About the discovery of the late vendian basement within the Blyb metamorphic complex of the Greater Caucasus Fore Range Zone

New data are presented concerning the age and relationships with the overlapping rocks of the Balkan massif of quartz diorites located in the central part of the Blyb metamorphic complex of the Fore Range of the Greater Caucasus in the Malaya Laba river basin. For the first time, using modern geochronological methods, it is shown that the Balkan massif has Precambrian age. An estimate of the age of the rocks of the Balkan massif using the SHRIMP II method for three U-Pb datings gives an interval of 549 ± 7,4-574,1 ± 6,7 Ma. A new interpretation of the structure of the basement of the Fore Range is suggested, according to which the rocks of the Late Vendian basement are exposed in a tectonic window and overlapped by the Middle Paleozoic metamorphic rocks of the Armovka nappe, first identified by the combination of geological features. The lower boundary of the nappe is characterized by a sharp change in composition and a change in the orientation of planar structures. On the border with the Armovka nappe there is a thick blastomilonite pack.