Quantifying Water Diffusivity and Metamorphic Reaction Rates Within Mountain Belts, and Their Implications for the Rheology of Cratons

The distribution of rheologically strong cratons, and their weakening by metamorphic hydration reactions, is fundamental importance for understanding first-order strength contrasts within the crust resulting controls on tectonic evolution continents. In this study, Douglas Harbor structural window Paleoproterozoic Trans-Hudson orogen Canada used to study footwall Archean Superior craton basement water released from overlying Cape Smith thrust-fold belt. Phase equilibria modeling applied quantify conditions, determine effect mineralogy. amount structurally bound calculated shown decrease as a function distance below basal décollement Applying reactive fluid transport model these results, rate coefficient fluid-rock reaction constrained be , diffusivity through grain boundary network at ambient conditions 570C 7.5 kbar. This newly documented diffusion three orders magnitude slower than thermal diffusion, implying that may rate-limiting factor in therefore plays an important role geological persistence. conclusion consistent with field observations strain restricted hydrated portions basement.