The Occurrence of Niobian Zirconolite, Pyrochlore and Baddeleyite in the Kovdor Carbonatite Complex, Kola Peninsula, Russia

C. Terry Williams
Department of Mineralogy, The Natural History Museum, Cromwell Road, London SW7 5BD, UK

Abstract: The compositions and textural relationships of the oxide minerals zirconolite, pyrochlore and baddeleyite are described. These occur as accessory minerals, often intergrown with each other, from a phoscorite rock associated with the Kovdor carbonatite complex. Both the zirconolite and baddeleyite have relatively high concentrations of Nb and Ta; the pyrochlore is rich in U and Ta. Backscattered electron images, coupled with detailed microprobe analyses, reveal complex compositional zoning in zirconolite and pyrochlore which reflect changes in the fluid composition during growth of these minerals. A comparison is made of incompatible element ratios Zr/Hf, Nb/Ta and Th/U between the three accessory minerals.

Keywords: zirconolite • baddeleyite • pyrochlore • carbonatites • Kola Peninsula • Russia

Mineralogical Magazine; August 1996 v. 60; no. 401; p. 639-646; DOI: 10.1180/minmag.1996.060.401.09
© 1996, The Mineralogical Society
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