The origin and evolution process of ore-forming fluids in the Jizvan area (northwest of Zanjan): based on fluid inclusions study

The Jizvan region with an area of ​​45 km2 is located about 70 km northwest of Zanjan town in the Tarom-Hashtjin metallogenic zone. The major rock units in the Jizvan area consist of a regular sequence of thin-layered tuff and breccia tuff with intermediate to basic compositions, interlayered with andesites and basalts. In addition, volcanic trachytic and porphyry andesitic rock units are also scattered in the region. Parts of the tuff and breccia tuff sequence are intruded by hypabyssal quartz monzonite, monzodiorite and syenite intrusions in the east of the region. As a result of this event, due to the presence of linear structures and the invasion of hydrothermal fluids, the above-mentioned rocks are affected by advanced argillic alteration. Carbonatic (malachite) and sulfidic (chalcopyrite, bornite, tetrahedrite-tennantite and chalcocite-covellite) copper mineralizations, along with pyrite, galena, sphalerite, arsenopyrite, quartz, calcite and goethite minerals are developed with a vein-veinlet texture in the above-mentioned units. Using the study of primary biphase fluid inclusions containing liquid and gas phases, homogenization temperatures from 95.6 °C to 268.9 °C with the highest frequency at 185 °C are recorded. The salinity of mineralizing fluids is between 4.65 and 23.8 wt% NaCl equivalent, while their density falls in the range from 0.77 to 1.08 g/cm3. Based on the fluid inclusion data, the mixing between magmatic and meteoric waters is the main cause for precipitation of metallic elements and the occurrence of mineralization in Jizvan area. These data overlap with the representative data of epithermal deposits.