Precambrian Research最新文献

{"title":"Paleoenvironmental constraints of iron formation in the Fushun Area, northern Liaoning: insights from petrography, geochemistry, and isotope analysis","authors":"Yuxuan Hong ,&nbsp;Chenyue Liang ,&nbsp;Hongyu Guo ,&nbsp;Franz Neubauer ,&nbsp;Changqing Zheng ,&nbsp;Tao Xu","doi":"10.1016/j.precamres.2026.108028","DOIUrl":"10.1016/j.precamres.2026.108028","url":null,"abstract":"<div><div>Iron Formations (IFs) are critical records for reconstructing the surface environment and geochemical evolution of early Earth. As economically significant Precambrian sedimentary rocks, they serve as key archives for reconstructing early Earth’s tectonic settings and paleoenvironmental conditions. This study focuses on a unique silicate IF at Nianpan (NP), Fushun area, northern Liaoning Province, which differs from typical Banded Iron Formations (BIFs) in its distinctive mineral assemblage. By integrating petrographic, mineral-chemical, geochemical, geochronological, and isotopic analyses, we reconstruct the protolith composition and depositional environment of this specific type of IF. The NP IF comprises two main rock types: magnetite-bearing two-pyroxene ore and banded ferrosilicate quartzite, both exhibiting a well-developed compositional banding. Thermobarometric calculations using the two-pyroxene thermometer and the garnet-orthopyroxene barometer constrain peak metamorphic conditions to granulite-facies (815 °C/1.05 GPa). Zircon U-Pb dating yields a depositional age of 2533.0 ± 6.8 Ma and a metamorphic age of 2485.7 ± 7.8 Ma. Systematic geochemical and isotopic analyses demonstrate that the protolith sediments were primarily derived from seawater, with a minor hydrothermal contribution (&lt;0.1 %). The absence of a negative Ce anomaly (whole rock), coupled with significant enrichment in δ⁵⁶Fe and the presence of pyrite, collectively suggest deposition occurred in a reducing, weakly acidic marine environment. Our results support a genetic model involving: (1) initial precipitation of ferruginous-siliceous sediments from seawater with minor hydrothermal input under anoxic conditions, followed by (2) regional granulite-facies metamorphism in the late Archean to early Paleoproterozoic, ultimately forming the distinctive silicate IF at NP in the Fushun area (northern Liaoning Province) of the North China Craton (NCC).</div></div>","PeriodicalId":49674,"journal":{"name":"Precambrian Research","volume":"435 ","pages":"Article 108028"},"PeriodicalIF":3.2,"publicationDate":"2026-01-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146080776","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":"Neoproterozoic dolomitization, ocean redox evolution and mineralization in the Aozigang Zn deposit, Yangtze Block, South China","authors":"Xing-Yu Bai ,&nbsp;Suo-Fei Xiong ,&nbsp;Shao-Yong Jiang ,&nbsp;Ying Ma ,&nbsp;Yue Wu ,&nbsp;Guo-Qi Liu ,&nbsp;Xiao-Hua Zeng","doi":"10.1016/j.precamres.2026.108018","DOIUrl":"10.1016/j.precamres.2026.108018","url":null,"abstract":"<div><div>The origin and evolution of dolomitization in carbonate-hosted Zn-(Pb) deposits are essential for understanding ore-forming processes and reconstructing ancient marine environments. However, establishing a temporal link between dolomitization and mineralization in these deposits remains challenging due to the scarcity of direct geochronological constraints. This limitation hinders a comprehensive understanding of metallogenic processes and paleoenvironmental reconstructions. To address this issue, we present an integrated study of the Aozigang Zn deposit in Hubei Province of South China.