Deep-Seated Boundary Structures of the Siberian Craton and the Baikal-Patom Fold-and-Thrust Belt in the Cross-Section of the 1-Sb-Vostochny Profile and Its Continuation Along the Vitim River

The deep-seated boundary structures of the Siberian craton and the Baikal-Patom fold-and-thrust belt have been considered in the cross-section of the 1-SB-Vostochny reference geophysical profile and its continuation along the Vitim River. The deep crustal CDP seismic reflection profiling, with regard to the distribution of potential fields, made it possible to construct a geodynamic model of the junction zone of the Siberian craton and the Baikal-Patom belt. The model highlights the Siberian craton basement structures, overlain in the marginal part by a complicated series of nappes including the Chuya allochthon, the Baikal-Patom pericratonic trough, and deformed complexes of the sedimentary cover of the craton. There has been the south-easterly increase in the cover thickness from 5 to 15 km, as well as the cover saturation with salts and gabbroid sills. The structures of the folded framing of the craton are represented by the Mama block, the complexes of which surround the wedge-shaped end of the basement of the Siberian craton, splitting from the mid-crustal level. The upper plates of the Mama block, with the 3–4 km thick Chuya allochthon at the base, are thrust over the craton, and the lower plates are thrust under the craton, sinking into the mantle. The southern boundary of the Siberian craton has been traced on the basis of geophysical data complex.