Figure 2
From: Depletion of the upper mantle by convergent tectonics in the Early Earth
Subduction with relatively thin depleted mantle at constant convergence velocity of 5 cm/year. (a) Modern style of subduction with slab retreat and formation of island arcs with basaltic and dacitic volcanism, back-arc basins with a new oceanic crust at modern mantle temperature ΔT = 0 °C (Tp = 1300 °C). (b) One-sided subduction with voluminous serpentinization in the mantle wedge, dacitic and basaltic volcanism and elevated mantle temperature ΔT = 150 °C (Tp = 1450 °C). Dotted dark-blue lines indicate an actual upper and lower boundaries of the initial mantle transition zone. Arrows show direction of plate motion (not to scale) and viscous flow of the depleted mantle. The colour key is shown at the bottom of the figure. Prescribed velocity of the left-hand plate is 5 cm/year.
