Pyatistennyi

This occurrence consists of dykes and lava flows of alkaline basaltic rocks which are overlain by tuffs and tuff breccias. The lavas are porphyritic with phenocrysts of zoned clinopyroxene, olivine replaced by chlorite, altered biotite, magnetite and accessory apatite; the presence of euhedral analcime has been demonstrated by Bazarova et al. (1981). Abundant micro-inclusions occur in the pyroxene including leucite, analcime and glass, and homogenisation temperatures of 1140-1240°C have been obtained from the inclusions (Bazarova et al., 1981). The leucite and analcime is readily apparent on weathered surfaces as circular spots. The groundmass consists essentially of brown glass, which is sometimes devitrified, in which are set acicular crystals of clinopyroxene and Ti-Fe oxide minerals; leucite and analcime co-exist in the groundmass. The tuffs consist of lava fragments together with crystals of augite, leucite, orthoclase and plagioclase. Dykes of hauyne monchiquite are found.