Geochemistry and Nd, Sr isotopes of the Pohrenk fluorites (Kırsehir-Turkey)

Abstract

The Pohrenk fluorite mineralisation which makes up Central Anatolia’s most extensive fluorite region is Lutetian aged, and hosted in carbonate rocks that have undergone occasional karstification and silicification along a N–S fault trend. Fluid inclusion values and the position of fluorites in the Tb/La–Tb/Ca diagram show that mineralisation occurred in a hydrothermal environment with homogenisation temperatures ranging from 78.1–363°C. The presence of fluorite as a space filler in carbonate rocks and its association with silicification indicates that the solutions contained considerable amounts of Si alongside F (fluorine). The Pohrenk fluorite samples have ¹⁴³Nd/¹⁴⁴Nd values of between 0.512349 and 0.512497, whilst ⁸⁷Sr/⁸⁶Sr values vary between 0.708161 and 0.708772. These values indicate a mantle origin where continental contamination could occur. When the Nd–Sr values are compared to magmatic and young volcanics, the Pohrenk fluorites are seen to be enriched and exhibit similar isotopic signatures to Upper Cretaceous aged magmatics, Early-Middle Miocene volcanics and Mio-Quaternary volcanics.