Kurylo S. Geochemistry and geochronology of dual feldspar granites of Middle Dnieper

Results of investigation of the two-feldspar granites of the Middle Dnieper terrain (TGMD) are reported. Petrographical and mineralogical characteristics of granitoids are presented. The investigations of the internal structure of zircon crystals has proved the possibility of their use for dating by local methods. It is shown for the first time that TGMD were formed during the time interval that embraced over 200 myr at Mid-Neoarchaean. Age limits of formation of the Aulska Series and two stages of their migmatization are set for the first time. The geochemical specialization of TGMD is established. Concentration and distribution of the minor and REEs is determined and it is shown that granitoids of each of the massifs reveal specific composition. As a result of the study of the Sr isotope composition and of the chemical composition it is established that all of the TGMD were formed after the crustal precursor. A direct relationship between Sr isotope composition in the two-feldspar granites and concentration of Ba, La, Ce that reflects role of the crustal material in their formation is demonstrated for the first time.