Variscan granitoids of the East Serbian Carpatho-Balkanides: new insight inferred from U–Pb zircon ages and geochemical data

Abstract

The study reports and discusses new LA–ICP–MS zircon U–Pb data and major and trace element analyses for 16 samples from nine different plutons intruding the Getic (Brnjica, Neresnica, Ziman, Gornjane–Tanda–Blizna), and the Danubian (Aldinac, Janja, Ravno Bucje, Plavna and Suvodol) units of the East Serbian Carpatho-Balkanides (ESCB). Within the entire ESCB belt predominate slightly peraluminous granitoids, ranging in composition from biotite–hornblende tonalite through granodiorite to monzogranite. They contain mafic enclaves and are often cut by lamprophyre shallow intrusions and show gradual transitions to, or are cut by muscovite-bearing granitoids. All the above mentioned rocks formed under post-collisional conditions with some of them displaying evidence of post-emplacement shearing and recrystallization. By contrast, the garnet-bearing muscovite granite of Ziman (Getic unit) is distinctively peraluminous and shows evidence of syn-collisional emplacement and crystallization. The most reliable U–Pb zircon ages on the post-collisional granitoids show an age range between ~ 323 and ~ 290 Ma. The granitoids of the Getic unit reveal better concordia ages suggesting that Variscan magmatism lasted longer than previously thought, i.e., even until Permian times. On the other hand, the concordia age of 325.8 ± 1.2 Ma for the syn-collisional Ziman granitoid likely represents a minimum age for the collision event in this part of the Variscan belt. The ages of the Danubian plutons at least allow for discussing still open questions, such as (1) whether the Danubian intrusives are systematically older than those intruding the Getic basement, (2) if Variscan syn-collisional plutons do exist in the Danubian unit, and (3) what role the Variscan magmatism played in the formation of uranium mineralization in the area.