Peraluminous granites are often found in collision-related geotectonic frameworks and usually were attributed to various crustal melting. Their composition proved to be very important as an indicator of particular conditions or specific tectonic phases in the frame of the existence of an orogen. The tectonic framework of the southern margin of the Pannonian realm and northern Dinarides was finally established during the Miocene. In this area, fingerprints of transitional tectonics, from the Oligocene post-collision, which dominated in the Dinarides, to the
Miocene extension, occurring predominantly within the Pannonian/Intra-Carpathian area, may be reconciled.
In this context, granitoid rocks of Mt. Bukulja show characteristics that should be linked to specific geodynamics: (1) it is situated at the very southern margin of the Pannonian Basin, (2) it is characterized by Neogene peraluminous granitic rocks, and (3) it shows Nb- Ta-Sn metalogenetic features. Therewith, they differ from the widespread plutono-volcanoplutonic provinces in Serbia, which are dominated by Late Oligocene, mostly calc-alkaline igneous rocks related to Pb/Zn±Ag±Sb metallogeny.
The granitic mass of Mt. Bukulja crops out about 60 km southern of Belgrade as an EW laccolite-shaped igneous body covering an area of about 40 km2. It is concordantly intruded into low-grade metamorphosed Devonian/Carboniferous schists in the West and into Cretaceous sandy marbles, clay sandstones and limestones in the East.
The bulk of the granitoid mass is represented by medium-grained to slightly porphyritic, slightly peraluminous two-mica granite (TMG). Metaluminous hornblende-biotite and biotite-bearing (H-BG) granite and rare aplitic granite are subordinate, and the former occur as patches or enclaves of various dimensions (from several decimeters to several tens of meters) or as isolated outcrops within deep creeks. The available radiometric age suggests that TMG was emplaced around 20 Ma whereas the age of H-BG is inadequately constrained. A lamprophyre dyke (BLD) similar in composition and age to other Serbian primitive minettes with a K/Ar age of 26 Ma has been found in the vicinity of Mt. Bukulja. TMG and H-BG show similar petrographic characteristics but the evidence of magma interaction processes are found only in H-BG. In comparison to H-BG, TMG are less enriched in most trace elements including REE and have a more fractionated REE-pattern and higher Euanomaly. TMG display a wider range of initial Sr-Nd isotope ratios normalized on 20 Ma (87Sr/86Sri=0.70652-0.71368 and 143Nd/144Ndi=0.51223-0.51283) than do H-BG (87Sr/86Sri=0.70768-0.70781 and 143Nd/144Ndi=0.51242-0.51256). Geochemical modelling suggests that H-BG could have derived from a BLD-like melt by mixing plus fractionation processes assuming a batch of TMG-like magma as the acid end-member. On the other hand, the geochemical variability of TMG is reproduced by an AFC model with assimilation/fractionation ratio r=0.5 and with high amount of crustal component (~20-50 %) starting from the least evolved TMG rocks. In the modelling, the average composition of the least evolved TMG samples were used to represent parental magma composition whereas the composition of adjacent metamorphic rocks was adopted as possible contaminant. The composition of the least evolved TMG implies that TMG parental magma likely originated by melting of a mafic lithology such as earlier basalts underplating in the lower crust. The high proportions of assimilation along with other geochemical and geological evidence suggest that the Mt. Bukulja TMG originated within the same geotectonic setting as acid volcanics of the north Pannonian Basin. The results of this study support the hypothesis that the Mt. Bukulja pluton is related to tectonomagmatic events controlled by the early extensional phases in the opening of the Pannonian basin.