Slab break-off and subduction polarity reversal after collision can be very fast

Abstract

Slab break-off and polarity reversal are tectonic events that often occur in relation to the subduction process. For example, the Western Alps and Ontong Java are high profile cases of slab break-off and polarity reversal. A sufficient number of high-quality geological examples indicate a very short time frame (an average of <6 m.y.) for slab break-off and polarity reversal after a collisional event. On the other hand, previous numerical modeling studies propose the timing of these collision break-off events to be on an average time scale between 7.5 and 23.2 m.y. This study reconciles the geological observations from 17 ancient and contemporary subduction zones with a suite of numerical experiments. By synthesizing geological evidence and our geodynamic models, we propose that the majority of slab break-off and polarity reversal processes can be geologically fast (average <6 m.y.), contrary to current thinking.