Precambrian Research最新文献

{"title":"Chemostratigraphy of the Ediacaran Old Fort Point Formation in the southern Canadian Cordillera","authors":"Connor S. van Wieren, Jon M. Husson, Blake Dyer","doi":"10.1016/j.precamres.2024.107525","DOIUrl":"10.1016/j.precamres.2024.107525","url":null,"abstract":"<div><p>The Ediacaran Old Fort Point Formation in the southern Canadian Cordillera records a large, highly negative carbon isotope excursion, with a minimum in the <span><math><mrow><msup><mrow><mi>δ</mi></mrow><mrow><mn>13</mn></mrow></msup></mrow></math></span>C values of marine carbonates of –12‰. Carbon isotope excursions are often interpreted to be broadly synchronous and to reflect shifts in the <span><math><mrow><msup><mrow><mi>δ</mi></mrow><mrow><mn>13</mn></mrow></msup></mrow></math></span>C value of marine dissolved inorganic carbon, possibly reflecting either fluctuations in the global proportion of organic matter burial, or post-depositional diagenesis. As diagenesis can create large discrepancies between the original <span><math><mrow><msup><mrow><mi>δ</mi></mrow><mrow><mn>13</mn></mrow></msup></mrow></math></span>C<sub><em>carb</em></sub> value of the sediment and what is preserved today, it is essential to determine to what extent diagenesis has impacted these records. We measured carbon and oxygen isotopes on eight stratigraphic sections (<em>n</em> = 360), carbonate clasts from debris-flow deposits from the Old Fort Point Formation (<em>n</em> = 968), and major and trace elemental abundances (<em>n</em> = 249). We used these geochemical datasets to investigate whether local processes leverage a larger control on carbon and oxygen isotopic values rather than global processes. We argue that the carbonate strata with the lowest <span><math><mrow><msup><mrow><mi>δ</mi></mrow><mrow><mn>13</mn></mrow></msup></mrow></math></span>C<sub><em>carb</em></sub> values (<span><math><mrow><mo>∼</mo></mrow></math></span> –12‰) are now calcitic but were neomorphosed from an aragonite precursor in a fluid-buffered, early diagenetic environment conducive to dolomite growth. Additionally, the recovery of the expressed excursion is preserved in carbonates that underwent early-marine diagenesis under more sediment-buffered conditions, with its geochemistry closer to the aragonite precursors. Tremendous variability, up to 17‰, is observed in <span><math><mrow><msup><mrow><mi>δ</mi></mrow><mrow><mn>13</mn></mrow></msup></mrow></math></span>C<sub><em>carb</em></sub> values of clast populations from individual breccia horizons found in the in-fill of submarine paleocanyons, filled with material from underlying carbonates of the Temple Lake and Geikie Siding Members. The presence of such a large range of clast <span><math><mrow><msup><mrow><mi>δ</mi></mrow><mrow><mn>13</mn></mrow></msup></mrow></math></span>C<sub><em>carb</em></sub> values requires an early acquisition of the observed Old Fort Point Formation <span><math><mrow><msup><mrow><mi>δ</mi></mrow><mrow><mn>13</mn></mrow></msup></mrow></math></span>C<sub><em>carb</em></sub> values (pre-brecciation and submarine canyon incision) and precludes late-stage burial diagenesis. Moreover, despite disagreement with previously published geochronological constraints, we propose that the carbon isotope excursio","PeriodicalId":49674,"journal":{"name":"Precambrian Research","volume":"411 ","pages":"Article 107525"},"PeriodicalIF":3.2,"publicationDate":"2024-07-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141950124","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":"Transition from vertical to horizontal tectonic regime during the Paleoarchean-Mesoarchean: Evidence from mafic-ultramafic rocks of the Holenarsipur Greenstone Belt, Western Dharwar Craton, Southern India","authors":"Arathi G. Panicker ,&nbsp;M. Ram Mohan ,&nbsp;Ravi Shankar","doi":"10.1016/j.precamres.2024.107492","DOIUrl":"10.1016/j.precamres.2024.107492","url":null,"abstract":"<div><p>The Dharwar Craton (DC) in southern India is one of the classic Archean terrains, preserving an evolutionary history from the Paleoarchean to Mesoarchean. The present study attempts to understand the origin and evolution of mafic (amphibolites) and ultramafic (harzburgite) rocks from the Holenarsipur Greenstone