Efficiency and depth of H2O recycling from a modelling perspective

The recycling of volatiles like H₂O from the surface into the interior is critical as it influences the physical and chemical properties of the mantle. One of the essential effects H₂O has on the mantle is the reduction of the solidus temperature, as this can trigger partial melting. On the one hand, the process of partial melting is vital for arc and ore deposit formation. On the other hand, it is thought to be a requirement for the generation of the continental crust.

Even though intensive work has been done on investigating the stability fields of hydrous phases experimentally and thermodynamically depending on pressure, temperature, and composition, it is still debated to which depths and in which quantities H₂O can be recycled. However, the parameters influencing the mineral stability and break-down (e.g., pressure, temperature, composition, oxygen fugacity) change constantly during the recycling process. To include these changes, global convection models are required which take the varying conditions over time into account. While numerous studies exist, that model the subduction process itself, the recycling of H₂O is not considered to date in most of the simulations, or strongly simplified models are applied.

We model the quantity of H₂O that can be recycled as well as the depth to which the recycling is possible. For this purpose, we test individual parameters affecting the H₂O recycling and dehydration from the subducting slab. To benchmark our simulations, we compare our results with seismological observations of the Pacific plate subducting beneath northeast Japan.