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3. Mineralogy and geochemistry of a giant agpaitic magma reservoir: The Late Cretaceous Poços de Caldas potassic alkaline complex (SE Brazil)

Author

Guarino V.[1], Lustrino M.[2, Zanetti A.[4], Tassinari C.C.G.[5], Ruberti E.[5], de' Gennaro R.[1], Melluso L.[1], Guarino, V., Lustrino, M., Zanetti, A., Tassinari, C. C. G., Ruberti, E., de' Gennaro, R., and Melluso, L.

Subjects
Agpaitic, Brazil, Eudialyte, F-disilicates, Nepheline syenites, Phonolite, Poços de Caldas, Titanite, 010504 meteorology & atmospheric sciences, Outcrop, Geochemistry, 010502 geochemistry & geophysics, 01 natural sciences, Peralkaline rock, chemistry.chemical_compound, agpaitic: titanite: eudialyte: F-disilicates: phonolite: nepheline syenites, Poços de Caldas: Brazil, Geochemistry and Petrology, Nepheline, 0105 earth and related environmental sciences, Poços de Calda, geography, geography.geographical_feature_category, Fractional crystallization (geology), F-disilicate, Nepheline syenite, Geology, Massif, Cretaceous, Igneous rock, chemistry, Magma, CRISTALIZAÇÃO
Abstract

The Late Cretaceous (~78 Ma) Poços de Caldas massif is the largest alkaline complex in Brazil and the second in the world by extension (>800 km2). It is considered the westernmost outcrop of the Cabo Frio magmatic lineament, in the northern sector of Serra do Mar potassic-ultrapotassic igneous province, central-eastern Brazil. The outcropping rocks are peralkaline phonolites (~80%) and nepheline syenites (~15%) with rarer (

Published
2021

11. U–Pb ages, Sr–Nd- isotope geochemistry, and petrogenesis of kimberlites, kamafugites and phlogopite-picrites of the Alto Paranaíba Igneous Province, Brazil

Author

Vincenza Guarino(a), Fu-Yuan Wu(b), Michele Lustrino(c, Leone Melluso(a), Pietro Brotzu(a), Celso de Barros Gomes(e), Excelso Ruberti(e), Colombo Celso Gaeta Tassinari(e), Darcy Pedro Svisero(e), Guarino, Vincenza, Wu, F. Y., Lustrino, M., Melluso, Leone, Brotzu, P., Gomes, C. B., Ruberti, E., Tassinari, C. C. G., and Svisero, D. P.

Subjects
geochronology, Geochemistry, engineering.material, Phlogopite-picrites, GEOCRONOLOGIA, sr nd perovskite isotopes, Geochemistry and Petrology, Petrogenesis, u pb perovskite, Kamafugites, Olivine, Partial melting, Geology, phlogopite picrites, Porphyritic, brazil, sr-nd perovskite isotopes, phlogopite-picrites, u-pb perovskite geochronology, kamafugites, kimberlites, Kimberlites, Igneous rock, engineering, Phenocryst, Phlogopite, U-Pb perovskite geochronology, Sr-Nd perovskite isotopes, Kimberlite, Brazil
Abstract

The kimberlites, kamafugites and phlogopite-picrites of Alto Paranaiba Igneous Province (APIP), southern Brazil, span a range between ~ 91 and 78 Ma with new in-situ, more tightly constrained U–Pb ages. The kimberlites show porphyritic texture with olivine xeno- and phenocrysts plus phlogopite, Fe-Ti-Cr oxides and perovskite microcrysts set in a carbonate-rich matrix. The kamafugites are feldspar-free rocks represented by ugandites and mafurites. Ugandites and mafurites are porphyritic and contain olivine and clinopyroxene phenocrysts in a fine-grained groundmass composed by clinopyroxene, perovskite, apatite, magnetite, phlogopite, leucite and/or analcime in ugandites, and by olivine, clinopyroxene, amphibole, phlogopite, perovskite, magnetite, kalsilite and Ba-zeolites in mafurites. Phlogopite-picrites have a pseudo-fluidal porphyritic texture with olivine phenocrysts and abundant phlogopite microcrysts in a groundmass composed by olivine, spinel, apatite, perovskite, calcite and rare garnet. New in‐situ Sr and Nd isotopic data on perovskites ( 87 Sr/ 86 Sr i = 0.70467–0.70565 and 143 Nd/ 144 Nd i = 0.51222–0.51233) fall within the known ranges of APIP rocks ( 87 Sr/ 86 Sr i = 0.70431–0.70686; 143 Nd/ 144 Nd i = 0.51205–0.51280). The APIP magmas derived from a source assemblage made up of an old metasomatized mica-carbonate garnet lherzolite, that did not suffer interaction with convective mantle, nor with any hypothetical melts derived from a Trindade mantle plume. Geochemical modelling show that low degree melting ( f = 0.5–2%) of such a source can produce compositions resembling the APIP rocks. The geochemical and isotopic composition of the magmas, the calculated degrees of partial melting, the composition of the calculated source and the absence of a hot spot track from Goias to Alto Paranaiba igneous provinces can be explained with the presence of chemically and mineralogically heterogeneous mantle sources that melted at different pressures.