Belt (HGB), to decipher the evolution of the cratonic core of the Western Dharwar Craton (WDC). Relict olivine and orthopyroxene pseudomorphs and Neodymium isotopic compositions reveal that harzburgites from the HGB represent a preserved section of the early Archean mantle, re-fertilized by fluid/rock interaction during serpentinization. The ultramafic and mafic rocks from the southern and northern parts of the belt exhibit coherent whole-rock geochemical and Nd isotopic compositions. Ultramafic rocks were derived from a depleted mantle source (ƐNd_(t=3300)= +0.65 to +8.70) while, the amphibolites were generated by partial melting of an enriched mantle source (ƐNd_(t=3300) = -4.16 to +0.92). The ultramafic rocks with fore-arc affinity may signify the prevalence of a subduction setting during the early stages of the first accretionary event in the WDC. The compositionally uniform mafic rocks from the HGB with oceanic plateau affinity affirm a plume environment. Our study establishes the prevalence and transition from vertical to horizontal tectonics during the Paleoarchean-Mesoarchean evolution of the WDC.</p></div>","PeriodicalId":49674,"journal":{"name":"Precambrian Research","volume":"411 ","pages":"Article 107492"},"PeriodicalIF":3.2,"publicationDate":"2024-07-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141950073","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A revised stratigraphic model for the ∼ 1910–1835 Ma Tanami Group, the northern Territory, Australia: Implications for exploration targeting","authors":"Andrew F. Crawford ,&nbsp;David W. Maidment ,&nbsp;Nicolas Thebaud ,&nbsp;Quentin Masurel ,&nbsp;Noreen J. Evans","doi":"10.1016/j.precamres.2024.107510","DOIUrl":"10.1016/j.precamres.2024.107510","url":null,"abstract":"<div><p>The Paleoproterozoic Tanami Group of the Granites—Tanami Orogen hosts a known endowment of &gt; 20 Moz of gold mineralization across numerous deposits. Throughout the region, host lithologies impart a first-order control on the style, grade and endowment of mineralization. However, the genetic relationship and regional distribution of three regionally correlative formations (the Dead Bullock, Mount Charles and Stubbins formations) remains enigmatic. Here, we combine lithostratigraphic analysis, lithogeochemistry, detrital zircon geochronology and geophysical observations to propose a new evolutionary model for the Tanami Group. We find that the Tanami Group was deposited in a continental back-arc basin setting and developed in four stages. Package A marked the onset of the rifting of the continental Archean basement. Sedimentary rocks within Package A are dominantly felsic in composition and display a unimodal detrital zircon age population at ∼ 2530 Ma. Package B marks the onset of mafic volcanism; consequently, volcaniclastic and sedimentary rocks within Package B display a distinct mafic geochemical signature. Detritus shed from an Archean basement persisted throughout this period, and a unimodal detrital age component at ∼ 2530 Ma persists. Package C marked the waning stages of voluminous mafic volcanism across the Tanami Basin. Sedimentary volcaniclastic rocks within Package C display a mixed mafic and felsic composition. Detrital zircon age spectra record multiple peaks at ∼ 2500, 3000 and 3350 Ma, which may reflect erosion of older Archean basement domains or changes in paleo-drainage. Package D marked a significant change in the source of detritus entering the basin from dominantly Archean to Paleoproterozoic, with dominant detrital age peaks at ∼ 1860 Ma. Despite significant lithofacies variations, the presented model highlights multiple correlations between the Dead Bullock and Mount Charles formations. The Mount Charles Formation likely represents a volcanic source-proximal, high-energy depocenter. In contrast, the Dead Bullock Formation was deposited in a lower energy setting, distal to volcanic centers. These observations are important to mineral exploration. Notably, the Mount Charles Formation is distributed over a significantly greater area than previously thought, and the under-represented Hangingwall and Footwall sequences of this formation are interpreted to host significant gold mineralization at the Oberon and Groundrush deposits.