Stability of a Chemical Boundary Layer Within a Convecting Mantle

Chemical lithosphere can be stabilized from deformation by possessing a higher viscosity and/or a higher plastic yield strength than the convecting mantle. Numerical simulations were conducted to determine the transitions between viscous and localized plastic deformation of a chemical lithosphere within a convecting mantle. Several deformation modes were mapped as were the parameter conditions required for lithosphere stability. The value of the friction coefficient that lead to lithosphere stability was found to be dependent upon the thickness of the chemical lithosphere and the mantle Rayleigh number. The value of the viscosity contrast that lead to stability was found to depend on chemical lithosphere thickness, but only weakly on the mantle Rayleigh number. These results are consistent with simple physical scaling laws. Outside of the stability parameter windows, both localized and distributed deformation modes were observed. Further scaling laws are being developed to help physically explain the parameter space transitions from localized to distributed deformation regimes.