Rubidium-strontium isotopic data for Vitoša Pluton, Srednogorie Zone

The age of the monzonitic phase of Vitosa Pluton is determined by Rb-Sr whole-rock isochron on 8 samples as 91 ± 10 Ma, the initial ⁸⁷Sr/ ⁸⁶Sr ratio being 0.704. Therefore, the pluton was co-eval with the Upper Cretaceous (Turonian - Lower Senonian) volcanic activity of the Srednogorie Zone, and with the granitoid intrusions in the west part of the Rhodope Massif. It is supposed that subduction along the east margin of Vardar Zone, extension and island-arc formation in the Srednogorie Zone, and thickening in parts of Rhodope Massif created magma hearths at different depths of the crust and in the upper mantle during the Late Cretaceous.