Abstract
The distribution and main features of metamorphic zones within the diagenesis-metamorphism transition have been established from illite crystallinity and conodont colour alteration index data, and have permitted to distinguish two episodes of Variscan metamorphism in the Cantabrian Zone (CZ). The first episode is the regional metamorphism of NW Iberia; it is represented in small areas of the W, NW and SW parts of the CZ, where epizonal conditions are reached; a generalised cleavage is associated with this metamorphism; it is also present as a burial metamorphism which reaches anchizonal conditions in the basal part of some nappes, with the thermal peak occurring prior to the emplacement of the nappes. The second episode is a late-Variscan metamorphism which appears in two different forms: a diastathermal metamorphism which mainly develops in the central and south-eastern parts of the CZ and axhibits an associated cleavage which overprints most of the structures; and a contact metamorphism associated with minor intrusive bodies.
