DEGEO - Departamento de Geologia

URI permanente desta comunidadehttp://www.hml.repositorio.ufop.br/handle/123456789/8

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1996 - 199912000 - 200932010 - 20206

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Assunto: search.filters.subject.São Francisco Craton

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    Detrital zircon records of the Paleo-Mesoproterozoic rift-sag Tamanduá group in its type-section, Northern Quadrilátero Ferrífero, Minas Gerais, Brazil.
    (2020) Dutra, Luiz Fernandes; Dias, Sérgio Patusco; Martins, Maximiliano de Souza; Lana, Cristiano de Carvalho; Batista, Ana Carolina; Tavares, Túlio Delôgo
    The Quadrilátero Ferrífero metallogenetic province is located in the southernmost portion of the São Francisco craton, SE Brazil. The Tamanduá and Cambotas ridges stand out topographically in the northeastern portion of Quadrilátero Ferrífero and show NE-SW and N-S directions, respectively. Those ridges involve metasedimentary rocks of the Tamanduá Group bounded by a fault system. Due to stratigraphic and structural complexities, there is little consensus about the maximum sedimentation age and the stratigraphic position in which Tamanduá Group sediments were deposited. In this work, we took advantage of the excellent exposures in the Tamanduá and Cambotas ridges to present detailed stratigraphic observations combined with U-Pb zircon geochronological data from samples of different stratigraphic levels of Tamanduá Group. Furthermore, we provide U-Pb data from samples of the intrusive Pedra Formosa Suite that cut the whole Tamanduá sequence in the study area. Our observations showed that the Tamanduá Group represents a rift-sag basin-fill succession developed along the eastern border of the São Francisco paleoplate. The basal metaconglomerate and metasandstone package grades upward into marine metasandstone and phyllite. Detrital zircon obtained from the basal unit, Antônio dos Santos Formation, reveals maximum depositional ages between ca. 1981 and 1770 Ma. The upper succession, Cambotas Formation, shows a maximum depositional age from 1769 to 1740 Ma. The Pedra Formosa Suite shows zircons that crystallized at ca. 1740 Ma. The stratigraphic framework and the Orosirian-Statherian ages suggest a correlation with the first rifting event within the São Francisco paleoplate, the precursor of Paleo- to Mesoproterozoic Espinhaço basin.
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    Pseudosection modeling and U-Pb geochronology on Piranga schists : role of Brasiliano Orogeny in the Southeastern Quadrilátero Ferrífero, Minas Gerais, Brazil.
    (2019) Queiroz, Yanne da Silva; Queiroga, Gláucia Nascimento; Moraes, Renato de; Fernandes, Victor Matheus Tavares; Medeiros Júnior, Edgar Batista de; Evangelista, Hanna Jordt; Schulz, Bernhard; Schmiedel, Julia; Martins, Maximiliano de Souza; Castro, Marco Paulo de; Lana, Cristiano de Carvalho
    In the Southeastern Quadrilátero Ferrífero, a package of metapelitic rocks previously attributed to the Archean Rio das Velhas Supergroup crops out in Piranga locality. This study presents the mineral chemistry and U-Pb-Hf zircon geochronology on foliated staurolite-garnet mica schists. Garnet and staurolite index minerals are syn- to post-kinematic towards the main schistosity. Garnet porphyroblasts display well-developed compositional zoning of Mg-Fe-Mn-Ca, with increase of almandine and pyrope and decrease of spessartine towards the rim, implying in prograde metamorphic pattern. Estimates of P-T values for the metamorphic peak resulted in temperatures between 630 to 650ºC and pressure around 7 kbar. Pseudosections show well-defined stability fields in amphibolite facies, with a metamorphic path displaying progressive increase in P-T conditions. Maximum depositional age of 1,875 ± 51 Ma is established for the Piranga mica schists pointing to a depositional history that is younger than those previously described. Metamorphic Cambrian ages characterize the strong influence of deformational processes related to the final stages of Brasiliano Orogeny in the Southeastern Quadrilátero Ferrífero.
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    Metamorphism and exhumation of basement gneiss domes in the Quadrilátero Ferrífero : two stage dome-and-keel evolution?
