Electron microprobe analyses of amphiboles and other metamorphic minerals give new information about
the metamorphic development in the Major and Minor Bergen Arcs in the Scandinavian Caledonides. The
composition of metamorphic amphiboles in Ashgillian-Llandoverian metasediments indicates that the
Caledonian metamorphism in the two arcs reached its peak of upper greenschist close to lower amphibolite
facies during the main Caledonian (Scandian) event (M2). This result is supported by high Al₂O_3/FeO + Fe₂O₃ ratios in white micas and by almandine-rich garnets. Medium pressures are indicated for this event. Old, unstable amphibole porphyroclasts are actinolites to actinolitic hornblendes, and indicate a pre-Ashgillian event (M1) of lower metamorphic grade.