Geology, mineralogy and fluid inclusion studies of the Kajah deposit, northwest of Ferdows, South Khorasan

The study area is situated within the Lut Block, 40 Km northeast of Ferdows. The oldest exposed rocks are Cretaceous limestone. The composition ranges of Volcanic rocks between andesite, andesite-basalt and rhyolitic tuff. Sub-volcanic diorite porphyry intruded in the volcanic rocks. Alteration zones are propylitic, silicified and argillic around the vein and surrounding host rocks. Sulfide minerals include pyrite, galena and sphalerit the secondary minerals comprise covelite, malachite, azurite, chrysocolla, hemimorphite and iron oxides. The veins contain an average of 2.14 percent of lead and 4.40 percent of zinc. Fluid inclusion petrography and microthermometry results reveal that the fluid inclusion assemblages developed in the different types, including single-phase vapor fluid inclusion, vapor-rich two-phase fluid inclusions and liquid-rich two-phase fluid inclusions. On the basis of fluid inclusion studiel, the ore-forming fluids has temperature 204–321 °C), and salinity 6.2–15wt% NaCl equiv. Fluid boiling and mixing most likely were the vital factors controlled the metal precipitation. The fluid pressure during the formation of the ore minerals was estimated to be between 50 to 150 bars. Based on the data obtained from fluid inclusions, it is suggested that the ore minerals were formed at a depth of 700 meters below the old water table