stripes
The Ishkul occurrence is located near to the Ishkul and Uveldy lakes and is an elongate body extending north-south for 10 km and having a width of about 0.6 km. It lies within granites of the western sector of the Ilmenogorskii anticlinorium. The complex is situated in the so-called intermediate zone between the Vishnevogorskii and Ilmenogorskii occurrences (Fig. 56). The massif is composed predominantly of miaskitic nepheline syenites with lepidomelane; miaskitic hastingsite-nepheline syenites and peralkaline hastingsite syenites also occur. Both to the west and east of the complex are numerous sheets and veins of nepheline syenite and peralkaline syenite which vary in thickness from several centimetres to several metres and which lie within fenitized country rocks. The following sequences of rocks are typical: intrusive nepheline syenite - alkaline syenite - syenitic migmatite - fenite - unaltered gneiss. The biotite-nepheline syenite of this zone has Rb-Sr ratios of 0.70337±0.00036 (Kramm et al., 1983). Silicates from nepheline-feldspar migmatites gave d18Oo/oo values of +8.2 (Kononova et al., 1979).
*CHERNYSHEV, I.V., KONONOVA, V.A., KRAMM, U. and GRAUERT B. 1987. Isotope dating of Urals alkaline rocks in the light of U-Pb data for zircons. Geochemistry International, 24 (10): 1-15.
KONONOVA, V.A., DONTSOVA, E.I. and KUZNETSOVA, L.D. 1979. Isotopic composition of oxygen and strontium of the Ilmen-Vishnevy Gory alkaline complex and problems of miaskite genesis. Geokhimiya, 12: 1784-95.
*KRAMM, U., BLAXLAND, A.B., KONONOVA, V.A. and GRAUERT, B. 1983. Origin of the Ilmenogorsk-Vishnevogorsk nepheline syenites, Urals, USSR, and their time of emplacement during the history of the Ural fold belt: a Rb-Sr study. Journal of Geology, 91: 427-35.
RONENSON, B.M. 1966. Origin of the miaskites and their relationship with the rare-metal ores. In. A.I. Ginzburg (ed) Geology of the rare elements deposits 28: Nedra. Moscow. 174 pp.