</div><div>We reveal distinct generations of dolomite, which include sedimentary breccia dolomite (SBD), fascicular fast dolomite (FFD), fascicular slow dolomite (FSD), bladed dolomite (BD), radial slow dolomite (RSD), and medium-crystalline to coarse-crystalline dolomite (MD). The dull-red CL color and fabric features of the FSD suggest that dolomitization occurred under near-surface to shallow-burial, anoxic marine conditions. Uranium-Pb dating of FSD yields an age of 546.9 ± 7.4 Ma (MSWD = 2.8, n = 74), indicating that dolomitization took place during the Neoproterozoic. By combining the <em>in situ</em> carbon isotope composition of sedimentary dolomite, we provide direct chronological evidence for the delayed oxygenation of the Neoproterozoic ocean. The elevated Mn/Sr ratios and Mn enrichment observed in later MD are consistent with hydrothermal recrystallization under reducing conditions. The clear rim and cloudy core of MD serve as direct petrography evidence of the recrystallization from early dolomite. Meanwhile, the δ¹³C and δ¹⁸O values of hydrothermal calcite (peak at +0.27‰ to +1.43‰ and −11.81‰ to −7.40‰, respectively) reflect the influence of relatively high-temperature fluids and lower oxygen fugacity. The Pb isotopes of sphalerite indicate a mixed metal source that involves contributions from both the upper crust and basement. This study integrates geochronological and geochemical methods to provide direct dating evidence for Precambrian dolomitization, which is associated with the global oxygenation event known as the Neoproterozoic Oxygenation Event (NOE). The results offer a new perspective for investigating carbonate-hosted ore deposits on a global scale.</div></div>","PeriodicalId":49674,"journal":{"name":"Precambrian Research","volume":"435 ","pages":"Article 108018"},"PeriodicalIF":3.2,"publicationDate":"2026-01-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146080777","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":"Columbia supercontinent remnants in the Tuareg Shield (Iforas, Mali)","authors":"Delphine Bosch ,&nbsp;Olivier Bruguier ,&nbsp;Vincent Monchal ,&nbsp;Heloise Pinon","doi":"10.1016/j.precamres.2026.108019","DOIUrl":"10.1016/j.precamres.2026.108019","url":null,"abstract":"<div><div>The Iforas Granulitic Unit (Tuareg Shield), east of the West African Craton, is a key place to help reconstructing the Columbia supercontinent evolution. In this area, the emplacement of magmatic protoliths is constrained at c. 2.05–2.06 Ga and the production of the magmas involved recycling of a Paleoproterozoic to Archean crustal component (up to 3.0 Ga). For the first time, this study emphasizes two distinct Paleoproterozoic granulitic events. The first one occurs at ca. 2.0 Ga and was followed by a second event of very-high temperature (up to 920°C) at ca. 1.89 Ga. Rocks from the Iforas Granulitic Unit subsequently remained at high temperature (≥500°C) for a protracted period of <em>c.</em> 150 Myrs and record multiple phases of accessory mineral growth, dissolution and recrystallisation. This is illustrated by U-Pb monazite ages, peaking at 1780–1760 Ma, reflecting fluid driven replacement reactions as documented by apatite / allanite coronas around monazite. Cooling of the granulites, down to <em>c.</em> 500°C, occurred in the range 1720–1700 Ma (apatite and rutile ages). The chronology of the magmatic/metamorphic events is consistent with a collisional setting involving a micro-continental block consisting of the Iforas / In Ouzzal granulitic units sandwiched between the West African Craton and an eastern landmass which may be the Saharan metacraton. This study has major consequences for global reconstructions of the Columbia supercontinent as it demonstrates that, at <em>c.</em> 1.8 Ga, this microcontinent fits as a continuation of the Khondalite Belt or Trans North China Belt of the North China Craton.</div></div>","PeriodicalId":49674,"journal":{"name":"Precambrian Research","volume":"435 ","pages":"Article 108019"},"PeriodicalIF":3.2,"publicationDate":"2026-01-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146080775","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":"Age of the Acraman impact ejecta layer in the adelaide superbasin and Implications on clay-mineral provenance from the Rb–Sr systematics of middle Ediacaran shales","authors":"Alan S. Collins ,&nbsp;Morgan L. Blades ,&nbsp;Darwinaji Subarkah ,&nbsp;Holly Cooke ,&nbsp;Lesley Edwards ,&nbsp;Chelsea Forbister ,&nbsp;Jake Jolly ,&nbsp;Jarred C. Lloyd ,&nbsp;Sarah E. Gilbert ,&nbsp;Stefan Löhr ,&nbsp;Juraj Farkaš ,&nbsp;Victor Gostin","doi":"10.1016/j.precamres.2026.108015","DOIUrl":"10.1016/j.precamres.2026.108015","url":null,"abstract":"<div><div>The Acraman bolide hit the Gawler Craton of South Australia in the middle Ediacaran. Debris from this impact punctuates the Ediacaran sequences of the Adelaide Superbasin and the eastern Officer Basin. Here we date an argillaceous Acraman impactite layer sampled from Arkaba Creek, in the Bunyeroo Formation of the Adelaide Superbasin at 585 ± 15 Ma (MSWD = 1.8, 2σ error) using the <em>in-situ</em> Rb–Sr ICP-MS/MS technique that we interpret to date the impact event. The analyses have a radiogenic ⁸⁷Sr/⁸⁶Sr initial ratio of 0.7210 ± 0.0028 and elevated light rare earth element values.</div><div>Shales from both above and below the impact horizon yielded ages significantly pre-dating deposition and are interpreted to reflect detrital input into the Bunyeroo Formation, which is consistent with previous petrographic studies. Intriguingly, all 10 shales analysed yielded Rb–Sr ages within error of each other, with a Tonian weighted mean age of 778 ± 17 Ma (MSWD = 0.83). This is interpreted to reflect a very similar clay mineral age provenance for these shales despite being found in samples over 600 km apart. A similar mix of detrital mineral ages cannot be discounted. However, considering the spatial distribution, an alternative interpretation that the age similarity reflects Tonian pedogenic clay formation on the Gawler Craton, is thought more likely.</div></div>","PeriodicalId":49674,"journal":{"name":"Precambrian Research","volume":"435 ","pages":"Article 108015"},"PeriodicalIF":3.2,"publicationDate":"2026-01-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146015904","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":"Corrigendum to “Eoarchean low δ18O zircon indicates emergent land at 3.73 Ga” [Precambrian Res. 408 (2024) 107416]","authors":"Piotr Król ,&nbsp;Monika A. Kusiak ,&nbsp;Martin J. Whitehouse ,&nbsp;Daniel J. Dunkley ,&nbsp;Simon A. Wilde","doi":"10.1016/j.precamres.2026.108014","DOIUrl":"10.1016/j.precamres.2026.108014","url":null,"abstract":"","PeriodicalId":49674,"journal":{"name":"Precambrian Research","volume":"434 ","pages":"Article 108014"},"PeriodicalIF":3.2,"publicationDate":"2026-01-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146023580","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 window on the amalgamation of Western Gondwana: Geological history of the Ouaddaï massif (E. Chad)","authors":"Alexis Plunder ,&nbsp;Olivier Blein ,&nbsp;Moussa Isseini ,&nbsp;Issaka Ousman Al-Gadam ,&nbsp;Matthieu Chevillard ,&nbsp;Emanuel Djedouboum ,&nbsp;Philippe Lach ,&nbsp;Abdeltif Lahfid ,&nbsp;Jérémie Melleton ,&nbsp;Olivier Rouzeau ,&nbsp;Guillaume Vic","doi":"10.1016/j.precamres.2025.108000","DOIUrl":"10.1016/j.precamres.2025.108000","url":null,"abstract":"<div><div>The Saharan metacraton was assembled during pre-Neoproterozoic to Neoproterozoic times and was strongly remobilised during the Pan African orogeny. The Ouaddaï massif in eastern Chad represents the core of the Saharan metacraton, yet its geological history remains poorly documented. In this study, we combine of field observations, petrological analysis of metamorphic rocks, and geochemical and geochronological constraints to reconstruct the tectono-metamorphic evolution of the Ouaddaï massif. The study area is dominated by collision-related plutonic rocks and migmatitic gneisses, within which inliers of older basement occur. Geochemical data indicate a transition from active-margin to collisional magmatism, with a compositional evolution from diorite to granite. This suite is cross-cut by syenogranites and alkaline granites with shoshonitic affinities, interpreted as post-collisional granitoids derived from tonalitic rocks to sedimentary protoliths. Geochronological data (U-Pb on zircon and monazite) point to a ca. 1000 Ma age for orthogneisses inliers. Granitoids of the Ouaddaï massif record emplacement ages from 620 to 590 Ma, coeval with high-temperature metamorphism characterized by peak pressure–temperature conditions of 1.2 GPa and 850 °C (mafic granulite) and around 0.8 GPa and 700 °C (sillimanite-garnet bearing migmatites). Integrating our new results with regional data, we discuss the existence and geodynamic evolution of the Saharan Metacraton. Our findings emphasize the significance of the Saharan Metacraton as a key region for understanding the extensive reworking of cratonic lithosphere during both a Tonian magmatic phase prior and the assembly of Gondwana.