GEOLOGY AND PETROGRAPHY OF OYMAAÃAÇ (BEYPAZARI ANKARA) GRANITOID
The study area comprises a part of the Beypazarı granitoids and is exposed in Oymaağaç and its vicinity, appoximately to 50 km south of Beypazarı (Ankara).On the basis of field observation and petrographical features, the granitoid is differentiated into Oymaağaç granodiorite, İsmailkayası granodiorite, Tavuktaşı granodiorite and Çayırpınar alkali feldspar granite. The latter forms the youngest unit, cutting all the other subunits in the form of aplitic dykes. The abudance of amphibole minerals decrease from Oymaağaç granodiorite at the rim of the pluton towards İsmailkayası and Tavuktaşı granodiorite at the inner part of the pluton respectively. Mafic microgranular enclaves are observed within Oymaağaç granodiorite, İsmailkayası granodiorite and Tavuktaşı granodiorite and their compositions change from diorite to quartz diorite and monzodiorite respectively. Acicular apatite, poiklitic megacrysts of feldspars and sharp contact with the host rock are the main common features of the mafic enclaves, suggesting magma mixing/mingling origin for the enclaves.
Key Words: Beypazarı, oymaağaç, granite, enclave, petrography