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Samples from plutonic belts and individual intrusions in the Sakha Republic (Yakutia), northeastern Russia, were analyzed using [sup.40]Ar/[sup.39]Ar geochronology and trace element geochemistry. Four phases of activity were identified: a subduction event along the southwest margin of the Kolyma-Omolon superterrane with apparent ages of ca. 160-140 Ma, a superposed collisional event dated at 143-138 Ma, a subduction event along the northern margin of the superterrane dated at 130-123 Ma with a slightly older to contemporaneous extensional event to the west; and intrusions associated with east-west extension between 106 and 92 Ma. These phases are interpreted to represent (1) subduction under and (2) accretion to Asia of Kolyma-Omolon followed by local extension, (3) subduction along the northern edge of this superterrane, and (4) regional extension following closure of the South Anyui suture and/or the start of subduction associated with the Okhotsk-Chukotka volcanic belt. Keywords: [sup.40]Ar/[sup.39]Ar, geochemistry, geochronology, Russia, tectonics, terranes, Yakutia Region.

Analyzes the plutonic belts and individual intrusions in Yakutia, Russia using argon isotope geochronology and trace element geochemistry. Characteristics of biotites from granites; Age range and nature of granitic belts; Phases of deformation in the northern Chersky Range.