Age of the Ribeirão Da Folha Ophiolite, Araçuaí Orogen: The U-Pb Zircon (La-Icpms) Dating of a Plagiogranite

Queiroga, Gláucia Nascimento; Pedrosa-Soares, Antônio Carlos; Noce, Carlos Maurício; Alkmim, Fernando Flecha de; Pimentel, Márcio Martins; Dantas, Elton Luiz; Martins, Maximiliano; Castañeda, Cristiane; Suita, Marcos Tadeu de Freitas; Prichard, Hazel Margaret

doi:10.18285/geonomos.v15i1.107

Cited by 23 publications

(37 citation statements)

References 12 publications

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“…Detrital zircon grains from a quartzite suggest a maximum depositional age of around 750 Ma (Kuchenbecker et al 2015). The Upper Chapada Acauã Formation passes laterally into Ribeirão da Folha Formation, which contains distal passive-margin and ocean-floor deposits (Pedrosa-Soares et al 1992, 2011, Queiroga et al 2007. Detrital zircon grains suggest a maximum depositional age of around 806 Ma (Peixoto et al 2015).…”

Section: Central Espinhaço -Southern Portionmentioning

confidence: 99%

“…Metamafic and meta-ultramafic rocks with an ocean-floor lithochemical signature yielded Ediacaran magmatic crystallization U-Pb ages, which suggest oceanic spreading from at least ca. 660 to 600 Ma (Queiroga et al 2007, Queiroga 2010.…”

Section: Central Espinhaço -Southern Portionmentioning

confidence: 99%

“…The youngest U-Pb ages of detrital zircons produced maximum depositional ages of around 750 Ma (Kuchenbecker et al 2015). However, ophiolite ages acquired by Queiroga et al (2007) indicate the ocean basin related to the development of this passive margin extended into the Cryogenian.…”

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confidence: 97%

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Tectonics and sedimentation of the central sector of the Santo Onofre rift, north Minas Gerais, Brazil

Costa

Filho

2017

Braz. J. Geol.

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ABSTRACT:The Santo Onofre Group registers the filling of a Tonian, intracontinental paleo-rift that developed along the northern and central Espinhaço regions. This paper examines this unit in the central Espinhaço region with stratigraphic analysis and U-Pb geochronology, reviewing and dividing into the Canatiba and Rio Peixe Bravo Formations, which include the Barrinha Member. The Canatiba Formation mainly comprises carbon-rich mudstones that were deposited through low-density turbidity flows that alternated with sediment settling under anoxic conditions. The Rio Peixe Bravo Formation consists of a succession of sandstones and minor mudstones, which were deposited through low-to high-density turbidity flows. The Barrinha Member mainly consists of conglomerates and is related to channelized debris flows. Detrital zircon grains show maximum depositional ages of 930 ± 33 Ma and around 865 Ma for the Canatiba and Rio Peixe Bravo Formations, respectively. We interpret the Santo Onofre rifting to be relative younger than that for the Sítio Novo Group and to be a precursor stage of the glacial and post-glacial rift-to-passive margin-related sequences of the Macaúbas Group. The lithostratigraphic term "Macaúbas Supergroup" would be of better use to accommodate the unconformity-bounded Tonian sequences that were related to the Rodinia breakup in the Congo-São Francisco paleocontinent. (Hoffman 1991, Meert 2001. Several phases that involved the breaking of Rodinia occurred, either through passive or active rifting, which were induced by remotely applied tensions (in-plane stress) and mantle plumes, respectively . These processes operated diachronically through a continental mass, and the full disintegration of the continent was complete at the end of the Tonian Period (Hoffman 1991, Cawood et al. 2016. Many rifts were formed before reaching this stage, some of which were aborted, and mafic dyke swarms intruded, which became dispersed in the scattered continents (Chew et al. 2010, Volkert et al. 2015. Investigations of these features have provided a better understanding of the space-temporal evolution of the Rodinia, for reconstructions (Hoffman 1991, Meert 2001. KEYWORDS:The Congo-São Francisco paleocontinent is characterized as one of several fragments of the Rodinia (Hoffman 1991. This paleocontinent encompasses the cover and basement rocks of São Francisco and Congo cratons and their marginal orogenic belts ( Fig. 1; Almeida 1977, Alkmim et al. 1993, Trompette 1994. The Espinhaço mountain range is a remarkable feature that extends with a sub-meridian direction across the entire extent of the Congo-São Francisco paleocontinent. The southern and central Espinhaço range regions integrate the Araçuaí fold and thrust belt as one of the external domains of the Neoproterozoic Araçuaí-West Congo orogen (Almeida 1977, Pedrosa-Soares et al. 1992, while the northern extension occurs along the eastern border of the Paramirim aulacogen, which was partially inverted, and involves the basement in the cover deformation (Schobbenhau...

