Potential study of massive sulfide mineralization in southern central Alborz zone (North of Tehran)

The study area is located in north of Tehran province. This area is a part of central Alborzzone. Intrusive (basic) and extrusive bodies of late Eocene, have caused several alterationzones. Au- Cu and Pb-Zn mineralization evidences have been found in Darband and Pass-Qaleh areas. The average grade of Pb and Zn in this area is 5% and 3% and the average of Au-Ag is 600 – 10 ppm respectively. Also the amount of 25 and 65 gram per tons has been reported for Au – Ag in this area. Main lithology of this area are volcano-sedimentary rocks of the Eocene. Considering the fact that there is an appropriate stratigraphic situation between lower shale and lithic tuffs for mineralization and due to structural conditions of the area, the conditions of massive sulfide ore forming (Kuroko type) are provided.The major and most important field evidences of this opinion are: The presence of propylitic, serisitic, argillic alterations and their placement; the mineralization type (pyrite, chalcopyrite, galena, sphalerite, jasperoides and Mn-bearing minerals and barite and its sequences and zoning; the existence of thin layers of pyrite in silicified tuffs; Gold mineralization in sulfides minerals; the existence of late hydrothermal phases with increasing of gold ratio and the presence of hydrothermal breccia and silicified veinlet which cut the massive sulfides. Inaddition, geochemical halos which have extended about 150 meters lead to a polymetalic massive sulfide mineralization that is similar to Kuroko type mineralization.