Mineralogy and chemical variations of Sulfosalts of epithermal deposit of Ay-Qalasi (southeast of Takab, northwest of Iran)

The Ay Qalasi Pb-Zn (Ag) epithermal deposit is located in the south east of Takab, northwest of Iran and is formd at the Urmia-Dokhtar magmatic belt and the Sanandaj-Sirjan zone intersection. Based on microscopic and EPMA analysis, the composition of this series is tennantite-tetrahedrite. These minerals are mainly replaced in host minerals. The EPMA analysis data show that their chemical composition is a function of the mineralogical composition of the sulfide ores in which they have been replaced. Tertiary dacitic domes replacement adjacent to the deposit has led to the formation of hydrothermal solutions with high fugacity of sulfur and arsenic, and to a lesser extent antimony. Due to the fault's reactivation, the initial sulfide minerals to be brecciated and provides the conditions for the penetration of these fluids. The penetration and circulation of these fluids in the brecciated parts of the deposit, due to the high fugacity of sulfur and arsenic, impose new thermodynamic conditions on the system, which in turn leads to the instability of sulfide minerals. In the new condition, the clasts of sphalerite, chalcopyrite, and pyrite ores react with these fluids to form sulfosalt minerals of tennantite-tetrahedrite series.