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Niobian K–Ba–V titanates from micaceous kimberlite, Star mine, Orange Free State, South Africa

Published online by Cambridge University Press:  05 July 2018

Roger H. Mitchell
Affiliation:
Department of Geology, Lakehead University, Thunder Bay, Ontario P7B 5E1, Canada
Henry O. A. Meyer
Affiliation:
Department of Earth and Atmospheric Sciences, Purdue University, West Lafayette, Indiana 47907, U.S.A.

Abstract

Compositional data are presented for Nb-Ba-K-V titanates from micaceous kimberlite (Star mine, S. Africa). These data significantly extend the previously known range of solid solutions in naturally occurring members of the hollandite group. Two distinct suites of crystals occur. One is a suite of primary groundmass prismatic crystals that are Ba-K-V-rich and represent solid-solutions from the priderite series towards mannardite. The second suite consists of anhedral xenocrysts that are Ba-free. In this suite relatively Nb-rich varieties (>4.0% Nb2O5) represent solid-solution towards a niobian-bearing potassian analogue of mannardite, whereas relative Nb-poor (<3.0% Nb2O5) varieties are Nb-bearing vanadian priderites. These hollandite-group minerals have compositions that differ significantly from priderites found in lamproites.

Type
Mineralogy
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 1989

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