The genesis and age of the two-feldspar gneissic granites from Moshchevaya and Beskes rivers of the Great Caucasus are a key point for the understanding of early periods of magmatic evolution of the province. There are two views on the age of these granites: the first one that they are Paleozoic, the second one — Middle Paleozoic rocks. Data obtained by the authors on the disturbation of the whole-rock Rb-Sr system supports the pre-Paleozoic age of these granites.