Metamorphic and Tectonic Evolution of the Hırkadağ Block, Central Anatolian Crystalline Complex

The H›rkadametamorphic block is a NE-SW-trending horst structure that is part of the K›rflehir Massif in the Central Anatolian Crystalline Complex (CACC). Along its southwestern margin, the block contains upper amphibolite facies metapelitic rocks that record peak metamorphic conditions of 670-710 iC, ~ 7 kbar, as determined by garnet-biotite geothermometry and garnet-sillimanite-plagioclase-quartz, garnet-rutile-sillimanite- ilmenite-quartz, and garnet-rutile-ilmenite-plagioclase-quartz geobarometry. A clockwise pressure-temperature path is inferred from thermobarometric results and analysis of reaction textures among aluminous phases. Following this medium-pressure metamorphism, low-pressure — high-temperature metamorphism resulted in widespread replacement of garnet by cordierite + spinel + sillimanite, partial replacement of spinel by corundum, and partial melting to produce granitic leucosomes. Garnet-cordierite thermobarometry indicates that low-P — high-T metamorphism occurred at 3 kbar, > 650 iC. This event may have occurred owing to isothermal decompression at high temperatures, or may have been related to magmatism, similar to intrusion-related low-P — high-T metamorphism elsewhere in the CACC. High-angle normal faults bounding the southwestern and northeastern margins of the block truncate metamorphic structures and a granitic intrusion. These faults are part of a crustal-scale extension zone that uplifted the southern part of the K›rflehir Massif in the Late Tertiary, following its erosional exhumation in the Late Eocene. Ozet: KD-GB yonelimli bir horst yap›s› gosteren H›rkadablou Orta Anadolu Kristalen Kompleksi icerisinde yer alan K›rflehir metamorfik masifinin bir parcas›d›r. H›rkadablounun GB kesiminde yer alan metapelitik kayalar yuksek amfibolit derecesinde metamorfize olup, jeotermometrik ve jeobarometrik hesaplamalar s›cakl›k ve bas›nc›n 670-710 iC ve yaklafl›k 7 kilobara kadar c›kt›¤›n› gostermektedir. Termobarometrik hesaplamalar ve aluminyumlu mineral fazlar›n›n gosterdii reaksiyon dokular›n›n ozellikleri, H›rkadablounun genelde saat yonunde ilerleyen bir bas›nc-s›cakl›k evrimi gecirdiini ifade ederler. Bu orta bas›nc metamorfizmas›n› takiben, H›rkada¤ metamorfitleri bir alcak bas›nc-yuksek s›cakl›k metamorfizmas›na uram›fl olup, granatlar kordiyerit + spinel + sillimanite parajenezi, spinel ise korundum faz› taraf›ndan replase edilmifllerdir. Ayn› zamanda geliflen k›smi ergime de metamorfitler icerisinde yerleflen granitik sokulumlar›n› oluflturmufltur. Granat-kordiyerit termobarometrik hesaplamalar› bu alcak bas›nc-yuksek s›cakl›k metamorfizmas›n›n yaklafl›k 3 kilobarda ve 650 iC den yuksek s›cakl›klarda gelifltiini gostermektedir. Soz konusu alcak bas›nc-yuksek s›cakl›k metamorfizmas›, Orta Anadolu Kristalen Kompleksi icerisindeki oteki masiflerde de gozlendii gibi, carp›flma sonras› geliflen mamatizma ile yak›ndan iliflkilidir. H›rkadablounu guneybat›dan ve kuzeydoudan cevreleyen normal faylar ayn› zamanda hem blok icerisindeki metamorfik yap›lar› hem de granitik sokulumunu kesmektedir. Bu faylar, K›rflehir Masifi'nin Gec Eosen'deki erozyonal yukselimini takiben geliflen ve masifin guney kesiminin yukselimine yol acan Gec Tersiyer yafll› k›ta- kabuu olceindeki bir gerilmeli tektonizman›n urunleridir.