSE depletions and modest LREE–LILE enrichment. Unaltered rocks yield εNd_i from −0.8 to +0.8 and ⁸⁷Sr/⁸⁶Sr_i of 0.7028–0.7035; Pb isotopes are heterogeneous and non-diagnostic. Interstitial quartz records δ¹⁸O = +11.4 to +13.2 ‰, and with no evidence for crustal assimilation, are interpreted as reflecting a modestly elevated lithospheric mantle source. Stratigraphic constancy of Sr–Nd isotopes across a ∼500 m-thick sill, together with the absence of covariation between isotope ratios and fractionation-sensitive trace elements, argues against assimilation–fractional crystallisation processes. Constraints from regional geophysics, supported by xenolith and xenocryst observations, place melting within spinel-facies CLM at ∼2–3 GPa (∼60–90 km), where hydrous peridotite crosses the solidus during post-orogenic extension. A subduction-modified CLM reservoir that became metasomatised and then reworked during later 1870 – 1805 Ma orogenic cycles was reactivated at 1793 Ma to yield low-degree melts that were emplaced at shallow crustal levels. In this geodynamic context, coeval uplift, radial dyke swarms, and OIB-like chemistry are absent. The Hart Dolerite therefore documents intraplate magmatism generated without plume input, produced instead by decompression melting of preconditioned mantle lithosphere. This framework provides a testable template for modest-volume, sill-dominated provinces, emphasising lithospheric memory and the coupling of metasomatism with later extensional triggers.</div></div>","PeriodicalId":49674,"journal":{"name":"Precambrian Research","volume":"433 ","pages":"Article 107978"},"PeriodicalIF":3.2,"publicationDate":"2025-12-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145798578","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A lost fragment of Siderian oceanic and juvenile arc crust preserved in the Borborema province, northeast Brazil","authors":"Paula F.T. Alvim,&nbsp;Elton L. Dantas,&nbsp;Reinhardt A. Fuck,&nbsp;Alanielson C.D. Ferreira","doi":"10.1016/j.precamres.2025.107979","DOIUrl":"10.1016/j.precamres.2025.107979","url":null,"abstract":"<div><div>The Tectono-Magmatic Lull (TML), or Siderian Quiet Interval, represents a pivotal stage in Earth’s history between 2.36 and 2.23 Ga, marked by a global reduction in tectonic activity, magmatism, and crustal growth. It features a global decline in tectonic activity, magmatism, and crustal formation, creating a major gap in the geotectonic record worldwide. To investigate this interval, detailed field mapping, petrography, U–Pb zircon geochronology, whole-rock geochemistry, and Sm–Nd isotopic analyses were carried out on rocks from the Santa Luzia Sequence in the Lajes Block, Borborema Province (NE Brazil). The sequence, consisting of amphibolites, calc-silicate rocks, and hornblendites, yields U–Pb zircon ages ranging from 2.48 to 2.31 Ga, along with an older amphibolite dated at 3.14 Ga. Whole-rock geochemical patterns exhibit pronounced negative Nb, Ta, and Ti anomalies, indicating oceanic and arc-related affinities. Sm–Nd isotopic data reinforce this framework: juvenile lithotypes show positive εNd_(t) values and Nd T_DM ages of 2.36–2.12 Ga, whereas a subset of amphibolites preserves significantly older Nd T_DM ages (3.97–2.62 Ga), revealing an Archean crustal substrate predating arc assembly. Coeval plutonic rocks document continued crustal reworking and juvenile addition from the Siderian into the Rhyacian. Spatial, geochemical, and isotopic relationships indicate that the calc-silicate rocks formed through metasomatic alteration of mafic precursors. Despite later metasomatic and hydrothermal overprints that produced LREE enrichment and fluid-driven metamorphism, the primary magmatic signatures remain well preserved. Collectively, these results show that subduction-related magmatism persisted locally in Borborema, in contrast with the TML and tectonic shutdown theories.</div></div>","PeriodicalId":49674,"journal":{"name":"Precambrian Research","volume":"433 ","pages":"Article 107979"},"PeriodicalIF":3.2,"publicationDate":"2025-12-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145749403","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Identification of eclogites that record Palaeoproterozoic and Triassic metamorphism in the Dabie UHP orogenic belt, eastern-central China","authors":"Jianhui Liu ,&nbsp;Wei Jin ,&nbsp;Fulai Liu ,&nbsp;Zhengjiang Ding ,&nbsp;Yuanshuo Li ,&nbsp;Weinan Xu","doi":"10.1016/j.precamres.2025.107990","DOIUrl":"10.1016/j.precamres.2025.107990","url":null,"abstract":"<div><div>In this study, zircon U–Th–Pb dating coupled with zircon morphology and texture observations, and trace element and Hf isotope analyses conducted on ultrahigh-pressure (UHP) eclogites and the host granitic gneiss in the central Dabie UHP belt has identified Neoarchean (ca. 2.5 Ga), Palaeoproterozoic (ca. 1.9 Ga) metamorphic events and Triassic UHP metamorphism at ca. 236 Ma. The Palaeoproterozoic metamorphic zircons from two eclogite samples and one granitic gneiss sample have consistent weighted mean ages of 1871 ± 26, 1890 ± 15, and 1915 ± 41 Ma, respectively. They exhibit low Th/U ratios (mostly &lt; 0.1), depletions in light rare earth elements (LREE) and enrichments in heavy rare earth elements (HREE) characterized by steep chondrite-normalized patterns, and yielded a large range of Ti-in-zircon temperatures varying from 892 ℃ to 642 ℃, indicating their metamorphic recrystallization or growth under wide metamorphic condition. The Palaeoproterozoic metamorphic zircons from the eclogites have mostly uniform Hf compositions and positive ε_Hf(t) values distinctly different from the Palaeoproterozoic metamorphic zircons with variable Hf compositions and negative ε_Hf(t) values from the host granitic gneiss. The Triassic metamorphic zircons from two eclogite samples and one granitic gneiss sample gave weighted-mean ages of 236 ± 2, 236 ± 1 and 234 ± 3 Ma, respectively. They exhibit low Th/U ratios (mostly &lt; 0.1), depletions in LREE and distinctively flat chondrite-normalized HREE patterns, and mostly consistent Hf isotope compositions with extremely low ¹⁷⁶Lu/¹⁷⁷Hf ratios and negative ε_Hf(t) values, and yielded Ti-in-zircon temperature of ca. 724℃ consistent with Triassic UHP metamorphic temperature, thus, these zircons is interpreted to be formed under Triassic UHP metamorphism. The host granitic gneiss has a minimum estimate of magmatic crystallization age of 2723 Ma. Therefore, it can be concluded that mafic protolith of the eclogite and the host granitic gneiss together experienced Palaeoproterozoic metamorphism at ca. 1.9 Ga and then Triassic UHP metamorphism at ca. 236 Ma. Additionally, it has further been suggested that the Early Precambrian basement exists and was involved in Triassic UHP metamorphism in the central Dabie UHP belt.</div></div>","PeriodicalId":49674,"journal":{"name":"Precambrian Research","volume":"433 ","pages":"Article 107990"},"PeriodicalIF":3.2,"publicationDate":"2025-12-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145749410","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}