Composition of Priderite in Phlogopitites from the Catalão I Carbonatite Complex, Brazil

José C. Gaspar, Antônio J. G. Conceição e Silva and Débora P. de Araújo
Departamento de Mineralogia e Petrologia, Instituto de Geociências, Universidade de Brasília, 70910-900 Brasilia D.F., Brazil

Abstract: Magnetite grains with exsolved ilmenite lamellae may be replaced by pyrite or carbonate in phlogopitites of the Catalão I carbonatite complex, Goiás State, Brazil. The ilmenite is transformed in part to priderite and sometimes to rutile. Priderite occurs as small anhedral grains (< 0.2mm) or composite crystals associated with ilmenite and rutile. Chalcopyrite, magnetite, monazite, and pyrochlore also occur inside the area of original magnetite grains. The priderite belongs to the K2FeTi7O16-BaFeTi7O16 series with K/(K + Ba) ranging from 1.0 to 0.53. The highest contents for other elements are: V2O3 2.65, Cr2O3 4.1, and Nb2O5 1.98 wt.%. Priderites associated with magnetite have the highest V, Cr, and Nb contents whereas others have the highest Ba content. Zoning characterized by K-Ba substitution is patchy but always present. V-and Cr-poor priderites are similar in composition to priderites from lamproites, and the V- and Cr-rich ones are compositionally similar to hollandite-group minerals found in kimberlites.

Keywords: priderite • carbonatite • phlogopite • ilmenite • Brazil

Mineralogical Magazine; September 1994 v. 58; no. 392; p. 409-415; DOI: 10.1180/minmag.1994.058.392.06
© 1994, The Mineralogical Society
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