Kultaiginskii

This oval-shaped intrusion, having an area of about 40 km2, cuts lower Cambrian sequences of sedimentary and metamorphic rocks which consist mainly of limestones. The southern part of the complex is composed of gabbro and the central and northern parts of peralkaline syenite and nordmarkite. The gabbro formed a funnel-shaped body the northern part of which was destroyed by emplacement of the syenite and nordmarkite intrusion which takes the form of a stock. Altered xenoliths of gabbro are preserved in the syenite. In the central parts of the stock the peralkaline syenites change to nordmarkite and quartz syenite and in some places into granosyenite and granite. At the southern outer contact of the gabbro a small, 100-200 m long, occurrence of miaskitic nepheline syenite has been found. The nepheline syenite cuts both the gabbro and country rock marble and quartzite. The peralkaline syenites are coarse-grained, sometimes porphyritic, rocks consisting of orthoclase perthite (70-80%), albite (8%), aegirine-augite (7-10%), biotite, amphibole and accessory apatite, magnetite and sparse zircon.