The Alteration of Pyrochlore to Columbite in Carbonatites in Tanganyika1

T. C. James and Duncan McKie
Geological Survey, Dodoma, Tanganyika.
1Published by permission of the Director, Geologieal Survey of Tanganyika.

Summary: The formation of columbite has been observed in two earbonatites in south-west Tanganyika where it is due to autometasomatism following the emplacement of the bodies. Disoriented aggregates of columbite crystallites are formed as pseudomorphs after eubo-octahedra of pyrochlore in sövite. This alteration is accompanied by the addition of Fe, conversion of amphibole and biotite in the sövite to a ferruginous tale. the formation of an iron-bearing carbonate, and the introduction of colloform silica: Ca and Na are lost in part. The general alteration of the sövite can be ascribed to the influx of iron-bearing solutions at relatively low temperature and high pressure.

Mineralogical Magazine; September 1958 v. 31; no. 242; p. 889-900; DOI: 10.1180/minmag.1958.031.242.01
© 1958, The Mineralogical Society
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