| A representative collection of minerals from two niobium deposits found within the Oka carbonatite complex: the Bond Zone deposit; and the NIOCAN deposit, were analysed using an electron microprobe, and compared with existing data from the St. Lawrence Columbium deposit. These minerals are good indicators of the petrological evolution of alkaline rocks, and can be used to re-evaluate the paragenesis of niobium mineralization, and the relationships between Nb-bearing minerals. In addition, this study has revealed the presence of zirconolite as an accessory mineral in calciocarbonatite.; Latrappite and Nb-rich members of the perovskite-group are found occurring as euhedral- to subhedral crystals. Zirconolite is commonly found as lath-shaped discrete crystals or intergrown with perovskite and pyrochlore-group minerals.; The crystallization history of the NIOCAN and Bond Zone deposits cannot be deduced from the observed mineral assemblage. The calciocarbonatite does not represent a liquid composition, as it has a bulk composition which is determined by mixing material derived from several batches of magma. (Abstract shortened by UMI.)... |
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