Precambrian Research最新文献

{"title":"Orogenic unroofing of the Taltson and Thelon orogens depicted through detrital zircon geochronology of the Sosan Group, Great Slave Lake Supergroup (Northwest Territories, Canada)","authors":"Jade Lockie ,&nbsp;Alessandro Ielpi ,&nbsp;Rebecca Canam ,&nbsp;Morgann G. Perrot ,&nbsp;Joshua H.F.L. Davies ,&nbsp;Luke Ootes","doi":"10.1016/j.precamres.2025.107706","DOIUrl":"10.1016/j.precamres.2025.107706","url":null,"abstract":"<div><div>The investigation of sedimentary successions broadly contemporaneous with supercontinent amalgamation is critical to understand sediment dispersal in response to collisional tectonics. The Paleoproterozoic Great Slave Supergroup of the East Arm basin is one of three sedimentary successions located along the margins of the Archean Slave craton. U-Pb detrital zircon geochronology with chemical-abrasion laser-ablation inductively-coupled plasma mass spectrometry is employed here to investigate the onset of sedimentation, provenance, and regional correlations of the Sosan Group (the Great Slave Supergroup’s basal succession). Although a detrital age signature of the Slave craton is found in the &lt; 1.97–1.95 Ga Hornby Channel Formation (lowermost Sosan Group) – the dominant component through the strata has a distinct ∼ 2.0–1.97 Ga detrital age population, suggesting that the Sosan Group sediments were derived from the collapsing Thelon-Taltson orogenic topography. Data presented herein support novel correlations in the region, specifically between the East Arm basin and the nearby Kilohigok basin, Coronation margin and Hottah terrane. By these means, this study highlights the importance of stratigraphically complete geochronological analyses to propose regional correlations.</div></div>","PeriodicalId":49674,"journal":{"name":"Precambrian Research","volume":"419 ","pages":"Article 107706"},"PeriodicalIF":3.2,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143096739","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":"Isotopic constraints on the architecture and early (ca. 2.4–2.3 Ga) Paleoproterozoic evolution of the northwestern Rae craton, Canada","authors":"R.G. Berman,&nbsp;W.J. Davis,&nbsp;M. Sanborn-Barrie","doi":"10.1016/j.precamres.2024.107617","DOIUrl":"10.1016/j.precamres.2024.107617","url":null,"abstract":"<div><div>Queen Maud block (QMb) is re-defined as an area of dominantly Mesoarchean crust forming the northwestern part of the Rae craton. Four U-Pb zircon age determinations (ca. 3.3–2.97 Ga) extend QMb ∼40 km farther west than previously known to a major tectonic boundary marked by a &gt;450 km-long belt of ca. 1.9 Ga peraluminous leucogranite in the Thelon tectonic zone. Crust older than 3.3 Ga is indicated by inherited zircon up to 3.95 Ga in one sample. The absence within QMb of 2.6 Ga plutonic rocks, a dominant component of the central Rae craton, suggests distinct Neoarchean tectonic histories and separation of these crustal blocks prior to accretion of ca. 2.56–2.51 Ga Boothia terrane, stitching by ca. 2.5 Ga Queen Maud granitoids and a shared post-2.5 Ga history.</div><div>Tonalite dated at 2.41 Ga in QMb and monzogranite dated at 2.34 Ga in the adjacent Thelon tectonic zone have geochemical characteristics of convergent plate margin magmatism (arc ± slab-failure). Similarity in the Nd isotopic compositions of 2.34 Ga Thelon monzogranite and ca. 2.3 Ga plutonic rocks in Buffalo Head terrane, as well as 2.07 Ga and 2.0 Ga plutonic rocks in both regions point to a similar Neoarchean basement component. This basement terrane is proposed to have collided with the Rae at ca. 2.41 Ga and driven ca. 2.4–2.3 Ga tectonometamorphism during the Arrowsmith Orogeny.</div><div>The western Rae represented a convergent margin at 2.41–2.3 Ga and potentially 2.6–2.5 Ga, the latter broadly synchronous with the MacQuoid orogeny on the southeastern Rae margin. Throughout this time period, the central Rae craton was in an upper-plate position. Sustained mantle downwelling driving plate convergence towards the central Rae craton, as previously recognized at 2.0–1.9 Ga, was maintained from the Neoarchean through multiple Paleoproterozic orogenies (Arrowsmith, Taltson-Thelon and Hudsonian), establishing the Rae craton as the nucleus of proto-Laurentia within the Nuna supercontinent.