Deep structure beneath the Baikal rift zone and adjacent areas

Abstract:

The Baikal rift zone is one of the most typical continental rift systems in the world, which may represent early stages of continental break-up (Petit and Déverchère, 2006). Therefore, it is well-suited to study the evolution of intracontinental rifting which is an important issue of modern tectonics. Despite massive studies devoted to the Baikal rift zone, the two classic hypotheses of “active” versus “passive” rifting (Mats and Perepelova, 2011) are still under intense debate and no simple scenario can perfectly explain its origin, deep structure and evolution.

In this research, mainly focusing on the southwestern flank of the Baikal rift zone, we selected a large amount of high-quality teleseismic P-wave arrival time data and applied a tomographic inversion method. We discover low-velocity anomalies under the southwestern flank of the Baikal rift zone, interpreted as mantle upwelling from under the Siberian craton, indicating possible hot material arising from beneath the craton to beneath the rift.

Our images also reveal low-velocity anomalies under the Hangai Dome, suggesting that delamination occurred within the Mongol-Okhotsk suture zone between two main thrusts. Hot material transferring from beneath the Siberian craton also reached the upper mantle beneath the Hangai Dome and might have positive effects on the process of delamination.

We think that mantle upwellings from the mantle transition zone under the Siberia craton play an important role in the formation of deep structures and geological settings of the research area. We favor a more active mode in terms of the development of the Baikal rift zone.

References

Mats, V.D., Perepelova, T.I., 2011. A new perspective on evolution of the Baikal Rift. Geoscience Frontiers 2, 349–365. doi:10.1016/j.gsf.2011.06.002

Petit, C., Déverchère, J., 2006. Structure and evolution of the Baikal rift: A synthesis. Geochemistry, Geophysics, Geosystems 7, Q11016. doi:10.1029/2006GC001265