Precambrian Research最新文献

{"title":"Reassessing early traces of life from the Eoarchean metasedimentary rocks in Labrador, Canada: carbon isotope compositions for individual graphitic grains","authors":"Motoko Igisu ,&nbsp;Kentaro Tanaka ,&nbsp;Naoto Takahata ,&nbsp;Ken Takai ,&nbsp;Yuji Sano ,&nbsp;Tsuyoshi Komiya","doi":"10.1016/j.precamres.2026.108074","DOIUrl":"10.1016/j.precamres.2026.108074","url":null,"abstract":"<div><div>Graphite with low carbon isotope ratios (δ¹³C_gr) in the Eoarchean metasedimentary rocks from the Labrador region of northern Canada has attracted attention as possible evidence for the oldest traces of life on the Earth. However, δ¹³C_gr values were primarily determined through whole-rock analysis, and maturation degree was assessed in a limited number of samples. Whether all ¹³C-depleted carbons existed before the peak metamorphism remains unclear. Here, we performed in situ micro-Raman spectroscopy and nanoscale secondary ion mass spectrometry on graphitic grains to determine their crystallinity and carbon isotopic compositions. Based on the occurrence of graphitic grains in thin sections and Raman spectra, we classified the grains into four types: (1) inclusion graphite within matrix minerals, (2) inclusion poorly crystallized graphite (PCG), (3) boundary graphite among mineral grains, and (4) boundary PCG. Inclusion graphite is considered the most primary. The δ¹³C_gr values ranged from −35‰ to 7‰ and were heterogeneous within single hand specimens of pelitic rocks, conglomerates, and chert nodules, regardless of whether grains were inclusions or boundary types, or whether they were graphite or PCG. Carbonate rocks contain grains with relatively homogeneous δ¹³C_gr values. Overall, the δ¹³C_gr values correlate with lithology, increasing from pelitic rocks to conglomerates and carbonate rocks with chert nodules. These data suggest that determining the origin of all graphitic grains from a single source is difficult. Graphitic grains with positive δ¹³C_gr values may have an abiological origin; however, the wide range of δ¹³C_gr values, together with their geological occurrence, does not allow a unique interpretation, but is consistent with multiple origins, including both abiotic and biotic organic carbon.</div></div>","PeriodicalId":49674,"journal":{"name":"Precambrian Research","volume":"437 ","pages":"Article 108074"},"PeriodicalIF":3.2,"publicationDate":"2026-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147387541","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":"TTG plutonism in the Archean Abitibi greenstone belt, Superior craton: geodynamic and metallogenic perspectives","authors":"Silvain Rafini ,&nbsp;Morgane Gigoux ,&nbsp;Michel Jébrak","doi":"10.1016/j.precamres.2026.108039","DOIUrl":"10.1016/j.precamres.2026.108039","url":null,"abstract":"<div><div>This study of the Abitibi greenstone belt (Quebec, Canada) relies on TTG (tonalite, trondhjemite, and granodiorite) composition to investigate the spatiotemporal evolution of the Archean crust and evaluate its metallogenic significance. Trace element signatures (e.g., La/Yb, Sr/Y, Eu/Eu*, Nb, Ta) of 32 dated TTG intrusions is analyzed using the FI-FII-FIII fertility typology developed for felsic volcanic rocks, which links mineral systems to melting depth and crustal architecture. Crystallization depths estimated from normative felsic mineralogy correlated with melting depth and showed a crustal thickness increase during incipient tectonics. The spatiotemporal distribution of TTG types indicates an early partitioning of the Abitibi crust into three distinct domains. The Northeastern Abitibi is characterized by FI types, early crustal thickening, and arc-like settings. These geological characteristics are favorable for porphyry-type deposition within syn-volcanic shallow plutons (e.g., the Chibougamau camp) or Windfall-like intrusion-related gold mineralization within syn-tectonic, LILE-enriched intrusions crystallized at deeper levels, possibly below the brittle crust. The southern volcanic zone is dominated by FIII and FIIb types, consistent with thin-crust, high–heat flux environments linked to the major volcanogenic massive sulfide camps. Finally, the western North Volcanic Zone exhibits an intermediate crustal thickness response and a transition from FII to FI types, associated with syn-tectonic crustal thickening; punctual occurrences of FIII-type intrusions occur, which indicate trenches or thermal corridors prospective for volcanogenic massive sulfides. This research emphasizes the utility of TTG geochemistry as a proxy for crustal processes and mineral potential. It demonstrates that TTG compositional variability offers a robust framework for reconstructing Archean crustal evolution and guiding metallogenic models.