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Extended Data Fig. 8 | Protokeel formation in the reference model after
switching off the prescribed plate convergence. The reference model is
described in Fig. 1 : Tp = 1, 500 °C, ΔT = 200 °C. a–d, Slab-pull controlled
retreating subduction and slab break-off of the oceanic plate with highly
depleted mantle. Prescribed convergence is switched off at 4.8 Myr after the
beginning of the experiment; e–h, Building of the mantle protokeel during
slab-pull controlled retreating subduction and slab break-off of the oceanic
plate with highly depleted mantle after switching of the prescribed
convergence at 8.4 Myr from the beginning of the experiment. Dotted lines
indicate boundaries of the mantle transition zone. We note the reduced volume
of the protokeel in h (see Fig. 1d). The colour-code is shown in Fig. 1. Protokeel
source mantle (T >1,300 °C, melt depletion >20%) under subducting plate is
outlined by magenta colour for better visibility.