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

摘要

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 (δ~(34)S) 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 δ~(34)S values around zero"0". Oxygen isotope values δ~(18)O of quartz vary between +10.5 and +19.9‰_((SMOW))· However, δ~(18)O and δ~(13)C values of calcite related to re-crystallized limestone (Keban Metamorphic Formation) reach up to +27.3‰_((SMOW )) and +1.6‰_((PDB)), respectively. The δ~(34)S, δ~(13)C and δ~(18)O 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.