The Archean Rio das Velhas greenstone belt revisited: new insights into the stratigraphy

Araújo, Joanna Chaves Souto; Ferreira, Raianny Carolini Ramos; Freitas, Frederico Moreira; Magalhães, Joana Reis

doi:10.29396/jgsb.2020.v3.n3.1

Cited by 10 publications

(3 citation statements)

References 59 publications

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“…The southern region of the São Francisco Craton, in which the Pitangui Synclinorium is located (Figure 1), is composed of Meso-to Neoarchean complexes represented by TTG (tonalite-trondhjemite-granodiorite) gneisses and migmatites, Neoarchean medium-and high-K granitoids, and Mesoto Neoarchean greenstones belts covered by Proterozoic supracrustal rocks (Machado et al 1996;Alkmim and Marshak 1998;Romano 2007;Lana et al 2013;Romano et al 2013;Farina et al 2015;Brando-Soares et al 2017;Araújo et al 2020).…”

Section: Geological Contextmentioning

confidence: 99%

Stratigraphy of the Pitangui Synclinorium, northwest of the Quadrilátero Ferrífero mineral province - Brazil: magmatism and sedimentation from Archean to Neoproterozoic

Marinho¹,

Magalhães²,

Lombello³

et al. 2023

JGSB

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The Pitangui Synclinorium is located in the northwestern portion of the Quadrilátero Ferrífero mineral province, São Francisco Craton, in southeast Brazil. It corresponds to a NW-SE-trending synformal structure composed of an Archean greenstone belt sequence, which is covered by Paleoproterozoic metasedimentary rocks to Neoproterozoic sedimentary rocks, and surrounded by Archean granitegneiss complexes. This study reports the first detailed 1:25,000 scale geological mapping in the Pitangui Synclinorium and provides cartographic, stratigraphic and petrographic improvements, allowing the formalization of its lithostratigraphic units and unraveling the sedimentary and volcanic depositional environments. The Archean Pitangui greenstone belt occurs in most parts of the homonymous synclinorium, and is subdivided into the Pitangui Group and the Antimes Formation. The metavolcanosedimentary sequence of the Pitangui Group comprises basal mafic/ultramafic metavolcanic rocks with subordinate felsic/intermediate metavolcanic and metavolcaniclastic rocks of the Rio Pará Formation, suggesting a bimodal volcanism. It is followed by volcanogenic and chemical metasedimentary rocks of the Rio São João Formation, and pelitic to sandy metasedimentary rocks of the Onça do Pitangui Formation deposited in subaqueous environments mainly corresponding to submarine fan systems. The occurrence of clastic rocks increases towards the top of the sequence. The Antimes Formation comprises quartzites and metaconglomerates related to fluvial and fan delta depositional environments. The Pitangui greenstone belt is overlapped, in the central and northwest regions of the study area, by the Fazenda Tapera Formation, a Paleoproterozoic siliciclastic package containing arkosic metasandstones, metagreywackes and metarhythmites deposited in a shallow marine environment. Subordinated tuff layers occur as ash/fall deposits from distal volcanism. Neoproterozoic clastic-chemical sedimentary rocks of the Bambuí Group cover the northern portions of the synclinorium, and are mainly composed of diamictites, limestones, marls and rhythmites from the Carrancas (lacustrine or restricted marine), Sete Lagoas (shallow marine) and Serra de Santa Helena formations (deep water grading to prodelta and delta front).Stratigraphy of the Pitangui Synclinorium, northwest of the Quadrilátero Ferrífero mineral province -Brazil: magmatism and sedimentation from Archean to Neoproterozoic Accepted manuscript -Uncorrected pre-proof This is a PDF file containing an unedited and non-definitive version of a manuscript that has been accepted for publication by the Journal of the Geological Survey of Brazil -JGSB, which serves to provide early visibility of the article. Being an uncorrected preproof version, errors may appear during the production process (language review, formatting and proof review), and these can affect the final content of the article and all legal disclaimers (https://jgsb.cprm.gov.br/index.php/journal/6).

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Section: Geological Contextmentioning

confidence: 99%

Stratigraphy of the Pitangui Synclinorium, northwest of the Quadrilátero Ferrífero mineral province - Brazil: magmatism and sedimentation from Archean to Neoproterozoic

Marinho¹,

Magalhães²,

Lombello³

et al. 2023

JGSB

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“…Its basal group, the Caraça Group, is composed essentially of clastic metasedimentary rocks, the pelitic part of which grades upwards into the Itabira iron formation. The Caraça Group rests on a regional unconformity over the Rio das Velhas Supergroup, an Archaean greenstone‐belt sequence (Araújo, Ferreira, Freitas, & Magalhães, 2020; Baltazar & Zucchetti, 2007; Dorr, 1969). Its basement rocks are gneissic complexes that record magmatic and tectonothermal events between 3.38 and 2.60 Ga, with reworking of continental crust (Lana et al, 2013; Teixeira et al, 1996).…”

