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A perspective on potassic and ultrapotassic rocks:Constraints on the Paleoproterozoic late to post-collisional event in the São Francisco paleocontinent

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Geoscience Frontiers 2022年第5期13卷 242-266页

作者： samuel moreira bersan AndréDanderfer Craig Storey Henrique Bruno Hugo moreira Francisco Abreu Cristiano Lana Leonardo Gonçalves Isabela Nahas Universidade Federal de Ouro Preto Departamento de GeologiaCampus Morro do CruzeiroOuro PretoMG CEP 35400-000Brazil University of Portsmouth School of the EnvironmentGeography and GeosciencesBurnaby BuildingBurnaby RoadPortsmouth PO13QLUK Tektos Research Group UERJ-Rio de Janeiro State UniversityBrazil Sustain Geologia Belo HorizonteBrazil

The late-to post-collisional stage in orogenic systems is characterized by the coeval existence of bimodal potassic to ultrapotassic magmatic activity related to partial melting of an enriched lithospheric mantle together with crustal derived *** this paper,we present new whole rock geochemical analyses combined with zircon and titanite U–Pb and zircon Hf isotopic data from potassic to ultrapotassic rocks from six plutons that occur within the Archean Itacambira-Monte Azul block(BIMA),to discuss their petrogenesis and the tectonic implications for the São Francisco *** new U–Pb ages range from ca.2.06 Ga to 1.98 Ga and reveal long-lasting potassic magmatism within the BIMA,which is within the late-to-post-collisional stage of the São Francisco paleocontinent *** ultrapotassic rocks are compatible with a fluid-related metasomatized mantle source enriched by previous subduction events,whereas the potassic rocks are bimodal and have a transitional shoshonitic to A-type *** rocks have a hybrid nature,possible related to the mixing between the mafic potassic/ultrapotassic rocks and high temperature crustal melts of the Archean continental *** results also show an increase of within-plate signature towards the younger potassic *** participation of an important Archean crustal component in the genesis of these rocks is highlighted by the common and occasionally abundant occurrence of Archean inherited *** Hf isotopic record shows that most of the zircon inheritance has dominantly subchondriticεHf(t)values,which fits a crustal reworking derivation from a similar Eo-to Paleoarchean precursor ***,the presence of juvenile 2.36 Ga zircon inheritance in an ultrapotassic sample reveal the existence of a hidden reservoir that is somewhat similar to the described for the Mineiro Belt in southern São Francisco paleocontinent.

关键词： Late-to post-collisional Potassic-ultrapotassic rocks U–Pb dating São Francisco paleocontinent Rhyacian-Orosirian orogenic system

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Paleoproterozoic juvenile magmatism within the northeastern sector of the Sao Francisco paleocontinent:Insights from the shoshonitic high Ba-Sr Montezuma granitoids

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Geoscience Frontiers 2020年第5期11卷 1821-1840页

作者： samuel moreira bersan Alice Fernanda de Oliveira Costa Andre Danderfer Francisco Roberio de Abreu Cristiano Lana Glaucia Queiroga Craig Storey Hugo moreira Universidade Federal de Ouro Preto Programa de Pos-graduacaoDepartamento de GeologiaCampus Morro do CruzeiroOuro PretoMGCEP 35400-000Brazil Universidade Federal de Ouro Preto Departamento de GeologiaCampus Morro do CruzeiroOuro PretoMGCEP 35400-000Brazil Sustain Geologia Ltda Teresa M.Valadares 503/502Belo HorizonteMGCEP 30575-160Brazil University of Portsmouth School of Earth and Environmental SciencesBurnaby BuildingBurnaby RoadPortsmouthPO13QLUK

