The Talyshskii folded zone is situated in the southeastern part of Azerbai'an and during the Eocene an extensive area of alkaline basaltic volcanic rocks were erupted. A series of leucite-sanidine tuffs and leucite tephrites and basanites, having a thickness of about 500 m, were ejected, during early, mid and late Eocene times, in the southern part of the Talyshskii zone; they extend into Iran. The leucite tuffs occur in the volcanic domes of Shandan-Kalasy and Green Hill. Mineralogically the tuffs consist of sanidine, plagioclase, leucite, augite, aegirine-augite, hornblende and volcanic glass. The leucite tephrites and basanites are found in the volcanoes of Geldar, Govery, Kiz-Kalashym Pashgra and Rasgov. They contain phenocrysts of plagioclase, leucite, olivine and augite set in a groundmass of glass, feldspar, augite, leucite and magnetite. The leucite tephrites also form dykes and sills including the Dimansky sill. The largest centre is the Kalakhanskaya subvolcanic intrusion, which forms a cone with a height of 1732 m; it is oval in plan. The rocks developed within Kalakhanskaya are trachyandesites, gabbro-teschenites, picrobasalts and leucite-bearing basalts. The gabbro-teschenites are composed of plagioclase (35-40%), augite (15-20%), biotite (3-5%), amphibole (1-6%), analcime (10-12%) and natrolite (2%) with accessory apatite, titanite and titanomagnetite.