</p></div>","PeriodicalId":49674,"journal":{"name":"Precambrian Research","volume":"411 ","pages":"Article 107510"},"PeriodicalIF":3.2,"publicationDate":"2024-07-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0301926824002237/pdfft?md5=3bbecc1d998993b11d140740c9a68233&pid=1-s2.0-S0301926824002237-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141883472","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":"Precambrian impact structures and ejecta on earth: A review","authors":"Christian Koeberl ,&nbsp;Toni Schulz ,&nbsp;Matthew S. Huber","doi":"10.1016/j.precamres.2024.107511","DOIUrl":"10.1016/j.precamres.2024.107511","url":null,"abstract":"<div><p>Impact cratering is an important geological process on Earth. This review summarizes the state of knowledge of the Precambrian (Hadean, Archean, and Proterozoic) impact record on Earth. After an early collision that may have led to the formation of the Moon, both Earth and Moon suffered intense post-accretionary bombardment at about 4.5 and 3.9 billion years ago. Evidence for a “late heavy bombardment” phase at about 3.85 Ga is currently debated because the lunar rock record might be biased, and no relevant impact record has yet been confirmed on Earth. Several 3.5 to 2.5 Ga old spherule layers in South Africa and Australia, and two large impact structures, Vredefort and Sudbury, at about 2 Ga, represent most of the oldest actual terrestrial impact record. The impact record for more than half of the geological history of the Earth is incomplete, and, as a result of the lack of old continental crust on Earth, there is also only limited evidence for impact processes during the first 2.5 billion years of Earth history. Some more (mostly badly dated) impact structures are (partly) preserved for the Proterozoic period, as are a couple of ejecta layers. Given that the rock record preserved on Earth is very restricted for this early time period, the limited impact record is not surprising, but as recent discoveries show, there is still room for more research and new findings.</p></div>","PeriodicalId":49674,"journal":{"name":"Precambrian Research","volume":"411 ","pages":"Article 107511"},"PeriodicalIF":3.2,"publicationDate":"2024-07-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0301926824002249/pdfft?md5=826293ead61665c56ed4b669ed36e172&pid=1-s2.0-S0301926824002249-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141729389","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":"Reply to comment on “The passive margin of the southern São Francisco paleocontinent, metamorphic record and implications for the assembly of West Gondwana: Evidence from the Lima Duarte Nappe, Ribeira orogen (SE Brazil)” by Trouw and Ribeiro","authors":"Brenda C. Rocha,&nbsp;Mario C. Campos Neto,&nbsp;Caue R. Cioffi,&nbsp;Alice Westin,&nbsp;Adriana Alves,&nbsp;Claudio A. Salazar-Mora,&nbsp;Marcos Egydio-Silva,&nbsp;Renato Moraes,&nbsp;Sara dos S. Souza,&nbsp;Victor C. Maurer","doi":"10.1016/j.precamres.2024.107523","DOIUrl":"10.1016/j.precamres.2024.107523","url":null,"abstract":"","PeriodicalId":49674,"journal":{"name":"Precambrian Research","volume":"411 ","pages":"Article 107523"},"PeriodicalIF":3.2,"publicationDate":"2024-07-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141638737","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 into the magma dynamics of the multi-pulsed ca. 2.08 Ga Devarabanda dyke swarm, eastern Dharwar craton: Constraints from integrated geochemical, magnetic fabric and emplacement studies","authors":"Srinjoy Datta ,&nbsp;Sayandeep Banerjee ,&nbsp;Amiya K. Samal ,&nbsp;Rajesh K. Srivastava ,&nbsp;Richard E. Ernst ,&nbsp;Aishwarya Mohan","doi":"10.1016/j.precamres.2024.107507","DOIUrl":"10.1016/j.precamres.2024.107507","url":null,"abstract":"<div><p>The ca. 2.08 Ga Devarabanda mafic dyke swarm in the eastern Dharwar craton exhibits a spectacular radiating geometry spanning 167˚. This study focuses on unravelling the intra-swarm variability in geochemistry and emplacement systematics across its three distinct sub-swarms designated as SS-1, SS-2 and SS-3, trending N, NW, and NE, respectively. Through an integrated study that includes whole rock geochemistry, anisotropy of magnetic susceptibility (AMS), and available