Effect of hydrothermal alteration in mineralization and geochemistry changing of Jurassic metamorphic basic volcanic rocks in west Isfahan

Metamorphic basic rocks are exposed in the west of Esfahan, Shahrekord-Dehsard terrane with Jurassic age. That is part of the structural zone of Sanandaj- Sirjan. These rocks in green schist and most important rock outcrops in this area. The whole rocks chemistry indicates a basalt to basaltic andesite composition for the rocks with sub alkaline and tholeiitic trend. These results indicated this rocks generated back arc basin volcanic subduction. This is mainly composed of plagioclase, amphibole, quartz, epidote, garnet, chlorite and opaque and indicated green schist facies regional metamorphic paragenesis. Amphibole is mainly minerals in metamorphic basic rocks as well as phenocryst and fine crystal in thin section these rocks can be seen. frequency amphibole crystals between 40 to 50 percent rock volume is changed.The most alteration halo are sericitization, chloritization, epidotization and silicification. With this hydrothermal alteration veins iron is present. NW-WS trend Fe-silicified veins cut this rock. These veins are diagnosed with a gossan from other outcrops. Field and laboratory evidence indicates a high potential of the region economically.This mineralized type is likely Au load quartz type in Precambrian green schist belts and Au mineralization probability in this region are increase.