Fig. 1

Schematic illustration of the subducting slab (middle) and phase diagram of dry Mg\(_2\)SiO\(_4\) (left) and “stability diagram” of wet systems (right). More detailed stability diagrams of hydrous phases are given in Ohtani et al. (2001b); Nishi et al. (2014); Ohtani (2020). The cross symbols indicate the seismicity observed in the subducting oceanic plate. The “choke point” is shown as the star symbol. Below the choke point temperature, hydrous mineral can transport water into the deeper part of the Earth’s interior