Geologia e Geocronologia do Maciço Alcalino Máfico-Ultramáfico Ponte Nova (SP-MG)

Azzone, Rogério Guitarrari; Ruberti, Excelso; Rojas, Gaston Eduardo Enrich; Gomes, Celso B.

doi:10.5327/z1519-874x2009000200002

Cited by 30 publications

(59 citation statements)

References 28 publications

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“…The abundance of evolved lithologies is noteworthy, including nepheline syenite and syenite, as in São Sebastião, Itatiaia, Poços de Caldas, Banhadão occurrences (Bellieni et al 1990;Brotzu et al 1997;Ulbrich et al 2005;Ruberti et al 2012). Cumulate associations often formed by clinopyroxenites and members of the ijolitic series with dunites and carbonatites to a lesser extent are also found like in Jacupiranga, Juquiá, Ponte Nova, Salitre and Tapira massifs (Beccaluva et al 1992;Azzone et al 2009;Gomes et al 2011;Barbosa et al 2012;Brod et al 2013).…”

Section: Magmatic Contextmentioning

confidence: 99%

“…Chemically, they have a composition that corresponds to alkaline basalts, basanites, and nephelinites. These dykes are particularly abundant in the alkaline provinces of Arco de Ponta Grossa and Serra do Mar (Beccaluva et al 1992;Alves et al 1992;Garda et al 1995;Valente 1997;Thompson et al 1998;Gibson et al 1999;Azzone et al 2009;Enrich et al 2009;Gomes et al 2011). They mostly occur near or crosscutting the alkaline intrusive suites.…”

Section: Magmatic Contextmentioning

confidence: 99%

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The antecryst compositional influence on Cretaceous alkaline lamprophyre dykes, SE Brazil

et al. 2015

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ABSTRACT:The question of whether the antecryst assemblage affects the bulk composition of lamprophyre dykes, and could be responsible for the compositional zonation between their centers and borders is addressed through a detailed study involving four monchiquite and camptonite dykes (basanites and tephrites) representative of the Arco de Ponta Grossa and Serra do Mar alkaline provinces. In them, antecrysts are interpreted as early-crystallized minerals that are no longer in equilibrium with their host-liquid, albeit still linked to the same magmatic system. They represent recycled crystals of earlier stages of the magmatic system at depth. The antecryst microtextures, such as zoned clinopyroxene megacrysts (augite cores and titanaugite rims) with partly corroded cores, olivine crystals with corroded rims surrounded by biotite coronas, chrome-spinel inclusions in clinopyroxene and olivine megacryst cores, and titanomagnetite crystals surrounded by biotite coronas, suggest chemical re-equilibrium with the matrix. The greatest antecryst cargo in these dykes is found in their centers. After subtracting the antecryst volume from the center analyses of each body, the calculated compositions are very similar to the border analyses. The mafic antecryst cargo of each occurrence proportionally leads to enrichment of MgO, FeO, TiO 2 , CaO, compatible trace elements (Cr, Ni and Co), and depletion of SiO 2 , K 2 O, Na 2 O, Al 2 O 3 and incompatible trace elements (Ba, Sr and REE). The whole-rock geochemical analyses of each dyke represent the combination of accumulated crystals and melt. The compositional zonation of the studied dykes is associated with the antecryst cargo rather than different magmatic pulses. KEYWORDS:Antecrysts; Alkaline lamprophyres; Petrology; Geochemistry. RESUMO: A questão de como a assembleia de antecristais influencia a composição química de diques de lamprófiro e se esta pode ser responsável pelo zoneamento composicional entre núcleos e bordas é abordada por meio de um estudo detalhado em quatro diques de monchiquito e camptonito, representativos das províncias alcalinas Arco de Ponta Grossa e Serra do Mar. Nestes diques, os antecristais são interpretados como minerais cristalizados precocemente que não se encontram mais em equi-

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Section: Magmatic Contextmentioning

confidence: 99%

Section: Magmatic Contextmentioning

confidence: 99%

The antecryst compositional influence on Cretaceous alkaline lamprophyre dykes, SE Brazil

et al. 2015

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“…The Ponte Nova massif (K-Ar, 87.6 Ma; Azzone et al 2009) is part of an extensive province of MesozoicCenozoic continental alkaline-carbonatitic magmatism spread over the central and southeastern regions of the Brazilian Platform (Almeida 1983, Morbidelli et al 1995. It is located in the northern sector of Serra do Mar Province (Riccomini et al 2005), which groups the Late Cretaceous alkaline occurrences of the western border of the Santos Basin (Fig.…”

Section: Geological Contextmentioning

confidence: 99%

“…According to Azzone et al (2009), the massif is primarily composed of a gabbroic association, generated by successive magmatic intrusions (Fig. 2).…”

Section: Geological Contextmentioning

confidence: 99%

Zr- AND Ba-RICH MINERALS FROM THE PONTE NOVA ALKALINE MAFIC-ULTRAMAFIC MASSIF, SOUTHEASTERN BRAZIL: INDICATION OF AN ENRICHED MANTLE SOURCE