geochronology and gravity data, we identify shared differentiation trends across all the sub-swarms, suggesting a common genetic linkage. While crustal influence is evident, the SS-3 displays relatively primitive geochemical signatures, the other two sub-swarms signify more highly differentiated pulses, indicating multiple magma pulses in the ca. 2.08 Ga dyke swarm. AMS analyses reveal lateral magma flow for SS-3, while vertical injection feeds the other two sub-swarms. Based on this study, we propose the role of a mantle plume for the formation of the three sub-swarms; SS-3 formed from a shallow crustal magma chamber during the pre-rift phase, due to a central domal uplift. Subsequently, SS-1 and SS-2 were emplaced at a later rift phase, where SS-2 was emplaced along a pre-existing NW-trending rift, and SS-1 formed during active rifting and crustal thinning. Evidence supporting an older NW-trending rifting event in the region corresponding to the SS-2 exposures was observed from available gravity data. The presence of discrete crustal magma reservoirs, separate for each sub-swarm, surrounding the domal uplift, explains the intervening dyke-poor areas, and suggests the formation of an apical graben as a precursor to the Proterozoic Cuddapah basin.</p></div>","PeriodicalId":49674,"journal":{"name":"Precambrian Research","volume":"411 ","pages":"Article 107507"},"PeriodicalIF":3.2,"publicationDate":"2024-07-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141638736","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":"Kinematics and geochronology of the ductile shear zones in the western Shandong granite-greenstone belt: Implications for the Neoarchean plate tectonics of the North China Craton","authors":"Dongming Wang ,&nbsp;Jianmin Hu ,&nbsp;Yuanfang Zhao ,&nbsp;Jiyuan Yan ,&nbsp;Wangbin Gong ,&nbsp;Ping Yu ,&nbsp;Zhigang Zhang ,&nbsp;Zhanlin Qiu","doi":"10.1016/j.precamres.2024.107509","DOIUrl":"10.1016/j.precamres.2024.107509","url":null,"abstract":"<div><p>The granite-greenstone belt is the main component of Archean crust, and is critical for resolving the disputes on the tectonic evolution and dominant regime of the early Earth. The North China Craton (NCC) is one of the oldest cratons in the world, and is composed of several continental micro-blocks. The greenstone belts, welding the micro-blocks, were generally considered to be continental or arc-continental collision belts during the amalgamation of the micro-blocks in the late Neoarchean. Thus, the structural pattern of these greenstone belts can provide essential clues for the crustal deformation style during early Precambrian orogeny. The western Shandong granite-greenstone belt (WSGB) located in the eastern NCC was considered as the collision belt of the Jiaoliao and Qianhuai Blocks. There exists a series of ductile shear zones with strike-slip kinematics, including Qixingtai, Nanliu, Yanlingguan, Xintai, Dongling–Huacun, Mengshan, Fengyang–Liangqiu, Qingyi and Baiyan. This paper conducts detailed geometric, kinematic and deformation geochronology studies, and reveal that the mylonitic foliation of the ductile shear zones in the WSGB strikes NW280–350° with angles of 60–80°. The mineral stretching lineation gently plunges to NE or SW at 2–25°. Kinematic indicators show sinistral strike-slip shearing sense. The deformation temperature can be divided into two ranges: 550–600 ℃ and 400–500 ℃, implying that the ductile shear zones in the WSGB was ought to experience early-stage high-temperature and late-stage low-temperature deformation. The deformation age is ∼ 2.58–2.47 Ga constrained by zircon LA-ICP-MS U–Pb and ⁴⁰Ar–³⁹Ar dating, and this age range includes early-stage high-temperature deformation. Structural restoration through balanced profiles and stereographic projection shows that the initial orientation of NW–NWW-trending ductile shear zones was dipping to the SW, and still were featured by strike-slip kinematics. Syn-kinematic arc-affinity magmatism and sedimentation demonstrate that the NW–NWW-trending ductile shear zones in the WSGB were caused by SE-ward plate convergence, which also led to the NW–SE-trending movement of different blocks along the strike of ductile shear zones. The WSGB represents an active continental margin in the southwestern Jiaoliao Block with intense arc-affinity magmatism and back-arc sedimentation, post-collision crustal-derived granites, traspressive shearing deformation, also indicating that the NCC was dominated by modern-style plate tectonism in the late Neoarchean.