DEGEO - Departamento de Geologia
URI permanente desta comunidadehttp://www.hml.repositorio.ufop.br/handle/123456789/8
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Item Implications for the refinement of the São Francisco Craton magmatic barcode and the North China link.(2022) Mendes, Mônica de Cássia Oliveira; Lobato, Lydia Maria; Caxito, Fabrício de Andrade; Rosière, Carlos Alberto; Lana, Cristiano de Carvalho; Silva, Rosaline Cristina Figueiredo eLate Archean to Paleoproterozoic dike swarms crosscut the basement and supracrustal sequences of the São Francisco Craton. Their spatial distribution and orientation patterns, as paleomagnetic signature, provide key evidence to the positioning of the cratonic area in ancient paleocontinental reconstructions through the refinement of the “magmatic barcode”. Zircon U–Pb data from dikes in the cratonic domain of the Quadrilátero Ferrífero Mineral Province, in the southern of São Francisco Craton, allowed the recognition of two magmatic stages: a Rhyacian-Orosirian pulse, belonging to the Paraopeba swarm, and a Statherian pulse that belongs to the Pará de Minas II swarm. The Ediacaran Brasiliano Orogeny later affected dikes from both swarms. The Paraopeba swarm consists of pulses related to the Rhyacian-Orosirian orogenic cycle, with dikes providing U–Pb zircon ages of 2019 + 23–11, 1944 ± 29 and 1918 ± 12 Ma. The zircon εHf values from these dikes are predominantly negative, suggesting reworking of preexisting crust, whereas the TDM ages vary from 4000 to 2500 Ma, which can be interpreted as a long period of crustal residence. The Statherian Pará de Minas II swarm, with a U–Pb zircon age of 1717 ± 9 Ma, is chronocorrelated to the lower stratigraphic sequence of the Espinhaço rift basin. Zircon grains from this dike have predominantly positive εHf values and TDM model ages between 3050 and 1950 Ma. Unlike the Paraopeba swarm, the Pará de Minas magmatism is marked by a striking input of juvenile mantle material with minor crustal contamination. The Ediacaran Brasiliano tectono-thermal event caused isotopic disturbance in both Paraopeba and Pará de Minas II swarms, resulting in lower intercepts at 595 ± 65 and 584 ± 27 Ma, respectively. Our data pinpoint dike emplacement related to tectonic events described in the southern of São Francisco. In the final stages of Rhyacian orogenic cycle, at ca. 2019–1918 Ma, data suggests an important crustal contamination. Thereafter, a crustal rifting event at ca. 1717 Ma involved dike swarm emplacement with magmatic source from a mantle plume. The Rhyacian-Orosirian ages obtained here are the first zircon U–Pb geochronological data presented for the Paraopeba dike swarm and allow for a refinement of the São Francisco Craton barcode, reinforcing previous suggestions of proximity with the North China Craton crosscut by the similarly aged Hengshan and Xiwangshan/Xuwujia dike swarms, whether or not those two cratonic pieces were part of the Columbia supercontinent.Item The tectonic evolution of the Quadrilfitero Ferrifero, Minas Gerais, Brazil.(1994) Chemale Júnior, Farid; Rosière, Carlos Alberto; Endo, IssamuThe structural framework of the Quadrilatero Ferrifero is the result of two main deformational events. The first is an extensional event of Palaeoproterozoic age (between 2100 and 1700 Ma, the Transamazonian Event), which resulted in the formation of Archaean granite-gneiss domes and the nucleation of regional synclines in the overlying Rio das Velbas and Minas supergroups strata. Such regional synclines are continuous with each other and are bordered by structural granite-gneiss highs. At the contact between these units, ductile-brittle to ductile extensional shear zones are developed, representing the dislocation surfaces of Archaean blocks. This tectonism is probably related to the evolution of a metamorphic core complex, formed in the hinterland to the west of a Transamazonian collision zone, which structured the Paramirim Craton. The second event is compressive and associated with the closure of the Pan-African/Brasiliano protoocean (650-500 Ma), situated to the east of Quadrilltero Ferrffero (QF). During this event, a west-verging foldandthrust belt (FTB) developed, causing inversion, amplification, translation and rotation of the basinal synclines. The FTB affected mainly the eastern portion of QF and obliterated many of the tectonic features of the extensional event.Item The Statherian itabirite-bearing sequence from the Morro Escuro Ridge, Santa Maria de Itabira, Minas Gerais, Brazil.