This 3-year PT excursion is the result of stress induced pressure (tectonic overpressure), frictional heating and melt assisted confined pressure (reaction overpressure). There is NO vertical movement of the rock. The PT diagram reflects the same scenario as that illustrated in the ‘logo’ for ShearToast.
I call this ‘pseudo-subduction’ because in a given rock it would appear as a subduction cycle, yet it is not.
Pseudo-Subduction:
Tectonic overpressure & Shear heating
When rocks record extreme excursions in a PT diagram has this traditionally been interpreted to reflect fast subduction and exhumation.
The rocks modeled to the left do not go up or down!!
