Geochemical and geophysical relationship of the potassium-rich fenite zone in surface and subsurface investigations of the giant Kuluncak (Malatya) Nb-U-REE-Zr-Li mineralization

The Kuluncak (Malatya) district hosts one of the most significant Nb–U–REE–Zr–Li mineralizations in Türkiye, spatially associated with alkaline and carbonatite-related rocks. In this study, geochemical and geophysical investigations were integrated with surface and drillhole data to evaluate the role of fenitization in rare earth element enrichment. The drillhole profiles reveal systematic variations: in marble-hosted sections, light rare earth element (LREE) anomalies occur near-surface zones coupled with K₂O enrichment, whereas in nepheline syenite-hosted drillholes, REE anomalies are concentrated at intermediate depths (~40–100 m) with heterogeneous distributions. High CaO concentrations, together with fluorite, barite, apatite, and Nb–REE-bearing minerals, confirm a strong carbonatitic contribution. Geophysical anomalies (spectral gamma, magnetic maps) support the geochemical evidence and were used to identify subsurface fenite zones. Comparison with other carbonatite-related systems in Türkiye, such as the Özvatan complex (Kayseri) and Eskişehir, indicates that Kuluncak represents one of the most carbonatite-dominant and LREE-enriched systems in the region. On a global scale, the geochemical features of Kuluncak resemble world-class deposits such as Bayan Obo (China) and Ilímaussaq (Greenland). These findings demonstrate that fenitization and carbonatite-related metasomatism are the principal processes controlling mineralization, highlighting the Kuluncak district as a strategic Nb–REE resource of both national and international importance.