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Title: Niobium and rare earth minerals from the Virulundo carbonatite, Namibe, Angola
Author: Torró i Abat, Lisard
Villanova, Cristina
Castillo Oliver, Montgarri
Campeny Crego, Marc
Gonçalves, Antonio Olimpio
Melgarejo i Draper, Joan-Carles
Keywords: Jaciments minerals
Mineral deposits
Issue Date: 1-Apr-2012
Publisher: Mineralogical Society
Abstract: The Virulundo carbonatite in Angola, one of the biggest in the world, contains pyrochlore as an accessory mineral in all of the carbonatite units (calciocarbonatites, ferrocarbonatites, carbonatite breccias, trachytoids). The composition of the primary pyrochlore crystals is very close to fluornatrocalciopyrochlore in all these units. High-temperature hydrothermal processes caused the pseudomorphic replacement of the above crystals by a second generation of pyrochlore, characterized by lower F and Na contents. Low-temperature hydrothermal replacement of the above pyrochlores, associated with production of quartz-carbonates-fluorite veins, controled the development of a third generation of pyrochlore, characterized by high Sr contents. Finally, supergene processes produced the development of a secondary paragenesis in the carbonatite, consisting in late carbonates, goethite, hollandite and REE minerals (mainly synchysite-(Ce), britholite-(Ce), britholite-(La), cerite-(Ce)). Separation of Ce from the other REE was allowed by oxidizing conditions. Therefore, Ce4+ was also incorporated into a late generation of pyrochlore, which is also strongly enriched in Ba and strongly depleted in Ca and Na
Note: Reproducció del document publicat a:
It is part of: Mineralogical Magazine, 2012, vol. 76, p. 393-409
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ISSN: 0026-461X
Appears in Collections:Articles publicats en revistes (Mineralogia, Petrologia i Geologia Aplicada)

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