Published
2013

12. Magmatism and fenitization at the Ipanema mafic-ultramafic alkaline-carbonatitic complex, São Paulo State, Brazil

Author

GUARINO, VINCENZA, MELLUSO, LEONE, Azzone R. G., Brotzu P., Gomes C. B., Morbidelli L., Ruberti E., Tassinari C. C. G., Brilli M., Guarino, Vincenza, Azzone, R. G., Brotzu, P., Gomes, C. B., Melluso, Leone, Morbidelli, L., Ruberti, E., Tassinari, C. C. G., and Brilli, M.

Abstract

The Ipanema alkaline-carbonatitic complex is part of the Meso-Cenozoic alkaline magmatism located within the southeastern part of the Brazilian Platform. Drill-core and field sampling have indicated the occurrence of glimmerites, with subordinate shonkinites (mela-syenites), clinopyroxene-bearing glimmerites, diorites and syenites. The glimmerites are cross-cut by lamprophyric dykes and calciocarbonatites. Fenitization has deeply affected the country rocks, originating dioritic and syenitic rocks. The Ipanema rocks show a distinct potassic affinity. The initial Sr-Nd- isotopic composition of the Ipanema rocks ( 87Sr/ 86Sr = 0.70661-0.70754 and 143Nd/ 144Nd = 0.51169-0.51181) is similar to that of tholeiitic and potassium-rich-alkaline rocks of the Eastern Paraguay. Stable isotope data for the Ipanema calciocarbonatite suggest interaction with fluids at temperatures typical of hydrothermal stages, as hypothesized for other carbonatite complexes from southeastern Brazil. The chemical differences between the lamprophyre, glimmerites, carbonatites, apatitites and magnetitites, and the absence of marked REE enrichment in the evolved lithologies, all indicate that fractional crystallization and accumulus of liquidus phases in a magma reservoir, likely coupled with liquid immiscibility processes, may have played an important role in the genesis of the Ipanema rocks.

Published
2012

23. Early Cretaceous felsic volcanism in SE Uruguay

Author

Lustrino, Michele, Marrazzo, M., Melluso, L., Tassinari, C. G. C., Brotzu, P., Gomes, C. B., Morbidelli, L., and Ruberti, E.

Subjects
paraná–etendeka, uruguay, crustal contamination, lower crust, rhyolite
Published
2010

50. Petrological, geochemical and Sr-Nd isotopic features of alkaline rocks from the Arraial do Cabo Frio peninsula (southeastern Brazil)

Author

Bennio, L., Brotzu, P., Celso de Barros Gomes, D Antonio, M., Lustrino, M., Melluso, L., Morbidelu, L., Ruberti, E., Bennio, Lucia, Brotzu, Pietro, Gomes, Celso, D'Antonio, Massimo, Lustrino, Michele, Melluso, Leone, Morbidelli, Lucio, Ruberti, Excelso, Bennio, L., Brotzu, P., Gomes, C. B., Lustrino, M., Morbidelli, L., and Ruberti, E.

Subjects
Isotope geochemistry, brazil, alkaline, alkaline magmas, arraial do arraial do cabo frio, geochemistry, magmatic evolution, petrology, Petrogenesi, eocene, Alkaline magmatism
Abstract

The alkaline activity in the Cabo Frio region is made up mainly of intermediate and felsic differentiate rocks emplaced about 55 Ma ago into the crystalline basement as sills, plugs and dykes. Two magma suites can be distinguished: (a) a strongly silica-undersaturated tephriphonolite to phonolite serie; (b) a weakly silica-undersaturated to satured trachyandesite-trachyte series. Petrography, mineral chemistry, whole-rock chemistry trends and isotopic data strongly support a genetic link among the lithotypes of each suites consistent with fractional crystallization processes dominated by the observed phases. The same data, however appear to exclude a link between the two groups of rocks, supporting a petrogenesis by prolonged differentiation processes starting from two distinct parental magma with a slight difference in the SiO2 saturation. The scarce basanites and trachybasalts reported in the same area could represent the most probable compositions for the parental magmas of the two suites. The initial 87Sr/86Sr (0.70401-0.70458) and 143Nd/144Nd (0.51239-0.51247) isotopic ratios and the significant potassic component indicate derivation of these rocks from an enriched lithospheric mantle source.

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