Wedge Subduction Controls on the Dynamic Modes of Terrane-Continent Collision: Subduction versus Collision

Summary Wedge subduction represents the final stage of the oceanic plates before terrane-continent collision. However, its influence on collision dynamics is often overlooked. The closure of the Paleo-Tethys Ocean, during which a mid-ocean ridge nearly parallel to the trench was subducted before continental collision, makes it an ideal natural laboratory for studying collision modes. Based on the tectonic background of Paleo-Tethys Ocean closure, this study systematically investigates the effects of wedge subduction on dynamic modes of terrane-continent collision through a finite-element method. The results show that low initial wedge subduction angles facilitate the terrane-continent collision (TCC) mode, whereas steep initial angles promote the continental-terrane subduction (CTS) mode. A slow convergence rate (1 cm/yr) increases the likelihood of the CTS mode, whereas faster convergence tends to promote the TCC mode. The Cimmeria-directed opposite-polarity configuration may cause overthrusting of the trailing oceanic plate onto the continental terrane and promote the TCC mode. Continental terrane strength is another critical factor. Weaker terranes favour the CTS mode, while stronger ones favour the TCC mode. Geological evidence and tomography results are broadly compatible with the tentative inference that the western and central segments of the Paleo-Tethys suture zone were more likely to experience the CTS mode, whereas the eastern segment may have been more likely to experience the TCC mode. These east–west differences may be explained by the modelled effects of convergence rate, depending on factors such as continental terrane strength and wedge subduction angle. This research establishes relationships between wedge subduction and continental collision modes, providing new perspectives for understanding structural diversity within suture zones globally.