PRESERVATION OF DELTA-O-18 VALUES OF FLUID INCLUSION WATER IN QUARTZ OVER GEOLOGICAL TIME IN AN EPITHERMAL ENVIRONMENT - BEREGOVO DEPOSIT, TRANSCARPATHIA, UKRAINE

DeltaO-18 and deltaD values were measured for water in fluid inclusions in minerals from the Beregovo epithermal deposit, Transcarpathia, Ukraine. Directly measured deltaO-18 values for the water in inclusions in quartz were compared to calculated deltaO-18(quartz) values, using fluid inclusion homogenization temperatures, and published isotope equilibria constants. On the basis of this comparison it was concluded that the deltaO-18 values of water in the fluid inclusions in quartz in epithermal environments are preserved over geological time. Further evidence for the lack of isotope exchange between fluid inclusion water and the quartz host is the similarity between the isotopic composition of water extracted from sulphides (sphalerite, deltaO-18 = -3.5 parts per thousand and deltaD = -82 parts per thousand; and galena, deltaO-18 = -2.5 parts per thousand and deltaD = - 79 parts per thousand) and water extracted from coexisting quartz (deltaO-18 = -2.8 parts per thousand and deltaD = -84 parts per thousand).