Horizontal mantle flow controls subduction dynamics

Subduction zones are central to plate tectonics, yet their behavior remains partially unexplained. While subduction is often attributed to slab buoyancy, observations show weak correlations between slab age and subduction velocity or dip angle. This discrepancy suggests additional forces may influence subduction dynamics. A global lithospheric rotation pattern has been observed, hinting at mantle flow effects. Existing models do not fully account for these patterns. The role of horizontal mantle flow in shaping subduction asymmetry remains unclear. Prior research has shown that slab dip angles vary significantly with subduction direction. This gap motivated investigations into how mantle flow might interact with subduction. The study aims to clarify whether mantle flow could explain observed subduction asymmetries.

The purpose of this study is to explore the influence of horizontal mantle flow on subduction dynamics. The specific problem is the observed asymmetry in subduction zone dip angles and velocities. The authors aim to test whether mantle flow direction affects subduction behavior. They propose that mantle flow could counteract or enhance slab buoyancy effects. The study uses numerical models to simulate subduction under varying mantle flow conditions. The goal is to determine if mantle flow can explain observed subduction asymmetries. This approach addresses a key gap in current tectonic models. The findings could refine understanding of subduction zone evolution.

The study employs high-resolution two-dimensional thermomechanical models of oceanic subduction. These models simulate interactions between subduction zones and mantle flow. The simulations incorporate varying mantle flow directions relative to subduction polarity. The models track slab dip angles, hinge motion, and overriding plate deformation. Results are compared to seismicity data and tomographic images of real subduction zones. The simulations test two scenarios: mantle flow opposing or aligning with subduction direction. The models account for slab age and buoyancy effects as background variables. This approach allows direct assessment of mantle flow’s influence on subduction dynamics.

When subduction polarity opposes mantle flow, slab dip angles become subvertical and hinge retreat occurs. This configuration leads to back-arc basin formation in the simulations. In contrast, aligned mantle flow and subduction polarity result in shallow slab dips and hinge advance. The overriding plate develops pronounced topography in these cases. These results match observed seismicity and tomographic data from real subduction zones. Slab age and buoyancy effects are secondary in these simulations. The models suggest mantle flow can override slab buoyancy in controlling subduction behavior. The simulations support the hypothesis that mantle wind influences subduction asymmetry.

The study concludes that horizontal mantle flow significantly influences subduction dynamics. The authors propose that mantle flow direction controls slab dip angles and subduction polarity. Their models align with observed seismic and tomographic data from subduction zones. The findings suggest mantle flow can override slab buoyancy effects in certain scenarios. The results explain why subduction asymmetry is common in convergent margins. The authors emphasize that mantle flow is a key factor in subduction zone evolution. These conclusions are based on numerical simulations and observational data. The study highlights the need for models that incorporate mantle flow effects.