Section: Geological Contextmentioning

confidence: 99%

Unconformity‐covering pillow lava dated at 2.14 Ga: Challenging the “stable‐shelf” Minas Supergroup of the Quadrilátero Ferrífero, Minas Gerais, Brazil

et al. 2022

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We report on the occurrence of pillow lava in the upper part of the banded‐iron‐formation (BIF) sequence of the Quadrilátero Ferrífero, famous for hosting world‐class iron‐ore deposits in Minas Gerais, Brazil. A pillow‐lava domain is found as an outlier within the BIF sequence, known as the Itabira iron formation or the Itabira Group. The pillow lava occurs as lateritized, indurated crusts in a sequence of ochreous itabirite, the weathered expression of dolomitic itabirite, a metamorphosed BIF rock containing dolomite. About 90 zircon grains, extracted from two samples of lateritized pillow lava, an indurated pillow rim and a friable pillow core, yielded Archaean to Palaeoproterozoic ages between 3.37 and 2.14 Ga, with age clusters at 2.98, 2.72, 2.25, and 2.14 Ga, and minor clusters at 3.37, 3.26, 3.16, and 2.82 Ga. The youngest grains, all exhibiting perfectly euhedral crystals, defined a Concordia age at 2,141 ± 6 Ma, interpreted as the age of subaqueous volcanism. This young zircon age and the perfectly euhedral zircon crystals suggest that the pillow‐lava domain represents an outlier of Palaeoproterozoic volcanic rocks, which covered the unconformity between the Itabira Group and the overlying Piracicaba Group. The finding of pillow lava lends support to previous, but usually ignored works, which described metavolcanic rocks in spatial association with the Itabira Group, and provides evidence for subaqueous volcanism that challenges the prevailing view of a stable‐shelf or passive‐margin setting for the geological evolution of the Minas Supergroup.

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“…The Quadrilátero Ferrífero (QF) comprises an area of approximately 7000Km2 in the southeast portion of the São Francisco craton, within the central and southern regions of Minas Gerais state (Almeida, 1967;Dorr II, 1969). It contains three main lithostratigraphic units: (i) an Archean granite-gneiss complex including the exposed Belo Horizonte, Caeté, Bonfim, Bação and Santa Bárbara domes (Teixeira et al, 2000); (ii) the Rio das Velhas greenstone belt (RVGB), an Archean volcanosedimentary sequence divided into the Quebra Osso, Nova Lima and Maquiné groups (Dorr II, 1969;Zucchetti and Baltazar, 2000;Araújo et al, 2020); and (iii) Neoarchean-Proterozoic metasedimentary sequences represented by the Minas Supergroup and the Sabará and Itacolomi groups (Dorr II, 1969).…”

Section: Introductionmentioning

confidence: 99%

2D Gravimetric Modelling of the central portion of Quadrilátero Ferrífero, Brazil

Araújo¹,

Matos²,

Dias³

2021

Proceeding of the 17th International Congress of the Brazilian Geophysical

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The Quadrilátero Ferrífero, located at the southern São Francisco craton, is one of the most important metallogenic districts in Brazil. Multiple deformational events affected this region and several studies, based mainly on structural field mapping argue about its tectonic evolution. Geophysical techniques applied to delineate subsurface can be useful for a better understanding of its tectonic framework. The present study consists of a gravimetric survey in the central portion of Quadrilátero Ferrífero, encompassing its three main geological units: the TTG basement, the Rio das Velhas greenstone belt, and the Minas Supergroup. The acquired data were processed in three gravimetric 2-D profiles and the modeling was based also on surface geological data and previous tectonic studies of the area. The geophysicalgeological profiles modeled suggest that the Rio das Velhas basin, in the Nova Lima-Caeté tectonostratigraphic block, shows distinct composition and thickness in its eastern and western regions. The eastern portion would be composed of a thin base layer with a predominance of mafic/ultramafic metavolcanic rocks and a thick top layer with metasedimentary rocks. On the other hand, the western area would have a remarkable predominance of mafic/ultramafic metavolcanic rocks belonging to a thick basal layer. For the Minas Supergroup in the Serra da Piedade region, an inverted syncline is the model that best suited the gravimetric data. The inverted flank is exposed by the Serra da Piedade and the normal flank doesn't outcrop.

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The Archean Rio das Velhas greenstone belt revisited: new insights into the stratigraphy

Abstract: Article InformationPublication type: Review articles

Cited by 10 publications

References 59 publications

Stratigraphy of the Pitangui Synclinorium, northwest of the Quadrilátero Ferrífero mineral province - Brazil: magmatism and sedimentation from Archean to Neoproterozoic

Stratigraphy of the Pitangui Synclinorium, northwest of the Quadrilátero Ferrífero mineral province - Brazil: magmatism and sedimentation from Archean to Neoproterozoic

Unconformity‐covering pillow lava dated at 2.14 Ga: Challenging the “stable‐shelf” Minas Supergroup of the Quadrilátero Ferrífero, Minas Gerais, Brazil

2D Gravimetric Modelling of the central portion of Quadrilátero Ferrífero, Brazil

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