Precambrian Research最新文献

{"title":"Stratigraphy, age and provenance of the metavolcano-sedimentary succession of the Gurupi Belt, northern Brazil: Implications for the tectonic setting and Rhyacian geodynamic evolution","authors":"Antonia Railine da Costa Silva ,&nbsp;Evandro L. Klein ,&nbsp;Jean-Michel Lafon","doi":"10.1016/j.precamres.2025.107815","DOIUrl":"10.1016/j.precamres.2025.107815","url":null,"abstract":"<div><div>The Gurupi Belt, northern Brazil, represents a Proterozoic belt, whose rocks were mainly formed during the orogenic events that occurred in the Rhyacian and Ediacaran-Cambrian periods. The Paleoproterozoic lithological association includes the metavolcano-sedimentary Chega Tudo Formation, the main host of gold deposits in the belt, batholiths and stocks of subduction-related and collisional granitoids, orogenic basins, and other minor units. To advance on the understanding of the depositional and tectonic settings of the metavolcano-sedimentary sequence, we investigated outcrop and drill core samples from the NW sector of the belt, which revealed rocks well-preserved from the effects of deformation and metamorphism, which affected the belt. Nine lithofacies were distinguished for the sequence and grouped into pyroclastic, volcaniclastic, epiclastic and volcanic-subvolcanic associations, which indicates a subaqueous depositional environment sedimentation and andesitic-dacitic volcanism interaction. The U-Pb ages in zircon from volcanic, volcaniclastic and epiclastic (detrital zircon) show that the Chega Tudo Formation was deposited between 2.20 and 2.14 Ga, with at least three episodes of volcanic activity at 2.20, 2.18 and 2.16 Ga. A back-arc setting, formed during early stages of the orogeny is indicated. Detrital zircons suggest that only arc-related sources (2.22 to 2.24 Ga) were involved in the early stages of sedimentation (accretionary arc), possibly derived from the São Luís cratonic fragment, switching to older populations (∼2.3 Ga) in the latter stages (collisional arc), probably from the basement of the West African Craton or the Bacajá Domain of the Amazonian Craton. Two subunits are proposed: a Lower Unit, with immature metapelitic and mafic-felsic volcanic rocks, associated to deep waters in the back-arc basin initiation stage; and, an Upper Unit, mainly formed by volcaniclastic rocks and andesite-dacite, formed later, under shallow waters.</div></div>","PeriodicalId":49674,"journal":{"name":"Precambrian Research","volume":"426 ","pages":"Article 107815"},"PeriodicalIF":3.2,"publicationDate":"2025-05-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144147884","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":"Nature and timing of polymetamorphic, anatectic and metasomatic events in mafic granulite in Archean high-grade terranes: Scenario from Central Zone of the Limpopo Complex, southern Africa","authors":"H.M. Rajesh ,&nbsp;O.G. Safonov ,&nbsp;G.A. Belyanin ,&nbsp;M. Santosh ,&nbsp;Z. Zhang ,&nbsp;T. Tsunogae ,&nbsp;M. Fukuyama ,&nbsp;C. Vorster ,&nbsp;P. Gao ,&nbsp;M. Keeditse","doi":"10.1016/j.precamres.2025.107831","DOIUrl":"10.1016/j.precamres.2025.107831","url":null,"abstract":"<div><div>Mafic granulite in Archean high-grade terranes are highly sensitive to reworking and overprint processes. Understanding the nature and timing of different events requires a careful approach with a combination of methods. This study presents field, petrographic, mineralogical, PERPLE_X phase equilibria modelling, U-Th-Hf-trace-REE-zircon and ⁴⁰Ar/³⁹Ar-amphibole systematics on mafic granulites from the Verbaard area in Central Zone of the Limpopo Complex, southern Africa. The mafic granulites are interlayered and infolded conformably with the oldest <em>meta</em>-supracrustal rocks including quartzites, <em>meta</em>-ironstone and migmatitic metapelites and are intruded by c.2.63–2.62 Ga granitoids. The granoblastic mafic granulites exhibit mineral assemblages representing various metamorphic transformations including minor partial melting during two metamorphic stages related