Mineral chemistry and crystallization of quaternary volcanoes in the Qorveh-Bijar axis

Qorveh-Bijar area is east of Kurdistan province, located in northern part of Sanandaj-Sirjan zone in northwest of Iran. Quaternary volcanic rocks composition include of Basanite-tephrite to olivine basalt, basalt and trachyte. These rocks main phenocrysts are clinopyroxene, olivine and plagioclase. Plagioclase, biotite, hornblende and apatite are the main phase of mesostase. The EPMA results show that the plagioclases are show delicate zoning and have oligoclase to labradorite composition. Amphibole have magnesian-hastingsite composition and clinopyroxene with magnesium-calcium element ploted in diopside field. Olivine show the chrysolite type near to the magnesium pole, Mica is a phlogopite type and opaqius minerals shown the titano-magnetite composition. Based on the composition of amphibole and biotite, the magma have been the high rate of oxygen fugacity during the crystallization. According to the chemical composition of clinopyroxene, the basaltic rocks show the alkaline nature and was formed in continental within plate with extensional conditions. The magma temperature during the clinopyroxene crystallization is between 1150 to 1200°C and in the 5 to 8 kb pressures. Also the reange of magma temperature during the plagioclases crystallization have been 650 to 900°C.