Ar-Ar ages, Sr-Nd isotope geochemistry, and implications for the origin of the silicate rocks of the Jacupiranga ultramafic-alkaline complex (Brazil)

Cretaceous carbonatites of the southeastern Brazilian Platform: a review

“…Additional multielement diagrams are also found for other areas: the Ponta Grossa Arch (Gomes et al 2011a, Azzone et al 2013, Beccaluva et al 2017, Chmyz et al 2017, Amambay (Gomes et al 2011b, Comin-Chiaramonti et al 2014, and the Alto Paranaíba province (Gomide et al 2016).…”

“…Other common features include structural flow with alignment of elongated crystals (e.g. apatite), presence of brecciated and xenolithic material, and typical banding from differential concentration of minerals, particularly apatite, phlogopite, olivine and magnetite, as well evidenced in Jacupiranga carbonatites (Melcher 1966, Morbidelli et al 1986, Chmyz et al 2017.…”

“…Except for a small number of occurrences such as Barra do Itapirapuã, Jacupiranga and Poços de Caldas , Chmyz et al 2017, Vlach et al 2003, whose ages were determined directly from carbonatites and their mineral constituents, most available data resulted from analysis of associated silicate alkaline rocks (whole-rock and mineral concentrates of different minerals). Data for all presently known alkaline-carbonatite occurrences indicates that these rocks are of Cretaceous age, with two clearly distinguished formation intervals, 120-140 Ma and 70-90 Ma, Lower Cretaceous and Upper Cretaceous (Ulbrich & Gomes 1981, Rodrigues & Lima 1984, Berbert 1984, Gomes et al 1990, Gibson et al 1995a, Ruberti et al 2005, Comin-Chiaramonti et al 2007a, 2007b, Gomes et al 2011a, 2011b, Gomes & Comin-Chiaramonti 2017.…”

“…REE fluorocarbonates are relatively abundant in late stage carbonatites (e.g., Barra do Itapirapuã, Cerro Manomó). Chondrite-normalized (Thompson 1982, Boynton 1984, McDonough & Sun 1995 REE distribution diagrams for various carbonatite complexes are discussed in several papers (e.g., Comin-Chiaramonti et al 2005c, 2007a, 2014, Gomes et al 2011a, 2011b, Azzone et al 2013, Gomide et al 2016, Beccaluva et al 2017, Chmyz et al 2017. Patterns are in general marked by high REE concentration and variable LREE/ HREE fractionation degrees.…”

“…In contrast, based on isotopic data, Huang et al (1995) refuted any significant contribution of contamination processes affecting the evolution of the carbonatites and clinopyroxenites. In a recent study, Chmyz et al (2017) provided mineralogical, textural and geochemical evidence of crustal contamination in the formation of the weakly silica-undersaturated rocks of Jacupiranga.…”