Stable isotopes (S, O and H) studies at the lead-zinc deposits in the ?Inler Yaylasi (Şebinkarahisar - Giresun), Northeast Turkey [?Inler Yaylasi (Şebinkarahisar-GIRESUN) kurşun-çinko yataklarinda kararli izotoplar (O, H ve S) jeokimyasi incelemeleri]

Abstract

inler Yaylasi lead and zinc deposits are the typical examples of the vein type lead-zinc deposits occur within the Eastern Black Sea Region in Turkey. In the study area; Upper Cretceous volcanics, Tertiary granitoids, Eocene and Plio-Quaternary aged volcanics are outcropped. Ore deposit are developed as ore veins along the the faults in the Upper Cretaceous volcanics. Three ore veins in E-W direction were identified and they were cut and displaced by NW-SE trending faults. Microscopic studies revealed that the ore veins contain sphalerite, galena, pyrite, chalcopyrite, fahlore group minerals, chalcosite and covellite as ore minerals, and quartz and calcite as gangue minerals. Sphalerite and galena are dominant. Opaque minerals occur among the quartz crystals. This indicates that suifide mineralisation occurred later than quartz crystalization. The sulphur isotope composition (? 34S) of sphalerite and galena ranges from -3.9 to +0.4‰ CDT and that of H2S in hydrothermal fluids was calculated around -5.0‰. These sulphur isotope values are light compared to that of direct magmatic activities and it may be assumed that the sulphur in the sulfide minerals was possibly leached from the Upper Cretaceous volcanics by epigenetic hydrothermal fluids, rather than having direct magmatic relation to Tertiary granitoids and the younger volcanics occuring in the area. The oxygene isotope composition of the water in the mineralising fluid was calculated using the ? 18O values analysed in quartz and homogenisation temperature values measured during the fluid inclusion studies. The calculated ? 18O values ( +4.2 to +6.7‰ (SMOW)) and ? D values analysed in inclusion fluid (-83.0 to -59.0 % (SMOW)) plot in or at the meteoric water line side of the the magmatic water box on the ? D - ? 18O diagram and indicate that mineralising fluid was dominated by magmatic water and minor amount of meteoric water might have been mixed.