Sari, Ekrem; Gücer, Mehmet Ali

The Eastern Pontides (NE Turkey) that formed during the Alpine-Himalayan orogeny\rin which geologically plays an important role in the formation of Anatolian Plate, is a\rsignificant area in term of containing different igneous rocks. Especially\rCarboniferous plutons are widely observed in the southern part of the Eastern\rPontides in larger outcrops and more commonly. This study presents new\rpetrography and whole-rock geochemistry data on granitic rocks in the Pamuktaş\rarea of Bayburt (NE Turkey). In addition, the source region of the magma,\rpetrological processes and geodynamic setting prevailing in the formation of these\rgranitic rocks are discussed. The Carboniferous Pamuktaş Pluton, which includes an\rarea of approximately 5 km2, represents the pre-Jurassic basement in the study area\rand is unconformably overlain by Lower-Middle Jurassic volcanoclastic and volcanic\rrocks and Upper Jurassic-Lower Cretaceous limestones. Pamuktaş Pluton mainly\rconsists of granite/granite porphyry and aplite (microgranite), to a lesser extent granodiorite and quartz microdiorite rocks. Granitic rocks mainly consist of alkali\rfeldspar (orthoclase), plagioclase feldspar, quartz, biotite, and amphibole\r(hornblende) minerals, as having euhedral and anhedral granular/microgranular\rtextures. The rocks have high SiO2 contents (65.62-75.09 wt.%) and a high K calc-\ralkali to shoshonitic affinities, and have been derived from an I-type source. The\rgranitic rocks are peralumine in character and are similar to post-collisional volcanic\rarc granitoids. Major and trace element trends show that the plagioclase, hornblende,\rapatite, and Fe-Ti oxide mineral fractionations play an important role in the formation\rof rocks. According to the petrological properties of the Pamuktaş Pluton, it has been\rrevealed that the fractional crystallization, magma mixing, and less assimilation and\rpartial melting processes play a role in the development of granites. The calculated\rzircon saturation temperatures (730-844°C) reflect lower initial magma temperatures.\rAll obtained data suggest that the parental magma of the Carboniferous Pamuktaş\rPluton has evolved from the mixing of lithospheric mantle and middle-lower crust-\rderived melts as a result of partial melting, differentiated and emplaced in the\rcontinental magma chamber.