Emplacement, Deformation and Exhumation of the Çatalda? Plutonic Complex: Implications for Neotectonic Evolution of NW Anatolia (Turkey)

Located in the Eastern Mediterranean region, NW Anatolia experienced widespread Cenozoic magmatism and deformation following the collision between the Sakarya continent (SC) and Anatolide-Tauride platform (ATP) in the pre-middle Eocene. This magmatic activity produced plutonic associations that emplaced into the basement rocks of SC and ATP. Among these, Çataldağ plutonic complex (ÇPC) represents a key area to constrain the magmatic and tectonic evolution of NW Anatolia because it consists of S- and I type granitic bodies of different ages (Eo-Oligocene and Early Miocene, respectively) in the same area. Two granitic bodies forming ÇPC display different textural, structural and also geochemical features. The S-type granite (STG) is a concordant granitic body, and contact metamorphism is not observed around it. STG contains garnet-bearing two mica granites, migmatitic granites, strongly deformed milonitic and gneissic leucogranites. U-Pb zircon (LA-ICPMS) ages of STG yielded emplacement ages of 34-32 Ma. By contrast, I-type granitoid body (ITG) represents a discordant, shallow level intrusive body that intruded into the neighboring STG and metamorphic basement rocks. It is formed mainly from weakly deformed K-feldspar megacryst biotite-granodiorites and associated dykes. ITG samples display commonly porphyritic and rare graphic-granophyric textures. 39Ar/40Ar and zircon SHRIMP ages obtained from ITG yield cooling and emplacement ages between 22 and 20 Ma indicating rapid cooling of the ITG immediately after its emplacement. Petrographic investigations and microscopic scale structural features indicate that deformations in STG develop in two different temperature ranges: (1) ductile deformation developed at 500-450°C and (2) brittle deformation developed at <450°C. Both ductile deformation at depth and overlying brittle deformation at shallower depths determine top-to-the-north extensional deformation. 40Ar-39Ar dating of biotite and muscovites from STG yielded deformation ages of 22-20 Ma which is similar to the emplacement age of ITG. In contrast with the STG, ITG is weakly deformed. This structural data and I-type character of ITG may indicate that deformation was softened by heating as a result of upwelling mantle melt during the early Miocene. Combined structural and geochronological data indicate that exhumation of ÇPC was controlled by detachment faults and associated shear zones. Top-to-the-north extension related deformation of ÇPC and NW Anatolia at large occurred during the Early Miocene. The exhumation of ÇPC (22-20 Ma) coincided with the exhumation of Uludağ Massif (21-20 Ma) and Kazdağ core complex (24 Ma).