I am looking for information on the dehydration of seamount chains (i.e. the Juan Fernández Ridge in the Andean subduction zone) and their effect on the thermal state of the lithosphere. Until which depth a seamount chain is dehydrated? What is the effect on seismic velocities? From what I understand, the increased seawater circulation would cool down the lithosphere, thus leading to an increase of seismic velocities. Nevertheless, the presence of fluids would have the opposite effect on the velocities. Which process is more important then?

I'm grateful for any information about this topic.