</div></div>","PeriodicalId":49674,"journal":{"name":"Precambrian Research","volume":"417 ","pages":"Article 107617"},"PeriodicalIF":3.2,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143137503","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":"Depositional sequence and detrital zircon age spectra from Ediacaran to Early Cambrian at the northwestern Yangtze craton: Implication for the basin dynamics","authors":"Qiyu Wang ,&nbsp;Zhengjiang Wang ,&nbsp;Jiahong Liu ,&nbsp;Qi Deng ,&nbsp;Hao Liu ,&nbsp;Zhiwu Li ,&nbsp;Gang Zhou ,&nbsp;Shuangjian Li ,&nbsp;Guoqing Xiong ,&nbsp;Yu Xia ,&nbsp;Long Ma","doi":"10.1016/j.precamres.2024.107667","DOIUrl":"10.1016/j.precamres.2024.107667","url":null,"abstract":"<div><div>The northwestern (NW) Yangtze craton during the Ediacaran–Cambrian period has been considered a passive continental margin; however, there remains contention regarding the timing and mechanisms of the initiation and evolution of the Mianyang–Changning cratonic rift (MCCR) within the NW Yangtze craton. In this study, we present the depositional sequences and detrital zircon geochronology from seven representative sections of the Ediacaran and Early Cambrian strata in the NW Yangtze craton to determine the onset time and evolution processes of this cratonic rift, along with its tectonic and sedimentary responses. Results indicate that multiple tectonic–sedimentary transitions occurred during the Ediacaran–Cambrian, accompanied by fluctuations in sea level and episodic uplift and erosion of carbonate platforms. Furthermore, the provenance of detrital zircon from the Ediacaran and lower Cambrian reveals substantial regional diversity in the Ediacaran, similarity and poly-cyclicity in the Early Cambrian, and temporal variability between the Ediacaran and Early Cambrian. Meanwhile, the summary plot of the detrital zircons from the Ediacaran and Early Cambrian strata indicates that their native basin is characterized neither by an extensional setting nor by a convergent setting, but rather by a collision background. Based on these depositional sequences and detrital zircon age spectra, and combined with previous studies, we conclude that the onset, expansion, filling, and uplift of the MCCR in the NW Yangtze craton during the Ediacaran to Early Cambrian be resulted from peripheral accretionary orogeny associated with the assembly of Gondwana, rather than a continuation of the breakup of Rodinia.</div></div>","PeriodicalId":49674,"journal":{"name":"Precambrian Research","volume":"417 ","pages":"Article 107667"},"PeriodicalIF":3.2,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143137434","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":"Evolving marine sedimentation, redox stratification, and biogeochemical cycling in mid- to low-latitudinal non-frozen waters during late Neoproterozoic global-scale climatic transitions","authors":"Arunava Sen ,&nbsp;Soumik Mukhopadhyay ,&nbsp;Eva E. Stüeken ,&nbsp;Pradip Samanta ,&nbsp;Subir Sarkar ,&nbsp;Soumyadeep Bose ,&nbsp;Shailesh Agarwal ,&nbsp;Anurag Kumar","doi":"10.1016/j.precamres.2024.107661","DOIUrl":"10.1016/j.precamres.2024.107661","url":null,"abstract":"<div><div>Indian Neoproterozoic successions offer unique insights into global paleoclimatic and biogeochemical transitions. This study presents a detailed sedimentological and geochemical analysis of marine siliciclastic sedimentary rocks from the Cave-Temple Arenite Member of the Kerur Formation, the lowermost formation of the Badami Basin within the Dharwar Craton of the South Indian Shield. Geochronological constraints on overlying carbonate rocks from the Konkankoppa Limestone Member of the uppermost Katageri Formation provide a post-Cryogenian to mid-Ediacaran age of 604 ± 25 (1σ) Ma for the upper limit of marine sedimentation. Sedimentological and geochemical proxies, accompanied with previous geochronological and provenance studies, indicate a rift-related intracratonic basin influenced by tectonic processes associated with the Rodinia supercontinent breakup. Provenance studies reveal sediment contributions predominantly from the Archaean to Mesoproterozoic quartzofeldspathic sources. Marine intervals exhibit distinct stratification, with oxic, brackish to mildly saline shallow waters transitioning to anoxic-euxinic, more saline deeper waters. These conditions emerged above a fluvio-alluvial cycle formed during cold, arid climatic conditions. However, CIA (Chemical Index of Alteration) values suggest