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Please use this identifier to cite or link to this item: https://hdl.handle.net/2445/34506
Niobium and rare earth minerals from the Virulundo carbonatite, Namibe, Angola
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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
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TORRÓ I ABAT, Lisard, et al. Niobium and rare earth minerals from the Virulundo carbonatite, Namibe, Angola. Mineralogical Magazine. 2012. Vol. 76, num. 393-409. ISSN 0026-461X. [consulted: 16 of June of 2026]. Available at: https://hdl.handle.net/2445/34506