Niobium and rare earth minerals from the Virulundo carbonatite, Namibe, Angola

L. Torró, C. Villanova, M. Castillo, M. Campeny, A. O. Gonçalves, J. C. Melgarejo*

*Corresponding author for this work

Research output: Contribution to journalArticle

26 Citations (Scopus)

Abstract

The Virulundo carbonatite in Angola is one of the largest in the world and contains pyrochlore as an accessory mineral in all of the carbonatite units (calciocarbonatites, ferrocarbonatites, carbonatite breccias and trachytoids). The primary magmatic pyrochlore is fluorine dominant and typically contains about equal molar quantities of Ca and Na at the A site. High-temperature hydrothermal processes have resulted in the pseudomorphic replacement of the primary pyrochlore by a second generation of pyrochlore with less F and Na. Low-temperature hydrothermal replacement of the first and second generation pyrochlore, associated with quartz-carbonate-fluorite vein formation in the carbonatite, has produced a third generation of pyrochlore, with a high Sr content. The Sr appears to have been released by low-temperature hydrothermal replacement of the primary magmatic carbonates. Finally, supergene alteration processes have produced late-stage carbonates, goethite, hollandite and rare earth element (REE) minerals (mainly synchysite-(Ce), britholite-(Ce), britholite-(La), cerite-(Ce)). Cerium separated from the other REE s in oxidizing conditions and Ce 4+ was incorporated into a late generation of supergene pyrochlore, which is strongly enriched in Ba and strongly depleted in Ca and Na.

Original languageEnglish
Pages (from-to)393-409
Number of pages17
JournalMineralogical Magazine
Volume76
Issue number2
DOIs
Publication statusPublished - 2012
Externally publishedYes

Keywords

  • Angola
  • carbonatite
  • hydrothermal
  • magmatic
  • pyrochlore
  • REE
  • Virulundo
  • weathering

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    Torró, L., Villanova, C., Castillo, M., Campeny, M., Gonçalves, A. O., & Melgarejo, J. C. (2012). Niobium and rare earth minerals from the Virulundo carbonatite, Namibe, Angola. Mineralogical Magazine, 76(2), 393-409. https://doi.org/10.1180/minmag.2012.076.2.08