Punctuated energetics of dehydration contributes to slow earthquake phenomena

The prograde breakdown of hydrous minerals like lawsonite is energy-intensive and releases fluids at depths coincident with extensive slow earthquake phenomena for many subduction geotherms. However, there remains inconsistency between the spatial occurrence and inferred temporal rates of these dehydration reactions relative to the episodic character of slow earthquakes. The example of lawsonite breakdown shows that dehydration reactions will dictate heat consumption, thus buffering the rate of temperature increase for a rock undergoing intervals of metamorphism (<30 °C) and delaying each small increment (∼1 °C) of fluid release. A nonlinear behavior is predicted involving periods of fast fluid release paused by periods of slower heat absorption. Such stepped reaction progress is consistent with natural rock textures of lawsonite breakdown indicating intermittent fluid-present crack propagation and associated step changes in mineral growth. Pulsed fluid flow into rocks of heterogeneous permeability may result in stress build-up enabling crack propagation and slip at different scales. Energetics of punctuated dehydration and resultant fluid flow match temporal and spatial characteristics of slow slip behavior. Consequently, episodic dehydration is suggested as a viable trigger for slow slip.