Precambrian Research最新文献

{"title":"Neoarchean accretionary and collisional tectonics in the southern North China Craton: Implications for crustal growth and plate tectonic styles","authors":"Bo Huang,&nbsp;Timothy Kusky,&nbsp;Dong Fu","doi":"10.1016/j.precamres.2025.107730","DOIUrl":"10.1016/j.precamres.2025.107730","url":null,"abstract":"<div><div>Archean continental crust primarily consists of TTG (tonalite–trondhjemite–granodiorite) gneisses and greenstone belts. Understanding their origins and tectonic settings is crucial to deciphering continental growth and associated geodynamic regimes on early Earth, which remain highly debated. The North China Craton, one of the largest cratons, experienced significant crustal growth and reworking during late Neoarchean (ca. 2.6–2.5 Ga), but the mechanisms and geodynamic settings remain uncertain. This review assesses the field relations, structural styles, metamorphic features, and magmatic evolution of two representative Neoarchean TTG-greenstone terranes (Dengfeng and Angou) in the southern North China Craton to evaluate different geodynamic models and their roles in continental crust growth. The Dengfeng and Angou complexes, dominated by ca. 2.55–2.50 Ga TTG gneisses, metavolcano-sedimentary assemblages, and high-Mg diorites, with several generations of mafic and felsic intrusions, are subdivided into several lithostructural units with distinct geochronological, structural, geochemical, and metamorphic characteristics. These are interpreted as juxtaposed remnants of intra-oceanic arc/forearc complexes, accretionary complexes, and a continental margin sequence, recording Neoarchean divergent and convergent plate margin processes from seafloor spreading, subduction initiation, forearc accretion to arc–continent collision. The formation of juvenile intra-oceanic arc/forearc complexes, accretion of ocean plate stratigraphy/mélanges, and final arc–continental collision reflects active plate tectonics driving both vertical and lateral continental growth during the late Neoarchean. Metamorphic and thermodynamic modeling suggests a warmer Neoarchean paleo-subduction zone compared to Phanerozoic average slab-top geotherms, likely due to the hotter mantle and subduction of young and short-lived oceanic crust (&lt;30 Myrs). Such accretionary and collision tectonics, characterized by intra-oceanic warm subduction and soft collision, alongside coexisting mantle plume tectonics elsewhere, may have been two key mechanisms in constructing and recycling late Archean continental crust, promoting mantle heat loss and regulating surface environments as today. Finally, we suggest some future research directions to further investigate crustal evolution and tectonic styles from the perspective of the North China Craton.</div></div>","PeriodicalId":49674,"journal":{"name":"Precambrian Research","volume":"420 ","pages":"Article 107730"},"PeriodicalIF":3.2,"publicationDate":"2025-02-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143438220","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":"Detrital zircon geochronology of the Paleoproterozoic Nonacho Basin (Northwest Territories, Canada): A record of post-collisional collapse amid supercontinent aggregation","authors":"Jade Lockie ,&nbsp;Alessandro Ielpi ,&nbsp;Sally J. Pehrsson ,&nbsp;Joshua H.F.L. Davies ,&nbsp;Beth J. Fischer","doi":"10.1016/j.precamres.2025.107731","DOIUrl":"10.1016/j.precamres.2025.107731","url":null,"abstract":"<div><div>The study of Paleoproterozoic sedimentary basins is critical to inform aspects of craton development during some of Earth’s earliest supercontinent cycles. The ∼ 1.9 Ga Nonacho Basin is located at the ancestral core of the Canadian Shield near the sutured margins of the Archean Slave and Rae cratons, making it ideal for a detrital zircon study examining evidence of orogenic unroofing during the ca. 1.9 Ga assembly of the supercontinent Nuna. Detrital zircon U–Pb geochronology with chemical-abrasion laser-ablation inductively-coupled plasma mass spectrometry is used to investigate the provenance and maximum depositional ages of the Nonacho Group throughout its alluvial, fluvial and marine deposition. Detritus preserved in the lower stratigraphy (Hjalmar formation) was largely derived locally from the ∼ 2.7–2.3 Ga Nonacho basement complex. The overlying strata (Tronka Chua, Chief Nataway, Newshethdezza, Thekulthili, and Taltson formations) display distinctive age peaks matching the ∼ 2.0–1.9 Ga Thelon and Taltson orogens, together with contributions