Akademik Veri Yönetim Sistemi
Yunanistan Jeoloji Derneği 15. Uluslararası Kongresi, Athens, Yunanistan, 22 - 24 Mayıs 2019, ss.320-321, (Özet Bildiri)
The study area is located in Hisarlıkaya region, Southwest (SW) of Ankara, Central Anatolia. Units cropping out throughout large areas consist of different sized and shaped xenoliths having a polygenetic origin in certain areas. Macroscopically blackish-greenish-greyish-greenish colored and porphyritic textured rocks contained mainly plagioclase, amphibole, opaque microlites and rarely pyroxene crystals. Plagioclases are generally euhedral in shape and are predominantly zoned. They show sieved texture at the rims and/or cores. The amphiboles have been completely or partly replaced by Fe-Ti oxides. According to the microprobe analysis, it was determined that the plagioclases in the host rocks are andesine and the amphiboles are calcic-chermakite in characters. As a result of geochemical analyses, volcanic rocks have been identified as trachytic rocks with calc-alkaline character. Major, trace element Harker variation diagrams indicate an effective fractional crystallization process in the formation of these rocks. SiO2 (62.6-63.7%), Al2O3 (16.5- 17.2 %), Na2O (4.9-5.6 %), Sr (1249-1397 ppm), Y (13.1-14.2 ppm) contents of these trachytic rocks indicate typical adakitic rocks features. Previous works in the study and vicinity areas revealed the presence of volcanic products carrying the evidences of post collisional Early Miocene magmatism. It is thought that the Hisarlıkaya volcanic rocks, having trachytic character, were formed in this period.