Karsakpai is situated in the central area of the Mai-Tubinskii anticlinorium and lies amongst Middle Proterozoic crystalline schists, amphibolites and granite gneisses. The complex is about 6x4 km and has a concentric ring structure. It is composed principally of alkaline melanocratic syenites, with rather less abundant leucocratic ones; liebenerite syenites and nepheline syenites are subordinate. The complex was generated by the intrusion of the following phases: (1) monzonite and syenite-diorite; (2) albite-hastingsite syenite; (3) feldspar-bearing urtite; (4) melanocratic alkaline syenite (lepidomelane-hastingsite, augite-hastingsite and lepidomelane); (5) nepheline syenite; (6) dykes including trachytic syenites, syenite porphyries and syenite pegmatites. Albitised and liebeneritized syenites occur throughout the complex.