Oxygen, carbon and sulphur isotope studies in the Keban Pb–Zn deposits, eastern Turkey: An approach on the origin of hydrothermal fluids

Pb–Zn deposits are widespread and common in various parts of the Taurus Belt. Most of the deposits are of pyrometasomatic and hydrothermal origin. The Keban Pb–Zn deposits are located along the intrusive contact between the Paleozoic – Lower Triassic Keban Metamorphic Formation and the syenite porphyry of the Upper Cretaceous Keban igneous rocks. Various studies have already been carried out; using fluid inclusion studies on fluorite, calcite and quartz on the pyrite–chalcopyrite bearing Keban ore deposits. This study focuses on the interpretation of stable isotope compositions in connexion with fluid inclusion data. Sulphur isotope values (δ34S) of pyrite are within the range of −0.59 to +0.17‰V-CDT (n = 10). Thus, the source of sulphur is considered to be magmatic, as evidenced by associated igneous rocks and δ34S values around zero“0”. Oxygen isotope values δ18O of quartz vary between +10.5 and +19.9‰(SMOW). However, δ18O and δ13C values of calcite related to re-crystallized limestone (Keban Metamorphic Formation) reach up to +27.3‰(SMOW) and +1.6‰(PDB), respectively. The δ34S, δ13C and δ18O values demonstrate that skarn-type Pb–Zn deposits formed within syeno-monzonitic rocks and calc-schist contacts could have developed at low temperatures, by mixing metamorphic and meteoric waters in the final stages of magmatism.

This study includes stable isotope geochemistry of Keban Pb–Zn deposits. Paleozoic – Lower Triassic Keban Metamorphic Formation and Upper Cretaceous Keban igneous rocks are observed in the study area. δ34S isotope compositions values in pyrite show that the source of sulphur is magmatic. The in both δ13C and δ18O values in calcites, and δ18O values in quartzes show that skarn-type Pb–Zn deposits formed within syeno-monzonitic rocks and calc-schist contacts could have developed at low temperatures, by mixing metamorphic and meteoric waters in the final stages of magmatism.Figure optionsDownload as PowerPoint slideResearch highlights
► In this study, different isotope composition variations and fluid inclusion data of ore-forming fluids are considered.
► Mixing between primary magmatic water and meteoric waters.
► Oxygen isotope exchange between syeno-monzonitic rocks and metasedimentary rocks leading to formation of shifted magmatic water.
► Carbon isotope exchange reactions between meteoric water and meta-sedimentary rocks leading to formation of shifted meteoric water.