The complex tale of Mantiqueira and Juiz de Fora : a comment on “Eoarchean to Neoproterozoic crustal evolution of the Mantiqueira and the Juiz de Fora Complexes, SE Brazil : petrology, geochemistry, zircon U-Pb geochronology and Lu-Hf isotopes”.

Abstract

In a recent volume of Precambrian Research (vol. 323, pp. 82–101), Kuribara et al. (2019) published a paper on the Eoarchean to Neoproterozoic evolution of the Mantiqueira and Juiz de Fora Complexes of SE Brazil. In this work, Kuribara et al. (2019) suggest that the complexes were previously indicated to be part of the Neoproterozoic to Cambrian Brasiliano Orogeny and that the results of their work instead show that these complexes are fragments of Archaean crust that accreted during the 590–560 Ma Brasiliano orogeny. Kuribara et al. (2019) also present conventional thermobarometry for both complexes that they interpret represents the single metamorphic event that they obtain zircon U-Pb age data for from the Juiz de Fora complex. No metamorphic ages were obtained from the Mantiqueira Complex, instead they have used the metamorphic ages that many workers have obtained from the Mantiqueira Province. In this comment we show that the Archaean crustal input in the Mantiqueira complex has long been known, and the Juiz de Fora Complex has long been considered a Palaeoproterozoic ocean arc. The Mantiqueira Complex records a polymetamorphic history with high-grade metamorphism occurring at ca. 2020–1940 Ma and a later amphibolite facies Brasiliano overprint at 580–540 Ma. The Mantiqueira Province and Mantiqueira Complex are different geological entities, and while the Mantiqueira Complex is affected by the Brasiliano event and occurs within the Mantiqueira Province, the use of metamorphic ages from the Mantiqueira Province is not appropriate for the Mantiqueira Complex. Finally we show that the data presented by Kuribara et al. (2019) actually fits in with the most recent version of the model for the formation of the two complexes.