to the Neoarchean (M1) and Paleoproterozoic (M2). The earliest M1 assemblage (Grt) + Opx + Cpx + Pl + Qz + Ilm formed at 830–850 °C, &gt;6.5 kbar, and was transformed to Opx + Cpx + Amp + Pl + Qz + Ilm during the Neoarchean decompression to c.6.5 kbar and subsequent cooling. The M2 assemblage (Grt) + Opx + Cpx + Amp + Pl + Qz + Ilm + Mag formed at &lt; 800 °C, c.5.5 kbar during the Paleoproterozoic overprint. CL-image, Lu-Hf isotope and trace-REE characteristics of zircons distinguish the effect of two metamorphic events at 2618 ± 11 Ma (M1) and 2057 ± 25 Ma (M2), both involving anatectic components. In contrast to the Neoarchean zircon cores, the Paleoproterozoic rims/newly grown grains show lower HREE abundance, suggesting their growth/overgrowth in equilibrium with garnet. The radiogenic Hf isotope compositions of both groups of zircons are explained by local subsolidus mineral reactions rather than an input of the juvenile material. The rocks show effects of late metasomatic alteration that is variably reflected in zircons in higher LREE concentrations and a flatter LREE profile. The c.1.95 Ga age is preserved in the Paleoproterozoic zircons with transgressive recrystallization structure, and supported by ⁴⁰Ar/³⁹Ar amphibole geochronology. The results highlight the textural and corresponding elemental signatures to look out for delineation of multiple overprint events involving metamorphism, anatexis and metasomatism in Archean mafic granulites.</div></div>","PeriodicalId":49674,"journal":{"name":"Precambrian Research","volume":"426 ","pages":"Article 107831"},"PeriodicalIF":3.2,"publicationDate":"2025-05-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144147883","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 and structural evolution of the orogenic gold deposits in Kullaa, SW Finland: Implications for fluid activity and gold precipitation during evolving orogeny","authors":"Jaakko Kara ,&nbsp;Jukka Manninen ,&nbsp;Pietari Skyttä ,&nbsp;Markku Väisänen ,&nbsp;Hugh O’Brien ,&nbsp;Kathryn Cutts ,&nbsp;Paavo Nikkola","doi":"10.1016/j.precamres.2025.107828","DOIUrl":"10.1016/j.precamres.2025.107828","url":null,"abstract":"<div><div>We have studied two gold deposits, Välimäki and Kultakallio, located in SW Finland, to understand the interplay between gold precipitation, fluid activity and structural evolution within the Paleoproterozoic Svecofennian orogen. The Välimäki deposit is hosted by paragneisses characterised by pervasive silicification and the occurrence of foliation parallel quartz veins. The Kultakallio garnet-bearing gabbro shows two generations of quartz veins associated with arsenopyrite and graphite. Zircons from the leucosome within Välimäki yield an age of 1887 ± 4 Ma interpreted as the first metamorphic event (M1) associated with partial melting. In contrast, monazites of the same sample give bimodal ages at 1817 ± 7 Ma and 1794 ± 5 Ma both reflecting hydrothermal activity. <em>In-situ</em> zircon dating in Kultakallio yielded three age peaks at 1885 ± 4 Ma, 1859 ± 5 Ma and 1805 ± 7 Ma interpreted to represent magmatism, a secondary metamorphic event (M2) and hydrothermal activity, respectively. <em>In-situ</em> dating of Kultakallio titanites gives an age of 1786 ± 58 Ma and garnet an age of 1809 ± 470 Ma, which reflect the timing of the fluid activity. Based on hydrothermal ages, gold mineralising events at (I) 1815–1805 Ma and (II) 1795–1785 Ma are recognised in the study area. Stage I is related to the injection of foliation-parallel quartz veins and precipitation of arsenopyrite in which gold occurs as inclusions. Stage II is characterised by precipitation of gold associated with Te- and Bi-minerals, abundant graphite, remobilisation of pyrite and breakdown of arsenopyrite within the brittle-ductile transition zone. The NW-SE −oriented transpressional setting formed the NE-SW −oriented gold critical structures originally at 1.89–1.88 Ga (D2), which were later reactivated in the 1.83–1.78 Ga WNW-ESE transpressional setting (D3). The NW-SE trending crustal scale shear zones are suggested to act as first order structures whereas the NE-SW oriented strike-slip structures form the second order setting. In the target scale, foliation parallel and intersecting quartz veins and narrow shear zones represent the third order structures hosting the mineralisations. We suggest the driver for the fluid activity at ca. 1.80 Ga is lower crustal delamination during crustal extension in a tectonic switching cycle.