Determining the source of mineralizing fluid in Gol-e-Zard Zn-Pb deposit, Aligudarz using geochemical and fluid inclusion studies

The Gol-e-Zard Zn-Pb deposit is located in northeastern of the Aligudarz region (Lorestan province). This deposit is exposed in phyllite and meta-sandstones of upper Triassic-Jurassic of the Sanandaj-Sirjan Zone. The mineralization includes sphalerite, galena and chalcopyrite, which are mainly along quartz veins. Two mineralized horizons are phyllite with high mineralization and meta-sandstone with low mineralization. The mineralogical studies show that galena, sphalerite and chalcopyrite are metallic ores and quartz is also the most abundant gang mineral in the studied deposit. The evidence indicate that the mineralization of the Gol-e-Zard deposit is syngeneic and epigenetic. The most significant structural pattern is the stratabound mineralization in the region. The aim of this study is to determine the type and characteristics the mineralizing fluid in the discriminating of mineralized horizons, besides the determining of source of the fluid in the Gol-e-Zard deposit. LREE enrichments (La/Lu average 4.8) and positive Eu anomalies (average 1.2) indicate the anoxic condition and hydrothermal fluids. Fluid inclusion data shows homogenization temperatures of 139-199.5°C, salinity 5.21-30.38 wt%equ.NaCl and density 0.9-1.1 gr/cm3 in this deposit. Investigation of evolution path of the fluids shows isothermal mixing of fluids during mineralization that comprises the mixing of magmatic water with sea water and also meteoric water. Thus, the mineralization can be summarized as: expulsion of the hydrothermal fluids from the depth, entering into sea water and reducing the temperature of hydrothermal fluids due to mixing with sea water, ascending to the sea level, moving through sediments and circulating in void spaces of and then the leaching of metals from sediments and deposited along the void space and quartz veins.