</div></div>","PeriodicalId":49674,"journal":{"name":"Precambrian Research","volume":"437 ","pages":"Article 108039"},"PeriodicalIF":3.2,"publicationDate":"2026-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147387544","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":"U-Pb zircon-monazite-apatite geochronology and zircon Hf isotope composition of syenite-clinopyroxenite suite from Nayagarh (Odisha) of the Eastern Ghats Province","authors":"Divyajyoti D. Rana ,&nbsp;Dewashish Upadhyay ,&nbsp;Jayanta Kumar Nanda ,&nbsp;Mousumi Bhattacharjee","doi":"10.1016/j.precamres.2026.108065","DOIUrl":"10.1016/j.precamres.2026.108065","url":null,"abstract":"<div><div>A clinopyroxene-bearing syenite suite, hosted in charnockitic orthogneiss in the Nayagarh region of the Eastern Ghats Province, records multiple magmatic and metamorphic events. This study combines petrography, mineral chemistry, U–Pb geochronology of zircon, monazite, and apatite, and zircon Hf isotopes to constrain its petrogenesis and tectonic evolution. The syenite comprises mainly K-feldspar with subordinate clinopyroxene and accessories like zircon, allanite, thorite, monazite, titanite, and apatite. Apatite veins cutting syenite–pyroxenite bodies are light rare earth element-enriched. Zircon grains feature magmatic cores and metamorphic overgrowths. Magmatic domains yield a concordant U–Pb age of 979 ± 6 Ma (2σ, n = 28; MSWD = 2.0), marking syenite intrusion. A xenocrystic zircon at 1744 ± 63 Ma indicates older crustal inheritance. Metamorphic overgrowths date to 792 ± 9 Ma (2σ, n = 9; MSWD = 0.060) and 541 ± 10 Ma (2σ, n = 2; MSWD = 0.000117). Monazite gives a concordant age of 458 ± 8 Ma (2σ, n = 5; MSWD = 0.27), while apatite yields a Tera–Wasserburg intercept of 410 ± 15 Ma (2σ; MSWD = 10). Zircon εHf(t) values range from –12.1 to + 4.7, signaling mixed juvenile and crustal sources, with depleted mantle model ages of 2.75–2.90 Ga for crustal extraction. The ∼ 979 Ma syenite emplacement aligns with Chilka Lake anorthosite and widespread anorthosite–charnockite–granitoid magmatism in the Eastern Ghats Belt, tying to Grenville-age post-orogenic extension after Eastern Ghats accretion to the Indian Shield and East Antarctica during Rodinia assembly. The ∼ 792 Ma event reflects high-grade metamorphism and decompression in Chilka Lake, linked to Rodinia breakup and East Antarctic–Indian separation. The ∼ 541 Ma zircons correlate with Kuunga orogeny, while 458 Ma monazite and 410 Ma apatite record hydrothermal alterations from later thermal pulses.</div></div>","PeriodicalId":49674,"journal":{"name":"Precambrian Research","volume":"437 ","pages":"Article 108065"},"PeriodicalIF":3.2,"publicationDate":"2026-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147387446","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 fluvial origin for conglomerates at the base of the Paleoproterozoic Sijizhuang Formation of the Wutai Mountains area, North China Craton","authors":"Li Tong ,&nbsp;Kuang Hongwei ,&nbsp;Liu Yongqing ,&nbsp;Peng Nan ,&nbsp;Li Jianrong ,&nbsp;Miao Peisen ,&nbsp;Peng Peng ,&nbsp;Wang Yuchong ,&nbsp;Chen Xiaoshuai ,&nbsp;Darrel G.F. Long","doi":"10.1016/j.precamres.2026.108043","DOIUrl":"10.1016/j.precamres.2026.108043","url":null,"abstract":"<div><div>Conglomerates in the Sijizhuang Formation, at the bottom of the Paleoproterozoic Hutuo Group in the Wutai Mountains area of the North China Craton, have recently been interpreted as products of glacial activity linked to a late stage of the Huronian glaciation. New observations show that strata interpreted as glacial diamictites are deformed framework supported