</div></div>","PeriodicalId":49674,"journal":{"name":"Precambrian Research","volume":"425 ","pages":"Article 107828"},"PeriodicalIF":3.2,"publicationDate":"2025-05-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144139197","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":"One-billion-year-old eukaryotic algal fossil Arctacellularia from North China and its implications for the evolution of pre-Cryogenian filamentous multicellularity","authors":"Rui Huang ,&nbsp;Guangjin Li ,&nbsp;Jiayue Wang ,&nbsp;Qing Tang ,&nbsp;Mingyang Qiu ,&nbsp;Qian Chen ,&nbsp;Hanzhi Qu ,&nbsp;Chengxi Wu ,&nbsp;Wenfei Cui ,&nbsp;Xianqin Yan ,&nbsp;Chuanming Zhou ,&nbsp;Xunlai Yuan ,&nbsp;Ke Pang","doi":"10.1016/j.precamres.2025.107823","DOIUrl":"10.1016/j.precamres.2025.107823","url":null,"abstract":"<div><div>Pre-Cryogenian organic-walled microfossils with delicate cellular preservation can provide pivotal information for the origin and early evolution of multicellular eukaryotes. With previously reported evidence for true dichotomous branching and photosynthesis, the filamentous fossil <em>Arctacellularia</em> is among one of the few examples of pre-Cryogenian unambiguous multicellular algae. However, the taxonomic diversity of this genus has remained controversial for decades, and its evolutionary implications for understanding the emergence and maintenance of filamentous multicellularity and branching in eukaryotes have been underexplored. Here, we report well-preserved <em>Arctacellularia</em> fossils extracted from the drill core samples of the early Tonian Liulaobei Formation (∼0.95–0.92 Ga), Huainan region, northern Anhui Province, North China. Two species have been recognized in the Liulaobei Formation, including the type species <em>Arctacellularia tetragonala</em>, with one trichome showing evidence of a possible nodal cell indicative of branching, and <em>Arctacellularia ellipsoidea</em>, distinguished by the presence/absence of barrel-like to long cylindrical cells (with a length/width ratio ≥ 1.5). <em>Arctacellularia</em> is reconstructed as a uniserial multicellular filamentous organism enveloped by common membrane in this study; it consists of three types of possibly differentiated cells that are characterized by terminal folds (or terminal extensions), and can occasionally bifurcate once via a nodal cell. This study suggests that the maintenance of filamentous multicellularity of <em>Arctacellularia</em> is achieved by a combination of common membrane, terminal folds, and siphonous construction. Furthermore, the dichotomous branching of <em>Arctacellularia</em> appears morphologically more primitive than those observed in other Pre-Cryogenian fossils, including <em>Cheilofilum</em>, <em>Jacutianema</em>, and <em>Proterocladus</em>. Given that <em>Arctacellularia</em> has been phylogenetically placed in the total group of Archaeplastida and the oldest <em>Arctacellularia</em> specimens date back to ∼1.7–1.4 Ga, if the early Mesoproterozoic material is confirmed to be biologically congeneric with the early Tonian counterpart, it suggests that Archaeplastida may have acquired multicellularity, siphonous construction, cellular differentiation, and possibly branching at least 1.4 billion years ago.