HISTORY AND GEODYNAMICS OF THE LAKE BAIKAL RIFT IN THE CONTEXT OF THEEASTERN SIBERIA RIFT SYSTEM - A REVIEW

The Eastern Siberian system of Cenozoic rift faults and depressions, extending for nearly 1 800 km, is associated with a large domal uplift which frames the craton area of the Siberian platform in the south an d southeast. The central segment of this system, in which the largest and oldest depression of Lake Baikal is located, runs immediately alon g the margin of the Siberian craton in the zone where it links with th e Sayan-Baikal mobile belt. This depression makes up 1/3 of the total rift zone. The Baikal rift has been expanding from the central segment towards the northeast and west. A maximum thickness of sediments (7 5 00-8 000 m) has been recorded in the Baikal basin, decreasing to 500-1 000 m at the limits of the rift system. Rifting was accompanied by ba saltic magmatism of fairly uniform petrochemical composition, dominate d by alkaline olivine basalts. Magmatic conduit centers and volcanic f ields are located quite independently of the rift faults and basins ex cept for in the Tunka rift valley. Rifting in Eastern Siberia is an in dependent geodynamic phenomenon which is thought to have no direct rel ation to the collision of the Hindustan subcontinent with Eurasia. The Baikal rifting is mainly driven by a local source of energy, resultin g from asthenospheric upwelling, heating and gravitational instability of the lithosphere.