Late Cretaceous-Paleogene tectonothermal evolution of the Akdag Massif in the central anatolian crystalline complex (northern Kayseri, central Turkey)

The Central Anatolian Crystalline Complex (CACC) is a Late Cretaceous continental crystalline basement exposed in central Turkey. Here, we report the metamorphic conditions and cooling history of the southern Akdag Massif, which is the northeastern margin of the CACC. Thermobarometry performed on the garnet-sillimanite-bearing metapelitic rocks indicate - 5-6 kbar/650-700 degrees C metamorphic conditions. Following HT-MP metamorphism, conditions of - 3-4 kbar and - 720 degrees C were also recorded by the metapelitic rocks. The replacement of sillimanite, cordierite, and biotite on the rims of garnet indicates LP-HT metamorphism. The HT decompression path described in this study is similar to conditions that have been previously proposed for the CACC. The LP-HT metamorphism resulted from the increased geothermal gradian arising from local granitoid intrusions, which are most likely related to Late Cretaceous subduction below the CACC, at - 82-72 Ma. The Ar/Ar geochronology indicates that cooling of the high-grade rocks occurred at 75 & PLUSMN; 0.8 Ma and the relatively younger Ar/Ar cooling ages of 61 & PLUSMN; 0.5 Ma (amphibole) and 55.0 & PLUSMN; 0.3 Ma (muscovite) were obtained from the medium/low grade metamorphic rocks of the Akdag Massif. These cooling ages and stratigraphic evidence from the middle Eocene sedimentary cover, suggests a rapid exhumation and cooling rate of the Akdag Massif is about - 40 degrees C/Ma. We suggest therefore, that the exhumation of the Akdag Massif was finalized by the Late Paleocene - Early Eocene and we suggest that this rapid exhumation can be explained by tectonic effects rather than by erosional alone.