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

Abstract

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-TiO 2 , TDM Nd ages between 1.80 and 1.41 Ga, negative ΕNd t and ( 87 Sr/ 86 Sr)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, TDM Nd ages between 2.58 and 2.16 Ga, positive ΕNd t 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.

Proterozoic to Ordovician geology and tectonic evolution of Rio de Janeiro State, SE-Brazil: insights on the central Ribeira Orogen from the new 1:400,000 scale geologic map

“…In the last decade, orthogneisses with magmatic arc geochemical and isotopic signatures have been described in Rio de Janeiro State (Heilbron & Machado 2003, Tupinambá et al 2012, Tedeschi et al 2016, Heilbron et al (2019) grouped the magmatic arcs of the Ribeira belt in Rio de Janeiro State into an inner arc system that crops out as dismembered inliers close to Minas Gerais State and continue northward into the Rio Doce Arc in the Araçuaí orogen, an Outer arc system, comprising juvenile orthogneisses in the Serra dos Órgãos mountain range and Rio de Janeiro city, extending onto coastal Angra dos Reis and Paraty towns to southwest. The arc magmatic rocks occupy ca.…”

Lithogeochemical and Nd-Sr isotope data of the orthogranulites of the Juiz de Fora complex, SE-Brazil: insights from a hidden Rhyacian Orogen within the Ribeira belt

“…2.98 Ga-old granulite was reported nearby Juiz de Fora (Silva et al 2002) with metamorphic age in zircon rims of 2,856 ± 44 Ma). In addition, (E-MORB tholeiitic) mafic granulites have been dated at 766 Ma, in the Miracema region (Heilbron et al 2019, Santos 2017.…”

“…More recently, one single intraplate basic body of ca. 766 Ma (Heilbron et al 2019) was interpreted as coeval with the development of the Andrelândia basin (Trouw et al 2000). Brasiliano Orogeny between ca.…”