Petrographical, geochemical and petrological investigation of the Egerler (Aydıntepe-Bayburt) Granitoid

In this study which focus on petrographic, geochemical and petrological characteristics of Egerler Granitoid and surrounding rocks in Aydıntepe (Bayburt) region, aims to reveal the origin of Egerler Granitoid by considering its petrogenetic process. The basement of the study area is Early Jurasic-Late Cretaceous limestones which are represented by dolomite, dolomitic limestone and crystalised limestone and gray-white coloured cherty limestone. This unit is cut by Eocene aged Egerler Granitoid which is main topic of the study. Alluvium unconformably overlies the Early Jurasic-Late Cretaceous limestones Late Cretaceous volcanic rocks and Eocene aged Egerler Granitoid. The granitoid-bearing rocks are coarse-to-medium and contain plagioclase, quartz, orthoclase, hornblende and opaque minerals. Egerler Granitoid is elliptical and covers an area about 35 km2. It consists of granite, granodiorite, quartz monzodiorite, quartz-monzonite and granitic rocks and contains mafic microgranular enclaves (MMA) the quartz monzodiorite and quartz-monzonite in composition. Simultaneously, rocks forming granitoids also showed poikilitic texture, imbricate texture, plagioclase and K-feldspar phenocrysts in mafic microgranular enclaves. The rocks forming the Egerler Granitoid are generally I-S type, calc-alkaline with high K content and have high SiO2 contents (51.12-72.22 wt%). The rock samples forming the granitoid indicate the transition from metal to perlite, showing the characteristic of volcanic arc granitoids. Main and trace element changes demonstrate that plagioclase, hornblende, apatite and Fe-Ti oxide fractionation play an significant role in the evolution of granitoid. Considering the petrological characteristics of Eğerler Granitoid, fractional crystallization, mixture of magma and assimilation and partial melting play a role in the development of granitoid. Geochemical data indicate that the lithospheric mantle components play an important role besides the partial melting of the granitoid subcontinental crustal rocks (amphibolitic).