conglomerates, in which the apparent matrix component consists of crushed volcanic clasts that have been elongated and squeezed between more resistant sub-rounded clasts of quartzite, chlorite schist, granite and banded iron formation derived from underlying rocks of the late Archean to early Paleoproterozoic Wutai Group and granitic gneiss. Detailed sections indicate an up-section transition from alluvial fan and gravel bed river deposits at the base, to mixed sandy-gravelly, then more distal sandy braided rivers, before submergence beneath shallow marine clastics and carbonates in overlying parts of the Hutuo Group. LA-ICP-MS analysis of detrital zircons from a sandstone in the Sijizhuang Formation indicates peaks at 2525 Ma, corresponding to the underlying Wutai Group and coeval granites. The inferred age of the Sijizhuang Formation is now constrained to 2.2–2.1 Ga, later than the 2.45–2.22 Ga age of the global Huronian glaciation event. The age and absence of unambiguous glacial features, such as till-pellets, clustered dropstones, erosional bedforms, and cryoturbation structures, indicates that the deposits are clearly post-Huronian, and represent the oldest known fluvial strata in China.</div></div>","PeriodicalId":49674,"journal":{"name":"Precambrian Research","volume":"437 ","pages":"Article 108043"},"PeriodicalIF":3.2,"publicationDate":"2026-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147387549","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":"Spatial analysis of Beltanelliformis (Nemiana) in Baltica","authors":"Emily G. Mitchell ,&nbsp;Ion Francovschi ,&nbsp;Heda Agić ,&nbsp;Andrey Bekker","doi":"10.1016/j.precamres.2026.108032","DOIUrl":"10.1016/j.precamres.2026.108032","url":null,"abstract":"<div><div>Discoidal fossils are some of the most abundant and widespread Ediacaran taxa found in many different environments throughout the late Ediacaran (580–539 Ma). They have a wide range of suggested affinities including microbial colonies, medusae, and the holdfasts of frondose taxa, including putative algal/bacterial discoidal taxa, such as <em>Beltanelliformis</em> and <em>Nemiana</em>, which are often found in large abundance in monospecific clusters. From their spatial patterns, we can infer the underlying biological and ecological processes governing their community ecology. Here, we analyzed four new Ediacaran communities from the ca. 567–539 Ma Moldova-Podillya Basin, with Vălcineț Area A and B, in the nearshore to shallow-marine environments, Cosăuți in the lower-energy marine environment, and Egoreni in the shallow-marine conditions (2352 specimens over 11.46 m²), as well as previously described two communities (196 specimens over 1.80 m²) from <span><span>Kolesnikov (2022)</span></span> data and 121 specimens over 0.46 m² from <span><span>Leonov (2007)</span></span> data from the Central Urals and the White Sea areas, respectively. These communities exhibited different community dynamics, with strong cluster orientation and dispersal processes in the Vălcineț and South Urals communities, in contrast to the strong association with habitat patchiness for the Cosăuți, Egoreni and White Sea area communities. Our results suggest two alternative drivers for <em>Beltanelliformis</em> communities, those controlled by dispersal in currents and those in a weaker flow by substrate patchiness. The White Sea assemblage Ediacaran biota show variation in environmental and dispersal dynamics and thus contrast with Avalonian assemblage Ediacaran biota, which show consistent drivers across large spatial and temporal scales.</div></div>","PeriodicalId":49674,"journal":{"name":"Precambrian Research","volume":"436 ","pages":"Article 108032"},"PeriodicalIF":3.2,"publicationDate":"2026-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146147064","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":"Neoarchean ultrahigh-temperature metamorphism in the Saglek–Hebron Complex, northern Labrador","authors":"Meiyun Huang ,&nbsp;Shujuan Jiao ,&nbsp;Tim E. Johnson ,&nbsp;Jonathan O’Neil ,&nbsp;Hanika Rizo ,&nbsp;Chris Clark ,&nbsp;Zhongwu Lan ,&nbsp;Qiuli Li ,&nbsp;Jinghui Guo","doi":"10.1016/j.precamres.2026.108046","DOIUrl":"10.1016/j.precamres.2026.108046","url":null,"abstract":"<div><div>Ultrahigh-temperature (UHT) metamorphism represents extremely hot crustal conditions, and is generally related to convergent plate margins during supercontinent assembly. However, the mechanisms to form Archean UHT metamorphism before supercontinent cycle are controversial. The Saglek–Hebron Complex (SHC) contains some of the oldest rocks on Earth that formed as early as ca 3.9 billion years ago and recorded polymetamorphism in Archean, although the exact metamorphic conditions and history are poorly understood. In this study, we investigate petrography, pressure–temperature (<em>P–T</em>) estimates, and zircon U–Pb geochronology of a metasedimentary rock from the SHC of northern Labrador, part of the North Atlantic Craton (NAC). The U–Pb age and trace element composition of zircon suggest zircon growth during melt crystallization and garnet resorption following an episode of ultrahigh-temperature (UHT) metamorphism at or before 2.72 Ga. Phase equilibrium modelling, two-felspar, and Zr-in-rutile thermometry together constrain UHT metamorphic <em>P–T</em> conditions to 7.2–9.2 kbar and 920–1000 °C. A rimward increase in the garnet grossular component, a change of garnet modes, and localized growth of matrix kyanite and rutile are consistent with a post-peak high-<em>T</em> retrograde stage within a <em>P–T</em> path associated with pressure increase and cooling (to ∼11 kbar at ∼850 °C). We propose that the UHT rocks formed previously in the lower crust of a hot and weak backarc region with elevated heat flow due to lithosphere extension and asthenosphere upwelling, which was closed by lateral thickening during subsequent multiple terrane convergence. Our findings are consistent with Hf isotopes in zircon from rocks of the NAC, the global record of metamorphism, and a period of cratonization of Earth’s ancient crustal nuclei during the Neoarchean era that may be coincident with the operation of plate tectonics.</div></div>","PeriodicalId":49674,"journal":{"name":"Precambrian Research","volume":"436 ","pages":"Article 108046"},"PeriodicalIF":3.2,"publicationDate":"2026-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146193228","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":"Paleoproterozoic tectonic evolution of the Dunhuang Block, eastern Tarim: insights from geochronology and petrogenesis of meta-igneous rocks","authors":"Xiang Ren ,&nbsp;Baoping Gan ,&nbsp;Inna Safonova ,&nbsp;Faqiao Li ,&nbsp;Qingfei Sun ,&nbsp;Hongrui Xu","doi":"10.1016/j.precamres.2026.108040","DOIUrl":"10.1016/j.precamres.2026.108040","url":null,"abstract":"<div><div>Identification of Paleoproterozoic tectonothermal events in ancient continental blocks is crucial for understanding the history of the Columbia supercontinent. The Dunhuang Block is located east of the Tarim Craton and it keeps archives of multiple events of Paleoproterozoic magmatism and metamorphism. It represents an excellent window to understand tectonic relationships between the Dunhuang Block and adjacent Tarim and North China cratons and to trace its tectonic evolution during the assembly of Columbia. In this paper, we present first data on zircon and apatite U-Pb geochronology, whole-rock geochemistry and Hf-in-zircon isotopes from newly discovered Paleoproterozoic <em>meta</em>-igneous rocks, amphibolite and granitic gneiss, that are exposed in the Dongshuigou area of the Dunhuang Block. Amphibolite and granitic gneiss yielded similar U-Pb zircon ages of crystallization of igneous protoliths, ∼2.02 and ∼ 2.04 Ga, respectively. Apatite U-Pb dating of both rocks indicates a late Paleozoic tectonothermal event, probably, superimposed metamorphism at 391–380 Ma. The amphibolites are enriched in light rare earth element (LREE) and large ion lithophile elements (LILE), depleted in high field strength elements (HFSE) and possess depleted Hf-in-zircon isotope characteristics (ε_Hf(t) = +0.71 to + 4.93); their igneous mafic protoliths were possibly derived by low-degree melting of an enriched mantle wedge source. The granitic gneisses possess geochemical affinities to TTG: SiO₂ of 73.03 to 78.05 wt%, low K₂O/Na₂O ratios (0.17–0.22 wt%), enriched LREE, depleted heavy REE, and