Skarn mineralization in north part of Kal-e Kafi and its relation with Kal-e Kafi intrusive body

The Kal-e Kafi granitoid body and related skarn, a part of the Central Iranian zone and the Yazd block, are located 60 Km Northeast of Anarak (Northeast of Isfahan province). This Late Eocene-Oligocene granitoid body intruded into the Eocene volcanic, volcaniclastic rocks and the Anarak metamorphic units, giving rise to the formation of widespread hornfels and limited skarn deposits. Different lithological units from gabbro to microgranite are the main constituents of this large and complex intrusive body. The geochemical data as well as the petrographic studies show that monzonite to quartz monzodiorite are in close relationship to skarn mineralization. Also, these rocks, display characteristics of high potassium calc-alkaline, metaluminous and I type magma. Using geochemical discrimination diagrams, the magmatism developed in VA related late geotectonical environment. On the base of the aforementioned data and comparison with chemical composition of some world's skarns forming granitoid, it can be concluded that the Kal-e Kafi skarn is Cu-Au-Fe type. Field and petrographic studies document that there are five stages in the skarn evolution. Several samples from mineralized quartz veins were used for fluid inclusion geothermometry. Considering the homogenization temperature of quartz veins and some secondary textures in ore minerals, the ore mineralization stage and veining are simultaneous. The boiling evidences in fluid inclusions are considered the most important factor for ore deposition in the temperature range of 250-375 °C. Boiling is also caused the occurrence of two distinct fluids together; high- (type V) and low-salinity (type I, IV) fluids. Metals transported as chloride complexes and precipitated as sulfide minerals while the boiling process was ended. The opaque minerals (chalcopyrite, pyrite and magnetite) formed in the final stage of skarn formation, due to decreasing temperature (150-200 °C) and increasing oxidation conditions, were altered into goethite, bornite, covellite and martite, respectively. Tectonic movement and the occurrence of many faults in the area, play an important role in the quartz veins emplacement and ore mineral alteration stage. The calc-alkaline and I type Kal-e Kafi intrusive body can be proposed as the source of Cu, Fe and Au bearing hydrothermal fluids and skarn mineralization.