Türkiye Jeoloji Bülteni

Fluid Inclusion Study of Bulancak Sulphide Veins

Abstract: Data based on a study of more than 2500 primary and secondary fluid inclusions in transparent oreand gangue minerals are given. The data include measurements on the temperature, pressure, density and salinity ofthe inclusions present in the Southern Bulancak Deposits, Eastern Black Sea Ore Province of Turkey.The inclusions were moderately saline, salinity varying within the range 13.2 equivalent wt. % NaCl to almostfresh water indicated by a density change from 0.74 gr/cm3in the early vein stage to 0.98 at the end of the basemetal sulphide stage. These variations may reflect the mixture of deeply circulating meteoric waters with rising,saline, hydrothermal fluids.Homogenization temperatures ranged from ca 80°C to 340°C. Inclusions show a temperature rise from ca 230to 330°C in the early vein stage, and eventually boiling conditions were reached. At a later stage the fluids cooledfrom 330°C to ca 80°C in the base metal sulphide stage. The highest temperatures were obtained from the Tekmezar Group of veins, in comparison to the Danköy group of veins, indicating a horizontal temperature zoning.Evidence of boiling conditions and geological data suggest that the depositional pressures were 85-90 bars indicating a 1000 m hydrostatic load.Data obtained from isotherms indicates that the ore-bearing fluids rose along NW-SE trending faults.Fluid inclusion studies combined with geological, data, are considered to be useful parameters in mineral exploration to pinpoint richest part of the orebody.