Petrographic and geochemical characteristics of the early miocene aged yürekli volcanite around Dereköy (Altieylül, Balikesir)

The petrographic and geochemical features of the Early Miocene aged Yurekli volcanite outcropping around Dereköy (Altıeylül, Balıkesir) were investigated in this study. There are 3 main units outcropping in the study area. These are the Bağburun Formation (Oligocene), the Hallaçlar Formation (Upper Oligocene-Lower Miocene) and the Yürekli volcanite (Lower Miocene), which is the subject of this study, respectively. Petrographic and geochemical analyzes were performed on the systematically collected samples from the Yurekli volcanite. According to the results from the analyzes; The dominant texture of the rocks is semi-crystalline porphyritic texture. In addition, special textures such as glomerophyric, glomeroporphyric textures, amygdoloidal texture and flow texture are also encountered. Mineralogical compositions of the rocks are quartz + alkaline feldspar + plagioclase + biotite + hornblende (amphibole) + opaque minerals ± pyroxene. According to the results of the chemical analysis, the rocks forming the Yürekli volcanite are calc-alkaline in character and high K, and their compositions are mostly andesite, basaltic andesite and dacite. All rocks were formed in a continental arc setting. When the rare earth element distribution diagrams of the Yürekli volcanite rocks are examined, it is observed that the negative Eu anomaly is typical. This is due to the fractional crystallization of plagioclase. According to the data, it was concluded that the unit called "Yürekli Dacite" in the literature until now would be a more accurate definition to say "Yürekli volcanite" due to the changing lithology.