Estruturação da seqüência vulcano-sedimentar Rio Mata Cavalo (Morro do Pilar, MG, Brasil) baseada na análise qualitativa de dados geofísicos

Machado, Sérgio Augusto Morais; Penha, Ulisses Cyrino

doi:10.1590/s0102-261x1997000200004

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“…The sample purportedly identified as belonging to the Pedro Pereira Group yielded a date of (2839 ±14) Ma and the igneous zircon grains from the assumed Costa Sena Group delivered the date of (2049 ±16) Ma. The Alvorada de Minas meta‐ultramafic suite (Almeida‐Abreu et al, ) and the Rio Mata Cavalo metavolcano‐sedimentary sequence (S. A. M. Machado & Penha, and references therein) are developed along the eastern part of the range. Hagedorn, Ebert, and Almeida‐Abreu () published U–Pb zircon dates for the strongly sheared rocks of the Alvorada de Minas Suite with significant variations (2.22–2.05 Ga) among different lithotypes and errors up to 130 Ma, which nevertheless suggest a Paleoproterozoic (Orosirian?)…”

Section: The Orosirian–statherian Iron Formation‐bearing Sequences Ofmentioning

confidence: 99%

Post‐Great Oxidation Event Orosirian–Statherian iron formations on the São Francisco craton: Geotectonic implications

Rosière

Bekker

Rolim³

et al. 2019

Island Arc

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The protocratonic core of the São Francisco craton assembled during the 2.1–2.0 Ga Transamazonian orogeny. Orosirian Fe‐rich sequences that extend from the northwestern border of the São Francisco protocraton (Colomi Group) to the southeast under the Espinhaço Belt (the < 1.99 Ga Serra da Serpentina Group) record the opening of an intracratonic basin with the episodically developed ferruginous waters prior to the initiation of the Espinhaço rift at 1.8 Ga. Ferruginous conditions developed again during deposition of the Canjica Iron Formation of the < 1.7 Ga Serra de São José Group in the Espinhaço rift (contemporaneously with felsic magmatism; Conceição do Mato Dentro Rhyolite and Borrachudos Granitic Suite) and extensive sandstones of the < (1666 ±32) Ma Itapanhoacanga and < (1683 ±11) Ma São João da Chapada Formations. In the upper São João da Chapada Formation, banded hematitic phyllite also records input of Fe‐rich fluids. The young age of these iron formations with respect to the conventionally accepted 1.88 Ga age for the youngest shallow‐marine Paleoproterozoic iron formations, the apparent absence of granular facies (granular iron formations), and yet shallow‐water (above fair‐weather base) depositional environment indicate that an unusual setting developed in a large basin after the Great Oxidation Event, in the aftermath of the Transamazonian orogeny. We propose that mantle plumes led to the opening of a previously unrecognized rift system, that could have caused the magmatism, supplied hydrothermal Fe and led to the opening of the Espinhaço, Pirapora, and Paramirim rifts, later obliterated by the Araçuaí orogenic belt during the Neoproterozoic to Early Paleozoic Brasiliano orogeny. The rift system did not develop into an open continental margin but probably evolved into a broad sag basin, stretching across the São Francisco and Congo cratons.

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Section: The Orosirian–statherian Iron Formation‐bearing Sequences Ofmentioning

confidence: 99%

Post‐Great Oxidation Event Orosirian–Statherian iron formations on the São Francisco craton: Geotectonic implications

Rosière

Bekker

Rolim³

et al. 2019

Island Arc

View full text Add to dashboard Cite

show abstract

Estruturação da seqüência vulcano-sedimentar Rio Mata Cavalo (Morro do Pilar, MG, Brasil) baseada na análise qualitativa de dados geofísicos

Cited by 1 publication

References 0 publications

Post‐Great Oxidation Event Orosirian–Statherian iron formations on the São Francisco craton: Geotectonic implications

Post‐Great Oxidation Event Orosirian–Statherian iron formations on the São Francisco craton: Geotectonic implications

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