The Hidden Magmatic Chamber from the Ponte Nova Mafic–Ultramafic Alkaline Massif, SE Brazil: Clues from Clinopyroxene and Olivine Antecrysts
Clinopyroxene and olivine primocrysts in the intrusions of the Ponte Nova mafic–ultramafic alkaline massif (SE Brazil) present several textures and zoning that indicate open-system processes. Important compositional differences were found in the clinopyroxene. Diopside relict cores (mostly partially...
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MDPI AG
2022-06-01
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| Series: | Minerals |
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| Online Access: | https://www.mdpi.com/2075-163X/12/6/775 |
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| author | Rogério Guitarrari Azzone Lina Maria Cetina Tarazona Mariana Robertti Ambrosio Vincenza Guarino Luanna Chmyz Nicholas Machado Lima Excelso Ruberti |
| author_facet | Rogério Guitarrari Azzone Lina Maria Cetina Tarazona Mariana Robertti Ambrosio Vincenza Guarino Luanna Chmyz Nicholas Machado Lima Excelso Ruberti |
| author_sort | Rogério Guitarrari Azzone |
| collection | DOAJ |
| description | Clinopyroxene and olivine primocrysts in the intrusions of the Ponte Nova mafic–ultramafic alkaline massif (SE Brazil) present several textures and zoning that indicate open-system processes. Important compositional differences were found in the clinopyroxene. Diopside relict cores (mostly partially corroded) present higher Mg, Cr and Ni and lower Ti, Na, Al, REE and Sr than Ti-augite mantling and rims. Subordinately, two types of olivine crystals were recognized, one related to very zoned crystals with high Mg (Fo up to 86 mol.%) and Ni cores (mostly with corroded rims), and other almost without clear zonation and with lower Mg contents. Relict cores of high-Mg clinopyroxene and olivine crystals are representative of antecrysts formed in deeper chamber environments. Temperature and pressure estimates based on clinopyroxene-liquid geothermobarometers indicate crystallization of the antecrysts at ~1171 ± 10 °C and ~5.7 ± 0.3 kbar, pointing to a deeper hidden magmatic chamber, whereas mantling and rim compositions indicate a shallow chamber environment. Clinopyroxenes of this hidden chamber have progressive enrichments of incompatible elements with the Mg# decrement and inflection points in Sr and REE due to the starting of co-precipitation of apatite. The evolution trend of clinopyroxene antecrysts indicates that the main intrusions in the Ponte Nova shallow chamber were fed by a single deeper hidden chamber mainly controlled by typical fractional crystallization processes. These antecrysts indicate the presence of a complex plumbing system, which is also supported by similar antecrysts found in the lamprophyre and alkali basalt dikes of this region. The preferred petrological model for the Ponte Nova massif could be summarized as repeated influxes of antecryst-laden basanite magmas that deposited most of their suspended crystals on the floor of the upper-crust magma chamber. |
| first_indexed | 2024-03-09T22:58:17Z |
| format | Article |
| id | doaj.art-8ef0519d0dd14f599eeff016a32eb6d3 |
| institution | Directory Open Access Journal |
| issn | 2075-163X |
| language | English |
| last_indexed | 2024-03-09T22:58:17Z |
| publishDate | 2022-06-01 |
| publisher | MDPI AG |
| record_format | Article |
| series | Minerals |
| spelling | doaj.art-8ef0519d0dd14f599eeff016a32eb6d32023-11-23T18:07:42ZengMDPI AGMinerals2075-163X2022-06-0112677510.3390/min12060775The Hidden Magmatic Chamber from the Ponte Nova Mafic–Ultramafic Alkaline Massif, SE Brazil: Clues from Clinopyroxene and Olivine AntecrystsRogério Guitarrari Azzone0Lina Maria Cetina Tarazona1Mariana Robertti Ambrosio2Vincenza Guarino3Luanna Chmyz4Nicholas Machado Lima5Excelso Ruberti6Department of Mineralogy and Geotectonics, Institute of Geosciences (IGc), University of São Paulo (USP), São Paulo 05508-080, BrazilDepartment of Mineralogy and Geotectonics, Institute of Geosciences (IGc), University of São Paulo (USP), São Paulo 05508-080, BrazilDepartment of Mineralogy and Geotectonics, Institute