THE TECTONICS OF THE CENTRAL ANATOLIAN CRYSTALLINE COMPLEX: A STRUCTURAL, METAMORPHIC AND PALEOMAGNETIC STUDY

The Anatolian region recorded the closure history of the Neotethyan Ocean(s) situated between the converging African and Eurasian continents during late Mesozoic – Cenozoic times. The Central Anatolian Crystalline Complex (CACC) is the largest metamorphic domain exposed in Turkey and mainly consists of metamorphic rocks, ophiolites and magmatic intrusions. This crystalline domain experienced a complex tectonic history involving late Cretaceous obduction of ophiolitic nappes, development of a regional Barrovian metamorphism, and widespread magmatic intrusions.

We present here a multi-scale and multi-disciplinary study of the tectono-metamorphic evolution of the CACC, and integrates the obtained results with data from the literature in order to propose a plausible tectonic model for the evolution of the CACC in the late Cretaceous. The tectono-metamorphic history of the central Anatolian metamorphic rocks has been investigated through detailed microstructural and metamorphic analysis, together with local and regional mapping of ductile structures and metamorphic field gradients. An extended set of paleomagnetic data from the central Anatolian granitoids provides constraints for restoring the large-scale geometry of the CACC into its late Cretaceous configuration.

The main results of this study revealed that during the late Cretaceous the CACC consisted of a NNE-SSW elongated and narrow dome-shaped antiformal structure (~500x150km). In this configuration, regional Barrovian metamorphism was accompanied with a top-to-the-SSW ductile crustal flow in the deeper part of the antiform, while shallower levels were synchronously affected by a WNW-ESE directed exhumation. Post-tectonic magmatism affected the western side of the antiform in three successive magmatic events showing a chemical evolution from calc-alkaline in the west to alkaline in the east (i.e. from an external to a more internal position in the antiform). This magmatic trend has been recognized as a typical evolution of a magmatic arc in a supra-subduction environment. Finally, during the Paleogene, the collision of the NNE-SSW-oriented antiformal structure with the central Pontides led to the break-up of the CACC into three distinctive domains as exposed today.