Figure 4.

Geological background of the hadal trench in the plate tectonic model

This model integrates available information on the hydration of the hadal lithosphere^37,56, the fluid activity,^55,59 and the carbon flux⁶⁴ in the subduction zone. The green arrow indicates relative plate motion. Red spikes show the hydration of the oceanic lithosphere, including the basaltic and gabbroic crust and upper mantle. Blue and yellow arrows depict fluid ingress or expulsion. Magma generated in the forearc mantle is shown in purplish red. Stars represent seismic zones. White arrows show major carbon fluxes in the subduction zone. The unit of values is million tonnes of carbon (Mt C) per year. Key geological processes that occur on, beneath, and above the seafloor of the hadal trench are highlighted in small boxes.