Nahid Rahmati; Mir Ali Asghar Mokhtari; Mohamad Ebrahimi; Ghasem Nabatian
Abstract
The Agh-Otagh mineralization area in the north of Takab, was formed within the andesistic tuffaceous rocks of the Oligo- Miocene age. Mineralization include polymetallic (Cu-Pb-Zn-Au-Ag) ...
Read More
The Agh-Otagh mineralization area in the north of Takab, was formed within the andesistic tuffaceous rocks of the Oligo- Miocene age. Mineralization include polymetallic (Cu-Pb-Zn-Au-Ag) quartz veins and silicified zones, which occurred as breccia and vein- veinlets with comb, cockade and disseminated textures. Chalcopyrite, pyrite, galena and sphalerite are common ore minerals. Alteration zones consist of silicification, sericitization, argillitic, propelitic and carbonatization. Cu-Au mineralization is associated with silicification and sericitization. Analytical results of the samples from the ore- bearing quartz veins and the silicified zones indicate that the highest grade for Au is 664 ppb (ave.181 ppb). The highest and the average grades for Ag, Cu, Pb, and Zn are 120 ppm (300 ppm), 1.3 % (0.38 %), 5.5 % (0.06 %) and 4.5 % (0.28 %), respectively. The investigations indicate that the Agh-Otagh mineralization was formed in four stages. In the first stage or the pre-mineralization stage, the host rock, as a result of hydrothermal process, underwent brecciation and some quartz veins and siliceous cap were formed. In the second stage or the mineralization stage the sulfide minerals formed within the quartz veins and silicification zones developed at the third stage, some unmineralized quartz, barite and carbonate vein- veinlets crosscut the previous stages. The last stage of mineralization related to supergene processes. Based on geological, mineralogical, alteration, structural and textural evidences, the Agh-Otagh base- precious metal mineralization is similar to the medium sulfidation epithermal deposits.
