Fig. 5: Representative numerical model of the second-type scenario in Fig. 2 (Run 71, Fig. 9).

a–h Model evolution regarding material, temperature (gray isolines), and velocity fields (gray arrows). Blue arrows illustrate the syn-SZI rifting locus in the upper plate, which also migrates towards the trench but slower than the melting locus. Material type: light blue—the ocean’s lithosphere mantle, green- lower oceanic crust, orange- upper oceanic crust (or altered oceanic crust), purple—sediments. i Volume evolution of scraped slab materials (demonstrated by the relative frequency of different material tracer types). Red and blue arrows denote the scraped materials’ sudden volume increase or decrease. The inset demonstrates the volume evolution of scraped slab materials in 30 Myr. j Time-space distribution of asthenospheric mantle melts. The red arrow demonstrates the migrating direction of mantle melts. k Dehydration behaviors of slab materials^34,43. The modeled melts/fluids are shown for every 10 km along the horizontal direction, with the symbol size representing the number of tracers. A complete evolution of this model is in Supplementary Movies 1 and 6.