The Ilica, Cataldag and Kozak granitoids, cropping out in the northern part ot the Izmir-Ankara (IA) suture zone in west Anatolia. Turkey, intrude metamorphic rocks of the Sakarya continent (SC) and Karakaya complex, and are unconformably overlain by Miocene volcanic and sedimentary rocks. The Ilica and Kozak granitoids comprirsed granodioritic and granitic rocks and include mafic microgranular enclaves. The Cataldag granitoid massif is subdivided into three lithological units; the Bozenkoy granodiorite, Cataltepe biotie granite and Turfaldag biotite granodiorite, Hornblende separates from the Ilica granitoid yield K-Ar cooling ages that range from Oligocene (29 Ma) to Early Miocene (21 Ma). Biotic separates from subunits of the Cataldag granitoid massif yield K-Ar cooling age of 21-22 Ma. The Kozak granitoid possesses hornblende and biotite K-Ar cooling ages ranging from 17 to 21 Ma. Fractional crystallization (FC), assimilation-combined FC, magma mixing and crustal contamination were the main processes which modified the compositions of magmas during crystallization. The Iliea, Cataldag and Kozak granitoids were derived from different magma sources generated by the partial melting of various sources such as metasomatized mantle and crustal material in a post-collisional extensional setting following continent-continent collision between the SC and Taurus-Menderes Massif along the IA suture zone in west Anatolia, Turkey. Oligo-Miocene K-Ar hornblende-biotie cooling ages seem to be driven with a rapid cooling and fast exhumation of a mid-crustal section that can be resulted from a regional extensional geodynamic setting related to the subduction roll-back of the present-day Mediterranean oceanic lithosphere in the Aegean region in west and northwest Anatolia, Turkey. Copyright (C) 2008 John Wiley & Sons, Ltd.