U-Pb-Th (zircon) geochronology, Sr and Nd isotopic composition and petrogenesis of granitoid pebbles of Qara Gheitan conglomerate, Aghdarband area, northeast Iran

The Qara Gheitan conglomerate (Late Permian-Early Triassic), is a part of Kopeh Dagh basement, situated in Aghdarband, northeast of Iran. The plutonic pebbles of conglomerate predominantly contain granite, alkali-granite and minor monzonite. Granitoids are highly potassic and strongly per to metaluminous nature. Magnetic susceptibility of granitoids are between 2-27×10-5 (SI units), chemical and mineralogical composition indicate that they belong to ilmenite-series (reduced type) granitoids. The results of U-Pb zircon age dating of the granitoids pebbles are 343 Ma (Carboniferous). They have a range of initial 87Sr/86Sr from 0.7062 to 0.7068, 143Nd/144Nd initial between 0.511938- 0.511936, initial εNd isotope values from -5.03 to -4.99 when recalculated to an age of 343 Ma (zircon age). These values could be considered as representative of continental crust-derived magmas. Based on 143Nd/144Nd and εNd isotope values, the meta-sedimentary source rock had a minimum age of 1400 Ma. Within the core of some zircons, there are rounded zircons with an age of, 1986, 1039 and 645 Ma. These zircons were brought with magma from the source rock. At the time of formation of source rock, rocks from Proterozoic were exposed. When compare the age of Dehnow-Kuhsangi and Khajeh Mourad granitoids (reduced S-Type) formed (Late Triassic) due to collision of Turan and Iran plates with the age of granitoid pebble (Carboniferous), it seems that the pebbles are the results of the much older continental collision taking place somewhere in their formation site (in the north of Aghdarband possibly in Turkemenistan).