Abstract
A large number of volcanogenic massive sulfide (VMS) deposits are associated with Late Cretaceous to Eocene arc-like volcanic rocks in the eastern Pontides of NE Turkey. Cu isotope studies on thirteen VMS and two vein deposits were undertaken to examine the nature of copper isotope variations and to compare these with other VMS and black smoker deposits. ϕ65Cu of chalcopyrite from these deposits range between +0.34 and -0.62‰. Chalcopyrite from the VMS deposits of the eastern Pontides have a mean ϕ65Cu = −0.13‰. ϕ65Cu of chalcopyrite is generally heavier than that of corresponding bornite. The range of ϕ65Cu for chalcopyrite from VMS deposits in the eastern Pontides is larger than that observed from Alexandrinka, a Devonian VMS deposit in the southern Urals, but is significantly smaller than the up to 3‰ variations observed from individual modern sea-floor hydrothermal fields along modern mid-ocean ridges. The range of Cu isotope variation in VMS deposits from the eastern Pontides is interpreted to result from processes related to both oxidation and leaching of previously deposited copper by seawater and to its subsequent deposition elsewhere in the hydrothermal system.
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