Vertical geochemical zonation in the Masjed Daghi porphyry copper-gold deposit, northwestern Iran: implications for exploration of blind mineral deposits

摘要

The geochemical zonation method allows distinction between sub-ore and supra-ore primary halos, prediction of erosion level of mineralization, and exploration of blind mineral deposits. In this study, the geochemical zonation of the Masjed Daghi porphyry-Cu deposit, located in the NW of Iran, was investigated to estimate the level of erosion of this deposit based on the geochemical data obtained from 46 drill cores. We used vertical zonation indices (Pb.Zn/Cu.Mo) and (Pb.Zn/Cu.Ag) as geochemical indicators in exploration of blind porphyry-Cu deposits. The values of Vz(x) varied in different parts of the study area. Its values are considerably higher in the eastern and southeastern parts of the area (7-100), and lower in the northwestern parts of the area (0.03-1), indicating the least amount of erosion in the east and SE in comparison with the northwestern parts of study area. Vertical variations of the Pb.Zn/Cu.Mo index show a significant decrease with increased depth; for example, the level decreases to 0.001 at a depth of 580 metres in the NW of the area, indicating a sub-ore zone of halo. With respect to the present level of erosion, high values of Vz indices imply the presence of sub-cropping to blind porphyry-Cu deposits in this area.