New,integrated petrographic,mineral chemistry,whole rock geochemical,zircon and titanite UPb geochronology,and zircon Hf isotopic data from the Montezuma granitoids,as well as new geochemical results for its host rocks represented by the Corrego Tingui Complex,provides new insights into the late-to post-collisional evolution of the northeastern Sao Francisco paleocontinent.U-Pb zircon dates from the Montezuma granitoids spread along the Concordia between ca.2.2 Ga to 1.8 Ga and comprise distinct *** I have crystallization ages between ca.2.15 Ga and 2.05 Ga and are interpreted as inherited *** II zircon dates vary from 2.04 Ga to1.9 Ga and corresponds to the crystallization of the Montezuma granitoids,which were constrained at ca.2.03 Ga by the titanite U-Pb *** age zoning is common within the ca.1.8 Ga Group III zircon ages,being related to fluid isotopic re-setting during the Espinhaco rifiting ***εHf(t)analysis show dominantly positive values for both Group I(-4 to+9)andⅡ(-3 to+8)zircons and TDM2 model ages of 2.7-2.1 Ga and 2.5-1.95 Ga,***,the Montezuma granitoids are weakly peraluminous to metaluminous magnesian granitoids,enriched in LILES and LREE,with high to moderate Mg#and depleted in some of the *** lithochemical signature,added to the juvenile signature of both inherited and crystallized zircons,allowed its classification as a shoshonitic high Ba-Sr granitoid related to a late-to post-collisional lithosphere delamination followed by asthenospheric *** this scenario,the partial melting of the lithospheric mantle interacted with the roots of an accreted juvenile intra-oceanic arc,being these hybrid magma interpreted as the source of the Montezuma *** Corrego Tingui Complex host rocks are akin to a syn-to late-collisional volcanic arc granitoids originated from the partial melting of ancient crustal *** results presented in this study have revealed the occurrence of j

关键词： Zircon U–Pb-Hf Titanite U–Pb High Ba–Sr Late-to post-collisional Sao Francisco paleocontinent

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Paleo-and Mesoarchean TTG-sanukitoid to high-K granite cycles in the southern São Francisco craton,SE Brazil

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Geoscience Frontiers 2022年第5期13卷 153-168页

作者： Claudio de Morisson Valeriano Caio Vinicius Gabrig Turbay Henrique Bruno Antonio Simonetti Monica Heilbron samuel moreira bersan Rob Strachan Universidade do Estado do Rio de Janeiro Faculdade de GeologiaRua São Francisco Xavier 524/4006-BMaracanãRio de JaneiroBrazil Universidade Federal do Sul da Bahia Centro de Formação em Ciências AmbientaisPorto SeguroBahiaBrazil University of Portsmouth School of EnvironmentGeography and GeosciencesBurnaby BuildingBurnaby RoadPortsmouth PO13QLUnited Kingdom University of Notre Dame Department of Civil and Environmental Engineering and Earth Sciences46556United States

The generation of the continental crust is widely accepted to have taken place predominantly in the Archean,when TTG magmatism associated with greenstone-belt supracrustal succession development was typically followed by emplacement of high-K granites before crustal *** study focuses on the Campos Gerais complex(CGC),which is an Archean granite-greenstone belt lithological association in a tectonic window located in the southwesternmost portion of the São Francisco craton(SFC).The CGC is an important segment of Paleo-to Mesoarchean continental crust to be integrated into paleogeographic reconstructions prior to the transition into the *** investigation reports field relationships,28 major and trace element compositions,U–Pb(zircon)geochronological results,and Hf and Sm–Nd isotope data for orthogneiss and amphibolite *** results indicate that the CGC records a complex Archean crustal evolution,where voluminous 2.97 Ga TTG tonalites and trondhjemites(ε_(Nd)(t)=-4.7;T_(DM)=3.24 Ga)were followed by 2.89 Ga sanukitoid tonalite production(ε_(Nd)(t)=-1.9;T_(DM)=3.02 Ga),broadly coeval with the development of the Fortaleza de Minas and Pitangui *** events are interpreted to represent the initial stage of an important subduction-accretion tectonic cycle,which ended with the emplacement of 2.82–2.81 Ga high-K leucogranites and migmatization of the TTG-sanukitoid crust,with hybrid and two-mica,peraluminous compositions(ε_(Nd)(t)=-8.0 to-8.6;T_(DM)=3.57–3.34 Ga).The presence of inherited zircons with207Pb/206Pb ages of 3.08 Ga,3.29 Ga,3.55 Ga and 3.62 Ga indicates that the Mesoarchean tectonic processes involved reworking of Meso-to Eo-archean *** TTG magmatism took place at ca.2.77 Ga represented by juvenile tonalite stocks(ε_(Nd)(t)=+1.0 to-1.5;T_(DM)=2.80–2.88 Ga)which intrude the TTG-greenstone belt *** stabilization was attained by 2.67 Ga,allowing for the emplacement of within-plate thol

