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

Published online by Cambridge University Press:  05 July 2018

L. Torró ,
C. Villanova ,
M. Castillo ,
M. Campeny ,
A. O. Gonçalves  and
J. C. Melgarejo
L. Torró
Affiliation:
Departament de Cristal·lografia, Mineralogía i Dipósits Minerals, Universitat de Barcelona, c/Martí i Franqués s/n, 08028 Barcelona, Catalonia, Spain
C. Villanova
Affiliation:
Departament de Cristal·lografia, Mineralogía i Dipósits Minerals, Universitat de Barcelona, c/Martí i Franqués s/n, 08028 Barcelona, Catalonia, Spain
M. Castillo
Affiliation:
Departament de Cristal·lografia, Mineralogía i Dipósits Minerals, Universitat de Barcelona, c/Martí i Franqués s/n, 08028 Barcelona, Catalonia, Spain
M. Campeny
Affiliation:
Departament de Cristal·lografia, Mineralogía i Dipósits Minerals, Universitat de Barcelona, c/Martí i Franqués s/n, 08028 Barcelona, Catalonia, Spain
A. O. Gonçalves
Affiliation:
Departamento de Geologia, Faculdade de Ciências, Universidade Agostinho Neto, Av. 4 de Fevereiro 7, 815 Luanda, Angola
J. C. Melgarejo*
Affiliation:
Departament de Cristal·lografia, Mineralogía i Dipósits Minerals, Universitat de Barcelona, c/Martí i Franqués s/n, 08028 Barcelona, Catalonia, Spain
*
*E-mail: joan.carles.melgarejo.draper@ub.edu
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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 Ce4+ was incorporated into a late generation of supergene pyrochlore, which is strongly enriched in Ba and strongly depleted in Ca and Na.

Keywords

angolacarbonatitepyrochloreREEmagmatichydrothermalweatheringVirulundo
Type
Research Article
Information
Mineralogical Magazine , Volume 76 , Issue 2 , April 2012 , pp. 393 - 409
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 2012

