This study presents new zircon U–Pb and molybdenite Re–Os geochronology, whole-rock geochemistry, Sr–Nd isotopes, and zircon Hf-isotope data from Eocene porphyritic intrusions at Kızıltoprak Tepe prospect in the Eastern Sakarya Zone (ESZ), NE Türkiye, to constrain the tectonomagmatic and metallogenic evolution of the ESZ. Field, drill-core, and petrographic observations define three intrusive stages: (i) pre-mineralization (barren) amphibole-bearing quartz diorite porphyries, (ii) syn-mineralization (mineralized) amphibole±clinopyroxene±biotite-bearing dioritic–andesitic to dacitic–rhyolitic porphyries, and (iii) post-mineralization plagioclase-phyric andesitic dikes. Zircon U–Pb ages indicate emplacement of barren porphyries at ~47 Ma and mineralized porphyries at ~45–40 Ma, whereas molybdenite Re–Os ages of ~43 and ~26 Ma record multi-stage hydrothermal mineralization. Geochemical and isotopic data indicate medium- to high-K calc-alkaline, metaluminous magmas derived from hybrid mantle–crust sources. Barren porphyries reflect stronger crustal contributions, whereas mineralized porphyries record increased juvenile mantle input, interpreted as enhanced magma recharge and mixing within a long-lived magmatic system favourable for ore formation. Elevated La/Yb, Gd/Yb, and Sm/Yb ratios support slab break-off of the northern Neotethyan lithosphere. These results highlight the critical role of magma evolution and source mixing in controlling porphyry–epithermal fertility and provide new constraints on early Cenozoic metallogenesis in the ESZ.