CONTINENTAL-CRUST AGE AND FORMATION STAGES IN THE CENTRAL ALDAN GRANULITE-GNEISS TERRAIN - U-PB AND SM-ND ISOTOPIC DATA FOR GRANITOIDS

The U-Pb dating of zircons from reference granitoid complexes located in structures of different ages revealed that the formation of the maj or structural elements of the central Aldan granulite-gneiss terrain - the Timpton thrust, the Lower Timpton and Sunnagin dome-shaped struct ures, and the Gonam-Sutam anticlinorium - occurred during the Early Pr oterozoic rather than the Early Archean period of the Aldan Shield's g eologic history. On the basis of Sm-Nd isotope data for granitoids of different ages, two stages of continental crust formation were recogni zed in the central Aldan granulite-gneiss terrain: the Early Proterozo ic event with an age of approximately 2.0 - 2.4 Ga and the Archean eve nt with an age of no less than 2.8 Ga.