Time-resolved grain-scale 3D imaging of hydrofracturing in halite layers induced by gypsum dehydration and pore fluid pressure buildup

Fluid release from dehydration reactions is considered to have significant effects on the strength and dynamics of tectonic faults at convergent plate boundaries. It classically assumed that production fluid leads increased pore pressures perturb a fault's stress state thereby facilitates enhances deformation. This important assumption has never been supported by direct microstructural observations. Here, we investigate role gypsum in deformation evaporitic rocks using synchrotron-based time-resolved X-ray computed microtomography (4D) imaging. approach enables documentation coupled chemical, hydraulic mechanical processes grain scale. In our experiments with deforming halite-gypsum-halite sandwiches observe released dehydrating accumulates gypsum-halite interface before distributed failure halite layer drains fluid. From observations conclude perceivedly impermeable layers evaporites are unlikely trap overpressured fluid, e.g., thin-skinned detachment horizons. Moreover, as diffuse not localized, suggest alone may explain intermediate depth seismicity subduction zones. Our data demonstrate potential in-situ 4D imaging for grain-scale investigation fundamental processes.