Karatag

Three intrusions, with a total area of about 45 km2, cut Upper Proterozoic and lower Cambrian limestones and Devonian sandstones. The occurrence of Bol'shoi (Big) Karatag Mountain is composed of peralkaline syenite, nepheline syenite, diorite and syenite-diorite. Maly (Small) Karatag Mountain, however, consists of granosyenite, granite, mildly alkaline syenite, syenite, diorite and gabbro. Two stages are distinguished with earlier gabbros followed by granite and syenite. Nepheline syenite from the Bol'shoi Karatag Mountain occurrence consists of alkali feldspar and albite (50-70%), nepheline and liebenerite (20-40%), aegirine-augite, barkevikite and biotite (4-11% total coloured minerals). The peralkaline syenites are rich in alkali feldspar (80-90%), with aegirine-augite (0-5%), barkevikite (0-7%) and biotite (2-12%).