Geochemical study of trace and rare elements and condittion of formation of barite and galena in Afsoo Area (south west Torbat-e-Jam, NE Iran)

Afsoo area is located in northeastern Iran. Limestone and shale are the main host mineralization and monzonite and pyroclastic rocks are exposed in this area. Barite and galena mineralization occurred mainly as veins and veinlets within the limestone or shale and limestone boundaries. Galena with bented triangular cleavage and barite with compressive and polysynthetic twinning are observed. The highest amounts of barium oxide present is about of 57.4%, strontium oxide 4.8%, lead oxide 3.3%, copper oxide 1.2% and zinc oxide 0.1% in ore containing barite and galena. Concentrations of Rare Earth Elements in barite, galena and exposed rocks in this area are different and indicate at least part of the ore-bearing fluid have originated from deeper sources. The Amount of all rare earth elements in the barite samples from the study area is very low and about 1 to 1.8 g/t that can be a sign of crystallization from a fluid that has originated far away. The low Al2O3 and the high Sr content in the deposit are also indicative of the origin from low temperature hydrothermal-type ore-bearing fluid. Comparison of the distribution pattern of these elements with the patterns presented globally indicates that most of the samples fall within the range of barites from low temperature hydrothermal fluids.