Bi- sulfosalt mineral series and their paragenetic associations in specularite-rich Cu-Ag-Au deposit, Qaleh-Zari mine, Iran

Qaleh-Zari specularite-rich Cu-Ag-Au deposit is located 180 Km south of Birjand, in eastern Iran. Host rocks are mainly Tertiary calc-alkaline to K-rich calc-alkaline of 40.52 Ma and Jurassic sandstones and shales. Three major sub-parallel steep quartz veins are identified in different rock types, in particular andesitic rocks. The Qaleh-Zari deposit is a specularite-rich hydrothermal, Cu-Ag-Au vein type deposit. Several complex Cu-Pb-Bi and Ag-Pb-Bi sulfosalt minerals have been identified in samples from different vein mineralization. Based on the paragenesis and fluid inclusion data temperature of homogenization, four ore-forming stages are identified in the area. In the first stage, specularite, chlorite, chalcopyrite and Bi-sulfosalts, (aikinite, matildite and wittichinite) were formed. The temperature of the homogenization of the fluid inclusions for the first stage ranges as 380 to 290C. In the second stage, pyrite, chalcopyrite, chlorite, aikinite, cosalite, wittichinite and bismuthinite-aikinite were deposited. Homogenization temperature of fluid inclusions for the second stage of the mineralization are between 290 and 230C. Within the third and fourth stages of the mineralization, specularite, quartz, calcite, pyrite, Ag-bearing aikinite, and an unknown Ag-sulfosalt were formed. The homogenization temperature for this stage ranges between 250 and 180C. The unknown Ag-rich sulfosalts and arcubisite have the highest Te, As, Sb, and Se contents. The salinity of ore fluid was between 1.0 and 6.0 wt% equiv. NaCl and the CO2 was < 0.1 mole%. Based on mineral paragenesis, the fluid was very oxidizing with a log fO2 between -13 and -28 (assuming a temperature of 300°C).