</div></div>","PeriodicalId":49674,"journal":{"name":"Precambrian Research","volume":"425 ","pages":"Article 107823"},"PeriodicalIF":3.2,"publicationDate":"2025-05-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144139198","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":"Insights for intraplate extensional settings revealed from geochemistry of metamorphosed magmatic rocks of the central Gondwana supercontinent","authors":"Sanjeewa P.K. Malaviarachchi ,&nbsp;Lei Zhao ,&nbsp;Jinghui Guo ,&nbsp;Xianhua Li ,&nbsp;Mingguo Zhai ,&nbsp;Prasanna L. Dharmapriya","doi":"10.1016/j.precamres.2025.107801","DOIUrl":"10.1016/j.precamres.2025.107801","url":null,"abstract":"<div><div>The extensional episodes related to the shaping of the Gondwanan margins with the collapse of the Cambrian Orogens have not been deeply investigated despite extensive studies on compressional tectonics. The rift-setting considered here in Sri Lanka at the boundary zone of eastern parts of Kadugannawa and Highland Complexes (KC and HC, respectively) may correspond to the central Gondwanan segments in the vicinity of India, Antarctica, and Madagascar. Hence this study offers a pathway to geochemical characterization of intra-continental extensional margins adding a new value for global tectono-geochemical knowledge. Analysed <em>meta</em>-mafic rocks of the KC display smooth Chondrite normalized rare earth element (REE) patterns with most of them having distinct heavy REE (HREE) depletions, with (La/Yb)_N ratios in the range of 2–20, and slightly negative to positive Eu anomaly. The majority of felsic-rocks also show HREE depletion with high light REE (LREE) enrichment accompanying variably-positive to slightly-negative Eu anomalies. In contrast, <em>meta</em>-mafic rocks of the HC mostly show flat middle REE (MREE) to HREE patterns with variably-enriched LREE with the majority showing discrete-negative or no Eu anomalies. All the <em>meta</em>-mafic rocks show that their protoliths were derived from enriched mantle/OIB sources. Characteristically, none of the <em>meta</em>-felsic rocks studied exhibits arc magmatic signatures, while all of them were consistent with the origin of A2-type anorogenic characteristics. Hence, the overall geochemistry of the protolith melts of both <em>meta</em>-mafic and <em>meta</em>-felsic rocks studied here mostly suggests their genesis at an intra-plate extensional setting, contrary to arc-tectonic settting observed in predominant previous studies. Our U-Pb age data correspond to magmatic pulses from ca. 2250 to ca. 550 Ma (ca. 2250–1750 Ma, 1050–850 Ma, 700–627 Ma, and 550–575 Ma) followed by a significant interaction with crustal components at ∼580––530 Ma which is consistent with the escalation of the Th/U and Ce/Ce* values in Zircon. The predominant age peaks match well with both collisional and rifting events associated with the dispersal and amalgamation of global supercratons (e.g. Superia), supercontinents (e.g. Columbia, Rodinia, and Gondwana) and regional micro-continents (e.g. Azania), spanning from early to late global geodynamic history from ca. 2250 to ca. 500 Ma. Hence, this study provides new insights into intra-continental rifting/extensional tectonic settings hitherto-unknown from the inner-central Gondwana.</div></div>","PeriodicalId":49674,"journal":{"name":"Precambrian Research","volume":"425 ","pages":"Article 107801"},"PeriodicalIF":3.2,"publicationDate":"2025-05-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144116939","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":"Silicified floating microbial mats from the Mesoproterozoic Wumishan Formation, North China: preservation and ecological significance","authors":"Chuxue Zhao ,&nbsp;Min Shi ,&nbsp;Yong Lei ,&nbsp;Qinglai Feng","doi":"10.1016/j.precamres.2025.107816","DOIUrl":"10.1016/j.precamres.2025.107816","url":null,"abstract":"<div><div>This study focused on microbial mats and associated structures from the early Mesoproterozoic Wumishan Formation in North China. Through detailed paleoecological analysis, we identified a unique layered void structure preserved by rapid silicification, sandwiched between two horizontally layered remains of microbial mat: a benthic mat below and a floating mat above. Within the three-dimensional preserved “mat-layered void-mat” structures, multiple lines of evidence indicate that the void was an aquatic environment before diagenesis: for example, organic aggregates and vertically aligned beaded structures “suspended” within the layered void may represent remnants of microbial colonies suspended in the water. In the microbial mat above the layered void, downward-protruding spherical caps exhibit stable morphology, a consistent V_cap/V ratio, and upper surfaces aligned along a common horizontal line. These features suggest that the caps likely result from balanced forces, possibly influenced by buoyancy.