Dynamics of intracontinental extension in the north Baikal rift from two-dimensional numerical deformation modeling

We model the recent deformation along a lithospheric-scale cross section pe rpendicular to the northern part of the Baikal rift zone (BRZ) with two-dim ensional finite element models. Using realistic lithospheric structure and rheological properties and imposing extension as a far-field boundary condi tion, we find a model that matches reasonably well the topography, observed deformation pattern, gravity anomalies, and age of formation of the northe rn BRZ. Our results suggest that (1) extensional strain can occur away from the main rift basin in the Sayan Baikal range and create, depending on the rheological properties of the lithosphere, a large "off-rift" basin analog ous to the Barguzin basin, or a series of basins and ranges, as observed in the southern part of the Sayan Baikal range, (2) anelasticity plays a majo r role by participating in the uplift of rift shoulders and hanging wall de formation, and allowing the subsidence and tilting of the hanging wall alon g high-angle planar normal faults. (3) the lower crust accommodates differe ntial strain between the brittle upper crust and upper mantle by horizontal shear and lateral flow towards the regions of crustal and mantle thinning, (4) far-field extensional stress and a lithospheric discontinuity inherite d from Paleozoic tectonic events are sufficient to initiate rifting and bas in subsidence. and (5) there is no, or very little, dynamic contribution of a hypothetic asthenospheric plume under the BRZ, at least in the recent ph ase of its evolution ("fast rifting stage", 3.5 Myr).