MCMC inversion of the transient and steady-state creep flow law parameters of dunite under dry and wet conditions

Abstract The rheology of the upper mantle impacts a variety geodynamic processes, including postseismic deformation following great earthquakes and post-glacial rebound. rocks is controlled by olivine, most abundant mineral. mechanical properties olivine at steady state are well constrained. However, physical mechanism underlying transient creep, an evolutionary, hardening phase converging to asymptotically, still poorly understood. Here, we constrain constitutive framework that captures creep consistently using data from laboratory experiments on natural dunites containing least 94% under both hydrous anhydrous conditions. represents Burgers assembly with thermally activated nonlinear stress-versus-strain-rate relationship for dashpots. Work obtained evolution variable internal stress. We determine flow law parameters Markov chain Monte Carlo method. find activation energy $$430\pm 20$$ 430 ± 20 $$250\pm 10$$ 250 10 kJ/mol dry wet conditions, respectively, stress exponent $$2.0\pm 0.1$$ 2.0 0.1 cases lower than those steady-state suggesting separate mechanism. For in grain-boundary sliding regime, grain-size dependence similar creep. could be due higher jog density corresponding soft-slip system. More experimental required estimate volume water content relation used its associated provide useful constraints geodynamics applications. Graphical