Magmatic Redox Evolution and Porphyry-Skarn Transition in Multiphase Cu-Mo-W-Au Systems of the Eocene Tavsanli Belt, NW Turkiye

This study explores the magmatic and hydrothermal evolution of porphyry-skarn-transitional Cu-Mo-W-Au systems within the Nilufer Mineralization Complex (NMC), located in the westernmost segment of the Eocene Tavsanli Metallogenic Belt, NW Turkiye. Through integration of field data, whole-rock geochemistry, Re-Os molybdenite dating, and amphibole-biotite mineral chemistry, the petrogenetic controls on mineralization across four spatially associated mineralized regions (Kirazgedik, Guneybudaklar, Kozbudaklar, and Delice) were examined. The earliest and thermally most distinct phase is represented by the Kirazgedik porphyry system, characterized by high temperature (similar to 930 degrees C), oxidized quartz monzodioritic intrusions emplaced at similar to 2.7 kbar. Rising fO(2) and volatile enrichment during magma ascent facilitated structurally focused Cu-Mo mineralization. At Guneybudaklar, Re-Os geochronology yields an age of similar to 49.9 Ma, linking Mo- and W-rich mineralization to a transitional porphyry-skarn environment developed under moderately oxidized (Delta FMQ + 1.8 to +0.5) and hydrous (up to 7 wt.% H2O) magmatic conditions. Kozbudaklar represents a more reduced, volatile-poor skarn system, leading to Mo-enriched scheelite mineralization typical of late-stage W-skarns. The Delice system, developed at the contact of felsic cupolas and carbonates, records the broadest range of redox and fluid compositions. Mixed oxidized-reduced fluid signatures and intense fluid-rock interaction reflect complex, multistage fluid evolution involving both magmatic and external inputs. Geochemical and mineralogical trends-from increasing silica and Rb to decreasing Sr and V-trace a systematic evolution from mantle-derived to felsic, volatile-rich magmas. Structurally, mineralization is controlled by oblique fault zones that localize magma emplacement and hydrothermal flow. These findings support a unified genetic model in which porphyry and skarn mineralization styles evolved continuously from multiphase magmatic systems during syn-to-post-subduction processes, offering implications for exploration models in the Western Tethyan domain.