Fluid evolution of the Fe-Zn skarn deposits in the Çiftehan (Ulukışla-Niğde) area, south-central Turkey

Abstract

This study investigated the compositional variations of fluid inclusions in the different stages of mineralization at the Esendemirtepe and Horoz Fe-Zn skarns, south-central Turkey. The skarn zones in the study area consist of volcano-sedimentary sequences intruded by intrusive bodies and marble–schist in contact with granitoids. The primary ore minerals in both locations are magnetite and hematite, with subordinate sphalerite, chalcopyrite, pyrite, and pyrrhotite. The Esendemirtepe Fe-Zn skarn deposit is a typical deep exoskarn characterized by irregular disseminated hematite and magnetite assemblages with blebs of chalcopyrite, accompanied by calcite, quartz, and epidote at the contact between the volcano-sedimentary units and the skarn. The Horoz Fe-Zn skarn deposit is also a relatively deep endoskarn characterized by massive garnet crystals. Rhythmic banded crystallization of sporadic nodular-shaped sphalerite, quartz, and calcite developed along with the marble–schist skarn contact. Two-phase liquid-rich (L + V) fluid inclusions were observed in garnet, epidote, quartz, calcite, and sphalerite mineral assemblages. The average homogenization temperatures and calculated salinities in all stages of mineralization range from 155 to 600 °C and 0.53 to 23.1 wt.% NaCl equ., respectively. The eutectic temperatures also range from −66.2 to −21.2 °C, implying that the early stages were dominated by fluids that reflect an H2O-NaCl-CaCl2 system and become an H2O-NaCl system in the later stage. The continuous evolution history of the fluids reveals a gradual change from early high-temperature-salinity magmatic fluids to late relatively low-temperature-salinity mixed magmatic fluids due to interaction with meteoric-derived fluids.