    (2019) Cutts, Kathryn Ann; Lana, Cristiano de Carvalho; Alkmim, Fernando Flecha de; Farina, Federico; Moreira, Hugo Souza; Coelho, Viviane Viana
    The presence of dome-and-keel provinces in Archean cratons has been connected with the initiation of plate tectonics on Earth as these features are most commonly observed in Archean rocks. The Quadrilátero Ferrífero in Brazil has been identified as a Paleoproterozoic dome-and-keel province for more than three decades. The prevailing model suggests that it formed during the Rhyacian Transamazonian orogeny, making it unique among dome-and-keel provinces. However, a lack of appropriate lithologies, datable minerals and the metamorphic overprint of later orogenesis has resulted in a cryptic metamorphic record for the formation of this dome-and-keel province. A clinopyroxene-bearing migmatite from the core of the Bação dome has peak PeT conditions of 5e7 kbar and 700e750 C and a published age of ca. 2730 Ma based on UePb ages of zircon from leucosomes, suggesting that this age represents the migmatisation event. A fine-grained epidote-albite-titanite assemblage overprints the coarse-grained clinopyroxene and amphibole, giving PeT conditions of 8e9 kbar and 550 C with an associated titanite age of ca. 2050 Ma. A garnet-bearing amphibolite sample also from the core of the dome has peak PeT conditions of 7e8 kbar and 650e700 C, and texturally late titanite from this sample produces an age of ca. 2060 Ma. Three additional samples were collected from the edges of the dome. A garnet-gedrite bearing felsic schist produces peak PeT conditions of 8e9 kbar and 650e700 C on a clockwise PeT evolution. This sample has a UePb zircon age of ca. 2775 Ma, which could date metamorphism or be the age of its volcaniclastic protolith. Texturally unconstrained titanite from the sample gives an age of ca. 2040 Ma. A garnet-bearing amphibolite that occurs as a boudin within the felsic schist gives both zircon and titanite ages of ca. 2050 Ma and has peak PeT conditions of 5e6 kbar and 650e700 C on a near isobaric PeT path. An amphibolite dike, observed to cross-cut the felsic schist produces a zircon UePb age of ca. 2760 Ma. Altogether this data suggests that the samples were metamorphosed in the Archean (ca. 2775e2730 Ma) and again during the Transamazonian event. The most plausible explanation for this data is that dome-and-keel formation occurred in the Archean with migmatisation and high-temperature metamorphism occurring at this time. The Paleoproterozoic event is interpreted as a reactivation of the dome-and-keel formation structures, with Paleoproterozoic keels crosscutting Archean keels and producing metamorphic aureoles. The high radiogenic heat production and the presence of dense sedimentary successions in Archean terranes make dome-and-keel provinces a uniquely Archean feature, but they are susceptible to reworking, resulting in an enigmatic record of formation.
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    Interpretation of the geomagnetic anomalies in the São Francisco craton region based on champ mission data.
    (2011) Oliveira, Natália Valadares de; Endo, Issamu; Shukowsky, Wladimir
    O presente trabalho apresenta as discussões dos resultados da análise de dados magnetométricos provenientes da missão CHAMP (CHAllenging Minisatellite Payload), que constituem o modelo geomagnético da litosfera MF4 (Magnetic Field), visando o avanço no conhecimento da estruturação litosférica da região do Cráton São Francisco. Estudos geofísicos nesta área tem sido realizados desde a década de 1970, fornecendo um conhecimento da crosta e do manto litosférico/astenosférico com um razoável grau de detalhamento e confiabilidade. Os mapas magnetométricos baseados no modelo MF4 apresentaram resultados satisfatórios que possibilitaram associar as estruturações resultantes de alguns eventos tectônicos distintos de orogenias de núcleos continentais e para margens passivas, envolvidos na geodinâmica da porção litosférica em questão.
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    The sedimentology, stratigraphy and tectonic context of the São Francisco Supergroup at the southwest boundary of the São Francisco Craton, Brazil.
    (2000) Castro, Paulo de Tarso Amorim; Dardenne, Marcel Auguste
    Neoproterozoic metasedimentary rocks of the São Francisco Supergroup occur in the Southwest part of São Francisco Craton. Three informal lithostratigraphic units composed mainly by psephites, pelites and carbonates represent the São Francisco Supergroup. The last two units formed in storm influenced muddy shelf and platform/ramp systems, respectively. The psephitic unit crops out as isolated bodies nearby the external zone of the southernmost part of Brasilia Fold and Thrust Belt. Its origin is related to fan delta systems that developed eastward, in a foreland basin, as a result of erosion of metamorphic rocks of Brasilia Fold and Thrust Belt.
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    Igneous charnockites in the southeastern transition zone between the São Francisco craton and the Costeiro mobile belt, Brazil.
