Siriktinskii

This stock-like massif intrudes crystalline limestones and amphibole schists of upper Proterozoic age. The massif predominantly comprises peralkaline syenites and medium-grained nepheline syenites. At the southern outer contact small areas of ijolite and urtite are present among the nepheline syenites. For the most part peralkaline granites are concentrated near the marginal parts of the complex. In the central area is a 600 x 100 m body composed of peralkaline granite and peralkaline syenite. The paragenesis of the alkaline minerals of all the alkaline rocks are very similar. Mafic minerals are biotite, aegirine and riebeckite, the syenites are dominantly alkali feldspar rocks, and quartz and nepheline are diagnostic of the granites and nepheline syenites. A vein facies is represented by granite-aplites and peralkaline pegmatites. Postmagmatic alteration caused albitization and microclinization which change the rock compositions throughout the massif, but mainly along faults.