Sulfur Isotope Study of Vent Chimneys from Upper Cretaceous Volcanogenic Massive Sulfide Deposits of the Eastern Pontide Metallogenic Belt, Ne Turkey

Abstract

We obtained sulfur isotope analysis results of sulfide samples from hydrothermal vent chimneys of the eastern Pontide volcanogenic massive sulfide (VMS) deposits. The total range of delta S-34 values for vent chimneys in the eastern Pontide VMS deposits is -2.7 to 6.5 per mil. Sulfide delta S-34 values show narrow variation in the Lahanos, Killik, and Kutlular deposits, but wider variation in the Kizilkaya and Cayeli deposits. The delta S-34 values of sulfides in epsilon ayeli chimney samples gave a slightly higher range than the other Pontide chimney samples. In some samples, a rough isotopic zonation pattern was observed throughout chimney zones. Variations in delta S-34 values of sulfides within chimney walls were probably caused by chemical reactions of reprecipitation and replacement between vent fluids and earlier sulfide minerals in the chimney. Ranges of delta S-34 values of sulfide minerals are similar for different deposits within the same region. Variations in the delta S-34 values of the Pontide deposits appear to be geographic rather than stratigraphic. The sulfur isotope values of the deposits have a narrow compositional range, indicative of a fairly specific origin. Although "deep-seated" sulfur may be a potential source in the Pontide district, a significant contribution of seawater sulfate cannot be ruled out. The delta S-34 values of selected samples from Pontide vent chimneys are within the range of sulfur values obtained from Phanerozoic VMS deposits. The range is similar to, but slightly broader than, the range of values reported for modern vent chimneys and ancient vent chimneys from the Yaman-Kasy deposit.