Drilling project in the Cu-Au bearing zones of Cu-Mo porphyry deposit of Kalkafi
The Kalkafi deposit is located 40 Km away from the east of Nakhlak lead-zinc mine in the Anarak County of Esfahan Province. The area belongs to the Central Iran structural zone and Khur-Anarak metamorphic subzone. The oldest rock units in the area include the Late Precambrian Anarak metamorphic complex that in its upper portion made of Lakh marble. The marble is equivalent to upper Soltaniyeh dolomite. It exposes at north of the deposit and contains the Khuni lead-zinc mineralization. This metamorphic complex is covered by Orbitolina-bearing limestone of Lower Cretaceous unconformably that itself is situated beneath the Eocene volcanosedimentary rocks.
The mentioned rock units are cut by granite to quartz monzonite intrusion with elliptical shape, i.e. Kalkafi mountain that is 5.6 * 5 Km in diameters. The late stage of magmatism has occurred as light microgranite- to monzosyenite porphyry in the center of the body causing Cu-Mo porphyry and Au-epithermal mineralization.
In continuation of exploration activity in the area, 1:1000 topography and geology maps were prepared. Drilling of two boreholes in the gold-bearing zones was led to identification of two mineralized zones, a quartz –sericitic cu-bearing zone and a silicic veinlet zone containing gold.
The current project started after a contract between the GSI and Toseye Olom Zaim Co. The project included sampling from three new boreholes in the ore bearing zones that drilled by Zamin Rad Co. The boreholes are 150m deep.
The study shows that the deposit is a Mo- Cu porphyry type deposit containing gold. Due to incirculation of hydrothermal fluids and lack of enrichment, sulfide minerals in the deposit are mainly hypogene and supergene zone has not been formed. Consequently, the copper grade is low (maximum 0.31%). But the molybdenum reaches to 370 ppm. Gold has concentrated in the veinlets and its average grade reaches to 50 milligrams per ton. The veinlet zone is not economical because of low copper content, while the altered Mo-Cu bearing zone may be economical and requires lab tests for processing of ore minerals.