Abstract
The Gentio metagranitoid presents equigranular and porphyritic facies, modal composition ranging from tonalite to monzogranite with calculated TZr<800 °C for most samples. Its mineralogy is dominated by quartz and feldspar (77% to 95%), biotite is the only mafic mineral present (2% to 18%) and, titanite, zircon, apatite, allanite are important accessory phases. These rocks range from metaluminous to weakly peraluminous, and have large variation in major and trace elements, and high alkali contents (>6 wt.%). Zircon analyses by LA-ICP-MS and SHRIMP yielded a concordia age of 2 119±10 Ma for the porphyritic facies and an upper intercept age of 2 111±15 Ma for the equigranular facies. The whole-rock Sm-Nd TDM ages vary from 2.4 to 2.8 Ga with εNd(2.1) values between −0.7 and −5.3, indicating crustal derivation from distinct and/or heterogeneous protoliths. Field observations indicate that the Gentio metagranitoid was formed through different pulses of magma. Individual batches were subject to little or even no fractionation process after its emplacement. Although the Gentio metagranitoid crosscuts metamafic and metaultramafic rocks akin to an oceanic arc setting, this pluton is likely originated by partial melting of a more evolved quartz-feldspathic crustal igneous rock in a post-collisional environment, after the accretion of the arcs from the Mineiro belt and rocks of the Mantiqueira Complex.
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We would like to thank Prof. Valdecir Janasi for the helpful comments. The manuscript also benefitted from comments and reviews from Tapani Rämö and an anonymous reviewer. Marize M. da Silva thanks the support of the CAPES and the Brazilian National Research Council (CNPq) for the Doctoral (No. 140411/2013-5). Ciro A. Ávila and Wilson Teixeira acknowledge CNPq and FAPERJ for providing continued support for the research in the Mineiro belt. The final publication is available at Springer via https://doi.org/10.1007/s12583-021-1469-0.
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da Silva, M.M., Ávila, C.A., Tavares, F.M. et al. Genesis of the Gentio Metagranitoid: Post-Collisional High-K Plutonism within the Mineiro Belt, São Francisco Craton, Brazil. J. Earth Sci. 32, 1374–1396 (2021). https://doi.org/10.1007/s12583-021-1469-0
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DOI: https://doi.org/10.1007/s12583-021-1469-0