Petrological-geochemical and lead-isotope evidence of Alpine metamorphism in the Rhodope crystalline complex

Abstract

The petrological-geochemical and lead-isotope characteristics of migmatic formations from the area of the town of Ardino (bedded leucosome, pegmatite and granite metatects) belonging to migmatic biotite gneisses in the Lyubinovo Formation of the so-called Prerhodopian Supergroup (presumed Archean), whose structural succession has been interpreted so far as the result of several regional-metamorphic cycles, provide evidence of an integral ultrametamorphic process which took place during the Alpine tectono-magmatic cycle. The model ages calculated from lead isotope ratios in potassic feldspars and the U-Pb ages of zircons from the migmatites stutied are in the range of 62–32 Ma. An analysis of the mineralogical, geochemical and radiogeochronological evidence available at present indicates that the migmatites of this study, the granitoids of the group of·”Southbulgarian granites” in the Rila and Rhodope Mts, the volcanics and the associated intrusive rocks, as well as the later ore mineralizations have been formed during a long period of Alpine activintion (from Cretaceous times on) in the Rhodope crystalline complex.