Subduction polarity reversal, an induced subduction initiation (SI), may occur frequently in geological history as exemplified by the Solomon subduction zone. However, the mechanism and dynamics of polarity reversal remain poorly understood. Here, we ...
Subduction polarity reversal, an induced subduction initiation (SI), may occur frequently in geological history as exemplified by the Solomon subduction zone. However, the mechanism and dynamics of polarity reversal remain poorly understood. Here, we use 2D thermomechanical numerical models to investigate the dynamics of subduction polarity reversal during oceanic plateau accretion. Model results show that larger and lighter oceanic plateaus favor subduction polarity reversal, which is manifested by the formation of the Solomon subduction zone after the large Ontong Java Plateau collided with the former Melanesian (Manus‐North Solomon‐Vitiaz) trench. We analyze the stress state during the transient SI process and find that rapid extension of the oceanic plateau is concomitant with subduction polarity reversal, thus questioning the use of extensional structures as geological criteria for spontaneous SI.
Subduction of dense oceanic lithosphere into the asthenospheric mantle plays an essential role in driving plate tectonics. However, the mechanism by which new subduction zones form remains poorly understood. Oceanic plateaus are topographic highs in the oceanic lithosphere and are characterized by a thick oceanic crust (10–35 km; Kerr, 2014, https://doi.org/10.1016/b978-0-08-095975-7.00320-x). The arrival of a buoyant oceanic plateau at a trench may block existing subduction and result in the formation of new subduction with reversed polarity, which provides an ideal object to understanding the dynamics of subduction initiation (SI). Here, we use thermomechanical numerical models to study the geodynamic processes of SI during oceanic plateau accretion. Our results show that collision of the oceanic plateau with the overriding plate could lead to the breakoff of the existing slab and subsequent foundering of the overriding plate. These processes could lead to subduction polarity reversal, which is favored by a larger and more buoyant oceanic plateau.
Subduction polarity reversal during oceanic plateau accretion is numerically studied
Buoyant and thick oceanic plateau favors subduction polarity reversal
Extension is not a unique phenomenon in spontaneous subduction initiation
Subduction polarity reversal during oceanic plateau accretion is numerically studied
Buoyant and thick oceanic plateau favors subduction polarity reversal
Extension is not a unique phenomenon in spontaneous subduction initiation