Two regional thrust-sheets of Neoproterozoic metasedimentary rocks occur in the Southern Brasília Belt, northwest Minas Gerais. The lower one comprises the Vazante Group, that is formed in the studied area, from base to top, by the Serra do Garrote (metapelites interlayered with carbonaceous phyllite), Serra do Poço Verde (beige to pink stromatolitic metadolomite with interlayered greenish slates), Morro do Calcário (gray stromatolitic metadolomite interlayered with gray slates) and Serra da Lapa (phyllite with dolarenitic lenses interlayered with slates) formations. The upper thrust sheet consists of the Canastra Group (Paracatu formation): laminated sericite phyllites and carbonaceous phyllites interlayered with quartzite. The Braziliano orogeny resulted in four phases of contractional deformation, associated with low-grade metamorphism. The first two (D 1 and D 2 ) are ductile, while the third and fourth ones (D 3 and D 4 ) are brittle-ductile. D 1 developed a slaty S 1 cleavage subparallel to the primary layering, with shallow to steep dips to NW. D 2 developed a crenulation cleavage (S 2 ) that dips moderately to NW and is associated with tight to isoclinal folds. D 3 and D 4 phases developed crenulations and open folds and kink bands. S 3 dips steeply to NW, while S 4 has moderate to steep dips to NE and SW. White mica crystallinity (Kübler index) measurements in metapelites indicate that both the Canastra and Vazante groups reached anchizone/epizone conditions, and metamorphic discontinuities along thrusts indicate that the peak of metamorphism is pre or syn-thrusting. KEYWORDS:Neoproterozoic, Zinc-Lead, X-Ray Diffraction, Thrust-fold Belt. RESUMO: O contato do empurrão dos grupos Canastra e Vazante na Faixa Brasília Meridional: evolução estrutural, cristalinidade de mica branca e implicações para a orogenia brasiliana. Duas escamas de cavalgamentos regionais de rochas metassedimentares neoproterozoicas ocorrem na Faixa Brasília Meridional, em Minas Gerais. A inferior compreende o Grupo Vazante, que na área de estudos é formado da base para o topo, pelas formações Serra do Garrote (metasiltitos e filitos carbonosos intercalados), Serra do Poço Verde (metadolomitos estromatolíti-cos bege a rosados com intercalações de ardósias e margas esverdeadas), Morro do Calcário (metadolomitos estromatolíticos cinza com intercalações de ardósias cinza) e Serra da Lapa (metarritmitos carbonosos com lentes de dolarenitos). A escama superior é composta do Grupo

Combined Sm-Nd isotope studies and U-Pb ages of detrital zircons have shown significant differences between the provenance patterns of Neoproterozoic metasedimentary successions in the Southern Brasília belt. The Vazante and Canastra groups are passive margin deposits with source areas in the Archean/Paleoproterozoic São Francisco Craton basement and Mesoproterozoic cover units. In literature, the younging trend of Nd model ages observed in the Vazante Group is interpreted as resulting from the contribution of the Neoproterozoic Goiás Magmatic Arc. Also, detrital zircons younger than 0.90 Ga were not recorded in the Vazante or Canastra groups, which zircon populations are older than 0.93 Ga. This work presents new Sm-Nd and Sr isotope data of metasedimentary rocks from the Vazante and Canastra groups, collected in a 400 km2 area in northwest Minas Gerais, Brazil. The improved database of previously published and new data corroborates with the younging pattern of TDM along the Vazante Group. Isochronic diagrams show that samples from Vazante and Canastra groups scatter along mixing lines between the fields defined by the older cratonic rocks and the more juvenile ones. Here we present the Tonian Intraplate Magmatism within the São Francisco Craton as the juvenile source.

This work presents Sm‐Nd and Sr isotopic ratios of the BRP‐1 (“Basalt Ribeirão Preto”) reference material (RM) based on repeated TIMS measurements over twelve years carried out by the LAGIR laboratory, Brazil. The BRP‐1 RM was produced by the Brazilian Geological Survey from a ca. 130 Ma within‐plate basalt, collected from a quarry near Ribeirão Preto city in the Paraná basin. Isotope ratios were measured using a TRITON mass spectrometer. Instrumental bias and fractionation corrections were performed based on repeated measurements of the certified RMs JNdi‐1 and NIST SRM 987. The measured Nd and Sr isotopic ratios of BRP‐1 are: 143Nd/144Nd = 0.512408 ± 0.000010 (2s), and 87Sr/86Sr = 0.706011 ± 0.000017 (2s). The mass fractions of Sm and Nd are 11.0 ± 0.2 and 51.9 ± 0.6 μg g‐1, respectively, showing no significant differences compared with the accepted values from the literature. No significant difference between measurements was observed, whether digesting samples in single or batch mode, using metal‐jacketed PTFE bombs or PFA vials, or with or without the addition of a spike. The accuracy of these results was evaluated through the measurement of well‐characterised USGS RMs, such as AGV‐1, BCR‐1, BHVO‐1, G‐2 and GSP‐1.

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