The giant Vergenoeg fluorite deposit in a magnetite-fluorite-fayalite REE pipe: a hydrothermally-altered carbonatite-related pegmatoid?

B.H. Goff, R. Weinberg, David Groves, N.M. Vielreicher, P.J. Fourie

    Research output: Contribution to journalArticle

    17 Citations (Scopus)

    Abstract

    The world-class Paleoproterozoic Vergenoeg fluorite deposit in South Africa is hosted in a breccia pipe comprising units with varying proportions of pegmatoidal fayalite, magnetite, fluorite and siderite. The adjacent A-type Bushveld granites also have associated fluorite deposits containing fluorite with similar REE patterns, fluid inclusion and Sr isotope compositions to those at Vergenoeg, leading to the proposal that there is a genetic relationship. This is despite the silica-undersaturated nature (SiO2<30%) of the Pipe and its extreme enrichment in Ca, F, Fe, Nb, P and REE compared to granites. Both liquid immiscibility from a granitic melt and granitic magmato-hydrothermal activity have been proposed as genetic mechanisms to explain this exotic composition. However, the Vergenoeg Pipe shows greater similarities to alkaline rocks, in particular the Phalaborwa carbonatite of similar age, including: i) size and shape, ii) associated maars, iii) mineralogical zoning, iv) geochemical, radiogenic and stable isotope composition, and v) presence of both high-T and low-T fluid inclusions. This suggests an alternative genetic relationship with alkaline magmas, in which some geochemical and radiogenic isotopic similarities to Bushveld granites are the consequence of broadly contemporaneous development in the same tectonic setting within the same lithosphere, whereas others may be due to hydrothermal overprinting. Similarities with Phalaborwa and also with Bayan Obo, Mongolia, indicate that the Vergenoeg pegmatoid pipe could be an extreme carbonatite-associated member of the Fe-oxide Cu-Au (&PLUSMN;REE &PLUSMN;P) group of deposits.
    Original languageEnglish
    Pages (from-to)173-199
    JournalMineralogy and Petrology
    Volume80
    Issue number3-4
    DOIs
    Publication statusPublished - 2004

    Fingerprint

    Ferrosoferric Oxide
    fayalite
    Fluorspar
    carbonatite
    fluorite
    magnetite
    rare earth element
    Deposits
    pipe
    deposits
    Pipe
    Isotopes
    fluid inclusion
    isotopes
    Chemical analysis
    inclusions
    siderites
    Mongolia
    diatreme
    Zoning

    Cite this

    @article{18d58db2c22b4faba851d05758c19a5b,
    title = "The giant Vergenoeg fluorite deposit in a magnetite-fluorite-fayalite REE pipe: a hydrothermally-altered carbonatite-related pegmatoid?",
    abstract = "The world-class Paleoproterozoic Vergenoeg fluorite deposit in South Africa is hosted in a breccia pipe comprising units with varying proportions of pegmatoidal fayalite, magnetite, fluorite and siderite. The adjacent A-type Bushveld granites also have associated fluorite deposits containing fluorite with similar REE patterns, fluid inclusion and Sr isotope compositions to those at Vergenoeg, leading to the proposal that there is a genetic relationship. This is despite the silica-undersaturated nature (SiO2<30{\%}) of the Pipe and its extreme enrichment in Ca, F, Fe, Nb, P and REE compared to granites. Both liquid immiscibility from a granitic melt and granitic magmato-hydrothermal activity have been proposed as genetic mechanisms to explain this exotic composition. However, the Vergenoeg Pipe shows greater similarities to alkaline rocks, in particular the Phalaborwa carbonatite of similar age, including: i) size and shape, ii) associated maars, iii) mineralogical zoning, iv) geochemical, radiogenic and stable isotope composition, and v) presence of both high-T and low-T fluid inclusions. This suggests an alternative genetic relationship with alkaline magmas, in which some geochemical and radiogenic isotopic similarities to Bushveld granites are the consequence of broadly contemporaneous development in the same tectonic setting within the same lithosphere, whereas others may be due to hydrothermal overprinting. Similarities with Phalaborwa and also with Bayan Obo, Mongolia, indicate that the Vergenoeg pegmatoid pipe could be an extreme carbonatite-associated member of the Fe-oxide Cu-Au (&PLUSMN;REE &PLUSMN;P) group of deposits.",
    author = "B.H. Goff and R. Weinberg and David Groves and N.M. Vielreicher and P.J. Fourie",
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    doi = "10.1007/s00710-003-0012-6",
    language = "English",
    volume = "80",
    pages = "173--199",
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    }

    The giant Vergenoeg fluorite deposit in a magnetite-fluorite-fayalite REE pipe: a hydrothermally-altered carbonatite-related pegmatoid? / Goff, B.H.; Weinberg, R.; Groves, David; Vielreicher, N.M.; Fourie, P.J.

    In: Mineralogy and Petrology, Vol. 80, No. 3-4, 2004, p. 173-199.

    Research output: Contribution to journalArticle

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    T1 - The giant Vergenoeg fluorite deposit in a magnetite-fluorite-fayalite REE pipe: a hydrothermally-altered carbonatite-related pegmatoid?

    AU - Goff, B.H.

    AU - Weinberg, R.

    AU - Groves, David

    AU - Vielreicher, N.M.

    AU - Fourie, P.J.

    PY - 2004

    Y1 - 2004

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    AB - The world-class Paleoproterozoic Vergenoeg fluorite deposit in South Africa is hosted in a breccia pipe comprising units with varying proportions of pegmatoidal fayalite, magnetite, fluorite and siderite. The adjacent A-type Bushveld granites also have associated fluorite deposits containing fluorite with similar REE patterns, fluid inclusion and Sr isotope compositions to those at Vergenoeg, leading to the proposal that there is a genetic relationship. This is despite the silica-undersaturated nature (SiO2<30%) of the Pipe and its extreme enrichment in Ca, F, Fe, Nb, P and REE compared to granites. Both liquid immiscibility from a granitic melt and granitic magmato-hydrothermal activity have been proposed as genetic mechanisms to explain this exotic composition. However, the Vergenoeg Pipe shows greater similarities to alkaline rocks, in particular the Phalaborwa carbonatite of similar age, including: i) size and shape, ii) associated maars, iii) mineralogical zoning, iv) geochemical, radiogenic and stable isotope composition, and v) presence of both high-T and low-T fluid inclusions. This suggests an alternative genetic relationship with alkaline magmas, in which some geochemical and radiogenic isotopic similarities to Bushveld granites are the consequence of broadly contemporaneous development in the same tectonic setting within the same lithosphere, whereas others may be due to hydrothermal overprinting. Similarities with Phalaborwa and also with Bayan Obo, Mongolia, indicate that the Vergenoeg pegmatoid pipe could be an extreme carbonatite-associated member of the Fe-oxide Cu-Au (&PLUSMN;REE &PLUSMN;P) group of deposits.

    U2 - 10.1007/s00710-003-0012-6

    DO - 10.1007/s00710-003-0012-6

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    JO - Mineralogy and Petrology

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