Self-replicating subduction zone initiation by polarity reversal

Jaime Almeida,Filipe M Rosas,Boris Kaus,Nicolas Riel,João C Duarte

doi:10.1038/s43247-022-00380-2

Jaime Almeida, Filipe M Rosas + Show 3 more

Open Access

https://doi.org/10.1038/s43247-022-00380-2

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Abstract

Subduction zones have recurrently formed on Earth. Previous studies have, however, suggested that they are unlikely to start in the interior of a pristine ocean. Instead, they seem to be more likely to form from another pre-existing subduction zone. One widely cited conceptual model to start new subduction zones is polarity reversal, resulting from the shutdown of a pre-existent subduction zone due to the arrival of a buoyant block at the trench. However, the dynamic conditions by which this process occurs remain elusive. Here, we present 3D numerical models of subduction zone initiation by polarity reversal resulting from the arrival of an oceanic plateau at the trench. Our results show that this process is more likely to occur for old subducting plates and narrow plateaus, and that new subduction zones can form from previous ones in a self-replicating manner, without requiring any other external tectonic forcing.

Highlights

Subduction zones have recurrently formed on Earth
One commonly proposed mechanism for Subduction zone initiation (SZI) is subduction polarity reversal[1–3]. This assumes that the arrival of a buoyant terrane[12–14] at the trench of an active intraoceanic subduction zone is capable of causing the local termination of the subduction system, and to force the overriding plate to subduct in the opposite direction
We show that polarity reversal subduction initiation by plateau collision is geodynamically viable in the absence of external driving forces, but that it is limited by the along-trench width of the oceanic plateau

Summary

Introduction

Subduction zones have recurrently formed on Earth. Previous studies have, suggested that they are unlikely to start in the interior of a pristine ocean. Our results show that this process is more likely to occur for old subducting plates and narrow plateaus, and that new subduction zones can form from previous ones in a self-replicating manner, without requiring any other external tectonic forcing. One commonly proposed mechanism for SZI is subduction polarity reversal[1–3] This assumes that the arrival of a buoyant terrane[12–14] at the trench of an active intraoceanic subduction zone is capable of causing the local termination of the subduction system, and to force the overriding plate to subduct in the opposite direction. This type of SZI has been proposed to have occurred in several different natural instances[15–18]. Varying the width of the plateau along the subduction trench allows us to simultaneously assess the impact of a narrower active subduction zone on the triggering of a new one by polarity reversal

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