HERCYNIAN I-TYPE AND S-TYPE GRANITOIDS FROM THE SLAVONIAN MOUNTAINS (SOUTHERN PANNONIAN BASIN, NORTHERN CROATIA)

Two genetically different groups of Hercynian granitoids occur in the Slavonian Mountains which are included in the southern Pannonian Basin . I-type granitoids occur in Barrovian-type progressive metamorphic se quences which originated during the Hercynian orogeny from the Late Si lurian to Lower Carboniferous magmatic-sedimentary complex. S-type gra nitoids, enriched in incompatible trace elements, are accompanied by p enecontemporaneous migmatites which originated from rocks of the same progressive metamorphic sequences and lower continental crust. I-type granitoids are represented mostly by granodiorite and monzogranite imp overished in incompatible trace elements, with rare diorite and monzod iorite and basic to intermediate rocks. Hercynian age of the crystalli ne rocks is supported by numerous K-Ar, Ar-40- Ar-39 and Rb-Sr measure ments carried out mostly on monomineralic concentrates. About 20 repre sentative samples of S-type and I-type granites and associated rocks w ere selected from over 1000 samples and analyzed in derail for major a nd trace elements, including REE, Sr and O isotopic compositions; micr oprobe chemical composition of the main rock-forming minerals was dete rmined. Although most major and trace element diagrams do not provide the best genetic discrimination between the Slavonian granitoids, Sr a nd O isotope composition, REE data and some other data for the S-type granitoids are indicative of their sedimentary and continental crust s ource, whereas the I-type granitoids were derived by partial melting o f the upper mantle with slight crustal contamination.