from varied source areas of the Rae craton. A maximum depositional age at 1887 ± 10 Ma for the Tronka Chua formation indicates that much of the sediment was deposited post ∼ 1.89 Ga, similarly to correlative supracrustal panels of the central Rae craton. This new depositional constraint, together with records of Taltson- and Thelon-derived detritus, corroborate a model whereby the Nonacho Basin evolved in a regime of crustal extension driven by thermal subsidence in the aftermath of the Slave and Rae craton collision, punctuated by crustal flexure as a distant response to the Snowbird orogeny. The Nonacho Group acted as a sink for sediment unroofed from nearby orogenic topography until crustal flexure originating from the Rae-Hearne craton boundary triggered alternate sources, providing an example of how multistage convergence during supercontinent amalgamation controls sediment provenance.</div></div>","PeriodicalId":49674,"journal":{"name":"Precambrian Research","volume":"420 ","pages":"Article 107731"},"PeriodicalIF":3.2,"publicationDate":"2025-02-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143438219","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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":"Petrogenesis and tectonic implications of the Neoproterozoic A-type granite in the Quanji Massif, northeastern of the Tibetan Plateau","authors":"Zhenwei Feng,&nbsp;Wei Li,&nbsp;Le Zhang,&nbsp;Li Liang,&nbsp;Falak Sheir,&nbsp;Liuqing Jiang,&nbsp;Chao Wang,&nbsp;Zhihao Ma","doi":"10.1016/j.precamres.2025.107732","DOIUrl":"10.1016/j.precamres.2025.107732","url":null,"abstract":"<div><div>A-type granites have unique geochemical characteristics, indicating an extensional tectonic environment, thus providing critical constraints on magma sources and tectonic mechanisms, and playing a crucial role in reconstructing orogenic events. In this contribution, we conducted a systematic study on zircon U-Pb geochronology, whole-rock geochemistry, and zircon Hf isotope of the new identified A-type granites in the Quanji Massif in the northeastern Tibetan Plateau to discuss its petrogenesis and the tectonic implications. The zircon U-Pb dating results show that the crystallization ages of granites and granite porphyries are 797 ± 8 Ma and 799 ± 7 Ma, respectively, indicating that they were formed in the Neoproterozoic. Geochemically, these rocks have high SiO₂ (67.47–75.74 wt%) and total alkali (Na₂O + K₂O = 6.89–8.84 wt%) contents, low MgO (0.11–1.37 wt%), CaO (0.76–1.29 wt%), and P₂O₅ (0.05–0.18 wt%) contents, with negative anomalies of Nb, Ta, Ti, Sr, and Eu elements. They have high FeO^T /(MgO + FeO^T) values, Zr + Nb + Ce + Y contents (343–562 ppm), 10000 × Ga/Al ratio (2.12–3.20), and zircon saturation temperature (804–860 ℃), which are consistent with the characteristics of typical A-type granites. Their high K₂O/Na₂O ratios, low Sr/Y and La/Yb ratios, combined with the zircon ε_Hf(t) values (–4.04 to 3.25) and the whole-rock ε_Nd(t) values (–8.28 to –4.91), indicate that the A-type granites were derived from partial melting of the calc-alkaline rocks in the ancient crust with a moderate contribution of juvenile crust under high temperature and low-pressure conditions. Based on the tectonic setting discrimination diagram combined with regional data, it is comprehensively determined that the A-type granites were formed in the post-collisional extensional environment, which is a response to the breakup of the Rodinia supercontinent. According to the comprehensive data of the Quanji Massif and adjacent areas show that the Quanji Massif, the Qaidam Block and the Qilian Block were combined into a unified block during the Late Mesoproterozoic-Neoproterozoic and participated in the evolution of the Rodinia supercontinent.</div></div>","PeriodicalId":49674,"journal":{"name":"Precambrian Research","volume":"419 ","pages":"Article 107732"},"PeriodicalIF":3.2,"publicationDate":"2025-02-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143430095","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":"Controls on the termination of the massive chert system in the Ediacaran-Cambrian Liuchapo Formation, South China","authors":"Yuxuan Wang ,&nbsp;Fang Hao ,&nbsp;Yangbo Lu ,&nbsp;Kaixun Zhang ,&nbsp;Yan Ye ,&nbsp;Shang Xu","doi":"10.1016/j.precamres.2025.107729","DOIUrl":"10.1016/j.precamres.2025.107729","url":null,"abstract":"<div><div>The widespread deposition of marine siliceous rocks marks a fundamental shift in the ancient ocean’s biogeochemical dynamics, transitioning