Themo-mechanical models for coupled lithosphere-surface processes

Category Other
Group GSI.IR
Location International Geological Congress,oslo 2008
Author Burov, Evgueni
Holding Date 27 September 2008

Surface processes provide a critical feedback on the surface tectonic deformation. Yet, the influence of these processes may spread well below the crustal levels. In this study, we use thermo-mechanical numerical models to investigate the impact of surface processes on styles of continental collision. With that goal we exploit our recent models of fast and slow continental subduction. We show that the total amount of subduction may largely vary as function of denudation rate (controlled by the coefficient of erosion, k). Very strong or very slow erosion/sedimentation enhance the possibility of plate coupling and promote whole-scale thickening or buckling. The maximal amount of subduction is achieved for some intermediate values of erosion rates when the tectonic uplift rate is fine-balanced by the denudation rate. For example, in case of fast convergence (5 cm/y), the optimal balance is achieved for k ~ 3000 m2/yr. The experiments suggest that both extra slow (k < 50-100 m2/yr) and extra rapid erosion (k > 6000-8000 m2/yr) limit, by up to 50%, the total amount of subduction, if not totally prevent it. The model demonstrates the large capability of surface processes to adopt to different deformation styles: the orogenic building and subduction successfully develop (subduction number, S > 0.5) in the range of k between 500 m2/yr and 6000 m2/yr at convergence rates ranging from 1 cm/y to 6 cm/y. Within this range, particular features of orogenic style such as the accretion prism geometry, amount of upper crustal subduction, horizontal progression of the mountain range/thrust fault and the amount of exhumation may be quite different.