Fluids, rather than pressure and temperature conditions, are the key thing that makes the process of eclogitization, and the delamination (falling away) of crustal roots, in collisional orogens (fold mountains), possible.
An influx of fluids into the subduction zone or from the underlying mantle is vital for these metamorphic reactions to continue - fluids play a much more significant role in eclogite metamorphism than either temperature or pressure [REF].