. Do you have the outcrop availablle? I think seeing this in the field may show you whether its a ontct metamorphic or igneous country rock
Usually that admix of sanidine and mucovite is a blueschist facies rock, so Id be looking for associates in thin section,(look for magnetite or other heavy) They usually lie along the pre metamorphic fbric.
So Id be looking at the microfabric in hand and under the scope. Then, Id do an oriented thin section.