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Fig. 12.29
Mantle-diapir
model of the Baikal rift zone;
(
a
) after Krylov et al. (1975,
1981) and Puzyrev (1997),
(
b
) after Grachev (1996); SP
-Siberian plate, BR-Baikal
rift, Mn - Mongolia; 1 -
sediments, 2 - the Earth's
crust, 3 - normal mantle, 4 -
anomalous mantle, 5 -
M-discontinuity
This model proposed by Puzyrev and Krylov has been constructed on the basis of
deep seismic soundings and seismological data (Krylov et al., 1975, 1981; Puzyrev,
1997). Here, the subhorizontal surface of the low-velocity asthenosphere is recog-
nized at a depth of about 100 km. A subvertical slitlike channel (associated with
a fault separating the Siberian Platform from the Baikal region) branches off from
asthenospheric layer. A subhorizontal low-velocity zone, the so-called anomalous
mantle, is contiguous to this channel. The anomalous low-velocity mantle has the
shape of a “visor” adjoining the Moho surface. The average thickness of this zone is
about 20 km. It is distinctly separated from the subhorizontal asthenosphere and
extends in a northeasterly direction for a distance greater than 1500 km. On a
transverse section of the Baikal Rift zone, the anomalous mantle gradually thins
out to the southeast.