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Section: Central Espinhaço -Southern Portionmentioning

confidence: 99%

Section: Central Espinhaço -Southern Portionmentioning

confidence: 99%

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Tectonics and sedimentation of the central sector of the Santo Onofre rift, north Minas Gerais, Brazil

Costa

Filho

2017

Braz. J. Geol.

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“…Apresenta polaridade sedimentar e desenvolvimento faciológico segmentado no sentido NNW-SSE, com registro localizado dos estágios de desenvolvimento bacinal de um rifte continental para uma margem passiva (Noce, 1997;Kuchenbecker et al, 2015). De maneira geral, comporta uma sequência proximal, formada por depósi-tos pré-glaciais, glaciais e transicionais, e outra distal, encerrando restos ofiolíticos de uma proto-crosta oceânica de 640 Ma (Pedrosa-Soares e Alkmim, 2011;Queiroga et al, 2007).…”

Section: Contextualização Regionalunclassified

Interação tectônica entre bacias sucessoras no domínio externo do Orógeno Araçuaí: estudo de caso da região de Planalto de Minas, Minas Gerais

Souza

Martins

Madeira

et al. 2017

Geol. USP. Sér. Cient.

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Resumo O Supergrupo Espinhaço Meridional e o Grupo Macaúbas, em Minas Gerais, são as maiores expressões geotectônicas dos ciclos de fragmentação sucessivos que atingiram o paleocontinente São Francisco-Congo desde o Estateriano até o Criogeniano. O mapeamento geológico em escala 1:25.000 da região de Planalto de Minas, localizada no centro-norte do estado, revelou a ocorrência da Formação São João da Chapada (ca. 1.7 Ga, Supergrupo Espinhaço) diretamente sobreposta por uma sequência metavulcano-sedimentar toniana do Grupo Macaúbas (ca. 889 Ma), aqui designada de Formação Planalto de Minas. A integração geológica-geofísica revelou ainda que esta área permaneceu como um alto estrutural do final do Estateriano até o Toniano. A existência do alto estrutural de Planalto de Minas é o reflexo do complexo arranjo estrutural de rifteamentos sobrepostos, com formação e interação de um meio-gráben, ou sistema ramificado de meio-grabens, que exerceram importante controle tectono-estratigráfico na arquitetura -formação e evolução -da bacia Macaúbas.Palavras-chave: Bacias do Tipo Rifte; Alto Estrutural de Planalto de Minas; Meio-gráben; Geofísica; Supergrupo Espinhaço; Grupo Macaúbas. AbstractIn Minas Gerais state, the Southern Espinhaço Supergroup and Macaúbas Group are the major geotectonic expression of the crustal sucessives fragmentation cycles that shaped the São Francisco-Congo paleocontinent between the Statherian and Cryogenian periods. The geological mapping (1:25.000) in Planalto de Minas region (central-northern portion of Minas Gerais) revealed the occurrence of the São João da Chapada Formation (ca. 1.7 Ga, Espinhaço Supergroup) directly superimposed by a Tonian metavolcano-sedimentary sequence, here called Planalto de Minas Formation (Macaúbas Group), dated at ca. 889 Ma. The geological-geophysical data integration revealed that the Planalto de Minas region remained as a structural high, and this is a reflection of the complex structural arrangement of superimposed rifts, with the formation and interaction among one half-graben or branched system of half-grabens, being important for the tectonic-stratigraphy control -on architecture and evolution -of the Macaúbas basin.

