Final report of exploration at gold-bearing porphyry Cu-Mo deposit of Kalkafi and gold-bearing polymetal vein deposit of Khuni
After a contract between the Overall Exploration Program of GSI and Toseye Oloom-e Zamin Company at 1999, two regions were set for detailed exploration: a 120-hectares wide area in the Kalkafi deposit and another 34-hecatres wide zone in the Khuni deposit. The project included geological mapping, 1:1000 topography mapping, drilling, geochemical survey (lithogeochemistry), preparing anomaly maps and the final report.
The Kalkafi and khuni deposits are located 40 Km away from the east of Naklak Pb-Zn mine and 60 Km far from northeast of Anarak County in the Esfahan Province.
The region belongs to the Central Iran structural zone and Anarak-Khur metamorphic subzone. Oldest rock units are the Late Precambrian schists, quartzite and amphibolite of Anarak Chah-Gorbeh complex. The complex is covered by a thick marble and then Cretaceous limestones. Upper rocks include grey to green volcanic and pyroclastic rocks of Eocene. A large granitic to monzosyenitic pluton (Kalkafi pluton) has intruded in the mentioned assumable. It is 6.5 by 5 Km in diameters. Northern boundary of the body is marked by hornfels, when the northeastern boundary contains garnet-epidote skarn with copper, lead and zinc, tungsten and gold mineralization.
Alteration in the Kalkafi Deposit has occurred as silicic, sericitic, and argillic types. Cu-Mo mineralization has occurred in the silicic zone. This zone includes two subzones: a quartz-sericitic and a quartz-sericitic-argillic subzone. The second subzone influenced by silica-bearing fluids to form a highly veined zone with gold geochemical anomaly.
In Kalkafi deposit, gold is mainly present in the silicic veins cutting the porphyry mass and its concentration in the Cu-Mo bearing body is less than 0.1 ppm. The veins contains up to 42 ppm gold that averagely leads to 4.4 ppm. Other elements include:
- Mo ranging between tens to more than 25000 ppm
- Pb ranging between tens to more than 15900 ppm
- Zn ranging between tens to more than 45000 ppm
- Silver between less than 1 to up to 10 ppm.
Finally, the Kalkafi deposit is a Cu-Mo porphyry deposit with 0.25% Cu, 0.025% Mo, 0.1 ppm Au. It contains 245 million tons ore. The Cu concentrate of the deposit (24%) comprises 4 ppm Au.