Hydrothermal mobilization of heavy rare earth elements in carbonate-rich systems: Implications from the Arıklı mineralization (NW Türkiye)

Abstract

The mobilization and enrichment of heavy rare earth elements (HREE) in carbonate-hosted hydrothermal sys tems remain poorly constrained due to limited thermodynamic and experimental data. This study re-evaluates the Arıklı Th–U–HREE mineralization in northwestern Türkiye to explore the geochemical plausibility of latestage fluid–rock interaction and ligand-controlled speciation processes in carbonate-bearing environments. Modeling of solubility trends suggests that moderate-temperature (120–180 ◦C), moderately alkaline (pH 10–11) fluids may facilitate the transport of HREE via carbonate–hydroxyl complexation. These inferred conditions are consistent with recent experimental and thermodynamic studies, indicating that late-stage HREE redistribution could occur without the direct involvement of high-temperature magmatic fluids. The findings highlight the importance of fluid chemistry and ligand availability in potentially modifying REE fractionation during postorogenic hydrothermal alteration.