Both Barrovian and Buchan Facies series develop at such margins. Those of Precambrian age may represent convergent margins. As was the case in occurrences of Contact and Buchan Facies series rocks, metamorphic belts exhibiting Barrovian Facies Series do not always exhibit all of the facies possible within the series. Clearly this is the case in the Scottish Highlands, where Zeolite and Prehnite-Pumpellyite Facies are not described as part of the sequence. At the lowest grade, in the Zeolite Facies, which forms under conditions just above those of diagenesis, assemblages are characterized by clay minerals.
New phases appear, including albite, white mica and stilpnomelane.
As was the case in Buchan Facies Series, K feldspar and smectites are among the first minerals to disappear from aluminous rocks. Kaolinite also is commonly absent from Prehnite-Pumpellyite Facies rocks. As the P-T conditions increase, Greenschist Facies assemblages with new minerals form. As is the case in the Buchan Facies Series, the Greenschist-Amphibolite Facies boundary is a broad zone. The disappearance of albite marks the maximum upper limit of the Greenschist Facies.