Metamorphic rocks of the Chukotka complex are exposed in the east Chukotka uplift and granitic-metamorphic domes (Koolen, Senyavin, Alyarmaut and etc.). K-Ar and Rb-Sr dates of these metamorphic rocks range from 2565 to 764 Ma and suggest the Archean ages for granulite(?) and amphibolite facies rocks and the Proterozoic ages for greenschist facies rocks (Shul’diner & Nedomolvkin, 1976; Til’man, 1980; Zhulanova, 1990; Ivanov, 1995; Kotlyar et al., 2001). Recently, orthogneises from the Koolen dome core yielded the late Proterozoic U-Pb ages (650-540 Ma, Natal’in et al., 1999) and the Devonian Rb-Sr (395±24 Ma, Kotlyar et al., 2001) and U-Pb ages (369±1.2, 374±0.5 Ma, Natal’in et al., 1999). Greenschist facies rocks contain organic remnants assuming the Devonian and early Carboniferous ages (Til’man, 1980; Natal’in et al., 1999). The amphibolite facies metamorphism is dated at 104-94 Ma (Natal’in et al., 1999; Akinin, Calvert, 2002). Deformations that are older than 124 Ma are unknown. Thus, the metamorphic complex is diachronous, and an age of its crystalline basement is not clear. The Paleozoic sequence is composed of middle Ordovician - middle Devonian carbonate deposits that are overlain by upper Devonian-middle Carboniferous carbonate-terrigenous rocks and the upper Carboniferous - Permian carbonaceous shales with sandstones.