Mineralization, Alteration, and Geochemical exploration in the eastern part of Keybarkuh (southwest of Khaf)

Keybarkuh is located about 70 Km southwest of Khaf city (Khorasan Razavi Province) in the northeast of the Lut block. Rock units in the area comprises of slate, phyllite, schist and recrystalized limestone with Paleozoic age that was intruded by granite to diorite as dikes and stocks of Cretaceous to Tertiary age. Based on magnetic susceptibility, intrusive bodies are oxidant and reducing which the oxidant bodies mostly having alteration and mineralization. The eastern Keybarkuh oxidant bodies are of Midlle Eocen, related to subduction environment of continental margin, often high-K to shoshonitic and metaluminous. Propylitic alteration zones with broader area and sericitic, argillic and silicic with less distribution were observed in the southern area. Mineralization is seen in the contact of intrusive bodies or in joint and fractures of them as veins and veinlets in south of the area. Veins and veinlets with northwest to southeast strike, 70 to 80 degrees dip to the northeast have thickness upto half meter. They can be divided into two sets: 1-Veins and veinlets associated with galena, sphalerite and barite as primary minerals, which formed the first generation of mineralization. 2- Veins and veinlets associated with pyrite, chalcopyrite and quartz as primary minerals; covellite, bornite, chalcocite, malachite, azurite and iron oxides (magnetite, hematite and limonite) as secondary minerals which is the second generation of mineralization. Paragenetic sequences of minerals and relationship between minerals are indicative of a hydrothermal activity and deposition of the above mentioned minerals in at least two stages in the upper part of oxidant intrusive bodies. Geochemical exploration of stream sediment show anomalous Cu (68 ppm), lead (1691 ppm), zinc (320 ppm), barium (5003 ppm) and the rock also show anomalous Cu (3%), gold (2657 ppb), silver (ppm 160), lead (4%), zinc (2159 ppm), barium (1466 ppm) bismuth (1767 ppm) and Mo (66 ppm) in the southern parts of the area which are relatively high.