subsequent warmer, humid climates during the transgression and evolution of the marine interval. This scenario of climate change and marine transgression likely reflects a global climatic shift during one of the two potential hothouse phases, depending on the estimated minimum and maximum depositional ages spanning approximately from 629 to 579 Ma. These ages correspond either to the post-Marinoan or the post-Gaskiers glaciations, both characterized by intense chemical weathering, high nutrient influx, and enhanced productivity along deeper marine shelves. The studied succession, marked by the absence of glacial deposits and a stratified non-frozen marine setting supposedly situated at mid- to low latitudes, offers evidence for a unique paleoenvironment that harboured active biogeochemical cycles amidst evolving climatic conditions.</div></div>","PeriodicalId":49674,"journal":{"name":"Precambrian Research","volume":"417 ","pages":"Article 107661"},"PeriodicalIF":3.2,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143137435","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Crustal maturation of the Yangtze Block during the Meso-Neoarchean","authors":"Zhongshan Shen,&nbsp;Guangyu Huang","doi":"10.1016/j.precamres.2024.107664","DOIUrl":"10.1016/j.precamres.2024.107664","url":null,"abstract":"<div><div>The transition in felsic magmatism from Na-rich TTG suites to K-rich granites during the Mesoarchean to Neoarchean varies from craton to craton, marking the crustal maturation of the ancient continental crust. However, the crustal maturation history of the Yangtze Block is less well constrained due to poor exposure of Archean igneous rocks. In this study, we report a suite of late Mesoarchean mozo-granites from the SW Yangtze Block by providing new whole-rock major and trace element data, along with zircon U-Pb-Hf-O isotopic analyses, to constrain their petrogenesis. Zircon U-Pb dating shows that the studied mozo-granites have a crystallization age of ∼2.8 Ga. Geochemically, they exhibit high heavy rare earth element (HREE) contents and elevated K/Na ratios, typical of potassic granites derived from a shallow crust source. By integrating zircon Hf-O isotopes with thermodynamic modelling, we propose that these potassic granites were products of partial melting of an isotopically juvenile tonalitic crust. Furthermore, Bayesian change-point analysis detected a step increase in K/Na ratios at ∼2.7 Ga, which we interpret as the final stage of crustal maturation for the Yangtze Block. The intracrustal melting of TTG crust during the late Mesoarchean to Neoarchean contributed significantly to stabilization of the Archean continental crust during that period.</div></div>","PeriodicalId":49674,"journal":{"name":"Precambrian Research","volume":"417 ","pages":"Article 107664"},"PeriodicalIF":3.2,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143137510","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":"Distinct mantle sources of two types of Neoproterozoic diabase in the North China Craton: Implications for mantle plume activity and ancient continent reconstruction","authors":"Qi Hou ,&nbsp;Xiao-Ying Gao ,&nbsp;Xiao-Yong Yang ,&nbsp;Jun Tang ,&nbsp;Shao-Bing Zhang ,&nbsp;Zhang-Ping Liu ,&nbsp;Cai-Yu Wan","doi":"10.1016/j.precamres.2024.107662","DOIUrl":"10.1016/j.precamres.2024.107662","url":null,"abstract":"&lt;div&gt;&lt;div&gt;Large igneous provinces (LIPs) are often used as powerful tools for constraining continental reconstructions. The configuration of the North China Craton (NCC) in the Rodinia supercontinent remains a subject of controversy due to limited reliable records of Neoproterozoic magmatism. In this study, two types of Neoproterozoic mafic magmatic rocks, known as the Langan diabase (∼913 Ma), have been identified in the southeastern margin of the NCC: (1) Group Ⅰ that exhibits low La/Yb ratios (3.8–6.4), ∑REE contents (51–74 ppm), ε&lt;sub&gt;Nd&lt;/sub&gt;(t) (-6.9 – -0.3), ε&lt;sub&gt;Hf&lt;/sub&gt;(t) (1.98–6.26) and relatively high &lt;sup&gt;87&lt;/sup&gt;Sr/&lt;sup&gt;86&lt;/sup&gt;Sr&lt;sub&gt;(i)&lt;/sub&gt; (0.705047 to 0.706353), Mg&lt;sup&gt;#&lt;/sup&gt; (58–63) and δ&lt;sup&gt;18&lt;/sup&gt;O values (6.65–7.82‰); (2) Group Ⅱ-1 that has high ∑REE contents (214–222 ppm), ε&lt;sub&gt;Nd&lt;/sub&gt;(t) (2.3–4.1), ε&lt;sub&gt;Hf&lt;/sub&gt;(t) (5.03–10.70), and low &lt;sup&gt;87&lt;/sup&gt;Sr/&lt;sup&gt;86&lt;/sup&gt;Sr&lt;sub&gt;(i)&lt;/sub&gt; (0.704479–0.704829), Mg&lt;sup&gt;#&lt;/sup&gt; (~33), La/Yb ratios (6.1–6.3) and δ&lt;sup&gt;18&lt;/sup&gt;O values (6.36–7.20‰). Meanwhile, Group Ⅱ-2 mafic rocks can be identified in previous studies that differ from the Group Ⅱ-1 samples in having much higher La/Yb ratios (8.0–19.0). The geochemical differences between Group Ⅰ and Group Ⅱ mafic rocks indicate that they might have originated from distinct mantle sources under varying melting conditions and undergone different differentiation and contamination processes. In the shallow magma chamber, Group Ⅰ samples underwent a process of fractionation involving olivine and clinopyroxene, whereas Group Ⅱ samples exhibited fractional crystallization encompassing olivine, clinopyroxene, plagioclase, and rutile. According to REE inversion calculations, the primary magma of Group Ⅰ samples were derived from the high degrees of partial melting (5–20 %) of a spinel-dominant peridotite mantle source, and the Sr-Nd-O-Hf isotope composition indicates that there are approximately 30 % continental lithospheric mantle components in their mantle source. In contrast, the Group Ⅱ-1 diabase’ parental magmas were generated by 5–20 % partial melting of a garnet-bearing pyroxenite mantle source, while the Group Ⅱ-2 samples were derived from low degrees of partial melting (3–10 %) of a garnet-dominant pyroxenite mantle. All Group Ⅱ sample mantle sources contain approximately 20 % lithospheric components.&lt;/div&gt;&lt;div&gt;Combining all Neoproterozoic mafic samples in the São Francisco Craton and the Congo Craton, this research pointed out that these rocks might have resulted from a mantle plume. In detail, at the beginning of mantle plume activity, the primary magma of Group Ⅱ-1 sample was derived from the mixing between the mantle plume margin and a small amount of overlying lithospheric mantle in the spinel-garnet transition zone. Shortly thereafter, in a brief span of time, the subsequent upwelling of high-temperature magma assimilated more lithospheric components in the plume’s axial area, producing the Group Ⅰ samples’ primary magm","PeriodicalId":49674,"journal":{"name":"Precambrian Research","volume":"417 ","pages":"Article 107662"},"PeriodicalIF":3.2,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143137436","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":"Precambrian tectonic evolution of the Songliao–Xilinhot block in the context of a supercontinent cycle: Evidence from Neoarchean granitoid rocks in the Longjiang area, NE China","authors":"Chao Zhang ,&nbsp;Jingyu Quan ,&nbsp;Zhenghong Liu ,&nbsp;Cheng Qian ,&nbsp;Chen Zhao ,&nbsp;XinWei Wu ,&nbsp;Jingsheng Chen ,&nbsp;Yan Wang","doi":"10.1016/j.precamres.2024.107663","DOIUrl":"10.1016/j.precamres.2024.107663","url":null,"abstract":"<div><div>The Songliao–Xilinhot block (SXB) in the eastern part of the Central Asian Orogenic Belt (CAOB) is a Precambrian continental block that provides clues to the evolution of the CAOB. However, its structural relationship with adjoining terranes and cratons, and its role in past supercontinent cycles remain unclear. Here, we describe the whole-rock geochemistry, zircon U–Pb ages, and Sr–Nd–Hf isotopic data of Neoarchean granitoid rocks in the Longjiang area of the SXB, NE China. Zircon U–Pb dating indicates that tonalite–trondhjemite–granodiorites (TTGs) and monzogranites were formed at 2.56–2.55 and 2.55–2.51 Ga, respectively. The TTGs have low MgO, Y, and Yb, and high Sr contents. Their Sr/Y and (La/Yb)_N ratios and Yb_N values vary widely, with <em>ε</em>Hf(<em>t</em>) values of –2.8 to + 3.1 and a <em>ε</em>Nd(<em>t</em>) value of + 2.4. Thus, the TTGs are medium- and low-pressure types, possibly formed by partial melting of middle Archean basic lower crust. The monzonitic granites have high K₂O contents, high K₂O/Na₂O, Sr/Y, and (La/Yb)_N ratios, low MgO contents and Mg^# values, and variable <em>ε</em>_Hf(<em>t</em>) and <em>ε</em>_Nd(<em>t</em>) values (–3.1 to + 6.3 and –0.9 to + 2.8). The geochemical characteristics and Hf–Nd isotopic compositions of then monzogranites indicate that their parental magmas were formed by partial melting of thickened lower crust derived from heterogeneous sources. Thickening of the lower crust during the late Neoarchean may have promoted the formation of the TTGs and monzogranites. U–Pb and Lu–Hf isotopic data for magmatic