The External Massifs, relics of Variscan basement in the Alps

Abstract

Chemical and structural data give new insight into the complex metamorphic evolution of crystalline basement of the Helvetic Realm (Central and Western Alps). The relics of pre-Carboniferous basement — the so called External Massifs — may be subdivided into an older basement unit with a younger cover, which together suffered the following metamorphic evolution from late Caledonian until Variscan times: These results confirm that the External Massifs have to be interpreted as pieces of a former continental crust with a metamorphic evolution known from the mid-European Variscan crystalline basement.