According to petrological and geochemical data, Cenozoic alkali basalts of East Siberia and Central Mongolia are related to mantle plumes. Analysis of geophysical data made it possible to outline tails of these plumes [3, 4] that are apparently confined to the upper mantle [4]. Calculations show that the upper and lower boundaries of plume tails can be located at 150–200 and 420–660 km, respectively.
