Supply rate of continental materials to the deep mantle through subduction channels

Geological studies have revealed that continental materials subduct from the Earth's surface via the following three mechanisms: tectonic erosion, sediment subduction, and direct subduction of immature oceanic arcs. Then, the continental materials are transported through subduction channels that are located between subducting slabs and mantle wedges. However, the depth that a subduction channel reaches and the magnitude of the flux of subducted materials at that depth are not clear. Here, in order to estimate the supply rate of continental materials to the deep mantle, we have conducted a numerical simulation of a subduction channel based on the finite difference method. We have found that a sustainable thickness of the channel in the deep mantle is ~ 2–3 km and its corresponding flux of continental materials integrated over the length of the current subduction zones is 2.2 km3/yr. These results indicate that almost all of the continental material that is subducted through the channel is capable of reaching the depth of the mantle transition zone. The total amount of continental materials conveyed to the deep mantle over 4 Gyr is estimated to be about 1010 km3, which is greater than the volume of the present continental crust at the surface of the Earth.

► We conducted numerical simulations of subduction channels.
► The thickness of the channels are estimated to be about 2–3 km.
► Almost all of the continental materials subducted at the surface reach 300 km depth.
► Large amount of radiogenic elements can be redistributed to the deep mantle.