Azzone

Ruberti

Enrich

et al. 2009

The Canadian Mineralogist

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Zirconium-and Ba-rich minerals are found in gabbroic rocks from the Ponte Nova alkaline mafic-ultramafic massif in southeastern Brazil. The unusual mineralogical assemblage includes zirconolite, baddeleyite, Ba-rich alkali feldspar, and Baand Ti-rich biotite. Zirconolite of the Ponte Nova massif has higher levels of Zr (up to 1.172 apfu) than those registered in other terrestrial rocks and a prominent enrichment in the light rare-earth elements. Baddeleyite contains small quantities of Hf, Ti, and Fe. The Ba-rich alkali feldspar and Ba-and Ti-rich biotite contain up to 9.25 and 7.35 wt% BaO, respectively, and the biotite contains up to 12.01 wt% TiO 2 . In the different intrusions of the Ponte Nova massif, such an unusual assemblage typifies the residual magma after the crystallization of clinopyroxene and olivine from previously enriched basanitic parental magma. The different trends of enrichments in REE and Th + U found for zirconolite of the intrusions of the Ponte Nova massif provide a better understanding of the variable degrees of enrichment of incompatible elements of the distinct gabbroic bodies. A lithospheric mantle source enriched in incompatible elements by the metasomatic action of volatile-rich fluids and with the presence of phlogopite or amphibole (or both) and other minor accessory phases could explain the presence of the Zr-and Ba-rich minerals in this gabbroic massif.

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“…Syenites and nepheline syenites of miaskitic affinity (i.e., nepheline syenites containing zircon or titanite or molar (Na 2 O+K 2 O)/Al 2 O 3 < 1 in bulk-rock composition; Sørensen 1997, Le Maitre 2002 prevail in many occurrences in the Serra do Mar Alkaline Province (Almeida 1983, Brotzu et al 2005. Mafic-ultramafic intrusive lithologies only occur as small, cumulate bodies associated with the syenitic stocks, such as in São Sebastião (Enrich et al 2005) and Morro de São João (Brotzu et al 2007), except for the Ponte Nova mafic-ultramafic massif, where felsic rocks are nearly absent (Azzone et al 2009). The presence of agpaitic rocks (i.e., nepheline syenites and phonolites with molar (Na 2 O+K 2 O)/Al 2 O 3 > 1 and complex silicates of Zr, Ti, REE, and F and others volatiles; Sørensen 1997, Le Maitre 2002) is restricted to a few localities in this province, usually in small volumes associated with large miaskitic bodies, as in the Poços de Caldas, Itatiaia, and Passa Quatro massifs ( Fig.…”

Section: Magmatic Contextmentioning

confidence: 99%

Eudialyte-group minerals from the Monte de Trigo alkaline suite, Brazil: composition and petrological implications

et al. 2016

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ABSTRACT:The Monte de Trigo alkaline suite is a SiO 2 -undersaturated syenite-gabbroid association from the Serra do Mar alkaline province. Eudialyte-group minerals (EGMs) occur in one nepheline microsyenite dyke, associated with aegirine-augite, wöhlerite, låvenite, magnetite, zircon, titanite, britholite, and pyrochlore. Major compositional variations include Si (25.09-25.57 apfu), Nb (0.31-0.76 apfu), Fe (1.40-2.13 apfu), and Mn (1.36-2.08 apfu). The EGMs also contain relatively high contents of Ca (6.13-7.10 apfu), moderate enrichment of rare earth elements (0.38-0.67 apfu), and a relatively low Na content (11.02-12.28 apfu), which can be correlated with their transitional agpaitic assemblage. EGM compositions indicate a complex solid solution that includes eudialyte, kentbrooksite, feklichevite, zirsilite-(Ce), georgbarsanovite, and manganoeudialyte components. EGM trace element analyses show low Sr and Ba contents and a negative Eu/Eu* anomaly, which are interpreted as characteristic of the parental magma due to the previous fractionation of plagioclase and/or alkali feldspar. The EGMs from the dyke border have higher contents of Fe, Sr (2,161-2,699 ppm), Mg (1,179-3,582 ppm), and Zn (732-852 ppm) than those at the dyke center. These differences are related to the incorporation of xenoliths and xenocrysts of melatheralitic host rock into the nephelinesyenitic magma followed by crystal-melt diffusive exchange.KEYWORDS: mineral chemistry; agpaitic rocks; Serra do Mar alkaline province. Ca (6,10 apfu), enriquecimento moderado de elementos terras raras (0,67 apfu) e concentrações relativamente baixas de Na (11,(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)28 de Fe, RESUMO: A suíte alcalina do Monte de Trigo é uma associação sienítico-gabroide que pertence à província alcalina da Serra do Mar. Minerais do grupo da eudialita (EGMs) ocorrem em um dique de nefelina microssienito associados a egirina-augita, wöhlerita, lavenita, magnetita, zircão, titanita, britolita e pirocloro. As principais variações composicionais incluem Si (25,09-25,57 apfu), Nb (0,31-0,76 apfu), Fe (1,40-2,13 apfu) e Mn (1,36-2,08 apfu). Os EGMs também contêm concentrações relativamente altas de

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Geologia e Geocronologia do Maciço Alcalino Máfico-Ultramáfico Ponte Nova (SP-MG)

Cited by 30 publications

References 28 publications

The antecryst compositional influence on Cretaceous alkaline lamprophyre dykes, SE Brazil

The antecryst compositional influence on Cretaceous alkaline lamprophyre dykes, SE Brazil

Zr- AND Ba-RICH MINERALS FROM THE PONTE NOVA ALKALINE MAFIC-ULTRAMAFIC MASSIF, SOUTHEASTERN BRAZIL: INDICATION OF AN ENRICHED MANTLE SOURCE

Eudialyte-group minerals from the Monte de Trigo alkaline suite, Brazil: composition and petrological implications

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