Geochemical, microthermometric, and isotopic constraints on the origin of fluorite deposits in central anatolia, Turkey

Abstract

We investigate rare earth element geochemistry, microthermometric characteristics, and radiogenic isotope systematics of fluorites and stable isotope compositions of gangue minerals from several fluorite deposits in central Turkey. In the deposits, fluorite is the main ore mineral and it is accompanied by quartz, calcite, and minor pyrite and barite. Veins are represented by three different fluorite types based on their color. Total REY contents of fluorites are highly variable, ranging from 24 to 693 ppm. LREE concentrations of fluorites of all colors are similar but medium and heavy REE abundances of green fluorites are nearly an order of magnitude greater than in both host rocks and purple and yellow fluorites, indicating multiple sources for crystallization. REEs show significant fractionation and purple fluorites with relatively low HREE contents were likely precipitated at an earlier stage. As crystallization continued, green fluorites were nucleated because of ion exchange of LREEs with the host rock/minerals. Fluid inclusions yielded a wide range of homogenization temperatures from 86 °C to 292 °C and salinities from 0 to 20 wt.% NaCl equiv. The87Sr/86Sr ratios of fluorites, varying from 0.707627 to 0.709380, overlap with the range of host rocks.143Nd/144Nd values suggest two populations: purple fluorites with less radiogenic and green fluorites with more radiogenic Nd isotope ratios. The Sr-Nd isotope systematics of Bayındır fluorites are consistent with that of the Bayındır syenite, indicating that hydrothermal solutions progressively reacted with the host rock until equilibrium was established. δ18O values of quartz are slightly higher than the magmatic range. δ13C and δ18O of calcites fall into the range of marine carbonates. δ34S values of barites indicate derivation from diverse reservoirs changing from marine to terrestrial sources. In contrast, sulfur in pyrites points to a magmatic origin. Therefore, is it suggested that magmatic fluids to some extent contributed to the precipitation of fluorite veins.