Subduction initiation triggered by collision: A review based on examples and models

Subduction initiation is one of the main unsolved issues in plate tectonics theory with different proposed mechanisms. In the arc (plateau, terrane)-continent collision models, a new subduction zone can be induced by subduction polarity reversal or subduction transference. In this study, I have reviewed the typical natural examples and numerical models for the subduction initiation of polarity reversal and subduction transference, and then summarized the key characteristics, geological records, and future directions of the subduction initiation. The subduction polarity reversal usually occurs at intraoceanic arc settings, but the subduction transference often happens at active continental margins as well as intraoceanic arc settings. Natural examples of subduction polarity reversal and subduction transference have representative geological records of supra-subduction zones (SSZ) ophiolites (ophiolitic mélanges) and metamorphic soles, which have long been recognized as the key to understanding the subduction initiation and geodynamic processes, because both are rock records of upper plate extension and lower plate burial, respectively. Weak zones and driving forces are required for the collision-induced subduction polarity reversal and subduction transference, which generally occurs about 10 Myr after collision both in natural observations and numerical models. However, subduction transference happens about 10–30 Myr after the collision in the Proto-, Paleo-, and Neo-Tethys oceans. Numerical models of the subduction initiation moving from 2D to 3D will break through the constraints of the 2D geometric model and better simulate the subduction initiation processes. However, the parameters used in the numerical modelling are not yet able to fully describe the various controlling factors of the subduction initiation. Moreover, the mechanism of weak rheology and its effect on the subduction initiation are still ambiguous and need further study by natural observations and numerical modelling.