Petrography of volcanic rocks of south Kahrizak (south Tehran) with an overview to Analcime genesis

Abstract:
      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.