Geodynamic Models of Accretionary Wedges with Smectite-Illite Transformation

Accretionary wedges, formed at convergent plate boundaries, are influenced by complex interactions between incoming deformation, fluid dynamics, and mineralogical changes. The smectite-illite transformation, driven by increasing temperature and pressure, releases bound water, creating fluid overpressure and altering wedge rheology. Post-transition illite strengthens wedge material while increasing fault stability, influencing the development of the décollement and wedge morphology. The depth of this transformation often aligns with the onset of interplate seismicity, highlighting its role in earthquake generation. Our study investigates the impact of smectite-illite transformation on wedge dynamics, incorporating phase transitions and models of empirical  fluid overpressure into geodynamic models to assess their role in wedge evolution and seismicity. Using I2VIS for a visco-plastic rheology framework, this study models thermal gradients and kinetic phase transitions to simulate their effects on wedge dynamics. Parameters such as fluid pressure, and internal friction are systematically varied to evaluate the influence of smectite-illite phase transition on wedge stability and morphology.  Numerical simulations reveal that fluid overpressure and mineralogical transitions significantly shape wedge geometry and contribute to zones of seismic hazard. Model predictions are validated against data from subduction zones such as the Nankai Trough, improving our understanding of wedge behavior and seismic hazards. These findings highlight the critical role of mineralogical transformations in subduction zone mechanics and their broader implications for earthquake and tsunami risk assessment.