The Role of Ridge Subduction on Slab Window Formation: Insight From 3D Numerical Modeling

Abstract Mid‐ocean ridges attached to subducting plates are occasionally transported to subduction zones, facilitating slab tearing and formation of slab windows. However, the observed slab windows along the Western and Eastern Pacific margins vary largely in terms of spatial extent, seismicity, magmatism and mantle flow. In this study, we utilize three‐dimensional numerical modeling of ridge subduction by considering end‐member different ridge activities, to specifically investigate how subduction of active or fossil ridge controls plate deformation and slab geometry. Our model results show that subduction of active mid‐ocean ridges tends to cause slab tearing and largely promotes the formation of slab windows, along with the presence of active adakitic volcanism and trench orthogonal mantle flow. Subduction of extinct ridges fails to form slab windows and instead establishes subduction with smaller slab dipping angles. This study suggests that the thermal structures of mid‐ocean ridge and lateral oceanic plate age difference affect subduction dynamics and the formation of slab windows. Furthermore, these findings align with the natural example of the Manila subduction zone, where the subduction of active ridges followed by extinct ridges, could explain vertical slab tearing and the observed deep slab windows.