Re-Os Age and Stable Isotope (O-H-S-Cu) Geochemistry of North Eastern Turkey's Kuroko-Type Volcanogenic Massive Sulfide Deposits: An Example from Cerattepe-Artvin

The eastern Pontide tectonic belt (EPTB) contains greater than 350 identified Kuroko type volcanogenic massive sulfide deposits/mineralization/occurrences (VMSD). The deposits are associated with Late Cretaceous felsic volcanics consisting mainly of dacitic and rhyolitic lavas and pyroclastics that outcrop within a narrow zone running parallel to the eastern Black Sea coast and represent the axial zone of a paleo-magmatic arc. The Cerattepe deposit is the second-largest and is a hybrid VMS system with some epithermal features. To date, no geochemical research constrains the origin and timing of mineralization in the Cerattepe VMS deposit. Here, we provide Cu, O, H and S, isotope analysis of ores and alteration minerals to understand the hydrothermal history of the deposit and date the massive ore with Re-Os geochronology. Secondary weathering mobilized and redistributed metals in the deposit. The copper isotope signatures of shallow ores in the gossan follow patterns resulting from oxidative weathering of copper minerals with gossan Fe oxides of delta Cu-65 = -2.59 parts per thousand, enrichment zone copper sulfide of d(65)Cu = +2.23 and +1.73 parts per thousand, and primary ores of delta Cu-65 = +0.71 and +0.41 parts per thousand. At the boundary of the enrichment zone, further cycling and migration of enrichment zone copper are evidenced by two samples having larger ranges of the delta Cu-65 = +3.59 parts per thousand, and -2.93 parts per thousand. Evidence for a magmatic source for fluids and S are evidenced by the O and H isotope values from quartz veins (delta O-18 = +7.93 parts per thousand to +10.82 parts per thousand, and delta D = -78 parts per thousand and -68 parts per thousand) and sulfides that possess delta S-34 ratios of -5 and 0 parts per thousand from drill core samples. Os-187/Os-188-Re-187/Os-188 ratios from drill core sulfide samples of Cerattepe VMS deposit yields a 62 +/- 3 Ma isochron age and a highly radiogenic Os initial ratio. This age is compatible with silicate alteration ages from a proximal deposit and clearly shows mineralization occurs at a much younger time than previously proposed for VMS mineralization in the eastern Pontides. The new Re-Os age and source of Os imply that mineralization in the area occurs at a distinctly younger interval in the back-arc basin and metals could be sourced from the surrounding host rocks.

Automated summary

The Cerattepe deposit in the eastern Pontide tectonic belt is a hybrid VMS system with some epithermal features. Isotope analysis and geochronology methods have been used to understand the hydrothermal history and age of the deposit. This research suggests a younger mineralization age than previously proposed for VMS mineralization in the eastern Pontides, with evidence of a distinct magmatic source for fluids and metals sourced from the surrounding host rocks.