</div><div>This research provides a rare glimpse into ancient microbial habitats, revealing the existence of free-floating cyanobacteria during the early Mesoproterozoic and suggesting their ancestors’ exploration of ecological niches, thereby enhancing our understanding of Mesoproterozoic microbial ecosystem evolution.</div></div>","PeriodicalId":49674,"journal":{"name":"Precambrian Research","volume":"425 ","pages":"Article 107816"},"PeriodicalIF":3.2,"publicationDate":"2025-05-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144116940","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":"Discrete Paleoproterozoic and Cretaceous mineralization events at the Liyuan gold deposit, central North China Craton","authors":"Ying Ma,&nbsp;Shao-Yong Jiang","doi":"10.1016/j.precamres.2025.107812","DOIUrl":"10.1016/j.precamres.2025.107812","url":null,"abstract":"<div><div>Accurate dating of Precambrian gold deposits is challenging due to the lack of suitable mineral chronometers. The North China Craton (NCC) is recognized as one of the world’s largest gold-producing regions; however, Precambrian-aged gold deposits within the NCC are relatively rare. This study aims to determine the formation age and evolutionary history of the Liyuan gold deposit (5 t Au), which is situated within high-grade metamorphic rocks of the Trans-North China Orogen. We employed U-Pb dating of hydrothermal apatite and rutile, as well as trace element analysis of texturally distinct pyrite. Two distinct stages of gold mineralization were identified. Stage I is characterized by the presence of disseminated pyrite that predominantly associated with lattice-bound gold. In contrast, stage II is marked by quartz-sulfide vein-style mineralization with visible gold and gold microinclusions within pyrite. Pyrite from Stage I (Py1) exhibits elevated As concentrations, whereas pyrite from stage II (Py2 and Py3) is distinguished by high levels of Te and Pb. Hydrothermal apatite intergrown with auriferous Py1 yielded U-Pb ages of 1895 ± 19 Ma and 1836 ± 28 Ma, which correspond to the deformation and metamorphism of the Trans-North China Orogen. The presence of positive Eu anomalies in the hydrothermal apatite suggests that it crystallized from a relatively oxidized fluid. The mechanism for the formation of hydrothermal rutile associated with the vein mineralization of stage II, is attributed to the alteration of biotite. Hydrothermal rutile was dated to 128.0 ± 6.4 Ma, which aligns with the Early Cretaceous granitic magmatism in the region. The Liyuan gold deposit was formed as a result of two distinct hydrothermal events occurring during the Paleoproterozoic and Early Cretaceous periods, respectively. This conclusion is supported by comprehensive field, textural, mineralogical, and geochronological analyses. The recently identified Paleoproterozoic orogenic gold mineralization event, which coincided with orogenic deformation and regional metamorphism during the collision between the Western and Eastern Blocks, presents new prospects for gold exploration in the well-endowed NCC. Furthermore, our study highlights the potential of apatite U-Pb dating as a reliable geochronological tool for investigating Precambrian gold deposits in other regions.