Precambrian Research最新文献

{"title":"Geochemical and geochronological evidence of a Neoproterozoic island-arc on the easternmost Sierras Pampeanas. New U-Pb LA-ICP-MS data from amphibolites and metacarbonate depositional sequences","authors":"Lisandro Gastón Rodríguez ,&nbsp;Mónica Patricia Escayola ,&nbsp;Gabriel Marcelo Martín ,&nbsp;Miguel Angelo Stipp Basei ,&nbsp;Víctor Alberto Ramos","doi":"10.1016/j.precamres.2024.107444","DOIUrl":"10.1016/j.precamres.2024.107444","url":null,"abstract":"<div><p>The first basement outcrops west of the Río de La Plata craton are metabasaltic and metasedimentary units of the Sierra Chica belt, part of the Eastern Sierras Pampeanas. These are orthoamphibolites and subordinate garnet-biotite gneisses and metacarbonate sequences that are intruded by Cambrian calc-alkaline and peraluminous rocks of the Pampean Orogeny. In accordance with one of the leading tectonic models for the region, new provenance data from this research suggest that the metabasaltic-metasedimentary association represents the proximal deposits of a Late Neoproterozoic island-arc. This contribution brings new geochemical and geochronological evidence from orthoamphibolites located on different sites along the Sierra Chica belt, which are interbedded with metacarbonate and gneisses outcrops, showing tholeiitic compositions, island-arc related tectonic settings, and Cryogenian to Ediacaran crystallization ages. Moreover, silicate-rich metacarbonates interbedded within the same sequences yielded a maximum depositional age of 569 Ma, reinforcing the assumed age for the sequence. All things considered, these rocks are interpreted as old basic lava flows and gabbro dikes linked to an island-arc activity, interspersed within the carbonatic and siliciclastic shelf sediments, together constituting the Neoproterozoic Córdoba Arc from the Sierra Chica belt. A depositional analogy with the present-day Caribbean island-arcs deposits suggests that these sequences could have been part of Oceanic Arc Depositional Systems (OADS) during the diachronous closure of the Goiás ocean and the final assembly of West Gondwana. Overlapping thermo-tectonic processes associated with the Pampean Orogeny are ubiquitous throughout all the studied outcrops, as evidenced by the petrography, the zircon morphology, and the U-Pb results, indicating a complex scenario towards a Late Cambrian slab break-off event.</p></div>","PeriodicalId":49674,"journal":{"name":"Precambrian Research","volume":null,"pages":null},"PeriodicalIF":3.8,"publicationDate":"2024-05-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141198256","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":"Key factors controlling Neoproterozoic tin metallogenic events in southwestern China: Multidisciplinary approach using geology, geochemistry, and geochronology","authors":"Hao Chen ,&nbsp;Xin Chen ,&nbsp;Youye Zheng ,&nbsp;Xiaojia Jiang ,&nbsp;Yongzhen Yang ,&nbsp;Shunbao Gao","doi":"10.1016/j.precamres.2024.107449","DOIUrl":"10.1016/j.precamres.2024.107449","url":null,"abstract":"<div><p>The scarcity of Precambrian tin deposits in China has drawn significant interest to their formation. The Chahe tin deposit (26 Mt @ 0.38 % Sn), one of the oldest in China, provides a valuable opportunity to investigate the key factors controlling the development of such deposits. Situated along the western margin of the Yangtze craton in southwestern China, this deposit exhibits diverse mineralization types, including greisen cassiterite mineralizations located on top of the granitic cupola, skarn-cassiterite-axinite-quartz veins, and cassiterite-sulfide veins at the granite-limestone contact, and structurally controlled occurrences within siliciclastic metasedimentary rocks along secondary faults. Extensive U-Pb dating reveals that both barren and tin-bearing granites associated with the deposit share similar ages, ranging from 851 ± 4 Ma to 848 ± 4 Ma. These ages closely match, within error, the cassiterite U-Pb age of 843–853 Ma and the rutile U-Pb age of 859 ± 27 Ma for greisen veins/veinlets hosted in granite. Additionally, a cassiterite U-Pb age of 844 ± 9 Ma has been identified in the cassiterite–axinite–quartz veins hosted in the skarn. These findings provide direct evidence for the spatial, temporal, and genetic association of tin mineralization with Neoproterozoic Mosuoying granites. The granites in the region are categorized as peraluminous calc-alkali granites, characterized by high FeO, Ga/Al ratios, and zircon saturation temperatures, indicative of A-type granite features. In comparison to regional