Строение и развитие Байкальской зоны

E. P. Vasiliev, A. I. Mel'nikov, V. G. Nikolaev. Structure and evolution of the Baikal Zone. The long-term evolution of the Baikal Zone which is a part of a major geosuture records several stages differing by specific features. The distinctly pronounced endogenic processes during the Early Proterozoic stage played a significant part in the development of the zone. At the end of this stage, the continental crust of the region had been formed. Its further vertical accretion continued during the Riphean, and a mature continental crust already existed at the beginning of the Devonian. The subsequent stage of the evolution was characterized by a tectono-magmatic activization. The Late Paleozoic activization was expressed into formation of numerous zones of superimposed schi stosity and greenschistfacies diaphthoresi s. The weaker Mesozoic activization was represented by thrusts and basalt dykes. During the most considerable Cenozoic activization a system of rift depressions was formed in several successive stages, vertical movements being dominant. Volcanism occurred in several sites and proved to be unrelated directly to grabens although young volcanics have been found in the depressions too (e. g. Tunkin depression). At the present stage the zone is characterized by high seismicity and sedimentation proceeding in the earlier formed depressions.