Fluid evolution of mixed base-metal gold mineralization in the Tethys belt: Koru deposit, Turkey

Koru is one of a number of base-metal gold deposits hosted by Oligo-Miocene volcano-sedimentary rocks of deposits in the Biga peninsula. Barite, quartz and galena are main minerals and are accompanied by minor amounts of sphalerite, pyrite, chalcopyrite, covellite and marcasite. Th of fluid inclusions indicates two distinct fluid pulses, one at high temperature (340 degrees C) commensurate with epithermal mineralization and boiling/near boiling conditions and the second approximately 150 degrees C lower. Salinity in both instances was from 11-0.2 wt. % NaCl. The range of temperatures within individual samples is consistent with variations from near lithostatic to hydrostatic pressure during vein and fracture opening. There are two different ranges of delta S-34 values of H2S in equilibrium with barite (+5.5 to +7.9 parts per thousand) and sulfide minerals (-2.1 to -0.5 parts per thousand), indicating that the sulfur in sulfide minerals and barite derived from different sources; magmatic and seawater respectively.