The geologic data indicate that Phanerozoic and probable late Proterozoic rocks of Chukotka and Alaska are very similar. The paleomagnetic results indicate that during most of the Phanerozoic, the drift of the North American craton did not conform to the drift of the Siberian craton. This contradiction can be settled only by searching for a suture within the bounds of northeastern Siberia, along which the North American plate once apparently collided with the Siberian plate. To the west of the Okhotsk-Chukotka belt there is only one suture possessing all the features of an ophiolitic suture--the South-Aniuy. Its characteristic features are linearity, large extent, and abundant ophiolites and turbidites. It is probably the site of the collision of the Hyperborean and North Asiatic plates. During the Late Jurassic these plates collided with the accompanying subduction of the oceanic lithosphere southwestward and the formation on the northern margin of the Omolon massif of a zone of island arcs and back-arc basins with characteristic sedimentation and magmatism. On the whole the geologic data on the structure, metallogeny, and history of development of West Chukotka agree with the hypothesis of a marginal-continental location of wide regions of the northern part of the Omolon massif over a former subduction zone. The Late Jurassic (Volgian) volcanism fixes the most active deformation along this zone and the bringing together of the plates. More clear becomes also the position of the Triassic volcanism of the Oloy-Aniuy interfluve which probably reflects anot er, but more transitory appearance of a subduction zone on the margin of the continent.

After collision (possibly with some transcurrent movements) of the Hyperborean and Asiatic plates, the geodynamic conditions in the northeastern part of Asia changed and the whole territory to the west and the north of the Okhotsk-Chukotka belt was already a united continental monolith with an old "cicatrice"--the South-Aniuy suture zone.

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