关键词： Crustal evolution Sm–Nd Lu–Hf LA-ICPMS zircon U–Pb

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Rhyacian-Orosirian tectonic history of the Juiz de Fora Complex:Evidence for an Archean crustal reservoir within an island-arc system

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Geoscience Frontiers 2022年第5期13卷 350-369页

作者： Rasec Almeida Vitalino Elizeu Henrique Bruno samuel moreira bersan Lucas Eduardo de Abreu Barbosa Araujo Ivo Dussin Claudio de Morisson Valeriano Carla Neto Monica Heilbron Universidade do Estado do Rio de Janeiro Faculdade de GeologiaTektos–Grupo de Pesquisa em GeotectônicaRua São Francisco Xavier 524MaracanãRio de JaneiroBrazil Laboratório de Geocronologia e Isótopos Radiogênicos Universidade do Estado do Rio de JaneiroRua São Francisco Xavier 524MaracanãRio de JaneiroBrazil

The southern São Francisco Paleocontinent(SFP)comprises Archean nuclei and Paleoproterozoic complexes encompassing magmatic arcs juxtaposed during a Rhyacian to Orosirian orogenic *** Juiz de Fora Complex(JFC)represents an imbricated thrust system that comprises orthogranulites with a wide compositional range formed in an intra-oceanic setting during the Siderian to the Orosirian and later accreted to the southeastern margin of the *** we report new petrological,geochemical,whole-rock Nd and Sr data,as well as zircon U–Pb ages from felsic and mafic orthogranulites from the *** new data is combined with a regional compilation that enables an evaluation of the interaction between magmatism and orogenetic episodes in the context of the consolidation of São Francisco Paleocontinent during the Rhyacian–*** collisional Island Arc tholeiites(IAT),Tonalites-Tron dhjemites-Granodiorites(TTGs)and sanukitoid magmatism occurred from 2200 Ma to 2085 *** was followed by post-collisional magmatism,which is represented by hybrid granitoids coeval with the emplacement of E-MORB basic *** signatures for the Rhyacian to Orosirian evolution are highlighted by the dominance of negativeεNd(t)associated with Meso-to Neoarchean Nd TDMmodel ages as well as inherited zircon grains from the hybrid *** JFC is extensively highlighted in the literature as a primitive intra-oceanic arc,but here we propose the reworking or recycling of ancient crustal segments within the mature arc stage of the JFC,suggesting a Mesoarchean crustal source involved in the JFC evolution.

关键词： Juiz de Fora complex Paleoproterozoic magmatic arc TTG and sanukitoid São Francisco Paleocontinent

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Record of Early Tonian mafic magmatism in the central Espinhaco(Brazil):New insights for break-up of the Neoproterozoic landmass ancestor of Sao Francisco-Congo paleocontinent

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Geoscience Frontiers 2020年第6期11卷 2323-2337页

作者： Helen F.moreira AndréDanderfer Alice F.O.Costa samuel M.bersan Cristiano C.Lana Gláucia N.Queiroga Post Graduate Program of Department of Geology Mine SchoolFederal University of Ouro PretoBrazil Department of Geology Mine SchoolFederal University of Ouro PretoBrazil

