New data on the Sm-Nd isotopic composition of the dolerites of the Nersa complex that are consistent with the petrographic study and the U-Pb dating of detrital zircon from the overlying sedimentary sequences of the Biryusa-Sayan area are presented. The data obtained indicate the absence of the supposed magmatic event 1.6 billion years ago and clearly indicate the Neoproterozoic age of the intrusions. Their source could have been the metasomatized mantle; dolerites went through several stages of metasomatism during their formation, which was reflected in the evolution of its isotopic systems.