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References

Alberti, A., Castorina, F., Censi, P., Comin-Chiaramoni, P. and de Barros Gomes, C. (1999) Geochemical characteristics of Cretaceous carbonatites from Angola. Journal of African Earth Sciences, 29, 735–759.CrossRefGoogle Scholar
Aral, H. and Bruckard, W.J. (2008) Characterisation of the Mt. Weld (Western Australia) niobium ore. Transactions of the Institutions of Mining and Metallurgy, Section C: Mineral Processing and Extractive Metallurgy, 117, 193–204.Google Scholar
Atencio, D., Andrade, M.B., Christy, A.G., Gieré, R. and Kartashov, P.M. (2010) The pyrochlore supergroup of minerals: nomenclature. The Canadian Mineralogist, 48, 673–698.CrossRefGoogle Scholar
Bagdasarov, Y.A. (2009) On the geochemistry of tantalum in the carbonatite process. Geochemistry International, 47, 163–173.CrossRefGoogle Scholar
Bambi, A.C.J.M, Costanzo, A., Gonçalves, A.O. and Melgarejo, J.C. (2012) Tracing the chemical evolution of primary pyrochlore from plutonic to volcanic carbonatites: the role of fluorine. Mineralogical Magazine 76, 377–392.Google Scholar
Castorina, F., Censi, P., Barbieri, M., Comin-Chiaramonti, P., Cundari, A., de Barros Gomes, C. and Pardini, G. (1996) Carbonatites from eastern Paraguay: a comparison with coeval carbonatites from Brazil and Angola.Pp. 231–248. in: Alkaline magmatism in central-eastern Paraguay; relationships with coeval magmatism in Brazil (Comin-Chiaramonti, P. and de, C.B. Barros Gomes, editors). Editora da Universidade de Sa˜o Paulo, Sa˜o Paulo, Brazil, 464 pp.Google Scholar
Chakhmouradian, A.R. and Mitchell, R.H. (1998) Lueshite, pyrochlore and monazite-(Ce) from apatite-dolomite carbonatite, Lesnaya Varaka complex, Kola Peninsula, Russia. Mineralogical Magazine, 62, 769–782.CrossRefGoogle Scholar
Coltorti, M., Alberti, A., Beccaluva, L., Dos Santos, A.B., Mazzucchelli, M., Morais, E., Rivalenti, G. and Siena, F. (1993) The Tchivira-Bonga alkalinecarbonatite complex (Angola): petrological study and comparison with some Brazilian analogues. European Journal of Mineralogy, 5, 1001–1024.CrossRefGoogle Scholar
Comin-Chiaramonti, P., Cundari, A., Piccirillo, E.M., de Barros Gomes, C., Castorina, F., Censi, P., De Min, A., Marzoli, A., Speziale, S. and Velázquez, V.F. (1997a) Potassic and sodic igneous rocks from Eastern Paraguay: their origin from the lithospheric mantle and genetic relationships with the associated Paraná flood tholeiites. Journal of Petrology, 38, 495–528.Google Scholar
Comin-Chiaramonti, P., Cundari, A., Piccirillo, E.M., de Barros Gomes, C. and de Min, A. (1997b) Carbonatitic magmatism in the Paraná-Angola mantle plume(?) system: petrological and isotopegeochemical bearing on the source mantle. Eos, Transactions, AGU, 78, F741.Google Scholar
Comin-Chiaramonti, P., de Barros Gomes, C., Cundari, A., Castorina, F. and Censi, P. (2007a) A review of carbonatitic magmatism in the Paraná–Angola– Etendeka system. Geophysical Research Abstracts, 9, 11507.Google Scholar
Comin-Chiaramonti, P., de Barros Gomes, C., Cundari, A., Castorina, F. and Censi, P. (2007b) A review of carbonatitic magmatism in the Paraná–Angola– Namibia (PAN) system.Periodico di Mineralogia, 76, 25–78.Google Scholar
Cooper, A.F. and Reid, D.L. (2000) The association of potassic trachytes and carbonatites at the Dicker Willem Complex, southwest Namibia: coexisting, immiscible, but not cogenetic magmas. Contributions to Mineralogy and Petrology, 139, 570–583.CrossRefGoogle Scholar
de Carvalho, H. Tassinari, C., Alves, P.H., Guimara˜es, F. and Simo˜ es, M.C. (2000) Geochronological review of the Precambrian in western Angola: links with Brazil. Journal of African Earth Sciences, 31, 383–402.CrossRefGoogle Scholar
Ercit, T.S., Hawthorne, F.C. and Černý, P. (1994) The structural chemistry of kalipyrochlore, a “hydropyrochlore”. The Canadian Mineralogist, 32, 415–420.Google Scholar
Ernst, R.E. and Bell, K. (2010) Large igneous provinces (LIPs) and carbonatites. Mineralogy and Petrology, 98, 55–76.CrossRefGoogle Scholar
Geisler, T., Berndt, J., Meyer, H.-W., Pollok, K. and Putnis, A. (2004) Low-temperature aqueous alteration of crystalline pyrochlore: correspondence between nature and experiment. Mineralogical Magazine, 68, 905–922.CrossRefGoogle Scholar
Hogarth, D.D. (1977) Classification and nomenclature of the pyrochlore group. American Mineralogist, 62, 403–410.Google Scholar
Hogarth, D.D., Williams, C.T. and Jones, P. (2000) Primary zoning in pyrochlore group minerals from carbonatites. Mineralogical Magazine, 64, 683–697.CrossRefGoogle Scholar
Issa Filho, A., Dos Santos, A.B.R.M.D., Riffel, B.F., Lapido-Loureiro, F.E.V. and McReath, I. (1991) Aspects of the geology, petrology and chemistry of some Angolan carbonatites. Journal of Geochemical Exploration, 40, 205–226.CrossRefGoogle Scholar