</div></div>","PeriodicalId":49674,"journal":{"name":"Precambrian Research","volume":"434 ","pages":"Article 108000"},"PeriodicalIF":3.2,"publicationDate":"2026-01-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145927927","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":"New occurrence of a postglacial Ediacaran macrofossil assemblage from North China and its evolutionary implication","authors":"Xin Wang ,&nbsp;Xingliang Zhang ,&nbsp;Tao Dai ,&nbsp;Wei Liu ,&nbsp;Yuan Zhang ,&nbsp;Luoyang Li","doi":"10.1016/j.precamres.2025.107992","DOIUrl":"10.1016/j.precamres.2025.107992","url":null,"abstract":"<div><div>The late Ediacaran witnessed a significant evolutionary junction, characterized by a pronounced decline in the diversity of Ediacara-type macrofossils and macroalgae, coinciding with the expansion of tubular organisms and mobile bilaterians as evidenced by trace fossils. The North China Craton (NCC), one of the oldest cratons with a geological history spanning more than 3.8 billion years, contains extensively distributed Ediacaran deposits along its western and southern margins. However, the Ediacaran fossil assemblages in NCC remain poorly understood, particularly due to the absence of Ediacara-type fossils. Here, we report a newly discovered macrofossil assemblage, the Dongpo biota (ca. 550–538.8 Ma), from the terminal Ediacaran Dongpo Formation, a shale-dominated sequence exposed along the southern margin of NCC. The biota comprises a diverse assemblage that includes frondose fossils, macroalgae, tubular forms, bilaterian trace fossils, and various problematic fossils, demonstrating a clear stratigraphic overlap. The new biota expands the known paleogeographic distribution of the Ediacaran macrofossils and offers crucial evidence enhancing our understanding of biotic communities inhabiting siliciclastic-dominated seafloors during the terminal Ediacaran period. Moreover, the fossil-bearing horizon conformably overlies the Luoquan diamictite, indicating that the Dongpo biota represents a postglacial Ediacaran macrofossil assemblage. Thus, this new biota provides key insights into the recovery and flourishing of benthic marine ecosystems after the ‘Great Ediacaran Glaciation’.</div></div>","PeriodicalId":49674,"journal":{"name":"Precambrian Research","volume":"434 ","pages":"Article 107992"},"PeriodicalIF":3.2,"publicationDate":"2026-01-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145886104","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":"Crustal structure in the Quadrilátero Ferrífero mineral province, SE Brazil: differentiating preserved and reworked Archean crust","authors":"Taghi Shirzad ,&nbsp;Marcelo Assumpção ,&nbsp;Marcelo B. Bianchi ,&nbsp;Bruno Collaço ,&nbsp;Fernando Alkmim ,&nbsp;Dionísio U. Carlos ,&nbsp;Luciano Assis ,&nbsp;Maximiliano Simão","doi":"10.1016/j.precamres.2025.108003","DOIUrl":"10.1016/j.precamres.2025.108003","url":null,"abstract":"<div><div>The <em>Quadrilátero Ferrífero</em> (QF; Iron Quadrangle) on the southeastern São Francisco craton exposes Paleoarchean to Paleoproterozoic rocks shaped by multiple Precambrian tectonic events. Despite extensive mapping, its deeper crustal structure remains poorly constrained, limiting insights into Archean stabilization and later Paleoproterozoic reworking. Clarifying whether the QF greenstone belt preserves Mesoarchean lithosphere or later modification is key to understanding the region’s tectonic evolution. The deeper crustal structure also informs mineral potential, as crustal architecture governs ore localization in stable cratons. Here we study the deep crustal structure using teleseismic