</p></div>","PeriodicalId":49674,"journal":{"name":"Precambrian Research","volume":"411 ","pages":"Article 107509"},"PeriodicalIF":3.2,"publicationDate":"2024-07-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141630491","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":"Heating–cooling–heating cycles within ca. 70 Myr recorded in UHT granulites in the Khondalite Belt, North China Craton","authors":"Yang Qi ,&nbsp;Shujuan Jiao ,&nbsp;Lin Chen ,&nbsp;Jiahui Liu ,&nbsp;Yu Liu ,&nbsp;Jinghui Guo","doi":"10.1016/j.precamres.2024.107508","DOIUrl":"10.1016/j.precamres.2024.107508","url":null,"abstract":"<div><p>Revealing the thermal evolution history of ultrahigh-temperature metamorphism (UHT) could help shed light on the genesis and evolution of the orogenic crust. However, it is generally difficult to constrain the duration of metamorphism, especially the heating stage due to the complex behavior of the datable accessory minerals (e.g., zircon and monazite). The Khondalite Belt of the North China Craton records Paleoproterozoic UHT metamorphic event which was previously constrained to be ca. 1920 Ma by using the weighted mean age of zircon U–Pb dating results, however, zircon could grow during both prograde and retrograde periods. Thus, the age of ca. 1920 Ma may be an oversimplified explanation and there could be a complex thermal evolution. In this study, combined with zircon U–Pb dating and Ti-in-zircon thermometry, the duration of the UHT metamorphism in the eastern Khondalite Belt was constrained to be 60–70 Myr with two short periods of decompression-heating (both lasting for ∼20 Myr) intervened by a period of cooling process (lasting for ∼30 Myr). This finding further expands our knowledge that there was a heating–cooling–heating cycle rather than a continuously prolonged cooling process in a long-lived UHT metamorphism. Our results show that the UHT metamorphism in the eastern Khondalite Belt requires two stages of lithosphere extension, which were possibly related to shallow slab breakoff and post-collisional lithospheric delamination, respectively. It further indicates that Paleoproterozoic orogenesis, although dominated by subduction of rheologically weak slab, is comparable to the formation of modern Himalaya orogens.</p></div>","PeriodicalId":49674,"journal":{"name":"Precambrian Research","volume":"411 ","pages":"Article 107508"},"PeriodicalIF":3.2,"publicationDate":"2024-07-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141622862","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":"Pongola Supergroup dolostones from the Buffalo River inlier, South Africa: facies, composition and implications for Mesoarchaean carbonate deposition","authors":"M. Siahi ,&nbsp;A. Hofmann ,&nbsp;J. Dixon ,&nbsp;A. Wilson ,&nbsp;C. Mayr ,&nbsp;L. Kapesi","doi":"10.1016/j.precamres.2024.107493","DOIUrl":"https://doi.org/10.1016/j.precamres.2024.107493","url":null,"abstract":"<div><p>The Mesoarchaean Pongola Supergroup of South Africa hosts the oldest succession of stromatolitic carbonates deposited in an intracontinental setting. In this study, carbonates within two (tectono-) stratigraphic units in the Buffalo River inlier were investigated. Stratiform stromatolite and wave-ripple-laminated dolostone facies are the most common and are interpreted to have formed in a tide-dominated shallow-marine environment. Dolostones typically contain a large amount of siliciclastic detritus, and small domal stromatolites are commonly found scattered in subtidal sandstone facies. The carbonates experienced deformation and greenschist facies metamorphic conditions at peak temperatures of ∼ 450 ± 50 °C. Analyses for major, trace and rare earth elements (REEs) along with carbon, oxygen and strontium isotopes have been undertaken on the best-preserved samples. Their REE + Y distribution patterns reflect their marine origin, with positive La_SN, Gd_SN and Y_SN anomalies, super-chondritic Y/Ho ratios, and depleted light REEs relative to heavy REEs. The δ¹³C_VPDB and δ¹⁸O_VPDB values least affected by diagenetic and metamorphic overprints are 2.2 ‰ and −16.1 ‰, respectively. The least radiogenic ⁸⁷Sr/⁸⁶Sr ratio is 0.704 and reflects isotopic exchange with a siliciclastic component. Despite their alteration, the carbonates of the Buffalo River inlier provide additional constraints on microbial carbonate deposition on the Earth oldest preserved craton. They can be traced laterally for several tens of kilometres and point to environmental conditions suitable for the deposition and preservation of marine carbonate rocks 3.0 Ga ago.