Pre-Alpine thermal history of the Juhor Mts., central Serbia (Northern Serbo-Macedonian Sub-unit): Constraints from zircon U-Pb geochronology and Lu-Hf isotope geochemistry

In this study, we present new zircon U-Pb geochronological and Lu-Hf isotope data from garnet-bearing micaschists and two-mica leucogranite exposed in the metamorphic core of the Juhor Mts., a part of the Northern Serbo-Macedonian Sub-unit (NSMU) in central Serbia. Zircon core analyses from both lithologies demonstrate total overlap in terms of geochronology and geochemistry, yielding dominant Middle Ordovician ages between ~460 and 480 Ma, and indicating widespread Ordovician thermo-magmatic activity within the NSMU. Subordinate inherited zircon populations record Neoproterozoic ages (~550-850 Ma), consistent with derivation from Cadomian peri-Gondwanan crustal domains. Zircon rims define several younger Silurian to Carboniferous age populations interpreted as reflecting prolonged tectonothermal evolution followed by Late Variscan thermal overprinting. Lu-Hf isotope compositions are characterized predominantly by mildly subchondritic εHf_(t) values, indicating evolved crustal sources, whereas several inherited Neoproterozoic grains and subordinate Ordovician zircons preserve juvenile isotopic signatures suggestive of variable mantle contribution during Cadomian crust formation. The granitoid exhibits petrographic, geochronological, and isotopic characteristics consistent with peraluminous S-type magmatism derived largely from partial melting of metasedimentary crust. The obtained data indicate that the NSMU preserves fragments of a peri-Gondwanan basement affected by prolonged Early Paleozoic thermo-magmatic evolution broadly comparable to other Alpine basement domains. Despite strong Alpine deformation and exhumation documented in the Juhor area, no Alpine zircon growth or zircon recrystallization was detected in the analyzed samples.