high Sr/Y (57–82). Such geochemical characteristics and the ε_Hf(t) values spanning −2.7 to + 1.2 suggest that the granitic gneisses could be derived by melting of TTG-type igneous protoliths triggered by intrusion of hot mantle-derived magmas. The protoliths of both types of <em>meta</em>-igneous rocks were probably emplaced in an active continental margin setting. The new data from the Dunhuang Block accord well with previous data from other Neoarchean-Paleoproterozoic magmatic and metamorphic rocks of the whole Dunhuang-Tarim region suggesting similar and nearly synchronous tectonic evolution: the Dunhuang Block approached northern Tarim during oceanic subduction at ca. 2.0–1.90 Ga and then experienced collisional orogeny at ca. 1.85–1.82 Ga. The Dunhuang and Tarim blocks could be both involved into the assembly of the Columbia supercontinent at ca. 2.1–1.8 Ga.</div></div>","PeriodicalId":49674,"journal":{"name":"Precambrian Research","volume":"436 ","pages":"Article 108040"},"PeriodicalIF":3.2,"publicationDate":"2026-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146193225","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":"Petrogenesis and tectonic implications of the Neoarchean metavolcanic rocks in the southeast Yinshan Block, north China Craton (NCC): Constraints from U–Pb–Hf–Nd isotopes and geochemistry","authors":"Zhongwei Shao ,&nbsp;Zhuang Li ,&nbsp;Chunjing Wei ,&nbsp;Ze-Fa Wang ,&nbsp;Cheng-Cheng Xue ,&nbsp;Tian-Xiang Shi","doi":"10.1016/j.precamres.2026.108042","DOIUrl":"10.1016/j.precamres.2026.108042","url":null,"abstract":"&lt;div&gt;&lt;div&gt;The Late Archean magmatic sequence, which transitions from an early-stage TTG (trondhjemite-tonalite-granodiorite) to a late-stage emplacement of sanukitoids and potassic granites, is considered to represent the first global subduction–collision cycle in Earth’s history. However, it is important to assess whether this observation holds universal significance across Archean cratonic terranes. The Yinshan Block from the northwest NCC exposes extensive Neoarchean TTGs and high-Mg diorites (or sanukitoids) intrusions, along with minor potassic granites and supracrustal rocks, but their petrogenesis and tectonic scenarios remain controversial. In this study we for the first time report acidic and intermediate metavolcanic rocks which are equivalent to the intrusive TTGs and high-Mg diorites (or sanukitoids) from the Menggusi area in the southeast Yinshan Block. We present detailed data of petrology, geochronology and geochemistry and Nd–Hf isotopes for the newly-reported metavolcanic rocks, and provide an overall discussion of the petrogenesis and tectonic scenarios of the metavolcanic rocks and also the TTGs and high-Mg diorites (or sanukitoids) from the Yinshan Block. The acidic metavolcanic rocks were erupted at ∼2.57 Ga and exhibit the dacite to rhyolite compositions of low-K tholeiitic to calc-alkaline series. They have low Mg&lt;sup&gt;#&lt;/sup&gt; (39–48) and low MgO content, showing highly fractioned LREE/HREE patterns with positive Eu anomalies, depleted in HFSEs but enriched in LILEs. Moreover, they have low Cr and Ni contents with high Sr/Y and (La/Yb)&lt;sub&gt;N&lt;/sub&gt; ratios. In addition, they have positive whole-rock ε&lt;sub&gt;Nd&lt;/sub&gt;(t) (+2.92) and continuously varying positive zircon ε&lt;sub&gt;Hf&lt;/sub&gt;(t) (+0.5 – +5.0) values. These geochemical characteristics are completely consistent with the TTG gneisses in the Yinshan Block. Both the acidic metavolcanic rocks and TTGs were mainly produced by partial melting of basaltic rocks within the garnet stability field, and some of them may have subjected to mingling and mixing with mantle-derived magmas. The intermediate metavolcanic rocks were formed during 2.55–2.53 Ga, and display andesite to dacite compositions of the low-K tholeiitic to high-K calc-alkaline series. They have high Mg&lt;sup&gt;#&lt;/sup&gt; (mostly &gt; 50), and high MgO content, exhibiting moderate LREE/HREE fractionation with no significant Eu anomalies, depleted in HFSEs but enriched in LILEs. They have relatively high Cr and Ni contents, but low Sr/Y and (La/Yb)&lt;sub&gt;N&lt;/sub&gt; ratios. Additionally, they have positive whole-rock