ALPINE SUBDUCTION-RELATED GEODYNAMICS OF WESTERN TO CENTRAL TURKEY: INSIGHTS FROM PETROLOGY OF HP METASEDIMENTS AND 40Ar/39Ar GEOCHRONOLOGY

In Western to Central Turkey, the closure of a Neotethyan oceanic branch resulted in the accretion of a Gondwana-related continental fragment, known as the Anatolide-Tauride Block, to southern Eurasia. As a result, the northern continental passive margin of the Anatolide-Tauride Block was tectonized and metamorphosed between the late Cretaceous and the early Cenozoic. Based on differing lithostratigraphy and metamorphic histories, several metamorphic units, referred to as Anatolides, are generally considered as follows. From north to south, they are the Tavsanli Zone, the Afyon Zone, the Menderes Massif and the Ören Unit. From the Aegean Coast to Cappadocia, blueschist-facies mineral assemblages were reported in coherent sedimentary series from all these units. Moreover, the Cycladic Blueschist Unit, which crops out mostly in the Aegean, is also recognized west of the Menderes Massif.

The timing of the subduction-related metamorphism is variously contrained from one unit to the other. Radiochronologic studies (using Ar/Ar and Rb/Sr on phengite and glaucophane) showed that HP metamorphic event occurred in middle Late Cretaceous (88-82 Ma) in the Tavsanli Zone, and in Eocene (45-40 Ma) in the Cycladic Blueschist Unit. In contrast, no radiometric but only vague stratigraphically-constrained metamorphic ages, were published for the HP metamorphism in the Ören Unit, the Menderes Massif cover and the Afyon Zone while accurate ages would constitute strong clues for understanding the evolution of Western and Central Turkey and its correlation with the Aegean Domain.

At the GSA Meeting “Tectonic Crossroads: Evolving Orogens Eurasia-Africa-Arabia” (Ankara, October 2010), we will present new results of ongoing Ar/Ar geochronologic and metamorphic petrological works from the Anatolide HP belts, and discuss their implication in understanding the evolution of the Eastern Mediterranean.