Petrography of volcanic rocks of south Kahrizak (south Tehran) with an overview to Analcime genesis
Tertiary Zeolite bearing volcanic series in south Kahrizak(south Tehran) vary greatly in chemical composition from basic to acid with a silica content between % 45 to %69 . These rocks are consisting of basalt, trachy-andesite to dacite and are mainly located in the calc-alkaline domain. Petrographic evidences show the nonequilibrium condition between melt and crystal during magma cooling and crystallization. Moreover, andesitic rocks are highly altered and contain Zeolite, Analcime, and a few other hydrothermal and secondary minerals. The source and genesis of these minerals are a controversial issue, whereas, the SEM study of some analcime crystals reveals a hydrothermal source for them.