contemporaneous granites, the barren and tin-bearing granites exhibit high Rb/Ba and Rb/Sr ratios, variable ε_Hf(t) values (–17.8 to + 3.1), and two-stage Hf model ages (T_DM2) spanning from 2.6 to 1.5 Ga. These characteristics indicate a common source and origin through the reworking of Paleo- to Mesoproterozoic metasedimentary crust in response to the breakup of the Rodinia supercontinent. Simultaneously, they display low whole-rock Fe₂O₃/FeO and zircon Ce⁴⁺/Ce³⁺ ratios, consistent with those observed in typical Sn-bearing ilmenite-series granites globally. Notably, the tin-bearing granites manifest a highly fractionated nature, evident in their REE distribution patterns with a pronounced tetrad effect, as well as lower Nb/Ta and Zr/Hf ratios for twin elements. In summary, this study emphasizes the significance of a metasediment-derived source and the presence of highly evolved, reduced, or ilmenite-series granitic magma in the development of highly fractionated A-type granites associated with Neoproterozoic tin mineralization. These findings provide insights into the crucial factors controlling Neoproterozoic tin metallogenic events, shedding light on metallogenic processes and systematic exploration strategies for tin in Precambrian terranes.</p></div>","PeriodicalId":49674,"journal":{"name":"Precambrian Research","volume":null,"pages":null},"PeriodicalIF":3.8,"publicationDate":"2024-05-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141198241","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":"An earliest Ediacaran oxygenation episode in the Wilpena Group, Adelaide Superbasin, South Australia","authors":"Kelsey G. Lamothe ,&nbsp;Malcolm W. Wallace ,&nbsp;Ashleigh V.S. Hood ,&nbsp;Catherine V. Rose","doi":"10.1016/j.precamres.2024.107433","DOIUrl":"10.1016/j.precamres.2024.107433","url":null,"abstract":"<div><p>The first appearance of animals during the Ediacaran is arguably related to an increase in oceanic oxygenation during this time. However, there is considerable ambiguity in the global record of Ediacaran oxygenation, making it difficult to assess the potential links between oxygen and metazoan evolution. Here, we examine the earliest Ediacaran Nuccaleena Formation cap dolomite and basal Brachina Formation of the Adelaide Superbasin, South Australia, to determine the redox landscape in which these units were deposited. Red shales are present at the base of the Brachina Formation (lower Moolooloo Siltstone Member) over much of the Adelaide Superbasin but these transition laterally into green shales in the north, correlating with a facies transition into a deeper water setting.</p><p>Fibrous dolomite cements within sheet cavities of the Nuccaleena Formation cap dolomite display evidence of a primary marine origin. Cathodoluminescence microscopy and laser ablation ICP-MS trace element analysis of these marine dolomite cements indicates a transition from an oxic environment in the south (with low Fe, Mn, and a Ce anomaly) to an anoxic (ferruginous) setting in the north (with high Fe, Mn and no Ce anomaly). This cap carbonate trace element geochemistry is spatially consistent with the overlying red to green shale transition in the basal Brachina Formation. Together, these data suggest the existence of a deep-water chemocline in this basin, separating an oxic upper water column from a ferruginous deeper water mass. This oxic interval directly post-dates the end-Cryogenian Marinoan Glaciation and is synchronous with an earliest Ediacaran oxygenation event previously described from South China.</p><p>This evidence from the Adelaide Superbasin provides direct evidence for an earliest Ediacaran oxic water mass penetrating to a substantial paleodepth. The synchronous development of oxic intervals in both Australia and South China supports the notion of a globally developed oceanic oxygenation event and is consistent with the hypothesis that Ediacaran continental margin settings were periodically bathed in oxic water, conducive to the evolution of metazoans.