Geological, mineralogical and geochemical properties of the Duzkoy skarn mineralizations (Kurtun-Gumushane)

The Düzköy skarn mineralization is hosted along the contact between limestones of Berdiga Formation and Harşit Granitoid. The endoskarn zone is characterized by pyroxenes, while garnet, epidote, quartz and calcite were common in the exoskarn zone. Ore in the skarns are mainly consist of magnetite and hematite with a lesser amount of pyrite, chalcopyrite and minor sphalerite. Fe-Cu-Zn type skarns were identified in the area according to the garnet and pyroxene compositions and mineralogical properties. The chemical zoning from grossular to andradite in zoned garnets and diopsidic pyroxenes are compatible with oxidized type skarns. Granitoides along the skarn zone are generally I type, medium-high K calc alkaline character, and peraluminous to metaluminous transitional. Harşit Granitoid show many similarities with Fe-Cu-Zn type skarn granitoides in the world according to the high MgO (2.41 wt.%) and low K2O (2.05 wt.%) contents, as well as Rb-Sc and Rb/Sr-Zr variations on the discrimination diagrams. Therefore, in addition to the magnetite and hematite, occurrences of sulphides were related to the geochemical features of granitoides. Homogenization temperatures of all fluid inclusions and salinity contents are in the range of 168 and 483 °C, and 1.1 and 44.4 wt.% NaCl equ. respectively. Positive correlation between Th and salinity values indicates that meteoric water was involved in the hydrothermal solutions. Eutectic temperatures correspond to the presence of CaCl2 in the early stage fluid inclusions whereas it corresponds to the presence of different salt combinations in the later stages. The δ13C isotope ratios of skarn calcites varying between -1.62 and 2.77‰ are compatible with marine carbonates, while their δ18O ratios ranging from 9.04 and 24.5‰ are extensively depleted. This depletion of skarn calcites refer to the mixing of meteoric and magmatic solutions.