ZIRCONOLITE OF ALKALINE PEGMATITES OF THE VISHNEVYE MOUNTAINS: THE FIRST FINDINGS IN THE SOUTH URALS
Zirconolite, a complex oxide with an idealized formula (Ca,REE)Zr(Ti,Fe,Nb) O, is an ac-2 7cessory mineral of Nb ores from alkali pegmatites and carbonatites of the Vishnevogorsk alkalinecomplex (South Urals, Russia). Tabular grains of zirconolite (3-25 μm across) occur in assemblag- es with pyrochlore, zircon, titanite, ilmenite, and calcite. The chemical composition of zirconolite (wt. %, Fe is considered as Fe2+) is as follows: CaO 8.5-9.3; Y O 0.0-1.3; REE O 10.0-12.2; ZrO2 3 2 3 228.8-29.6; TiO 24.4-25.5; Nb O 13.1-13.4; Ta O 1.1-2.0; FeO 7.3-8.6; total 97.9-99.5. The aver-2 2 5 2 5age chemical composition of the mineral is close to formula CaREEZr Ti NbFe2+O.Figures 4. Table 2. References 8.2 2 14