</p></div>","PeriodicalId":49674,"journal":{"name":"Precambrian Research","volume":null,"pages":null},"PeriodicalIF":3.8,"publicationDate":"2024-05-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141196863","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":"Quartz trace element geochemistry and internal morphology as proxies for provenance characterization: Results from the Marwar basin, NW India","authors":"Jun Zhang ,&nbsp;Rui Li ,&nbsp;Manoj K. Pandit ,&nbsp;Ting-Guang Lan ,&nbsp;Qing Xiong ,&nbsp;Yuan-Bao Wu ,&nbsp;Jun-Hong Zhao ,&nbsp;Wei Wang","doi":"10.1016/j.precamres.2024.107436","DOIUrl":"https://doi.org/10.1016/j.precamres.2024.107436","url":null,"abstract":"<div><p>Quartz as one of the most stable minerals in sedimentary processes, is widely distributed in clastic sedimentary rocks, making it a potential provenance tracer in the source-to-sink system. In this study, internal morphology and trace element geochemistry of detrital quartz from the Marwar sandstones in NW India were utilized to decipher the source lithologies. Quartz from various source rocks displays distinctive trace element characteristics that correspond to specific cathodoluminescence properties. Phenocrystic quartz in hypabyssal and volcanic rocks is characterized by higher Li (&gt;10 ppm), Al (&gt;90 ppm), and Ti (&gt;60 ppm) contents, medium to bright blue cathodoluminescences, and visible zoning. Quartz in plutonic rocks, especially diorite, contains a lower abundance of trace elements. It exhibits dark brownish red, violet to blue cathodoluminescence, and is marked by dark streaks, patches, and partial healing fractures. Pegmatitic quartz with the lowest Li (0.03 ppm) and the highest Ge (1.38 ppm) contents, displays brown to dark blue cathodoluminescences. Gneissic quartz with the highest Fe (3.98 ppm) and a moderate abundance of other trace elements, exhibits non-luminescence or dark brown to dark blue cathodoluminescence, occasional dark streaks, and healing fractures. Quartz in migmatites generally shows a lower trace elements abundance, non-luminescence, or dark brown to dark blue cathodoluminescence. A robust statistical correlation between the cathodoluminescence properties and trace element characteristics is discernible in the detrital quartz grains through the entire stratigraphy of the Marwar Supergroup, shedding light on the lithological and compositional make-up of the provenances. This study identifies that the early sedimentation in the Marwar basin was predominantly fed by detritus from the Neoproterozoic Malani Igneous Suite and Paleoproterozoic granitoids, whereas the younger strata document a marked increase in contributions from the older Aravalli Craton basement. Our findings demonstrate the utility of quartz trace element geochemistry and internal morphology as effective tools for provenance analysis in source-to-sink systems. Moreover, detrital quartz and zircon in combination can be effectively used in tracing the specific source and quantifying relative contributions from different source rocks that could be applied to provenance studies elsewhere.</p></div>","PeriodicalId":49674,"journal":{"name":"Precambrian Research","volume":null,"pages":null},"PeriodicalIF":3.8,"publicationDate":"2024-05-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141096009","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":"Comment on: Carbonaceous matter in ∼ 3.5 Ga black bedded barite from the Dresser Formation (Pilbara Craton, Western Australia) – Insights into organic cycling on the juvenile Earth","authors":"R.J. Baumgartner,&nbsp;S. Caruso","doi":"10.1016/j.precamres.2024.107446","DOIUrl":"https://doi.org/10.1016/j.precamres.2024.107446","url":null,"abstract":"<div><p>Weimann et al. (2024) offer important insights into carbonaceous matter (CM) preserved within bedded barite from the 3.48 billion-year-old Dresser Formation (Pilbara Craton). However, issues in the fitting of CM Raman spectra and the application of Raman CM thermometry cast doubts on the conclusion that 'CM in quartz veins yielded much lower temperatures of ∼ 220 °C, suggesting that quartz-vein associated CM entered the barite after 3.3 Ga' (Weimann et al., 2024). A primary concern is the inaccurate fitting of the CM's D1 band, whose spectral position (typically in the c. 1335–1355 cm⁻¹ range) and full width at half maximum (FWHM) are indicators of thermal maturity (Kouketsu et al., 2014). This commentary emphasizes the implications of misfitting D1 and other issues in fitting the broader CM signals between 1100 and 1700 cm⁻¹. Specifically, the omission of D4 (c. 1250 cm⁻¹) resulted in a systematic overestimation of D1-FWHM and, consequently, unreasonably low thermal maturity estimates. We show that a more precise fitting including D4 – recognizing that CM spectra with a thermal maturity below 300 °C generally display a corresponding shoulder at c. 1250 cm⁻¹ – yields much higher thermal maturity estimates that appear to align closely with the peak temperature (c. 290 °C) of the Dresser Formation's 3.3 Ga metamorphic event. This suggests a (near) syngenetic origin for the quartz-vein-hosted CM, challenging the notion of post-metamorphic infiltration. Consequently, these results also question Weimann et al.'s (2024) interpretation that the much higher thermal maturity (c. 350 °C) of a distinct CM generation, situated within the barite crystal’s growth zonations, stems from metamorphic overprinting. Instead, it can be reconciled with the thermal maturation of the CM during its transportation within the ancient Dresser hydrothermal system, prior to its concentration within the barite.