Structural field studies and geochemical and age analyses of the Eldivan ophiolite, which is dismembered within the Ankara Mélange, indicates that it developed as a supra-subduction zone basin within the İzmir-Ankara-Erzincan Ocean, which later subducted to form the İzmir-Ankara-Erzincan suture zone through continental block collision. Whole-rock and mineral geochemical evidence show a supra-subduction zone tectonomagmatic affinity for the ophiolitic crust and mantle, revealing that this basin formed in the upper plate of an intra-oceanic subduction zone. Structural restoration of the sheeted dike complex reveals that the supra-subduction zone spreading ridge of the Eldivan ophiolite was nearly parallel to the Sakarya-Pontide continental margin. U/Pb age analyses of detrital zircon in sandstone within the mélange and in the unconformably overlying Karadağ Formation indicate maximum depositional ages for the units of 143.2 ±2 Ma, and 105.2 ±5 Ma, respectively. Thus, thrust imbrication of the ophiolite and the development of serpentinite mélange were mostly complete by 105 Ma, as indicated by an angular unconformity between the ophiolitic units and the overlying Karadağ Formation. These results reveal how and when the Eldivan ophiolite was constructed, destructed, and incorporated into the serpentinite Ankara Mélange and İzmir-Ankara-Erzincan suture zone. The tectonic evolution of the İzmir-Ankara-Erzincan Ocean is similar to that of the Philippine Sea and Banda Sea ocean basins.