</div></div>","PeriodicalId":49674,"journal":{"name":"Precambrian Research","volume":"424 ","pages":"Article 107812"},"PeriodicalIF":3.2,"publicationDate":"2025-05-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144090204","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 implication of the Neoproterozoic Shuimo alkaline-carbonatite complex from Northwestern margin of the Yangtze Block (China)","authors":"Bin Lin ,&nbsp;Lian-Xun Wang ,&nbsp;Yu-Fang Zhong ,&nbsp;Xiao-Bing Qi ,&nbsp;Xue-Wei Fu ,&nbsp;Chang-Qian Ma","doi":"10.1016/j.precamres.2025.107813","DOIUrl":"10.1016/j.precamres.2025.107813","url":null,"abstract":"<div><div>To investigate the petrogenesis of the alkaline-carbonatite complex and the Neoproterozoic tectonic evolution for the northwestern margin of the Yangtze Block, we conducted a combined study of petrology, LA-ICP-MS zircon U-Pb geochronology, mineral chemistry, whole-rock geochemistry and Sr-Nd-C-O isotopes on the Shuimo alkaline-carbonatite complex in the area. The complex consists of ultrabasic alkaline rocks (jacupirangite and ijolite), syenites (aegirine-augite syenite and biotite syenite), and igneous carbonatites. Zircon U-Pb weighted mean age of the ijolite is 855 ± 4 Ma, consistent with previous studies that report ages of 860 ± 5 and 869 ± 4 Ma for syenites, indicating that the Shuimo alkaline magmatic activity occurred at approximately 860 Ma. The Shuimo alkaline rocks show relative enrichment in light rare earth elements (LREEs) and large ion lithophile elements (LILEs) while being depleted in high field strength elements (HFSEs). The alkaline rocks and carbonatites have similar Sr-Nd isotopes (I_Sr = 0.7045–0.7056 and εNd(t) = 0.28–4.97, I_Sr = 0.7042–0.7044 and εNd(t) = 1.07–2.55, respectively), indicating a common enriched lithospheric mantle source. Geochemical characteristics of minerals and whole rocks suggest that the Shuimo alkaline rocks originated from a nephelinitic alkaline magma formed by low-degree partial melting of garnet-bearing spinel lherzolite in the lithospheric mantle. The primary magma underwent fractionation of clinopyroxene during its early stage, resulting in gradual formation of jacupirangite and ijolite. In contrast, syenite formation involves crustal assimilation and fractional crystallization of the parent magma. Carbonatites are genetically associated with ultrabasic alkaline rocks and underwent fractional crystallization and liquid immiscibility during their formation. Tectonically, the Shuimo alkaline-carbonatite complex was formed in a continental back-arc extensional setting, where the mantle was metasomatized by slab-derived fluids, leading to carbonation and triggering partial melting. The results support the plate-subduction model for the northwestern margin of the Yangtze Block during the Neoproterozoic period and suggest that early back-arc extension occurred during the subduction. We propose a model for the formation of alkaline-carbonatite complexes in subduction-related extensional settings, which involves enriched mantle metasomatized by slab-derived fluids, fractional crystallization and crustal contamination of alkaline rocks, immiscible separation of carbonatites from evolved silica-undersaturated alkaline rocks, and late-stage fluid metasomatism that modifies the carbonatites.</div></div>","PeriodicalId":49674,"journal":{"name":"Precambrian Research","volume":"424 ","pages":"Article 107813"},"PeriodicalIF":3.2,"publicationDate":"2025-05-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144071307","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 U-Pb geochronology of Ediacaran siliciclastic carbonate rocks in eastern South China: Insights into the Precambrian assembly of the Yangtze and Cathaysia blocks","authors":"Fengqi Zhang ,&nbsp;Jinjun Zhou ,&nbsp;Yildirim Dilek ,&nbsp;Kongyang Zhu ,&nbsp;Hongxiang Wu ,&nbsp;Dahai Sun ,&nbsp;Hongdan Deng ,&nbsp;Yunhao Sun ,&nbsp;Hanlin Chen ,&nbsp;Shufeng Yang","doi":"10.1016/j.precamres.2025.107814","DOIUrl":"10.1016/j.precamres.2025.107814","url":null,"abstract":"<div><div>The Cathaysia block, a composite terrane comprising West and East Cathaysia along the East Asian continental margin, forms a critical constituent of the South China block. Despite its tectonic significance, the timing of the Cathaysia–Yangtze amalgamation remains contentious, with proposed ages spanning from the Precambrian to the Mesozoic. We present integrated sedimentological