from Precambrian systems dominated by direct inorganic silica precipitation as the primary silicon sink to modern environments where microbial processes strongly govern silica dissolution. The massive Liuchapo chert in the Nanhua Basin, South China, formed during the Ediacaran–Cambrian transition (ECT, ∼550–521 Ma), a critical interval of silicon cycle perturbations, rapid multicellular diversification, and significant environmental change. Its abrupt termination, followed by the widespread deposition of Niutitang black shales without a depositional hiatus, reflects a fundamental shift in the oceanic silicon cycle, linked to profound marine environmental evolution and dynamic biotic responses during the key period of the ECT. However, the biogeochemical processes driving the cessation of chert deposition remain poorly understood. Here, we present high-resolution geochemical data from the XAD1 borehole, situated in an an outer slope setting of the Nanhua Basin to assess controls on the termination of this widespread marine chert system. Our multi-proxy approach, including iron speciation, redox-sensitive trace metal analyses, and rare earth elements plus yttrium (REE + Y) systematics documents a highly fluctuated redox condition between oxic to ferruginous throughout the Liuchapo Formation, before giving way to persistent euxinic conditions in the lower Niutitang Formation. Hydrothermal activity likely played a key role in the Liuchapo chert formation, while its subsequent decline, coupled with the onset of euxinic conditions, weakened the Fe-Si loop essential for chert deposition. Furthermore, the emergence of silica-secreting organisms may have reduced dissolved silicon levels, further driving the cessation of chert deposition. These findings provide new insights into the environmental and biological factors controlling the termination of the Liuchapo massive chert system, contributing to a deeper understanding of the complex geochemical and ecological dynamics during this pivotal period in Earth’s history.</div></div>","PeriodicalId":49674,"journal":{"name":"Precambrian Research","volume":"419 ","pages":"Article 107729"},"PeriodicalIF":3.2,"publicationDate":"2025-02-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143419455","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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":"Paleoproterozoic orogenic event in the western North China Craton: Insights from zircon U-Pb-Lu-Hf isotopes and geochemistry of meta-supracrustal rocks in the Beidashan complex, Alxa block","authors":"Yi-Wei Rong ,&nbsp;Wen-Bin Zhu ,&nbsp;Xi Wang ,&nbsp;Jun-Yue Zhu ,&nbsp;Xiao Hu","doi":"10.1016/j.precamres.2025.107728","DOIUrl":"10.1016/j.precamres.2025.107728","url":null,"abstract":"<div><div>Recent studies have highlighted Paleoproterozoic magmatic and metamorphic events within the Alxa block. Although these geological records are generally believed to be associated with Paleoproterozoic orogenic events, the nature and location of the potential orogenic belt remains poorly understood. In this paper, we systematically investigate U-Pb-Lu-Hf isotope analyses of detrital zircons, alongside whole-rock major and trace element analyses from a suite of Paleoproterozoic <em>meta</em>-supracrustal rocks in the Beidashan complex, to provide new insights into this enigmatic orogenic event.</div><div>The formation age of the upper sequence of the <em>meta</em>-supracrustal rock suite is constrained to 1.89 ∼ 1.83 Ga, with detrital zircons exhibiting a unimodal distribution centered at ∼ 1.96 Ga and Hf model age peaks at ∼ 2.4 Ga and 2.6 ∼ 2.7 Ga. In contrast, the deposition age of the lower sequence is constrained to 2.08 ∼ 2.05 Ga, with detrital zircons show age peaks at ca. 2.20 Ga, 2.30 Ga and 2.41 Ga, and a Hf model age peak at ∼ 2.95 Ga. Geochemical analyses reveal that amphibolites from the upper sequence are enriched in light rare earth elements (LREE) and show negative Nb and Ta anomalies. Conversely, amphibolites from the lower sequence display relatively low REE differentiation and are depleted in high field strength elements (HFSE). Both sequences exhibit Nb-Ta troughs, characteristic of typical continental arc basalts and andesites. The amphibolites from the upper sequence are more enriched in LREE, which likely indicates their formation in a late-orogenic environment.