Petrographic and mineral-chemistry of the magmatic-alteration zones South of Salafchegan

The study area which lies along the Uromieh-Dokhtar volcanic belt, comprises andesibasalt,andesite, dacite, diorite and quartz-diorite with porphyry texture exposing as volcanic and subvolcanic bodies. The essential minerals of these rocks are plagioclase,amphibole, biotite and quartz accompanied by pyroxene and traces of K-feldspar. The propyllitic, potassic and phyllic alteration zones point to the occurrence of hydrothermal fluids. The studied amphiboles are Mg-enriched which ranges in composition from Mg-hornblende to actinolite. The biotites are also enriched in Mg, pointing to their formation in high oxygen fugacity conditions. The chemical features of these minerals are characteristics of porphyry Cu bearing intrusive rocks. The investigation of biotite chemistry shows that the fluid composition in the phyllic and potassic zones is different. The geothermometry of chlorites and biotites shows the temperatures of 275-323, 402-450 °C and 249-256, 280-344 °C for the potassic and phyllic zones respectively. These data are consistent with those of many worldwide porphyry Cu deposits.