ε&lt;sub&gt;Nd&lt;/sub&gt; (t) values of + 1.36 – +3.84, and zircon ε&lt;sub&gt;Hf&lt;/sub&gt; (t) values of + 1.2 – +9.5. These geochemical features are comparable to those of the sanukitoids or high-Mg diorites in the Yinshan Block. Both were generated from a strongly metasomatized and hydrated mantle source, followed by the factional crystallization of pyroxene and amphibole when the mantle-derived magma uplifted into the crust. A compilation","PeriodicalId":49674,"journal":{"name":"Precambrian Research","volume":"436 ","pages":"Article 108042"},"PeriodicalIF":3.2,"publicationDate":"2026-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146193229","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":"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":"2026-04-01","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":"Nitrogen isotope evidence for marine nitrate reservoir dynamics during the Ediacaran–Cambrian transition","authors":"Liu Chen ,&nbsp;Kun Zhao ,&nbsp;Kaiyun Ye ,&nbsp;Songzhuo Li ,&nbsp;Bolin Zhang ,&nbsp;Xianguo Lang","doi":"10.1016/j.precamres.2026.108030","DOIUrl":"10.1016/j.precamres.2026.108030","url":null,"abstract":"<div><div>The Ediacaran-Cambrian transition represents a critical interval for the co-evolution of early life and marine environments. Previous studies have suggested that nitrogen biogeochemical cycling played a key role in this biological succession. In particular, the size of the marine nitrate reservoir directly influences the availability of essential nutrients in the ocean, thereby regulating primary productivity and ecosystem evolution. Nevertheless, despite the abundance of nitrogen isotope data during this period, considerable disagreements persist in their interpretation. Consequently, our understanding of the scale of the marine nitrate reservoir and its constraining mechanisms on the nitrogen cycle and bioavailability remains poorly constrained. This study presents high-precision carbon and nitrogen isotope data from a drill core (ZK609) and an outcrop section (Longbizui), both deposited in deep-water slope settings of South China. By integrating these new data with published C and N isotope records from various sedimentary environments across the Nanhua Basin, we reconstruct changes in the marine nitrate reservoir across the Ediacaran–Cambrian transition and evaluate its relationship with nitrogen cycling and biological events. Our results indicate that the late Ediacaran is characterized by relatively high nitrogen isotope values (δ¹⁵N), with δ¹⁵N ranging from +4.4‰ to +5.2‰ in ZK609 and from +0.3‰ to +3.3‰ at the Longbizui section. These values are comparable to those of the modern ocean, suggesting that denitrification was the dominant process in the surface waters during the late Ediacaran. In contrast, the early Cambrian exhibits lower nitrogen isotope values, with δ¹⁵N ranging from −2.9‰ to +4.0‰ in ZK609 and from −2.4‰ to +3.3‰ at the Longbizui section, suggesting a heightened contribution from nitrogen fixation. This isotopic shift implies consumption of the nitrate reservoir via denitrification, leading to a greater reliance on biologically fixed nitrogen as the primary source. Regional correlation of δ¹⁵N data confirms that this transition occurred broadly across South China. We propose that the marine nitrogen cycle evolved from a denitrification-dominated system in the late Ediacaran to a nitrogen fixation-dominated system in the early Cambrian. This shift reflects an initial consumption of the nitrate reservoir by denitrification, followed by its replenishment and spatial expansion through enhanced nitrogen fixation and changing redox conditions. This represents a fundamental reconstruction of the marine nitrate inventory. This restructuring likely contributed to the decline of the Ediacaran biota, while simultaneously supplying a critical nutrient source that supported the subsequent radiation of Cambrian life.</div></div>","PeriodicalId":49674,"journal":{"name":"Precambrian Research","volume":"435 ","pages":"Article 108030"},"PeriodicalIF":3.2,"publicationDate":"2026-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146174432","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}