Tonian granitic magmatism of the Borborema Province, NE Brazil: A review

Accretion Tectonics in Western Gondwana Deduced From Sm‐Nd Isotope Mapping of Terranes in the Borborema Province, NE Brazil

“…In addition, Lages and Dantas () documented mafic and ultramafic rocks that present geochemical and isotopic characteristics compatible with arc‐root remnants and suprasubduction ophiolites of ~1.0 Ga, thus attesting to the orogenic nature of this event. Alternatively, based on specific trace element geochemistry, some studies such as those from Guimarães et al (, ), suggest that some coeval associations might have been emplaced via a within‐plate setting, being the nature of this the Cariris Velhos event still under debate.…”

New U-Pb (SHRIMP) and first Hf isotope constraints on the Tonian (1000-920 Ma) Cariris Velhos event, Borborema Province, NE Brazil

“…As discussed by Guimarães et al (2016), the majority of Tonian orthogneisses of the Borborema Province plot in the ferroan field in Frost et al (2001) SiO 2 x(FeO/FeO + MgO) diagram, specifically in the upper right part (SiO 2 > 70%) of the diagram. A scatter to the magnesian field is, however, evident, especially when using the SiO 2 x(FeOtot/FeOtot + MgO) diagram, recommended by Frost et al (2001) on the basis that most modern chemical analysis do not distinguish between ferric and ferrous iron.…”

“…An alternative geotectonic model for the Cariris Velhos augen-gneisses was proposed by Neves (2003) and Guimarães et al (2012Guimarães et al ( , 2016, where those rocks would have been emplaced in an extensional, continental rift-related setting. It is interesting to notice that, interpreting similar lithogeochemical datasets, Neves (2003) and Guimarães et al (2012Guimarães et al ( , 2016) propose a distinct model and tectonic setting than Kozuch (2003), Santos et al (2010 and Caxito et al (2014b). This highlights the difficulty of using lithogeochemical data to infer the tectonic settings of ancient metaigneous rocks.…”

“…In all of those diagrams, samples of the Afeição Suite augengneisses plot majoritarily in the Active Continental Margin, Volcanic Arc, or Collisional Calc-Alkaline/Syn-collisional fields, generally away from within-plate or anorogenic settings. Guimarães et al (2016), on the other hand, uses the classic diagram of Eby (1992) for the discrimination of anorogenic granites where samples of the Afeição Suite, along with other Cariris Velhos samples, plot in the A2-type field.…”

“…For example, in the (FeO/ MgO) versus (Zr + Nb + Ce + Y) tectonic discriminant diagram of Whalen et al (1987), most samples plot in the borderline between the A-type granites field and the other fields ( Fig. 10A of Guimarães et al 2016), straddling the fractionated granites field and even the field of unfractionated M, Iand S-type granites. Kozuch (2003), Santos et al (2010) and Caxito et al (2014b) interpret the fingerprints of subduction zones in normalized trace-element spidergram distributions of the Cariris Velhos orthogneisses.…”