receiver functions (RF), recorded at six stations of the VALE QF seismic network, together with Rayleigh and Love wave dispersion curves. We retrieved group velocities of Rayleigh and Love waves from ambient noise of local and regional stations between 0.3 and 4.4 s, sampling the upper crust. For longer periods (5 to 100 s), we used group and phase velocities of continental-scale tomography models. Joint inversion of receiver functions and surface-wave dispersion curves showed a thin crust (∼35 km) in the middle of the QF province, beneath the Rio das Velhas greenstone belt, and a thicker crust (∼42 km) in the eastern and western areas of the QF. The variations of crustal thickness resulting from the joint inversion are consistent with <em>H-k</em> stacking of receiver functions. Other stations in the São Francisco craton, outside the QF, show intermediate thicknesses of 36–39 km. Bulk crustal <em>Vp/</em>Vs ranged from 1.72 to 1.74, with no systematic variation across the QF. The QF central area, beneath the Rio das Velhas greenstone belt, has thin crust and normal S-wave velocities in the lower crust Vs (3.8–3.9 km/s) consistent with intermediate granulite composition, whereas the stations with thick crust, on either side of the central greenstone belt, show high Vs (∼3.9–4.1 km/s) in the lowermost crust suggesting a more mafic composition. This contrast in the lower crust properties can be interpreted as preservation of the stabilized Mesoarchean crust beneath the greenstone belt. Alternatively, the crust in the middle of the QF could have been thinned during the extensional collapse at the end of the Minas orogeny in the Paleoproterozoic.</div></div>","PeriodicalId":49674,"journal":{"name":"Precambrian Research","volume":"434 ","pages":"Article 108003"},"PeriodicalIF":3.2,"publicationDate":"2026-01-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145886107","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":"Marine evaporitic borate mineralization during the Lomagundi–Jatuli Event, Liaodong Peninsula, northeast China","authors":"Guyue Hu ,&nbsp;Chunlian Wang ,&nbsp;Kuidong Zhao ,&nbsp;Qian Li ,&nbsp;Yanhe Li ,&nbsp;Xinsheng Sun ,&nbsp;Jun Zheng ,&nbsp;Kunming Wang ,&nbsp;Jianghua Gong ,&nbsp;Peng Li ,&nbsp;Yue Zhao","doi":"10.1016/j.precamres.2025.107998","DOIUrl":"10.1016/j.precamres.2025.107998","url":null,"abstract":"<div><div>Many Paleoproterozoic borate deposits are hosted within the lower units of the volcanic–sedimentary sequence (<em>ca</em>. 2.2 Ga) of the Liaohe Group, Liaodong Peninsula, northeast China. It is debated as to whether these deposits were affected by marine evaporation. The borate ore bodies of the Zhuanmiao deposit in the Liaohe Group have stratiform or lenticular shapes and occur in serpentinized carbonates, with the ores being bordered by layered leptynites, leptites, amphibolites, and migmatites. We carried out a C–O–Mg stable isotope study of the ores and carbonate rocks in the Zhuanmiao deposit. The <em>δ</em>¹³C values of unserpentinized magnesite marbles in the ores of the Errengou block in the Zhuanmiao deposit range from +3.2 ‰ to +6.0 ‰ and preserve a positive C isotopic anomaly typical of the Lomagundi–Jatuli Event (2.306–2.057 Ga). The <em>δ</em>²⁶Mg values of these unserpentinized magnesite marbles in the Zhuanmiao borate deposit range from –1.01 ‰ to –0.84 ‰, which are typical of marine sediments. The positive C isotopic anomaly of the magnesite marbles in the Zhuanmiao deposit indicates that the C isotopic anomaly of magnesite that formed during the Lomagundi–Jatuli Event is not only a result of global oxygenation of the ocean–atmosphere, but also marine evaporation in individual basins. This evaporation even led to rare examples of borate mineralization.</div></div>","PeriodicalId":49674,"journal":{"name":"Precambrian Research","volume":"434 ","pages":"Article 107998"},"PeriodicalIF":3.2,"publicationDate":"2025-12-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145852427","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":"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}