Volcanism is overall basaltic, volcanic rocks erupted by the Azas Plateau include basalt and trachybasalt. Other volcanoes in the Baikal Rift Zone have erupted the same rocks. These rocks are alkaline and their texture is aphyric. Minerals contained in the rocks include augite, clinopyroxene, olivine, plagioclase, Ti-containing magnetite and nepheline in the more alkaline rocks. The total volume of volcanic rocks is about . Hematite is present in the rocks and gives many tuyas a red colour. Based on geochemistry, the magma formed at depths of . Volcaniclastic rocks were originally considered to be tuffs. Cumulates and xenoliths from the mantle have been found at some volcanoes.