We report new data on the mineralogy, petrography, geochemistry, U-Th-Pb geochronology, and Sm-Nd and Rb-Sr isotopy of granitoids and associating rocks of the Sup, Duzunya and Batyrchan plutons, including rocks with rapakivi texture, which we combine into the new Severookhotsk complex. These rocks were formed in the Cenomanian-Coniacian ages 94-88 Ma (U-Pb SHRIMP-II data) in the back-arc of the West Okhotsk flank zone of the Okhotsk-Chukotka volcanoplutonic belt. Sm-Nd and Rb-Sr isotopic data confirm the presence of both an enriched mantle and a continental crust component in the composition of the magmatic source of the rapakivi granites. We show that the Severookhotsk complex magmatism and the Sn-polymetallic and Au-Bi mineralization of the Allakh-Yun tectonic zone have the same origin.