and geochronological constraints derived from Ediacaran carbonate sequences in the Yuhang section of the southeastern Yangtze craton. Systematic analyses that combine sedimentary petrology with detrital zircon U-Pb-Hf isotopes reveal the following: 1) clastic components (30–45 % by volume) dominated by quartz exhibit a mixed siliciclastic carbonate rocks; 2) detrital zircon populations yield predominant Paleoproterozoic ages (2.0–1.75 Ga), showing remarkable similarities to the Precambrian basement of East Cathaysia, particularly through a characteristic age peak of 1.83–1.81 Ga; 3) Hf isotopic compositions demonstrate crustal residence ages that are indistinguishable from those of East Cathaysia sources. These convergent lines of evidence establish East Cathaysia as the primary sediment source for the southeastern Yangtze Ediacaran deposits. Consequently, we propose that the final amalgamation of the composite Cathaysia block with the Yangtze craton occurred during Precambrian crustal stabilization, fundamentally revising previous models that advocated for Phanerozoic accretion.</div></div>","PeriodicalId":49674,"journal":{"name":"Precambrian Research","volume":"424 ","pages":"Article 107814"},"PeriodicalIF":3.2,"publicationDate":"2025-05-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144068365","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":"Evolution and innovation of the metazoan burrowing behaviour from Ediacaran-Cambrian transition, eastern Yunnan","authors":"Da Li ,&nbsp;Man Li ,&nbsp;Yongan Qi ,&nbsp;Guochun Zhao ,&nbsp;Jian Fu ,&nbsp;Fuqiang Guo ,&nbsp;Chengjun Zhang ,&nbsp;Jianyu Guan ,&nbsp;Shishan Zhang","doi":"10.1016/j.precamres.2025.107796","DOIUrl":"10.1016/j.precamres.2025.107796","url":null,"abstract":"<div><div>The Precambrian–Cambrian transition represents a pivotal interval in Earth’s evolutionary history, marked by the demise of Ediacaran biota and the subsequent radiation of bilaterian organisms during the Cambrian Explosion. This study presents an integrated ichnological and sedimentological analysis of trace fossils across the Precambrian–Cambrian boundary interval in eastern Yunnan, South China, with the aim of reconstructing paleoecological dynamics and behavioral evolution during this critical transitional phase.Ichnotaxonomic diversity, architectural complexity, and tiering structure reveal a progressive intensification of metazoan–substrate interactions through the late Ediacaran. Trace fossils from this interval are predominantly horizontal and exhibit morphologies consistent with undermat-mining behaviors, indicating that benthic organisms were largely restricted to the mat-substrate interface. However, rare but distinct vertical burrows suggest the incipient development of exploratory and infaunal lifestyles.With the onset of the Cambrian, there is a notable increase in ichnodiversity, behavioral complexity, and substrate utilization, reflecting enhanced metazoan motility and ecological specialization. This period coincides with a shift from microbial-mat-dominated substrates to mixed-layer systems, driven by increasing bioturbation intensity. By Cambrian Stage 2, widespread bioturbation led to the progressive disruption of microbial mats and facilitated more extensive exploitation of three-dimensional ecological space.Benthic communities expanded their spatial occupation from surficial and semi-infaunal tiers into deeper substrate horizons, promoting greater ecological stratification and trophic complexity. These paleoecological transformations culminated in the replacement of Neoproterozoic-style matgrounds by Phanerozoic-type mix-grounds, representing a fundamental reorganization of marine ecosystems and a major milestone in the early ecosystem evolution of benthic communities.</div></div>","PeriodicalId":49674,"journal":{"name":"Precambrian Research","volume":"423 ","pages":"Article 107796"},"PeriodicalIF":3.2,"publicationDate":"2025-05-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143948584","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}