Research Information System
7th Internatıonal Symposıum On Eastern Medıterranean Geology, Adana, Turkey, 18 - 22 October 2010, pp.7
The Southeast Anatolian Orogenic Belt (SAOB) records well-preserved remnants of mountain building processes along the Alpine-Himalayan system. The evolution of the SAOB initiated with closure of the southern branch of the Neotethyan Ocean that is located between the Tauride platform to the north and Arabian platform to the south in late Cretaceous, and ceased by the continent-continent collision in Miocene. The tectono-magmatic/metamorphic units cropping out along the orogenic belt are key elements to better understand the evolution of the SAOB, which are located in Hatay-Kahramanmaras-Malatya-Elazig regions. These units are, structurally from top to bottom, a) metamorphic massifs, b) ophiolites, c) ophiolite-related metamorphic rocks and d) granitoids. The granitoids, which mark the Andean type active margin formation mainly in Late Cretaceous, crop out in three localities namely the Goksun, Dogansehir and Baskil regions. They intruded the metamorphic massifs, ophiolites and the related metamorphic rocks along the orogen. These granitoids are of typical I-type, calcalkaline Andean type volcanic arc granitoids. The LA-ICP-MS U-Pb zircon ages of the granitoids yielded 81.1±2.2 Ma (2σ) for Esence (Kahramanmaras) and 82.0±1.2 - 84.6±1.1 Ma (2σ) for the Baskil (Elazig) localities. These crystallization ages show that the granitoid bodies intruded after the formation of oceanic crust in the southern Neotethyan oceanic basin (~90 Ma). Four zircon ages measured from Dogansehir (Malatya) vary between 54.9±1.2 to 45.7±1.0 Ma (2σ). These crystallization ages indicate that the northward subduction was still in progress during Eocene time. The Ar-Ar ages (amphibole-biotite) of the Dogansehir granitoid vary between 54.1±0.99 to 48.3±0.3 Ma (2σ). The Ar-Ar ages (amphibole-biotite-K-feldspar) in the Baskil granitoid vary between 84.0±0.7 to 77.25±0.42 Ma (2σ). The Ar-Ar ages (amphibole-biotite-K-feldspar) in the Esence granitoid vary between 85.3±7.4 to 74.1±0.29 Ma (2σ). All these data support that the granitoids have formed in different episodes and have individual cooling histories. To the west, the Esence granitoid was formed in Santonian and cooled through ~200°C in ~10 Ma. To the east, the Baskil granitoid was formed in Santonian and cooled through ~200°C in ~6Ma. In the middle, The Dogansehir granitoid was formed in Early-Middle Eocene (episodic crystallization from Ypresian to Lutetian) and cooled through 300°C in ~1 Ma. Apatite Fission Track (AFT) samples were collected from these magmatic intrusions to find out the rate of the collision between Arabian and Tauride platforms. The ages are clustered in two groups, (i) Early-Middle Eocene and (ii) Middle Oligocene whereas one distinct sample yields 16.8±1.8 Ma. The cooling models were made from track length (TL) and age data indicates that these apatite FT ages yield mix ages, whereas three cooling time span from crystallization to unroofing of the granitoids occurred in the region. First cooling phase is Late Cretaceous observed in Esence and Baskil granitoids interpreted as the continuous cooling of the granitoids after a shallow emplacement. Second phase is Early to Middle Eocene time span observed in all granitoids interpreted as the continuous cooling of the Doğanşehir granitoid and uplift of the Esence & Baskil granitoids with a high uplift rate during an opening of Maden basin in the region. The last phase is the Late-Middle to Late Miocene time observed in all intrusions interpreted as the initiation and movement of the East Anatolian Fault Zone (EAFZ). The 16.8±1.8 Ma age data collected on the fault zone interpreted as resetting by frictional heating during faulting.