Eudialyte-group minerals from the Monte de Trigo alkaline suite, Brazil: composition and petrological implications
ABSTRACT: The Monte de Trigo alkaline suite is a SiO2-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, brit...
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Sociedade Brasileira de Geologia
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| Series: | Brazilian Journal of Geology |
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| Online Access: | http://www.scielo.br/scielo.php?script=sci_arttext&pid=S2317-48892016000300411&lng=en&tlng=en |
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| author | Gaston Eduardo Enrich Rojas Excelso Ruberti Rogério Guitarrari Azzone Celso de Barros Gomes |
| author_facet | Gaston Eduardo Enrich Rojas Excelso Ruberti Rogério Guitarrari Azzone Celso de Barros Gomes |
| author_sort | Gaston Eduardo Enrich Rojas |
| collection | DOAJ |
| description | ABSTRACT: The Monte de Trigo alkaline suite is a SiO2-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 nepheline-syenitic magma followed by crystal-melt diffusive exchange. |
| first_indexed | 2024-12-12T15:16:30Z |
| format | Article |
| id | doaj.art-4884a48abbac491da65e06cecf80ce06 |
| institution | Directory Open Access Journal |
| issn | 2317-4692 |
| language | English |
| last_indexed | 2024-12-12T15:16:30Z |
| publisher | Sociedade Brasileira de Geologia |
| record_format | Article |
| series | Brazilian Journal of Geology |
| spelling | doaj.art-4884a48abbac491da65e06cecf80ce062022-12-22T00:20:29ZengSociedade Brasileira de GeologiaBrazilian Journal of Geology2317-469246341142610.1590/2317-4889201620160075S2317-48892016000300411Eudialyte-group minerals from the Monte de Trigo alkaline suite, Brazil: composition and petrological implicationsGaston Eduardo Enrich RojasExcelso RubertiRogério Guitarrari AzzoneCelso de Barros GomesABSTRACT: The Monte de Trigo alkaline suite is a SiO2-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 nepheline-syenitic magma followed by crystal-melt diffusive exchange.http://www.scielo.br/scielo.php?script=sci_arttext&pid=S2317-48892016000300411&lng=en&tlng=enquímica mineralrochas agpaíticas, província alcalina da Serra do Mar |
| spellingShingle | Gaston Eduardo Enrich Rojas Excelso Ruberti Rogério Guitarrari Azzone Celso de Barros Gomes Eudialyte-group minerals from the Monte de Trigo alkaline suite, Brazil: composition and petrological implications Brazilian Journal of Geology química mineral rochas agpaíticas, província alcalina da Serra do Mar |
| title | Eudialyte-group minerals from the Monte de Trigo alkaline suite, Brazil: composition and petrological implications |
| title_full | Eudialyte-group minerals from the Monte de Trigo alkaline suite, Brazil: composition and petrological implications |
| title_fullStr | Eudialyte-group minerals from the Monte de Trigo alkaline suite, Brazil: composition and petrological implications |
| title_full_unstemmed | Eudialyte-group minerals from the Monte de Trigo alkaline suite, Brazil: composition and petrological implications |
| title_short | Eudialyte-group minerals from the Monte de Trigo alkaline suite, Brazil: composition and petrological implications |
| title_sort | eudialyte group minerals from the monte de trigo alkaline suite brazil composition and petrological implications |
| topic | química mineral rochas agpaíticas, província alcalina da Serra do Mar |
| url | http://www.scielo.br/scielo.php?script=sci_arttext&pid=S2317-48892016000300411&lng=en&tlng=en |
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