The complexities of convergent margins often include the interactions of subduction zones, with many geological records of “double” subduction. Here, we build 2D numerical models to explore the evolution of complex subduction systems by testing systematically single and inward-dipping double subduction beneath a continental upper plate, and the impact of continental collision on these systems. When compared to single subduction models, the in-dip double subduction shows hindered trench migrations and larger volumes of upwelling mantle enhanced by excess sinking slab mass. Double subduction draws larger volumes of hotter mantle beneath the continent, in an area much broader than the marginal basins of single subductions, where subcontinental temperatures are up to ~200 ˚C higher. As collision jams one margin of a double subduction system, the other margin follows the evolution of migrating single subduction zones, although characterized by persisting higher mantle temperatures and strong upwellings, inherited from the double subduction stage, and large-scale upper plate extension. The modelling outcomes are compared to scaling arguments to test the viability of the mechanism proposed for tectonics of the Cenozoic South China Sea and Neoproterozoic Yangtze Block, where the in-dip double subduction provides a context for protracted large-scale continental extension, hotter subcontinental temperatures and channeled mantle flow not easily reconciled with the dynamics of single subduction zones.
Details on https://doi.org/10.1130/G52232.1 
Li_et_al-2024-Geology-Double_subduction_controls_on_long-lived_continental_tectonics_and.pdf
This work has been highlighted by Nanjing University, GSA and other institutions.