Dynamic Evolution of Parallel Ridge Subduction Controlled by Stress State of Ridge Axis: Insights from Numerical Modelling

Geological observations suggest that the Izanagi-Pacific ridge subduction has caused a long-term subduction gap due to margin-wide slab detachment, whereas the Nazca-Antarctic ridge subduction has created a slab window beneath intracontinental lithosphere due to continuous ridge subduction. The dynamic mechanism controlling such different dynamic evolution is still unclear. Here, we use 2-D thermal-mechanical numerical models to demonstrate that parallel ridge-trench interaction can not only result in ridge subduction interrupted but also continuous, which are determined on the stress state of ridge axis. Coefficient of strong drag force from slab sinking and weak compressional force from overlying plate pushing, in the case of high subduction dip-angle and low convergence velocity, leads to slab detachment before ridge entering trench, otherwise ridge would enter trench continuously. Our results provide new insights into the dynamic evolution of ridge subduction, which is different the models from conventional kinematic geometrical analysis.