Geochemistry of Host and Altered Rocks in the Nahran Area, Tarom Zone (NW Iran): Implication for Determining of Mineralization Processes in the Alteration Environment

摘要

The Nahran area is located in the Northeast of Zanjan in the Northwest of Iran. This area with 20,000 km2 is part of the Tarom volcanic-plutonic zone which lies between the longitudes 49°7'7.8"E and 36°41'25.74"E near to the Nahran village. The Nahran altered zone is part of large-scale syncline, which is oriented from Sirdan to Altinkosh with an axial length of 9 km. A systematic study of petrographical and geochemical data of Nahran samples reveals they are andesite, trachyandesite to dacite composition and have metaluminous to peraluminous and calc-alkaline affinity. Four alteration zones of propylitic, medium and advanced argillic and silicific zones could be identified in the area. According to our finding, combination of both supergene and hypogene process has an effective role in the development of alteration in the Nahran alteration zone.