zircons from Precambrian intrusive rocks, and detrital zircons from Meso-Neoproterozoic metasedimentary rocks in the SXB were studied to elucidate the origin of the Precambrian SXB. Results indicate a close affinity of the SXB with Laurentia in the Precambrican, while geological evidence and the presence of 1.4 Ga A-type granite in the SXB preclude most cratons as being the source of the Precambrian SXB. Precambrian magmatic events, sedimentary sequences, and significant changes in zircon Hf isotopic compositions within the Precambrian SXB indicate that the block responded to the assembly of the Nuna supercontinents. It underwent a change in tectonic environment from long-term subduction and extension to short-term collision during the breakup of Nuna and subsequent amalgamation with Rodinia.</div></div>","PeriodicalId":49674,"journal":{"name":"Precambrian Research","volume":"417 ","pages":"Article 107663"},"PeriodicalIF":3.2,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143137505","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":"Environmental drivers of biotic turnover: Insight from tectono-sedimentary environment transition during the terminal Ediacaran to Early Cambrian","authors":"Li Deng ,&nbsp;Quanren Yan ,&nbsp;Jun Yang ,&nbsp;Shanlin Gao ,&nbsp;Quanlin Hou ,&nbsp;Haiquan Tang ,&nbsp;Bo Song ,&nbsp;Min Deng","doi":"10.1016/j.precamres.2024.107666","DOIUrl":"10.1016/j.precamres.2024.107666","url":null,"abstract":"<div><div>Biotic turnover and innovation during the terminal Ediacaran to Early Cambrian have been widely linked to tectonic, sedimentary, climatic, and oceanic environmental changes due to their temporal coincidence. However, the precise interconnections between these environmental factors and biological co-evolution remain uncertain. The Yangtze Block preserves essential records to investigate this issue. In this study, we use lithostratigraphic logs and correlations of the terminal Ediacaran to Early Cambrian successions across the upper Yangtze Block to suggest that, the significant lithological change from dolomite to siliciclastic-dominated sedimentation indicates the tectono-sedimentary environment transition from a shallow-water carbonate platform to a deep-water siliciclastic basin. Extensional tectonic activities, enhanced continental weathering, and rising sea levels led to rapid subsidence and extensive siliciclastic sediment accumulation during the Early Cambrian, facilitating this transformation. This sedimentary environment transition also correlates with marine transgression on a global scale. Further, qualitative comparisons of detrital zircon age spectra from this period place the Yangtze Block near northern India, confirming its paleogeographic and material connections with Gondwana. By integrating these findings and geological data on tectonism, sedimentation, marine environment, and biological evolution, this paper constructs a synthetic framework to propose that enhanced continental weathering and marine transgression during the assembly of Gondwana initially triggered changes in lithofacies and seawater conditions, potentially driving early bio-evolution. Our research highlights the interactions among multiple environmental factors during this critical geological period, which contributes to understanding the trigger of the Cambrian explosion.</div></div>","PeriodicalId":49674,"journal":{"name":"Precambrian Research","volume":"417 ","pages":"Article 107666"},"PeriodicalIF":3.2,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143137508","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Neoproterozoic paleogeography and displacement of the Mongolian blocks constrained by detrital zircon ages and Hf isotopic systematics (Zavkhan Block, W Mongolia)","authors":"Igor Soejono ,&nbsp;Stephen Collett ,&nbsp;Karel Schulmann ,&nbsp;Pavla Štípská ,&nbsp;Jitka Míková ,&nbsp;Vít Peřestý ,&nbsp;Nikol Novotná ,&nbsp;Alexandra Guy","doi":"10.1016/j.precamres.2024.107657","DOIUrl":"10.1016/j.precamres.2024.107657","url":null,"abstract":"<div><div>This study presents results of provenance analysis based on U–Pb ages and Hf isotopic composition of detrital zircons from (meta-)sedimentary rocks of two sections of the Zavkhan Block in W Mongolia. Detrital zircon age populations for most of the studied samples show a dominant Tonian–Cryogenian peak (c. 750 Ma), considered as detritus derived from the