</p></div>","PeriodicalId":49674,"journal":{"name":"Precambrian Research","volume":null,"pages":null},"PeriodicalIF":3.8,"publicationDate":"2024-05-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141096010","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Detrital zircon geochronology of Kilohigok basin: Record of Paleoproterozoic orogenesis and unroofing of the Thelon tectonic zone (Nunavut, Canada)","authors":"W.J. Davis ,&nbsp;A. Ielpi","doi":"10.1016/j.precamres.2024.107422","DOIUrl":"https://doi.org/10.1016/j.precamres.2024.107422","url":null,"abstract":"<div><p>The Paleoproterozoic Kilohigok foreland basin formed on the Archean Slave craton in response to 2.02–1.90 Ga collision in the adjacent Thelon tectonic zone (Ttz), the boundary between the Slave and Rae cratons within the nascent Nuna supercontinent. U-Pb and Hafnium isotopic data from detrital zircon are used to test the foreland basin model and examine the nature of crustal components within the Ttz. Changes in provenance within the basin can be linked with tectonic events in the Ttz. Platformal deposits of the Kimerot Group are derived from local Archean Slave sources, which also dominate the initial foredeep deposits of the ca. 1.97 Ga lower Bear Creek Group. Paleoproterozic 2.02––1.97 Ga detritus match ages of plutonic rocks within the overthrust Thelon tectonic zone and dominates the deposits of the upper Bear Creek Group (Beechey and Burnside River formations) within 10 Ma of foredeep initiation at 1.97 Ga. Significant populations of 2.3 Ga and 2.17–2.07 Ga detrital zircon were introduced to the basin at that time. Their relatively juvenile Hf isotopic compositions are characteristic of the Buffalo Head terrane, but not to potential sources in the western Rae, indicating that Buffalo Head-like crust extended north of the Great Slave Lake Shear zone and was involved in Slave-Thelon-Rae collision events. Basin rejuvenation occurred after 1.88 Ga with deposition of the Bathurst Group, in part coeval with basaltic magmatism correlated with the underlying Mara River sills, dated at 1.87 Ga. Magma transport within basin-wide sill-complexes indicates magma sources on the western side of the Slave, associated with contemporaneous Great Bear magmatism in the Wopmay orogen. Bathurst Group basin rejuvenation is synchronous with 1.88–1.87 Ga metamorphism and shortening in Wopmay orogen on the west side of the Slave. More diverse detrital zircon signatures in the Bathurst Group indicate a broader source region, including areas from the eastern side of the Ttz. The data are consistent with tectonic models that link Thelon tectonic zone to the Ksitusan terrane and involve a Slave-Buffalo Head terrane collision as part of the greater Slave-Rae amalgamation.</p></div>","PeriodicalId":49674,"journal":{"name":"Precambrian Research","volume":null,"pages":null},"PeriodicalIF":3.8,"publicationDate":"2024-05-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141084320","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":"Earth’s oldest terrestrial red beds as direct evidence for the Great Oxidation Event ca. 2.3 Ga","authors":"Nabil A. Shawwa ,&nbsp;Thomas R. McLoughlin-Coleman ,&nbsp;Michael G. Babechuk ,&nbsp;Maryam Shahabi Far ,&nbsp;James E. Mungall ,&nbsp;Robert H. Rainbird","doi":"10.1016/j.precamres.2024.107423","DOIUrl":"https://doi.org/10.1016/j.precamres.2024.107423","url":null,"abstract":"<div><p>Reconstructing the trajectory of Earth’s initial rise of atmospheric oxygen (i.e., the Great Oxidation Event, GOE) remains a significant but important challenge due to the intricate connections between oxygen and life. Further refinement in our understanding of the GOE requires establishing tighter links between geochemical and mineralogical oxygenation proxies specifically in terrestrial environments where signals reflect oxygen accumulation beyond realms of localized production. The appearance of terrestrial red beds in the Paleoproterozoic rock record is oft-cited evidence for the GOE; however, there is a lack of robust evidence that establishes Fe(III)-(oxy)(hydr)oxides (now hematite) as a primary clastic sedimentary feature, and often insufficient stratigraphic and geochronological context to link red beds to other oxygenation proxies. This study revisits the transition from the youngest detrital pyrite- and uraninite-hosting terrestrial (alluvial-fluvial) strata to the oldest reddened fluvial strata in the <em>ca.