TECTONIC CONTROL ON THE DEVELOPMENT OF THE NEOGENE QUATERNARY CENTRALANATOLIAN VOLCANIC PROVINCE, TURKEY

The Neogene-Quaternary Central Anatolian Volcanic Province (CAVP) is e longated in a north-east south-west direction within pre-Oligocene bas ement in central Turkey. This study investigates the field evidence re lating to the development of the CAVP. Two dominant fault systems are recognized in the area. The first consists of the major conjugate faul ts in the region, namely, the right-lateral Tuzgolu and left-lateral E cemis fault zones, and other faults parallel to these zones. The fault s in this system are mostly active and cut the CAVP almost at right an gles. The second fault system trends in a N60-degrees-70-degrees-E dir ection, parallel to the volcanic axis and to the alignment of the majo r eruption centres. These faults, which are of the normal type, are mo stly buried beneath the products of recent volcanic eruptions. The beh aviour of the first system is explained with reference to the present north-south convergence that occurs in the eastern Mediterranean regio n. These faults, which might be reactivated palaeotectonic structures, are a response to a present day compressive stress direction of about N10-degrees-W. The second fault system, in contrast, is the product o f a short-term tensional period that occurred during the Mid-Late Mioc ene to Pliocene. This extension is almost at right angles to the conve rgence. As a result, the pre-Oligocene basement in the area was fractu red in a N60-degrees-70-degrees-E direction and these fractures served as pathways for the extrusive rocks that formed the CAVP. The major e ruption centres of the CAVP (i.e. the Hasandag, Keciboyduran and Melen diz stratovolcanoes) are located at the intersection of the major faul ts of these two fault systems.