Thermometry and Origin of Mineralizing Fluid at Barika Gold Deposit, East of Sardasht

Barika gold (and silver)-rich volcanogenic massive sulfide deposit is located 18 km east of Sardasht city in the northwestern of Sanandaj–Sirjan metamorphic Zone. The rocks in the vicinity of the Barika deposit predominantly consist of Cretaceous volcanosedimentary sequences of phyllite, slate, andesite and tuffite, metamorphosed under greenschist facies grade. Barika deposit is composed of stratiform ore and stringer zone that both are hosted in an altered and sheared metaandesite unit. Fluid inclusion studies indicated that quartz (stringer zone) and barite (stratiform ore) samples homogenized between 132° and 283°C. Salinities of the fluids inclusions show a range from 1.4 to 9.6% wt NaCl equivalent that are close to that of normal seawater. The study indicates the colling occurred in the initial ore fluids, as a result of mixing with sea water, is an important process in the formation of Barika deposit. The δ34S values of sulfide minerals (pyrite, sphalerite and galena) from stockwork mineralization in the Barika deposit range from -0.8 to +5.6 per mil and fall within the range of values observed for volcanogenic massive sulfide deposits. The narrow range of measured δ34S values from the sulfide minerals suggests that similar to almost of Kuroko VMS deposits, the ore-forming sulfur derived from the leaching of igneous sulfur from the underlying andesitic rocks. Calculated sulfur isotope temperatures for twelve coexisting galena-sphalerite and galena-pyrite pairs range from 146-293 C that is consistent with temperatures estimated from fluid inclusion studies.