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“…The passive margin rocks are represented by mid to upper formations of the Macaúbas Group, including mafic-ultramafic rocks, pelites and cherts, part of an ophiolite complex that represents the oceanic portion of this basin (Pedrosa-Soares et al 1992, Aracema et al 2000. Zircon grains of plagiogranite, associated with the mafic oceanic rocks, yielded 660 ± 29 Ma, age considered as the time oceanic crust was formed (Queiroga et al 2007). The pelites that derived migmatites of the Jequitinhonha Complex (Almeida & Litwinski 1984) may as well be part of this passive margin (Pedrosa-Soares & Wiedemann-Leonardos 2000, Sampaio et al 2004, Heilbron et al 2004.…”

Section: Geological Setting Of the Araçuaí Orogenmentioning

confidence: 99%

Applications and limitations of thermobarometry in migmatites and granulites using as an example rocks of the Araçuaí Orogen in southern Bahia, including a discussion on the tectonic meaning of the current results

et al. 2015

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ABSTRACT:In southern Bahia, there are outcrops of migmatites and granulites in the Jequitinhonha Complex, which is part of the northern portion of the Araçuaí Orogen. Migmatites (garnet-cordierite diatexite) dominate the metamorphic rocks and host lenses and layers of felsic garnet granulite. The conditions of temperature and pressure of metamorphism were calculated using conventional thermobarometry and the software THERMOCALC. Values around 850 °C and 7 kbar were obtained with THERMOCALC. The calculations for the garnet-cordierite diatexite were made considering a H2O equal to 1, but the best results of calculations for the granulites are obtained with a H2O values of 0.3. Pressure values obtained with GAPES resulted in consistent values with THERMOCALC, but the pair garnet-orthopyroxene always produces low values for temperature and high ones for pressure. The results are consistent with the presence of the pair garnet and cordierite in diatexite and orthopyroxene in felsic granulite. From the tectonic point of view, the setting in which metamorphism of these rocks occurred requires high heat flow with a thermal anomaly in mid continental crust, as indicated by values of 7 kbar. Recent studies have favored the closure of a back-arc basin for this tectonic setting, but it does not solve the problem that the time span between metamorphic peak and the end of granite intrusions, involving large bodies of charnockite, is more than 80 million years. RESUMO: INTRODUCTIONTo calculate the conditions of pressure and temperature for rocks that underwent granulite facies metamorphism should be simple and straightforward, as the formation conditions overlap those used in most experiments to calibrate thermometers and barometers. However, several factors linked to the genesis of granulites and migmatites contribute negatively to make this task simple and easy. After the metamorphic peak temperature is achieved, often greater than 800°C, granulites and migmatites cool down slowly in the middle to lower portions of the continental crust, a situation that leads to their re-equilibration. Furthermore, the presence of a melt phase is common in granulite facies conditions and can enhance the rate of diffusion or even destroy anhydrous metamorphic peak mineralogy during cooling (Moraes et al. 2002;White & Powell 2002, 2010. For the effective calculation of P-T conditions, either corrections on mineral compositions or thermodynamic modeling must be done. The loss of simplicity makes the task complex, challenging, attractive and, particularly, an interesting subject.To illustrate some of the problems related to the P-T calculation in migmatites and granulites, rocks of the Araçuaí Orogen, in southern Bahia, will be used as an example. Once the results are obtained, an evaluation of their geological, metamorphic and tectonic meaning is undertaken. Thermobarometry applied to granulites and migmatites: problems and restrictionsIn continental crust granulite facies metamorphism, in addition to recrystallization of the protolith, condi...

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Age of the Ribeirão Da Folha Ophiolite, Araçuaí Orogen: The U-Pb Zircon (La-Icpms) Dating of a Plagiogranite

Cited by 23 publications

References 12 publications

Tectonics and sedimentation of the central sector of the Santo Onofre rift, north Minas Gerais, Brazil

Tectonics and sedimentation of the central sector of the Santo Onofre rift, north Minas Gerais, Brazil

Interação tectônica entre bacias sucessoras no domínio externo do Orógeno Araçuaí: estudo de caso da região de Planalto de Minas, Minas Gerais

Applications and limitations of thermobarometry in migmatites and granulites using as an example rocks of the Araçuaí Orogen in southern Bahia, including a discussion on the tectonic meaning of the current results

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