Variscan sutures in the Carpathian-Balkan belt revisited: a granitoid perspective on Late Palaeozoic closure of the Rheic Ocean, slab breakoff and tectonic exhumation

The integration of available geochronological and geophysical data from the Carpathian-Balkan basement, along with geochemical data related to the Variscan granitoid-decorated suture, indicates the presence of subduction-driven collision followed by post-collisional exhumation of the Inner Carpathian-Balkan (Rheic) suture configuration (ICBRS). The ICBRS as a Variscan crustal amalgamation (exposed in Serbia) collapsed due to slab breakoff (‘high-temperature’ orogeny) that occurred prior to the start of the Alpine rifting. The advancing edge of the Lower Palaeozoic north Gondwanan microcontinent, which includes the Serbo-Macedonian, Supragetic, and Getic-Kučaj nappes (Alpine basements) together with the attached oceanic lithosphere of Devonian age, was involved in subduction beneath the Danubian and Moesia (an external promontory of the East European craton). In contrast, the opposite side of the Carpathian-Balkan microcontinent (western Serbo-Macedonian Unit) exhibits less frequent granitic activity (Paleotethyan suture). Variscan deformation of ICBRS, characterized by pre-, syn-, and post-collisional magmatism, involves multiple episodes of granitoid emplacement spanning from the Late Devonian to the Carboniferous. Variscan-age granitoids extend along a 200-km-long north-south belt across the Getic/Kučaj and Danubian microcontinents, emerging through the Carpathian-Balkan fold-and-thrust belt of eastern Serbia (Brnjica, Neresnica, Gornjane, Plavna, Ravno Bučje, Suvodol, Radičevo, Janja). Devonian lithospheric underplating of the northern Gondwanan microcontinent led to the formation of the (latest Devonian) Carboniferous syn-collisional ‘high-temperature’ orogeny, associated with the Inner Carpathian-Balkan Rheic suture, characterized by modest crustal thickening. The combination of geochemical and geophysical data, including available regional geological reconstructions illustrating Late Palaeozoic crustal exhumation processes revolving around the ICBRS. Study further highlights the overlapping processes of reactivation of the Variscan-Alpine suture zones. However, due to the interference of Cimmerian and Alpine deformation stages, the mechanisms of crustal exhumation of lower crustal levels remain increasingly ambiguous, thus being absent from the available literature.