Subduction Polarity Reversal: Induced or Spontaneous?
Shengxing Zhang, Wei Leng
Abstract
Abstract Subduction polarity reversal (SPR) is the subduction initiation process following the arc‐continent collision. Previous models emphasized the need for the external compressional force to induce it. However, the explanation of different geological structures in the reported SPR zones was poor. Based on our new thermomechanical model, we confirm the possibility of establishing a spontaneous SPR system, which is self‐sustained by negative buoyancy. The spontaneous SPR will occur when the whole overriding oceanic plate has a small plastic strength, while the arc‐continent collision system with a strong overriding plate and a limited weak back‐arc/arc structure prefers the compression‐induced SPR. Moreover, a rather young oceanic plate (≤20 Ma) can trigger the SPR without any weak area. This study provides new insights into the different initiation mechanisms and evolutionary pathways of the potential Cenozoic SPR events in Ryukyu, Kamchatka, and New Hebrides.