Geochemical Features of Ozvatan (Central Anatolia, Turkey) Carbonatites and Potassic Fenite Zones .

The carbonatite complexes are famous for being hosts for various critical elements including Rare Metals (REE) Thorium (Th), and Uranium (U). Turkey hosts a number of carbonatite-related Light Rare Earth Element (LREE) deposits such as the Ozvatan nepheline syenite - carbonatite complex in Central Turkey.  The Upper Cretaceous Ozvatan complex is composed of nepheline syenites, multi-stage calcio-carbonatite dikes, and a metasomatic aureole around carbonatite dikes. The carbonatites of the complex are mainly sövites (coarse-grained calcites) with fluorites and relict silicate minerals such as nephelines. The Sövite dikes of the Özvatan complex are mainly enriched in terms of LREE (up to 2134 ppm). La, Ce, and Nd constitute most of the LREE values in Sövites. The repetitive emplacement of carbonatite emplacement also caused a wide alteration zone with euhedral nephelines, secondary K-feldspars, and garnets. The alteration zones around carbonatite dikes were identified as potassic fenites due to the enrichment of K and incompatible elements including REE, Ba, and Sr. The REE values of K- fenites in the study area are similar to sövite dikes and determined up to 1445 ppm. However, the brecciated K-fenites contain significantly higher values (up to 3596 ppm) than carbonatites and non-brecciated K-fenites. Other incompatible elements such as Th, U, and Nb are also enriched in brecciated K-fenite zones. Carbonatite veinlets in K-fenites are also observed, therefore it can be concluded that the brecciation and metasomatism processes are closely related to multistage carbonatite emplacements.

Keywords: Carbonatite, REE- Enrichments, Alkali-Potassic Rocks