(2015) Braga, Flávia Cristina Silveira; Rosière, Carlos Alberto; Queiroga, Gláucia Nascimento; Rolim, Vassily Khoury; Santos, João Orestes Schneider; McNaughton, Neal JesseThe itabirite-bearing metasedimentary sequence from Morro Escuro Ridge comprises the basal units of the Espinhaço Supergroup and makes up a small tectonic inlier developed during one of the Brasiliano orogenic events (800-500 Ma), amongst horses of the Archean TTG gneisses, including sheared granites of the anorogenic Borrachudos Suite (~1700 Ma). The metasedimentary rocks are comprised of low-to intermediate-amphibolite facies schists, quartzites, conglomerates and banded iron formation (itabirite) correlatable with the sequences of the Serro Group, which underlies the metasedimentary rocks of the Espinhaço Supergroup in the Serra da Serpentina Ridge. A maximum Statherian deposition age (1668 Ma) was established using SHRIMP UePb isotopic constraints on zircon grains from conglomerate and quartzite units overlying the itabirite. The itabirite is predominantly hematitic and its geochemical characteristics are typical of a Lake Superior-type BIF deposited in a platformal, suboxic to anoxic environment distant from Fe-bearing hydrothermal vents. Close to the contact zone with amphibolites of the Early Neoproterozoic Pedro Lessa mafic suite, an increase of the magnetite content and crystallization of metasomatic Mg-hornblende and Ce-allanite can be observed. These mineralogical changes developed preferentially along the igneous contact zone but are probably co-genetic with the formation of alteration haloes in zircon grains during the Neoproterozoic Brasiliano orogeny (506 ± 6 Ma).Item Roteiro da excursão geológica no Quadrilátero Ferrífero e regiões adjacentes.(1992) Endo, Issamu; Rosière, Carlos Alberto; Chemale Júnior, FaridItem Supergrupo Minas na Serra de Bom Sucesso, extremo sudoeste do Quadrilátero Ferrífero – MG : petrografia, geoquímica e isótopos de U-Pb.(2013) Neri, Marcos Eduardo Nilton Vieira; Rosière, Carlos Alberto; Lana, Cristiano de CarvalhoNo extremo sudoeste do Quadrilátero Ferrífero, porção sul do Cinturão Mineiro, está exposta uma faixa de metassedimentos que contém formações ferríferas bandadas, denominada, neste estudo, como Sequência Metassedimentar Bom Sucesso. A sequência tem empilhamento estratigráfico normal e é subdividida em três unidades, da base para o topo: xisto carbonático Lagoa da Prata, Formação Ferrífera Bandada Bom Sucesso e xisto Tabuãozinho. Dados U-Pb de zircão detrítico, de amostras da Unidade Lagoa da Prata, indicam idade máxima de deposição de 2603 ± 7,3 Ma, correlacionando essa unidade com a base do Supergrupo Minas, o Grupo Caraça. A formação ferrífera bandada é predominantemente anfibolítica e possui intercalação de dolomitos ferruginosos descontínuos, apresentando contato transicional com xisto ferruginoso no topo da unidade. A formação ferrífera bandada contém anomalias positivas de Eu, Y e La, enriquecimento relativo de Elementos Terras Raras (ETR) pesados e ausência de anomalia negativa de Ce, análoga aos Itabiritos da Formação Cauê, Grupo Itabira.A Sequência Metassedimentar Bom Sucesso sofreu metamorfismo de contato associado a metassomatismo alcalino, gerado pela intrusão do Granito Tabuões, durante a orogenia Transamazônica.Item Sobre a geologia estrutural do anticlinal de Mariana, região sudeste do Quadrilátero Ferrífero Minas Gerais : uma revisão.(1992) Nalini Júnior, Hermínio Arias; Rosière, Carlos Alberto; Endo, IssamuItem Análise cinemática mesoscópica dos cavalgamentos do cinturão espinhaço na região de Diamantina, MG.(1994) Rosière, Carlos Alberto; Uhlein, Alexandre; Fonseca, Marco Antônio; Torquato, Joaquim Raul FerreiraA análise geométrica e cinemática de um excepcional afloramento de quartzitos e filhos do Grupo Diamantina, nas proximidades da cidade homónima, permitiu a interpretação da história da evolução das estruturas ali formadas, que representam, em escala mesoscópica, a estruturação macroscópica da porção ocidental da Serra do Espinhaço. A evolução da tectônica compressional iniciou-se com intenso deslizamento interestratal, seguido de nucleação de dobras de deslizamento flexural e desenvolvimento de falhas de cavalgamento, aproximadamente dentro de um mesmo plano cinemático, com transporte de ENE para WSW. A deformação ocorreu dentro de tectônica epitelial, em condições rúpteis a dúctil-rúpteis, tendo as rochas sofrido fraco metamorfismo (fácies xisto verde) e a temperatura perdurado até o final do tectonismo.