Polarity-reversal subduction zone initiation triggered by buoyant plateau obstruction

Oceanic lithosphere worldwide is younger than ca. 200 Myr, suggesting that it must have been globally recycled by the recurrent formation of new subduction zones since the existence of subduction on Earth. However, postulated subduction zone initiation processes remain difficult to explain in many cases, and the specific geodynamic conditions under which these might occur are still largely unknown. We here use numerical models driven by the internal force balance of a subduction system to better understand the (geo)dynamics governing (intra-oceanic) polarity-reversal subduction zone initiation. This initiation mode assumes that the birth of a new subduction zone could be triggered by buoyant plateau-obstruction of a pre-existent one dipping in the opposite direction. Our work provides a new insight on the key geodynamic conditions governing this type of subduction zone initiation and discusses their general compliance with known natural examples.