</div><div>The detrital zircons from the Beidashan complex exhibit age distributions and Lu-Hf isotope compositions that align with the Archean-Paleoproterozoic magmatic rocks exposed in the Alxa block. This alignment suggests that the Beidashan, Longshoushan and Bayanwulashan regions to the south of the Alxa block likely served as the source area for the lower sequence, while the Diebusige region to the north may be the provenance for the upper sequence. This provenance shift around ∼1.9 Ga likely reflects the uplift of an accretionary orogen north to the research region, which not only introduced new juvenile material into the sedimentary record but also stopped the original material supply from the south. Therefore, we propose that the Alxa block experienced an orogenic event north to the Beidashan complex during 2.1 to 1.8 Ga, potentially related to the subduction and collision between an unknown continent and the Alxa block along its northern margin, contributing to the formation of the Columbia supercontinent.</div></div>","PeriodicalId":49674,"journal":{"name":"Precambrian Research","volume":"419 ","pages":"Article 107728"},"PeriodicalIF":3.2,"publicationDate":"2025-02-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143403260","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":"Paleomagnetism of the Mesoproterozoic Duguan Formation in Luonan, North China, and its geologic and paleogeographic implications","authors":"Xianqing Jing ,&nbsp;Zhenyu Yang ,&nbsp;Yabo Tong ,&nbsp;Zhiming Sun ,&nbsp;Ran Xiao ,&nbsp;J. Besse ,&nbsp;M. Macouin ,&nbsp;M. Ader","doi":"10.1016/j.precamres.2025.107727","DOIUrl":"10.1016/j.precamres.2025.107727","url":null,"abstract":"<div><div>Knowledge of the tectonic and paleogeographic context of North China during the Proterozoic is pivotal for unraveling the origins of early multicellular eukaryotes and the dynamics of supercontinents like Nuna and Rodinia. However, stratigraphic correlations across basins, the tectonic framework, and North China’s position within Nuna and Rodinia, particularly its relationship with the Congo-São Francisco plate, are contentious. To address these issues we conducted a detailed paleomagnetic and rock magnetic study of the red dolomite of the Duguan Formation in the Xiaoqinling-Luanchuan region, part of the Xiong’er block of North China. Thermal demagnetization revealed a high-temperature remanence component, with an unblocking temperature exceeding 670 °C, likely carried by detrital hematite. This component passed both fold and reversal tests. After tilt correction, the site-mean direction of the high-temperature component is Ds = 76.7°, Is = 16.9°, ks = 30.4, a95 = 7.3° (14 sites). This corresponds to a paleomagnetic pole at 15.8° N, 200.4° E (dp/dm = 3.9°/7.5°). Comparison of this pole with previous high-quality Proterozoic poles from North China indicates that the Duguan pole falls between the Yangzhuang and Mengyin dykes (1630 Ma). Considering the existing zircon U-Pb dating results, we conclude that the Duguan Formation is older than the Yangzhuang Formation, equivalent to the upper part of the Gaoyuzhuang Formation. Comparison with the Proterozoic apparent polar wander (APW) paths of North China and Congo-São Francisco indicates that these two blocks could only have amalgamated after 1080 Ma, with no earlier connection. However, due to the limited quantity of Proterozoic paleomagnetic data from Congo-São Francisco, the details of this Neoproterozoic connection remain uncertain.</div></div>","PeriodicalId":49674,"journal":{"name":"Precambrian Research","volume":"419 ","pages":"Article 107727"},"PeriodicalIF":3.2,"publicationDate":"2025-02-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143395486","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":"Pulsed oxygenation events at ∼ 1.44–1.43 Ga: Evidence from the Tieling Formation in the North China Platform","authors":"Yang Yu ,&nbsp;Yuelong Chen ,&nbsp;Dapeng Li ,&nbsp;Baoshan Xia","doi":"10.1016/j.precamres.2025.107723","DOIUrl":"10.1016/j.precamres.2025.107723","url":null,"abstract":"<div><div>The unique accumulation of oxygen (O₂) in Earth’s oceans and atmosphere distinguishes it from other rocky planets. The oxygenation of the Mesoproterozoic ocean–atmosphere system was a protracted process, yet it may have included transient oxygenation events, particularly before ∼ 1.4 billion years ago. Despite ongoing research, the detailed nature of redox conditions and the origin of a potential oxygenation event around 1.44–1.43 Ga remain poorly understood. Here, we present a suite of geochemical proxies, including iodine-to-calcium-magnesium [I/(Ca + Mg)], rare earth elements (REE) plus Y (REY), carbonate-associated sulfate sulfur isotopes (δ³⁴S_CAS), Rb/Al, and P/Al ratios for the carbonate rocks of the Tieling Formation (ca. 1.44–1.43 Ga) from two well-preserved sections of the North China Platform. The lower Tieling Formation (Daizhuangzi Member) exhibits middle REE-enriched patterns and elevated I/(Ca + Mg) values (up to 1.32 µmol/mol), suggesting potentially oxic or suboxic seawater conditions. The upper Tieling Formation (Laohuding Member) shows a pronounced increase in I/(Ca + Mg) at the basal interval, followed by a further marked rise in the middle to upper portion of this member. The rising I/(Ca + Mg) ratios, coupled with negative shifts in Ce anomalies, imply at least two pulses of oceanic oxygenation during deposition. Notably, the peak in I/(Ca + Mg) ratios in the middle-upper Laohuding Member corresponds with previously reported positive Cr isotope fractionation, indicating an oxygenation event that extended to the atmosphere. Similar oxygenation signals have also been recognized in the time-equivalent Fengjiawan Formation of southern North China and the Kaltasy Formation of the Russia, suggesting a multi-basin oxygenation process at ∼ 1.44–1.43 Ga. Additionally, elevated P/Al and Rb/Al ratios beneath the Laohuding Member point to intensified terrestrial weathering and nutrient delivery to the ocean that may have accelerated the pyrite burial and contributed to the oxygenated events during this period.</div></div>","PeriodicalId":49674,"journal":{"name":"Precambrian Research","volume":"419 ","pages":"Article 107723"},"PeriodicalIF":3.2,"publicationDate":"2025-02-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143377965","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":"Carbon cycling, redox condition and solute fluxes in the middle Paleoproterozoic Ocean: Constraints from elemental and C-O, Nd-Sr isotope geochemistry of stromatolitic carbonates from Vempalle Formation, Cuddapah Basin","authors":"M. Ashok,&nbsp;Nurul Absar","doi":"10.1016/j.precamres.2025.107724","DOIUrl":"10.1016/j.precamres.2025.107724","url":null,"abstract":"<div><div>The early Orosirian Period (2.05–1.9 Ga) was marked by unprecedented changes in carbon cycling and the redox state of the global ocean, and marine carbonates are a useful archive to study these changes. Here, we present detailed C-O, Nd-Sr isotopic, and trace element chemostratigraphy of a well-preserved stromatolitic carbonate sequence (∼1.2 Km thick) from ∼ 2.0–1.9 Ga Vempalle Formation (VF), Cuddapah basin, India; and aim to elucidate redox conditions, carbon cycling, and solute sources to the post-Great Oxidation Event (GOE) ocean. The basal VF (0–200 m) records a prominent negative δ¹³C excursion of magnitude ∼ 3 ‰, which is followed by an invariant δ¹³C (0.46–1.35 ‰) in the rest of the upper section. Oxidative remineralisation of organic matter in a relatively low dissolved inorganic carbon (DIC) oceanic reservoir explains the negative δ¹³C excursion, whereas muted δ¹³C variations in the upper part would suggest environmental stability under high <em>_p</em>CO₂. The ¹³Δ (δ¹³C_carbonate- δ¹³C_org) values between 24.9 and 28.8 (avg. 27.4) show photoautotrophic carbon fixation by primary producers. The transition from relatively well-oxygenated to less-oxygenated surface conditions and contraction of oceanic redox-sensitive elements (RSE) reservoir is indicated by a marked decline of U and V abundances after an initial high concentration recorded in the basal VF (0–80 m). The Light Rare Earth Element (LREE) or Middle Rare Earth Element (MREE) enriched patterns, very high Fe and Mn concentrations in the upper VFs suggest a predominant anoxic-ferruginous ocean and active redox cycling of REE below the Mn- or Fe-redoxcline. These data, combined with the shallow depositional bathymetry, imply a very shallow redoxcline. High radiogenic εNd_{2 Ga} values in the VF compared to the average Dharwar crust indicate significant inputs of mantle-derived hydrothermal fluid to the ocean. Large-scale advection of hydrothermal fluid onto the shallow carbonate platform would indicate a tectonically active basin.