    (1996) Evangelista, Hanna Jordt
    Charnoquitos ígneos na zona de transição entre o cráton do São Francisco e o cinturão móvel Costeiro, Brasil Rochas félsicas e máficas com ortopiroxênios são importantes componentes da zona de transição entre o Cráton do São Francisco, de idade arqueana, e o Cinturão Móvel Costeiro, do Neoproterozóico, no sudeste do Brasil. O Charnoquito Pedra Dourada é composto de rochas félsicas pertencentes às séries charnoquito-enderbito e granito-tonalito intrusivas em piribolitos gabróicos. Entre as rochas félsicas e máficas ocorrem, além dos contatos claramente intrusivos, também contatos transicionais, do tipo migmatítico. Os charnoquitos mostram texturas magmáticas reliquiares que contrastam com as metamórficas dos piribolitos. Cálculos termobarométricos baseados na composição química de minerais coexistentes sugerem temperaturas entre 605 e 716°C e uma pressão de 7.3kbar (~27km de profundidade) para a formação do corpo de Pedra Dourada. Pelas paragêneses de alto grau destas rochas, estas temperaturas são excessivamente baixas, possivelmente devido a um reequilíbrio nas composições químicas dos minerais durante o subseqüente soerguimento e deformação. Os dados de campo complementados pelas características mineralógicas, texturais e químicas do Charnoquito Pedra Dourada sugerem uma origem por fusão parcial de crosta continental profunda sob as condições anidras da fácies granulito. O magma félsico cristalizou em rochas das séries charnoquítica e granítica. Os piribolitos máficos são provavelmente restitos. Este estudo mostra que charnoquitos de origem ígnea podem ser muito mais comuns nos terrenos do embasamento no mundo do que se tem até então admitido.
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    Estudo geoquímico e petrológico dos diques máficos da região de Candeias-Campo Belo-Santo Antônio do amparo (MG), porção meridional do craton São Francisco.
    (2006) Costa, Paulo César Corrêa da; Carneiro, Maurício Antônio; Teixeira, Wilson; Girardi, Vicente Antonio Vitorio; Nalini Júnior, Hermínio Arias; Oliveira, Arildo Henrique de; Fernandes, Rinaldo Afrânio
    No Complexo Metamórfico Campo Belo, sul de Minas Gerais, ocorrem diques máficos divididos em quatro grupos em função de aspectos petrográficos, geoquímicos e tectônicos: Anfibolitos A1, Anfibolitos A2, Gabronoritos e Gabros. A grande maioria das amostras tem afinidade toleítica, porém os anfibolitos A2 e um gabronorito situam-se no campo cálcio-alcalino, sendo que alguns anfibolitos A1 e gabronoritos estão no limite dos campos. A análise dos diagramas geoquímicos mostrou que os tipos litológicos pertencem a quatro agrupamentos oriundos de magmas com diferentes graus de evolução, sendo os gabros os mais evoluídos (mg# 0,18 - 0,23), seguindo-se os gabronoritos (mg# 0,33 - 0,35), os anfibolitos A2 (mg# 0,34 - 0,37) e os anfibolitos A1 (mg# 0,24 - 0,45). Sua comparação com modelos de fusão de mantos a granada e espinélio peridotito evidenciou o enriquecimento desses magmas progenitores, especialmente o da suíte gábrica, fato atribuível à fonte mantélica enriquecida e/ou contaminação crustal. Essa comparação aliada ao comportamento geoquímico diverso desses grupos em termos de elementos maiores, menores e traços indica a improbabilidade de cogeneticidade entre si. A comparação dos padrões de elementos traços entre os diques estudados e os enxames de Salvador, Carajás e Crixás-Goiás, pertencentes respectivamente aos Cratons São Francisco, Amazônico, e ao Bloco Arqueano de Goiás, sugere ambiente intracratônico.
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    The ancestry and magmatic evolution of Archaean TTG rocks of the Quadrilátero Ferrífero province, southeast Brazil.
    (2013) Lana, Cristiano de Carvalho; Alkmim, Fernando Flecha de; Armstrong, Richard; Cipriano, Ricardo Augusto Scholz; Romano, Rafael Cotta
    Combined LA-ICP-MS and SHRIMP U–Pb ages from Quadrilatero Ferrifero (QF) province reveals for the first time three main periods of TTG magmatism in the southern part of the Sao Francisco Craton (Brazil). These periods – described here as the Santa Barbara (SB), Rio das Velhas I (RVI) and Rio das Velhas II (RVII) events – embody a significant part of a protracted tectonomagmatic history of the Craton, spanning from 3220 to 2770 Ma. The initial stages of TTG magmatism (the SB event) led to formation of a core of Palaeoarchaean TTG crust via magmatic additions of juvenile felsic rocks into mafic–ultramafic rocks, at ca. 3212–3210 Ma. The following event (RVI event) saw the growth of this Palaeoarchaean core into a more composite, polydefomed continental segment through magmatic additions of juvenile TTG rocks and tectonic accretion of mafic–ultramafic greenstone belt terrains. Our U–Pb data and regional constraints suggest that much of the TTG crust exposed in the QF region today was produced during the RVI event, between 2930 and 2900 Ma. The final stages of TTG crust production (RV II event) were marked by convergence-related magmatism, affecting an extensive Palaeo- to Mesoarchaean continental block (The RVI block). The timing and duration of the latest TTG event coincides with the felsic volcanism and deposition of turbiditic wackes of the main greenstone belt sequence.
