Mineral chemistry of sulfide and sulfosalt minerals in the Cheshmeh-Noghreh barite (gold- silver) deposit, Sabzevar subzone, NE Kashmar

The Sebandoon Barite (gold-silver) deposit is located about 20 km NW of the Kashmar in the Central Iran. The rock units exposed in the area consist of Eocene volcano-sedimentary sequences of lithic tuff, rhyolitic tuff, tuffaceouce shale, lapilli tuff and agglomerate associated with pyroxene andesite and trachyandesite. The barite is composed of lenticular, banded and stockwork mineralization and that is hosted in rhyolithic tuff. Lenticular, massive and banded barite contains pyrite, sphalerite,chalcopyrite, galena, tetrahedrite, argentite and electrum. The association of sulphide minerals with the barite indicates sub-oxic conditions during ore forming processes. In this study, the chemistry of sulfide minerals in the barite lenses was studied using Electron Microscope. Accordingly, the narrow range and low iron content within the sphalerite are similar to those of mineralization in a sub-oxic environments. The presence of elements with heavy atomic nuclei, such as gold and silver, in the pyrite indicates that the pyrites are formed in a sub-oxic environment and arsenic in the pyrite is replaced by metal (As3 +). The presence of large amounts of antimony, bismuth, arsenic, and silver in the sulfide and sulfosalt minerals of this deposit indicates that the ore forming fluid was rich in the metal elements.