Extrusion of subducted crust explains the emplacement of far-travelled ophiolites.

Continental subduction below oceanic plates and associated emplacement of ophiolite sheets remain enigmatic chapters in global plate tectonics. Numerous ophiolite belts on Earth exhibit a far-travelled ophiolite sheet that is separated from its oceanic root by tectonic windows exposing continental crust, which experienced subduction-related high pressure-low temperature metamorphism during obduction. However, the link between continental subduction-exhumation dynamics and far-travelled ophiolite emplacement remains poorly understood. Here we combine data collected from ophiolite belts worldwide with thermo-mechanical simulations of continental subduction dynamics to show the causal link between the extrusion of subducted continental crust and the emplacement of far-travelled ophiolites. Our results reveal that buoyancy-driven extrusion of subducted crust triggers necking and breaking of the overriding oceanic upper plate. The broken-off piece of oceanic lithosphere is then transported on top of the continent along a flat thrust segment and becomes a far-travelled ophiolite sheet separated from its root by the extruded continental crust. Our results indicate that the extrusion of the subducted continental crust and the emplacement of far-travelled ophiolite sheets are inseparable processes. The interplay between continental subduction exhumation dynamics and the obduction of ophiolite sheets remains enigmatic. Here, the authors show that the extrusion of the subducted continental upper crust triggers the necking and breaking of the oceanic upper plate and leads to far-travelled ophiolite sheet emplacement. [ABSTRACT FROM AUTHOR]