Study of alteration, mineralization and fluid inclusions of the Khoynaroud Cu-Au deposit, north of Varzaghan, East Azarbaidjan Province, NW Iran

The Khoynaroud area is located about 25 km north of Varzaghan city in the Arasbaran metallogenic district. The quartz vein-veinlets host rocks are quartz monzonite and diorite. Distinctive alterations around the quartz vein-veinlets include silicic, phyllic, argillic, and propylitic types. The quartz vein-veinlets display ribbon, comb, open-space filling, vuggy, and brecciated textures. The mineralization took place during two stages, hypogene and supergene. The hypogene minerals include sulfide minerals (chalcopyrite, pyrite, and bornite) and gold, which are associated with supergene minerals such as Fe oxides-hydroxides (goethite, hematite, and jarosite), copper carbonates (malachite and azurite), and secondary copper sulfides (covellite and chalcocite). Study of microthermometry on liquid-rich two-phase fluid inclusions in quartz mineral coexisting with mineralization indicates that values of salinity of fluid inclusions vary from 8 to 20 wt%. NaCl equiv and values of homogenization temperature of fluid inclusions range from 140º to 380ºC. According to the microthermometric data, the effective ligands in transporting metals are chloride and sulfide and the phenomenon of boiling, cooling, and surface fluid dilution are the most important mechanisms in the deposition of ore minerals. Study of geological, alteration, mineralogical, textural, and fluid inclusion shows that the mineralization in the Khoynaroud area is very similar to epithermal deposits of the low-sulfidation type.