</div></div>","PeriodicalId":49674,"journal":{"name":"Precambrian Research","volume":"419 ","pages":"Article 107724"},"PeriodicalIF":3.2,"publicationDate":"2025-02-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143377966","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":"Metamorphic remobilization of Archean Au: Insights from the world-class Hemlo deposit, Canada","authors":"O Nadeau ,&nbsp;M.I. Leybourne ,&nbsp;A Voinot ,&nbsp;A Poirier","doi":"10.1016/j.precamres.2025.107710","DOIUrl":"10.1016/j.precamres.2025.107710","url":null,"abstract":"<div><div>Although most Archean orogenic Au deposits formed after the related metamorphic events, numerous deposits have formed prior to peak metamorphic conditions, and abundant research has focused on the remobilization of Au by metamorphic-hydrothermal fluids. At the Archean Hemlo Au deposit, Canada, most recent research agrees that Au mineralization first occurred prior to metamorphism and that Au was subsequently remobilized. Given that Li is mobile, relatively compatible in micas and clay minerals, and experiences isotopic fractionation primarily as a result of fluid-rock reactions, here, Li isotopic composition is analyzed using multiple collector ICP-MS and used to investigate Au remobilization during metamorphic-hydrothermal alteration. It is shown that bulk rock Li concentrations and isotopic compositions changed simultaneously with Au remobilization, as a result of the metamorphic recrystallization of biotite, chlorite, muscovite, and white mica. The concentration of Li increased from 2.6-58 ppm in hydrothermally-altered rocks, and δ⁷Li values decreased simultaneously, from + 10.5 to + 1.4 ‰. Interestingly, the δ⁷Li values correlate positively with Au and Li concentrations, indicating that the metamorphic-hydrothermal fluid remobilized Au as the rocks were fluxed with Li, and the biotite-chlorite-muscovite-white mica assemblages were recrystallized. In addition to bulk rock analyses, the concentration of Li-Au was measured in minerals using laser ablation ICP-MS, in order to investigate why bulk rock δ⁷Li values and Li concentrations are systematically correlated with Au concentrations. The presence of Au in K-feldspar is ascribed to primary mineralization and related K-feldspar alteration, whereas that in prograde and retrograde biotite, as well as in retrograde chlorite, muscovite, and white mica, must have resulted from the metamorphic-hydrothermal alteration and related Au remobilization. The decrease in Au counts and concentrations in minerals representing the sequence of recrystallization support bulk rock results suggesting that some Au was remobilized during metamorphism. Overall, these results highlight the strong potential of Li isotopes for Au exploration and metallogenic studies.</div></div>","PeriodicalId":49674,"journal":{"name":"Precambrian Research","volume":"419 ","pages":"Article 107710"},"PeriodicalIF":3.2,"publicationDate":"2025-02-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143377058","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":"Carbonaceous macrofossils from the Ediacaran–Cambrian lower shale member of the Soltanieh formation, Northwestern Iran","authors":"Najmeh Etemad-Saeed ,&nbsp;Shuhai Xiao ,&nbsp;Steve C. Wang ,&nbsp;Kristin D. Bergmann ,&nbsp;Andrew H. Knoll","doi":"10.1016/j.precamres.2025.107722","DOIUrl":"10.1016/j.precamres.2025.107722","url":null,"abstract":"<div><div>The Ediacaran–lower Cambrian Soltanieh Formation exposed in the Soltanieh Mountains of northwestern Iran is a mixed siliciclastic-carbonate succession that hosts skeletal animals, metazoan trace fossils, and macroalgal compressions, in addition to a well-resolved C isotopic record. Here we attempt to clarify the systematic paleontology of carbonaceous compression macrofossils found at the base of the Lower Shale Member of this formation, close to the Ediacaran–Cambrian boundary, and discuss their implications for our understanding of the early evolution of complex multicellular organisms. We identified five distinct morphological groups: (1) small discoidal fossils (chuarids), (2) branching thalli (<em>Eoholynia corumbensis</em>), (3) large discoidal fossils (<em>Doulia rara</em>), (4) simple ribbon-like compressions, and (5) chuarid-like discoidal structures with an attached filament. These fossils display limited diversity but include representatives of the three groups that dominate Ediacaran–Cambrian macrophyte diversity globally. All are present at the stratigraphic level in which Cambrian animals and trace fossils first appear, providing broader biological context for understanding early animal diversification.</div></div>","PeriodicalId":49674,"journal":{"name":"Precambrian Research","volume":"419 ","pages":"Article 107722"},"PeriodicalIF":3.2,"publicationDate":"2025-02-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143349329","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}