local rift-related magmatic sources. Some samples also have significant Neoarchean–Paleoproterozoic (c. 2.7–1.7 Ga) zircons sourced from cratonic basement. The large range of ε_Hf(t) values (–30 to +15) of the Tonian–Cryogenian zircons indicates significant mixing of mantle-derived magmas with mature crustal material, interpreted as a result of crustal melting during rifting. The Hf isotopic composition of the older zircons suggests contributions from both juvenile magmas and crustal recycling. Maximum depositional ages indicate that although dominantly Tonian–Cryogenian, the studied sequences also include subordinate older (pre-rift) stratigraphic members. The zircon age and Hf isotopic systematics of the younger part of studied rocks are interpreted to reflect sedimentation in Tonian–Cryogenian post-rift sequences evolving towards continental passive margin during the break-up of Rodinia. On the other hand, the pre-Tonian detritus from post-rift strata were dominantly recycled directly from the older pre-rift strata or indirectly from the Tonian anatectic magmatic rocks. These data are correlated with corresponding datasets from potential cratonic sources, which indicate close similarity and possible paleogeographic connection of the Zavkhan Block to the western Siberian Craton. Thus, it is proposed that the Zavkhan Block together with other Mongolian continental fragments were rifted from western Siberia in the Tonian–Cryogenian. The whole archipelago was subsequently dextrally translated along the Siberian margin into its Ediacaran–early Paleozoic position south of the Siberia Craton.</div></div>","PeriodicalId":49674,"journal":{"name":"Precambrian Research","volume":"417 ","pages":"Article 107657"},"PeriodicalIF":3.2,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143137504","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":"Photosynthetic fractionation of carbon: A biological driver for the Neoproterozoic Shuram carbon isotope excursion","authors":"Euan N. Furness ,&nbsp;Emily G. Mitchell","doi":"10.1016/j.precamres.2025.107702","DOIUrl":"10.1016/j.precamres.2025.107702","url":null,"abstract":"<div><div>The Neoproterozoic Shuram excursion (574 to 567 Ma) is the single largest carbon isotope excursion in the past two billion years, yet its cause is still unclear. Previous suggestions have been contentious: suggestions of a diagenetic origin for the excursion cannot explain coeval shifts in organic carbon isotopes, but suggestions that the excursion represents a dramatic perturbation to the carbon cycle have faced criticism on the basis of the considerable flux of oxidants required to drive the observed change. Here, we present a third potential contributing factor: a change in the carbon isotope fractionation of photosynthesis. We investigate the explanatory power of this mechanism using a carbon box model, with comparison to empirical isotopic measurements from the Doushantuo Formation in China and the Shuram and Buah formations in Oman. Our results suggest that a ∼20 ‰ decrease in photosynthetic carbon isotope fractionation over the course of the Shuram excursion is sufficient to drive observed changes in both carbonate and organic carbon isotope ratios. Our modelling shows that this driver frequently outperforms other potential drivers of the Shuram excursion in terms of fit of model results to empirical data. Therefore, we suggest that a change in carbon isotope fractionation may have contributed to the Shuram excursion. However, this mechanism does not explain other contemporaneous phenomena, such as apparent changes in marine sulphur chemistry. Consequently, we suggest that a change in fractionation is unlikely to have been a sole driver of the excursion. A change in fractionation could have arisen either due to changes in the abiotic environment, which could have influenced producer physiology or partitioned carbonate and organic carbon formation, or as a consequence of the evolution of the first macroscopic animal communities in the Ediacaran, which could have modified plankton communities through feeding pressure, impacting the abiotic environment on a global scale.</div></div>","PeriodicalId":49674,"journal":{"name":"Precambrian Research","volume":"419 ","pages":"Article 107702"},"PeriodicalIF":3.2,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143140511","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}