The paper discusses the results of petrogeochemical and geochronological studies of the Tainsky granitoid stock containing the Tainsky gold deposit in the East Sayan. The Tainsky granitoid stock intrudes through ultrabasites of the Ospa-Kitoi ultrabasitic massif. Granitoids are the part of the ophiolite cover which overlap Archean basement rocks of the Tuva-Mongolian microcontinent of the Archean foundation. Consistent isotopic age values in the range of 850–860 Ma obtained by three independent methods (U–Pb, Re–Os, 40Ar/39Ar) are evidence of the Neoproterozoic age of granitoid magmatism and its genetic relationship with gold–(±copper)–porphyry mineralization. The geological setting, geochemical characteristics, and age of the Tainsky granitoid stock allow us to attribute these rocks to the Neoproterozoic Dunzhugur island arc sequences. Isotopic age values obtained by Rb–Sr and 40Ar/39Ar methods characterized by lower closure temperatures of isotopic systems make it possible to distinguish several tectonothermal events at 650, 435, 339–333, and 280–223 Ma, reflecting difference stages of tectonic evolution of the Eastern Sayan segment of the Central Asian folding belt.