Early to Late Eocene magmatic activity produced mafic to intemediate lavas, dikes, pyroclastic rocks and coeval granitic intrusions, forming similar to E-W trending magmatic belt in north of Izmir-Ankara suture zone (NW Anatolia). This study reports new Ar-40/Ar-39 geochronology, major-trace element geochemistry and Sr-Nd-Pb isotope data from Eocene mafic lavas and dikes of this magmatic belt in order to constrain mantle source charateristics and evolution of mafic volcanism beneath NW Anatolia. Ranging from basalt, basaltic andesite to basaltic trachyandesite, mafic dikes and lavas include both calc-alkaline and transitional (calc-alkaline to tholeiitic) affinity. They are slightly-moderately enriched in large ion lithophile elements and light rare earth elements with respect to high field strength elements and show negative Nb, Ta, and Ti anomalies typical of subduction related magmatic suites. Basaltic lavas and dikes are characterized by 87Sr/86Sr(i) compositions ranging from 0.70530 to 0.70415, positive eNd (2.7-6.6) and restricted Pb-isotope compositions (Pb-206/Pb-204: 18.6-18.7, Pb-207/Pb-204: 15.6-15.66 and Pb-208/Pb-204: 38.60-38.87). The Ar-40/Ar-39 cooling ages (37.8-41.1 Ma) obtained from this study combined with radiometric ages from literature indicate that mafic volcanism was dominant between early and late Eocene.