</em> 2.45–2.22 Ga Huronian Supergroup, with the aim to directly link the mineralogy of the latter deposits to environmental oxygenation and thus the GOE. Key fluvial sandstone units preserve hematite as rims of “dust” on detrital quartz encased by epitaxial quartz overgrowth cements, providing unequivocal evidence for Fe(III)-(oxy)(hydr)oxide adhesion to detrital quartz during early meteoric diagenesis, and thus indicating terrestrial Fe oxidation pathways were more widespread than oxidized paleosols formed at this time. Geochronological constraints place the appearance of these terrestrial red beds at ∼2.31 Ga, timing that closely matches with the S-isotope evidence for the GOE in correlative strata of the Transvaal Supergroup. The S-isotope and red bed proxy records show promise for a closely coupled oxygenation threshold, with the advantage that they are typically preserved in different depositional environments.</p></div>","PeriodicalId":49674,"journal":{"name":"Precambrian Research","volume":null,"pages":null},"PeriodicalIF":3.8,"publicationDate":"2024-05-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0301926824001360/pdfft?md5=a79c5e808986e4d014a735538664ae72&pid=1-s2.0-S0301926824001360-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141089890","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":"Shift from arc to within-plate magmatism at 635 Ma as recorded by Neoproterozoic dikes, southern Midyan terrane, NW Arabian Shield","authors":"Scott A. Whattam ,&nbsp;Robert J. Stern ,&nbsp;Hossein Azizi ,&nbsp;Keewook Yi ,&nbsp;Haitham M. Baggazi ,&nbsp;Abdullah Alquabalee ,&nbsp;Fatemeh Nouri ,&nbsp;Brian Jicha ,&nbsp;Yanick Brice Lemdjou ,&nbsp;Abdelhamid El Fakharani","doi":"10.1016/j.precamres.2024.107430","DOIUrl":"https://doi.org/10.1016/j.precamres.2024.107430","url":null,"abstract":"<div><p>The tectonic evolution of the Arabian-Nubian Shield began with formation of intra-oceanic arcs followed by collisions between these in Tonian-Cryogenian time and culminated in Ediacaran continental collision to form Gondwana. We provide new insights into the middle stage of this tectonic evolution by focusing on two Neoproterozoic dike swarms of different age in northern Arabia. The 695–700 Ma Za’am dikes were emplaced about the time of collision between the Midyan and Hijaz terranes whereas the 635 Ma Bayda dikes were emplaced ∼ 60 million years after collision. These record a shift from relatively unfractionated 695 Ma arc-type magmas in the south to fractionated 635 Ma within-plate alkaline magmas in the north. Our results document mantle source and crustal evolution beneath the Midyan terrane during and after terrane accretion, revealing a tectono-magmatic transition from SSZ-type magmas accompanying arc collision to post-terrane accretion within-plate magmatism through Cryogenian time. In addition, our results confirm the potential of dike studies for reconstructing the tectono-magmatic-metallogenic evolution of orogens.</p></div>","PeriodicalId":49674,"journal":{"name":"Precambrian Research","volume":null,"pages":null},"PeriodicalIF":3.8,"publicationDate":"2024-05-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141078497","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":"Early Earth “subduction”: short-lived, off-craton, shuffle tectonics, and no plate boundaries","authors":"O. Nebel ,&nbsp;E.D. Vandenburg ,&nbsp;F.A. Capitanio ,&nbsp;R.H. Smithies ,&nbsp;J. Mulder ,&nbsp;P.A. Cawood","doi":"10.1016/j.precamres.2024.107431","DOIUrl":"https://doi.org/10.1016/j.precamres.2024.107431","url":null,"abstract":"<div><p>Subduction is a key geodynamic feature on modern Earth that drives crustal chemical diversity, bridging the atmo-, hydro-, and lithosphere, but remains an enigmatic, unique planetary feature. Indisputable is the critical role of subduction in shaping Earth’s geomorphology and crustal dichotomy (ocean vs continental crust) and its impacts on long-term climate, making it arguably the most important process on present-day Earth across all geosciences. It is thus important to understand to what degree, or if at all, subduction was operational during the billions of years that led to our geological status quo.