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    New geochronological constraints on the geological evolution of Espinhaço basin within the São Francisco Craton - Brazil.
    (2009) Danderfer Filho, André; Waele, Bert De; Pedreira, Augusto José de Cerqueira Lima; Nalini Júnior, Hermínio Arias
    The São Francisco Craton, in the central-eastern region of Brazil, is a cratonic fragment stabilized after the Rhyacian tectono-metamorphic event (2.25–2.05 Ga). Volcanic and sedimentary rocks of the Espinhac¸ o (Paleo- to Mesoproterozoic) and São Francisco (Neoproterozoic) basins crop out on this craton. In the northern sector of the craton, the Espinhac¸ o basin crops out in two domains: the Northern Espinhac¸ o Range and the Chapada Diamantina, that are separated by the Paramirim Corridor, a Brasiliano/Pan African (650–500 Ma) deformation zone, which crosses the craton in NNW–SSE direction. The stratigraphic framework of the Northern Espinhac¸ o is characterized by eight synthems that comprise units bound by unconformities, or stratigraphic discontinuities with regional extent over the Espinhac¸ o basin. These synthems are: Algodão, São Simão, Sapiranga, Pajeú and Bom Retiro (lower interval), São Marcos and Sítio Novo (intermediate interval) and Santo Onofre (upper interval). For each interval the sedimentary processes, the depositional systems, the filling style of the basin and the tectonic settings were evaluated, based mainly on the facies association characteristics and their lateral/vertical changes. Zircon U–Pb SHRIMP and basin analysis studies carried out along the eastern border of the Northern Espinhac¸ o Range provide a few new or improved anchors upon which the tectonic evolution of the Espinhaco basin can be pinned. We identified Statherian rifting in the São Simão Synthem, by dating volcanic rocks at 1.73 Ga. This is followed by a previously unknown, minor intracratonic rift phase within the São Francisco Craton, dated at circa 1.57 Ga through a volcanic unit within the Pajeú Synthem. The entire lower interval is cut by mafic intrusive dykes of which we dated one at 850 Ma, which we correlate with a Tonian rifting phase affecting the eastern part of the São Francisco craton, and related to the break-up of the Rodinia Supercontinent. Our data showthat the development of the Northern Espinhac¸ o Range spans a large time interval, and comprises a discontinuous series of tectonic events that gave rise to the formation of the various synthems and are punctuated by the extrusion of minor volcanic units and emplacement of dykes within the eastern part of the São Francisco Craton.
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    Unravelling a Proterozoic basin history through detrital zircon geochronology : the case of the Espinhaço Supergroup, Minas Gerais, Brazil.
    (2012) Chemale Júnior, Farid; Dussin, Ivo Antonio; Alkmim, Fernando Flecha de; Martins, Maximiliano de Souza; Queiroga, Gláucia Nascimento; Armstrong, Richard; Santos, Marcelo Nascimento dos
    New U–Pb in situ zircon dating provides a new approach for the study of the Espinhaço Supergroup units exposed in the São Francisco Craton and Araçuaí Orogen. Located in Southern Espinhaço, Minas Gerais, the following two basins were formed in intraplate conditions: (i) the Lower Espinhaço Basin is marked by a volcano-sedimentary sequence with alluvial, fluvial and eolian deposits that were formed from 1.68 Ga to 1.80 Ga; (ii) the overlying sequence, called the Upper Espinhaço Basin, is a rift-sag basin that presents basal diamond-bearing continental deposits (the Sopa–Brumadinho Formation) with a younger zircon peak at 1192 Ma, which is the maximum age for deposition of the upper units. The obtained U–Pb detrital zircon data of the studied units show age groupings related to the orogenic cycles of Jequié (Neoarchean) and Transamazonian (Paleoproterozoic), which are associated with the stability period from 1.8 Ga to 0.91 Ga in the São Franscico Craton, and record deposition during at least the three basinal cycles. The Stenian–Tonian ages of the Upper Espinhaço Basin units (906 Ma to 1192 Ma) suggest a direct link with the evolution of the Rodinia Supercontinent and represent a marker for Mesoproterozoic to Early Neoproterozoic evolution in the São Franscico Craton and adjacent areas.