Petrological characterization,U-Pb geochronology,Lu-Hf analyses and major and trace element data from mafic intrusions in the Central Espinhaco(central portion of the Brazilian shield)are used here to investigate the geological significance of the Early Neoproterozoic magmatism in the context of the Sao Francisco-Congo *** mafic bodies are represented by medium to coarse-grained metagabbros with plagioclase,amphibole and *** U-Pb isotopic data from two samples yielded weighted mean 206pb/238U ages of 895±3.4 Ma(MSWD=1.7)and 896±2.4 Ma(MSWD=0.64),regarded as the best estimates for the crystallization age of these mafic *** and trace element data(including REEs)show that the gabbros originated from a subalkaline tholeiitic magma,typical of intraplate *** rocks are slightly enriched in LREEs and LILEs and depleted in *** new isotope and geochemical data,along with regional knowledge,indicate that these metagabbros mark the beginning of an important Tonian-age extensional tectonic event of the landmass of which the Sao Francisco-Congo paleocontinent was part(Rodinia supercontinent or Central African block?).We furthermore suggest that these rocks belong to a prominent suite of Tonian-age mafic rocks that mark a diachronic breakup attempt of this landmass which may have occurred from south to north along the Espinhaco mountain range.

关键词： Mafic rocks Espinhaco basin Sao Francisco-Congo paleocontinent Tonian rifting U–Pb geochronology

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Neoarchean and Rhyacian TTG-Sanukitoid suites in the southern S?o Francisco Paleocontinent,Brazil:Evidence for diachronous change towards modern tectonics

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Geoscience Frontiers 2020年第5期11卷 1763-1787页

作者： Henrique Bruno Vitalino Elizeu Monica Heilbron Claudio de Morisson Valeriano Rob Strachan Mike Fowler samuel bersan Hugo moreira Ivo Dussin Luiz Guilherme do Eirado Silva Miguel Tupinamba Julio Almeida Carla Neto Craig Storey Universidade Do Estado Do Rio de Janeiro Faculdade de GeologiaTektosGrupo de Pesquisa Em GeotectonicaRua Sao Francisco Xavier 524MaracanaRio de JaneiroBrazil University of Portsmouth School of Earth and Environmental SciencesBurnaby BuildingBurnaby RoadPortsmouthUK Universit€at Salzburg Department of Geography and GeologyKapitelgasse4-65020SalzburgAustria Universidade Federal de Ouro Preto Departamento de GeologiaCampus Morro Do CruzeiroOuro PretoMGBrazil Laboratorio de Geocronologia e Isotopos Radiog^enicos Universidade Do Estado Do Rio de JaneiroRua Sao Francisco Xavier 524MaracanaRio de JaneiroBrazil

The southern portion of the Sao Francisco Palaeocontinent in Brazil is denoted by Archean nuclei and Paleoproterozoic magmatic arcs that were amalgamated during Siderian to Orosirian orogenic processes(ca.2.4-2.1 Ga).New isotopic U-Pb in zircon and Sm-Nd whole rock combined with major and trace element composition analyses constrain the crystallization history of the Neoarchean Piedade block(at ca.2.6 Ga)and the Paleoproterozoic Mantiqueira Complex(ca.2.1-1.9 Ga).These therefore display quite different magmatic histories prior to their amalgamation at ca.2.05 ***-Nd and Rb-Sr isotopes imply a mixed mantle-crustal origin for the samples in both units.A complete Palaeoproterozoic orogenic cycle,from subduction to collision and collapse,is recorded in the Piedade Block and the Mantiqueira *** to Orosirian subduction processes(ca.2.2-2.1 Ga)led to the generation of coeval(ca.2.16 Ga)TTG suites and sanukitoids,followed by late(2.10-2.02 Ga)high-K granitoids that mark the collisional *** collisional accretion of the Mantiqueira Complex against the Piedade Block at 2.08-2.04 Ga is also recorded by granulite facies metamorphism in the latter terrane,along the Ponte Nova suture *** collisional stage was closely followed by the emplacement of within-plate tholeiites at ca.2.04 Ga and by alkaline rocks(syenites and enriched basic rocks)at ca.1.98 Ga,marking the transition to an extensional tectonic *** discovery of two episodes of TTG and sanukitoid magmatism,one during the Neoarchean in the Piedade Complex and another during the Rhyacian in the Mantiqueira Complex,indicates that the onset of subduction-related melting of metasomatized mantle was not restricted to Neoarchean times,as generally believed,but persisted much later into the Paleoproterozoic.

关键词： Geodynamics High Ba–Sr granitoids Diachronous TTG-Sanukitoid transition Paleoproterozoic Mantiqueira complex

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