of Geosciences (IGc), University of São Paulo (USP), São Paulo 05508-080, BrazilDipartimento di Scienze della Terra, dell’Ambiente e delle Risorse, Università di Napoli Federico II, 80138 Naples, ItalyDepartment of Mineralogy and Geotectonics, Institute of Geosciences (IGc), University of São Paulo (USP), São Paulo 05508-080, BrazilPetróleo Brasileiro S.A., Centro de Pesquisa e Desenvolvimento Leopoldo Miguez de Mello (CENPES), Rio de Janeiro 21941-915, BrazilDepartment of Mineralogy and Geotectonics, Institute of Geosciences (IGc), University of São Paulo (USP), São Paulo 05508-080, BrazilClinopyroxene and olivine primocrysts in the intrusions of the Ponte Nova mafic–ultramafic alkaline massif (SE Brazil) present several textures and zoning that indicate open-system processes. Important compositional differences were found in the clinopyroxene. Diopside relict cores (mostly partially corroded) present higher Mg, Cr and Ni and lower Ti, Na, Al, REE and Sr than Ti-augite mantling and rims. Subordinately, two types of olivine crystals were recognized, one related to very zoned crystals with high Mg (Fo up to 86 mol.%) and Ni cores (mostly with corroded rims), and other almost without clear zonation and with lower Mg contents. Relict cores of high-Mg clinopyroxene and olivine crystals are representative of antecrysts formed in deeper chamber environments. Temperature and pressure estimates based on clinopyroxene-liquid geothermobarometers indicate crystallization of the antecrysts at ~1171 ± 10 °C and ~5.7 ± 0.3 kbar, pointing to a deeper hidden magmatic chamber, whereas mantling and rim compositions indicate a shallow chamber environment. Clinopyroxenes of this hidden chamber have progressive enrichments of incompatible elements with the Mg# decrement and inflection points in Sr and REE due to the starting of co-precipitation of apatite. The evolution trend of clinopyroxene antecrysts indicates that the main intrusions in the Ponte Nova shallow chamber were fed by a single deeper hidden chamber mainly controlled by typical fractional crystallization processes. These antecrysts indicate the presence of a complex plumbing system, which is also supported by similar antecrysts found in the lamprophyre and alkali basalt dikes of this region. The preferred petrological model for the Ponte Nova massif could be summarized as repeated influxes of antecryst-laden basanite magmas that deposited most of their suspended crystals on the floor of the upper-crust magma chamber.https://www.mdpi.com/2075-163X/12/6/775antecrystscomplex plumbing systemolivineclinopyroxenealkaline magmatismREE |
| spellingShingle | Rogério Guitarrari Azzone Lina Maria Cetina Tarazona Mariana Robertti Ambrosio Vincenza Guarino Luanna Chmyz Nicholas Machado Lima Excelso Ruberti The Hidden Magmatic Chamber from the Ponte Nova Mafic–Ultramafic Alkaline Massif, SE Brazil: Clues from Clinopyroxene and Olivine Antecrysts Minerals antecrysts complex plumbing system olivine clinopyroxene alkaline magmatism REE |
| title | The Hidden Magmatic Chamber from the Ponte Nova Mafic–Ultramafic Alkaline Massif, SE Brazil: Clues from Clinopyroxene and Olivine Antecrysts |
| title_full | The Hidden Magmatic Chamber from the Ponte Nova Mafic–Ultramafic Alkaline Massif, SE Brazil: Clues from Clinopyroxene and Olivine Antecrysts |
| title_fullStr | The Hidden Magmatic Chamber from the Ponte Nova Mafic–Ultramafic Alkaline Massif, SE Brazil: Clues from Clinopyroxene and Olivine Antecrysts |
| title_full_unstemmed | The Hidden Magmatic Chamber from the Ponte Nova Mafic–Ultramafic Alkaline Massif, SE Brazil: Clues from Clinopyroxene and Olivine Antecrysts |
| title_short | The Hidden Magmatic Chamber from the Ponte Nova Mafic–Ultramafic Alkaline Massif, SE Brazil: Clues from Clinopyroxene and Olivine Antecrysts |
| title_sort | hidden magmatic chamber from the ponte nova mafic ultramafic alkaline massif se brazil clues from clinopyroxene and olivine antecrysts |
| topic | antecrysts complex plumbing system olivine clinopyroxene alkaline magmatism REE |
| url | https://www.mdpi.com/2075-163X/12/6/775 |
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