</p></div>","PeriodicalId":49674,"journal":{"name":"Precambrian Research","volume":"411 ","pages":"Article 107493"},"PeriodicalIF":3.2,"publicationDate":"2024-07-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0301926824002067/pdfft?md5=69e1759e425b6dfd2302b7028c5bee4a&pid=1-s2.0-S0301926824002067-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141607733","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":"Two stages of late Paleoproterozoic A-type granites at the southern North China Craton: Geochemical constraints and implications for supercontinent breakup","authors":"Zhiyi Wang ,&nbsp;Jingxin Zhao ,&nbsp;Zeqiu Qi ,&nbsp;Dongyang Huo ,&nbsp;Wolfgang Siebel ,&nbsp;Jun He ,&nbsp;Shuangqing Li ,&nbsp;Fukun Chen","doi":"10.1016/j.precamres.2024.107500","DOIUrl":"https://doi.org/10.1016/j.precamres.2024.107500","url":null,"abstract":"<div><p>Paleoproterozoic and Mesoproterozoic A-type granites occur on many cratons and possess important information for our understanding of the formation and breakup history of the supercontinent Columbia. It was argued previously, that Proterozoic A-type granites (∼1.8–1.5 Ga), exposed along the southern margin of the North China Craton formed in a post-collisional or anorogenic setting related to the final amalgamation of the North China Craton or to the breakup of Columbia. In the present study, we report zircon ages and geochemical data of the Maping A-type granite. This intrusion consists of a quartz monzonite porphyry and a granite porphyry that, based on U-Pb age dating, formed at ∼ 1.65 and ∼ 1.60 Ga, respectively. The granites show high contents in alkaline and high field strength elements, high Ga/Al and Fe/Mg ratios. The quartz monzonite porphyry of the early stage is metaluminous and relatively depleted in Hf-Nd isotopic compositions (whole-rock initial ε_Nd values −5.4 to −4.5; zircon initial ε_Hf values −8.5 to −1.5), while granite porphyry of the late stage is peraluminous and has lower initial ε_Nd and ε_Hf values (−6.4 to −5.9; −9.6 to −3.3). Inherited zircon grains in the Maping intrusion have relatively high initial ε_Hf values (&gt;-0.7), likely originating from juvenile crust. The Pb isotopes of the quartz monzonite porphyry show characteristics similar to the lower crust, whereas the granite porphyry has more radiogenic Pb isotopic compositions. Apatite grains from the quartz monzonite porphyry have initial ⁸⁷Sr/⁸⁶Sr ratios of ∼ 0.7109–0.7133 and those from the granite porphyry have noticeably high initial ⁸⁷Sr/⁸⁶Sr ratios of ∼ 0.7862–0.8812. These isotopic characteristics imply the presence of various crustal rocks underneath the North China Craton with variable isotopic compositions. From the early to late magmatic stages, the Sr/Y ratios of granitic rocks decrease from 1.6 – 7.6 to 0.2–0.4, while the estimated magma temperatures, calculated from whole-rock compositions, slightly increase from approximately 900 °C to about 930 °C. These concurrent changes in temperature and chemical composition reflect ongoing asthenospheric mantle upwelling during crustal extension. This suggests a transition in the southern margin of the North China Craton from a post-collisional setting before 1.65 Ga to an anorogenic setting by 1.6 Ga.</p></div>","PeriodicalId":49674,"journal":{"name":"Precambrian Research","volume":"411 ","pages":"Article 107500"},"PeriodicalIF":3.2,"publicationDate":"2024-07-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0301926824002134/pdfft?md5=72fcb26b96f1e665f6e48bb32a6f9542&pid=1-s2.0-S0301926824002134-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141594813","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}