</p><p>Here, we assess the feasibility of Archean subduction with a focus on early Earth geodynamics. We argue that convection-driven rifting, but not spreading, formed the first keels under the primordial crust, providing the necessary stability for crustal survival. These sections of crustal rejuvenation would counterintuitively forge the first stable proto-cratonic terranes, which later evolved into cratons. Hydrated upper crustal rocks were vital in generating early fluxed mantle melting and related volcanism, but also for partial melting in hydrated lower crustal sections within proto-cratons, giving rise to tonalite-trondhjemite granodiorites (TTGs). Both processes operated off- and on-craton, respectively, and required melting of hydrated crust and crustal convergence but are unrelated. Away from proto-cratonic regions of minor episodic divergence and rifting, relative motions were accommodated by convergence and shuffle tectonics, leading to Archean-style subduction in localised regions that were prone to destruction. This primitive form of subduction and crustal maturation has operated from the earliest Archean time in a plate-and-lid regime. Crucially, this ‘Archean subduction’ represents short-lived crustal shuffle-tectonics outside areas of today’s cratons with fluxed melting in upper mantle regions but does not resemble present-day Benioff-style subduction. The development of subduction akin to present-day processes towards the end of the Archean could plausibly have driven atmospheric oxygenation over a few hundred million years between ca. 2.8–2.3 Ga, with H-loss to space accompanied by atmospheric oxidation through subduction-related global volcanic SO₂ emissions.</p></div>","PeriodicalId":49674,"journal":{"name":"Precambrian Research","volume":null,"pages":null},"PeriodicalIF":3.8,"publicationDate":"2024-05-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S030192682400144X/pdfft?md5=320061267135e151c13e0ced0292341d&pid=1-s2.0-S030192682400144X-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141067853","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":"Prolonged parallel chronology of distinct TTG types in the Lake Inari terrain, Arctic Fennoscandia: Implications for a stationary plume-related source","authors":"Kumar Batuk Joshi ,&nbsp;Jaana Halla ,&nbsp;Matti Kurhila ,&nbsp;Esa Heilimo","doi":"10.1016/j.precamres.2024.107418","DOIUrl":"https://doi.org/10.1016/j.precamres.2024.107418","url":null,"abstract":"<div><p>Revealing Archaean crust-formation processes requires understanding of geochemical and chronological differences in granitoids. During the early evolution of Earth’s felsic crust, large amounts of tonalite-trondhjemite-granodiorites (TTGs) were formed, making up most of the Archaean crust preserved until today. TTGs have two geochemical endmembers, the low-HREE and high-HREE (heavy rare earth elements) TTGs. The genesis of TTGs has been explained by the dehydration melting of basaltic crust, but the formation of the different types of TTGs is a subject of debate. This study provides new U–Pb zircon ages for deciphering the temporal relationships between the different TTG types in the Lake Inari terrain, Arctic Fennoscandia. The interpretation of the FIRE (Finnish Reflection Experiment) 4A line shows the existence of two tectonic blocks for the terrain. Our results from zircon populations of low- and high-HREE TTGs and adjacent porphyritic granitoids show a large time spread suggesting a prolonged migmatization in the Lake Inari terrain from 2900 to 2600 Ma. This supports a long-term source of heat such as a stationary plume related to stagnant or sluggish lid -tectonics. The high- and low-HREE TTGs show parallel ages and occur intermingled, which points to a common source instead of different tectonic settings. There is no distinct age difference between the two tectonic blocks identified in the FIRE 4A seismic reflection profile. Prolonged melting episodes of thickened felsic crust produced porphyritic granites between 2650–2500 Ma. The ∼ 1.9 Ga Lapland-Kola orogeny caused minor zircon recrystallization but did not influence Archaean migmatite morphology. The Lake Inari TTGs peak approximately at 2.8 Ga, i.e., 100 Ma before the formation of the suggested Kenorland supercontinent.</p></div>","PeriodicalId":49674,"journal":{"name":"Precambrian Research","volume":null,"pages":null},"PeriodicalIF":3.8,"publicationDate":"2024-05-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0301926824001311/pdfft?md5=d77544bda1d66c55791909e445681da6&pid=1-s2.0-S0301926824001311-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140951130","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}