Earth Planets Space, Vol. 51 (No. 10), pp. 1079-1089, 1999
A. M. Popov, A. I. Kiselev, and V. V. Mordvinova
Institute of the Earth's Crust, Russian Academy of Sciences, Irkutsk, Russia
(Received November 16, 1998; Revised April 12, 1999; Accepted April 12, 1999)
Abstract: There exists a number of models that account for the deep structure of the Sayan-Baikal province on the basis of different geophysical data. The models based on magnetotelluric soundings differ from those obtained from seismology with no regard to magnetotelluric soundings (MTS) results. To decide between the active and passive mechanisms of Baikal rifting, we propose to correlate the modeling results to the available seismological and petrological data, as well as to the model of asthenospheric diapirism put forward by Zorin et al.(1989, 1990, 1995). Inasmuch as the reality of MTS-based models depends on removal of static-shift effects, the reported three-dimensional modeling of the Baikal rift deep structure was preceded by normalization of the original MT curves by the global magnetovariation curve. The enhanced electrical conductivities of the crust and upper mantle of the region is interpreted in terms of geodynamics where the Cenozoic activity is suggested to be driven by convective mantle flow and triggered by the associated plate collisions. The origin and evolution of the Baikal rift can be explained in terms of reactivation of a pre-existing lithospheric inhomogeneity between the Siberian craton and the Sayan-Baikal fold area.