Ma to happen. It was preceded by ophiolite obduction and post-dated by orogenic collapse and basin formation. Our main area of interest, the Western Gneiss Region, contains important occurrences of continental crust, parts of which were once buried very deeply within the lithosphere. Just how deeply, and how these rocks reached the surface, are issues that we shall address here. You can link to the specific task list here Timing.
Metamorphic rocks are complex.
They record a history of events. So unlike many igneous rocks for example, the geochronology of metamorphic rocks is complex. A metamorphic rock may have formed and been reformed again. These give parts of the cooling history of the rocks. They are effectively unmetamorphosed.