Geochemistry, Isotope Characteristics, and Evolution of the Kesikköprü Iron Deposit (Türkiye)

The Kesikköprü iron deposit, located in the Central Anatolian Crystalline Complex, occurs in the triple contact of Kesikköprü granitoid, mafic–ultramafic rocks, and marble. The causative Kesikköprü granitoid, consisting of diorite, granodiorite, and granite, is classified as sub-alkaline, calc-alkaline, and shoshonitic, displaying metaluminous to partially peraluminous properties. Sr-Nd isotope data and the geochemical characteristics of the Kesikköprü granitoid indicate a metasomatized mantle origin, with its ultimate composition arising from crustal contamination and magma mixing along with fractional crystallization in a post-collisional setting. The 40Ar/39Ar geochronology reveals a total fusion age of 73.41 ± 0.32 Ma for the biotite of the Kesikköprü granitoid. The alteration pattern in the deposit is characterized by an endoskarn zone comprising garnet–pyroxene (±phlogopite ± epidote) and an exoskarn zone displaying a zoning of garnet (±pyroxene ± phlogopite), pyroxene (±garnet ± phlogopite ± epidote), epidote–garnet, and epidote-rich subzones. Magnetite is extracted from massive lenses within the exoskarn zones and shows vein, disseminated, banded, massive, and brecciated textures. The low potassium content of phlogopites which are associated with magnetite mineralization prevents the determination of a reliable alteration age. δ18O thermometry reveals a temperature range between 462 and 528 °C for the magnetite mineralization. According to geochemical (trace and rare earth elements), stable (δ18O, δ2H, δ34S, and δ13C), and radiogenic (87Sr/86Sr and 143Nd/144Nd) isotope data, the hydrothermal fluid responsible for the alteration and mineralization is related to the Kesikköprü granitoid, from which a significant magmatic component originates initially, followed by meteoric fluids at lower temperatures (123 °C) during the late-stage formation of calcite–quartz veins.