The Barreiro suite in the central Ribeira Belt (SE-Brazil): a late Tonian tholeiitic intraplate magmatic event in the distal passive margin of the São Francisco Paleocontinent

Monica Heilbron, Caroline Oliveira, Marcela Lobato, Claudio de Morisson Valeriano, Ivo Dussin, Elton Dantas, Antonio Simonetti, Henrique Bruno, Felipe Corrales, Eduardo Socoloff

Resumo


New geochemical, U-Pb, Lu-Hf and Sr-Nd data from the Barreiro Suite metabasites in comparison with enclaves within the distal Andrelândia Group and the orthogranulites of the Juiz de Fora Complex are presented. Geochemical data suggest intraplate setting, with high and low- TiO2, TDMNd ages between 1.80 and 1.41 Ga, negative ΕNdt and (87Sr/86Sr)i between 0.714 and 0.747. Results contrast with part of the Juiz de Fora Complex enclaves, with island arc tholeiites- calcalkaline basalts (IAT-CAB) geochemical signatures, TDMNd ages between 2.58 and 2.16 Ga, positive ΕNdt values and (87Sr/86Sr)i between 0.700 and 0.712. U-Pb data for the Barreiro Suite yielded a crystallization age of 766 ± 13 Ma and a metamorphic overprint of 619 ± 6 Ma. The results indicate three episodes of mafic magmatism in the Occidental terrane of the Ribeira Belt. The two older episodes are related to Rhyacian arc evolution (ca. 2.2 to 2.1 Ga) and to the Statherian (ca. 1.7 Ga) tectonics, and occur only within the Juiz de Fora Complex, while the younger ca. 766 Ma episode constrains the timing of distal passive margin evolution. An important implication is that these late Tonian metabasic rocks could have been a source of detrital zircons for the sedimentation along the distal Andrelândia basin.


Palavras-chave


Andrelândia Group; U-Pb; Sm-Nd; Lu-Hf; Within-plate basalts.

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DOI: http://dx.doi.org/10.1590/2317-4889201920180129

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