Near-ridge initiation of intraoceanic subduction: Effects of inheritance in 3D numerical models of the Wilson Cycle

Abstract

Despite its global significance, much of the Wilson Cycle, which infers kinematic inversion from plate divergence to convergence, remains conjectural, in particular for what concerns subduction initiation. We present a high-resolution 3D thermomechanical numerical model of the Wilson Cycle, evolving from continental rifting through breakup and oceanic spreading to convergence and self-consistent subduction initiation. In the models, intra-oceanic subduction initiates off-ridge and is an intrinsically three-dimensional process. Its location is controlled by convergence-induced ridge swelling, and the subduction geometry is controlled by three main factors: (1) the inherited compositional and thermal heterogeneity of the ridge and oceanic lithosphere from rifting and seafloor spreading; (2) the curvature/obliquity of the ridge with respect to the convergence direction and (3) the duration of transition from plate divergence to convergence. The modelled mechanisms are consistent with geological records, for example in the Oman subduction-obduction system, and are undervalued elements of the Wilson Cycle.