Jago, B.C. and Gittins, J. (1991) The role of fluorine in carbonatite magma evolution. Nature, 349, 56–58.CrossRefGoogle Scholar
Jago, B.C. and Gittins, J. (1993) Pyrochlore crystallization in carbonatites: the role of fluorine. South African Journal of Geology, 96, 149–159.Google Scholar
Lapido-Loureiro, F.E. de, V. (1973) Carbonatitos de Angola. Memórias e Trabalhos do Instituto de Investigaça˜o Científica de Angola, 11, 1–242.Google Scholar
Laval, M., Johan, V. and Tourlière, B. (1988) La carbonatite de Mabounié: exemple de formation d’un gîte résiduel à pyrochlore. Chronique de la Recherche Minière, 56, 125–136.Google Scholar
Le Bas, M.J. (2008) Fenites associated with carbonatites. The Canadian Mineralogist 46, 915–932.Google Scholar
Lee, M.J., Lee, J.I., García, D., Moutte, J., Williams, C.T., Wall, F. and Kim, Y. (2006) Pyrochlore chemistry from the Sokli phoscorite-carbonatite complex, Finland: implications for the genesis of phoscorite and carbonatite association. Geochemical Journal, 40, 1–13.CrossRefGoogle Scholar
Lottermoser, B.G. and England, B.M. (1988) Compositional variation in pyrochlores from the Mt. Weld carbonatite laterite, Western Australia. Mineralogy and Petrology, 38, 37–51.CrossRefGoogle Scholar
Lumpkin, G.R. and Ewing, R.C. (1995) Geochemical alteration of pyrochlore group minerals: pyrochlore subgroup. American Mineralogist, 80, 732–743.CrossRefGoogle Scholar
Lumpkin, G.R. and Mariano, A.N. (1996) Natural occurrence and stability of pyrochlore in carbonatites, related hydrothermal systems, and weathering environments. Materials Research Society Symposium Proceedings, (Scientific Basis for Nuclear Waste Management XIX), 412, 831–838.CrossRefGoogle Scholar
Mitchell, R.H. and Kjarsgaard, B.A. (2004) Solubility of niobium in the system CaCO3-CaF2-NaNbO3 at 0.1 GPa pressure: implications for the crystallization of pyrochlore from carbonatite magma. Contributions to Mineralogy and Petrology, 148, 281–287.CrossRefGoogle Scholar
Nasraoui, M. and Bilal, E. (2000) Pyrochlores from the Lueshe carbonatite complex (Democratic Republic of Congo): a geochemical record of different alteration stages. Journal of Asian Earth Sciences, 18, 237–251.CrossRefGoogle Scholar
Nasraoui, M. and Waerenborgh, J.C. (2001) Fe speciation in weathered pyrochlore-group minerals from the Lueshe and Araxa (Barreiro) carbonatites by 57Fe Mössbauer spectroscopy. The Canadian Mineralogist, 39, 1073–1080.CrossRefGoogle Scholar
Nasraoui, M., Bilal, E. and Gibert, R. (1999) Fresh and weathered pyrochlore studies by Fourier transform infrared spectroscopy coupled with thermal analysis. Mineralogical Magazine, 63, 567–578.CrossRefGoogle Scholar
Pichou, J.L. and Pichoir, F. (1984) A new model for quantitative X-ray microanalysis.Part I: application to the analysis of homogeneous samples. La Recherche A ´ erospatiale, 3, 13–38.Google Scholar
Platt, R.G. (1994) Perovskite, loparite and Ba-Fe hollandite from the Schryburt Lake carbonatite complex, northwestern Ontario, Canada. Mineralogical Magazine, 58, 49–57.CrossRefGoogle Scholar
Renne, P.R., Ernesto, M., Pacca, I.G., Coe, R.S., Glen, J.M., Prevot, M. and Perrin, M. (1992) The age of Paraná flood volcanism, rifting of Gondwanaland, and the Jurassic-Cretaceous boundary. Science, 258, 975–979.CrossRefGoogle ScholarPubMed
Renne, P., Ernesto, M. and Milner, S.C. (1997) Geochronology of the Paraná-Angola-Etendeka magmatic Province. Eos, Transactions, AGU, 78, F742. Rocha, E., Nasraoui, M., Soubies, F., Bilal, E. and De Parseval, Ph. (2001) Geochemical evolution of pyrochlore during supergene alteration of Catala˜o II ore deposit. Comptes Rendus de l’Academie des Sciences, Série IIa: Sciences de la Terre et des Planetes, 332, 91–98.Google Scholar
Waber, N. (1992) The supergene thorium and rare-earth element deposit at Morro do Ferro, Poços de Caldas, Minas Gerais, Brazil. Journal of Geochemical Exploration, 45, 113–157.CrossRefGoogle Scholar
Wall, F., Williams, C.T., Woolley, A.R. and Nasraoui, M. (1996) Pyrochlore from weathered carbonatite at Lueshe, Zaire. Mineralogical Magazine, 60, 731–750.CrossRefGoogle Scholar
Williams, C.T., Wall, F., Woolley, A.R. and Phillipo, S. (1997) Compositional variation in pyrochlore from the Bingo carbonatite, Zaire. Journal of African Earth Science, 25, 137–145.CrossRefGoogle Scholar
Whitney, D.L. and Evans, B.D. (2010) Abbreviations for names of rock-forming minerals. American Mineralogist, 95, 185–187.CrossRefGoogle Scholar
Woolley, A.R. (2001) Alkaline Rocks and Carbonatites of the World. 3. Africa. The Geological Society Publishing House, Bath, UK, 372 pp.Google Scholar
Yaroshevskii, A.A. and Y.A., Bagdasarov (2008) Geochemical diversity of minerals of the pyrochlore group. Geochemistry International, 46, 1245–1266.CrossRefGoogle Scholar