Post-orogenic extension in the Aegean Sea has produced several metamorphic domes. Some domes ("b-type") are elongated perpendicular to the main N-S direction of extension, and they correspond to the exhumation of the middle crust along northdipping detachments. The example of Tinos shows the progressive localization of deformation from the initial boudinage at all scales to the formation of brittle structures at the tips of boudins and the selection of one of those, which becomes the main detachment. The progressive deformation leading to strain localization is described alongside the P-T-t evolution and the role of fl uid circulation. The second type of domes ("a-type") has a long axis parallel to the direction of extension. Extension is accommodated by a detachment that exhumes high-temperature gneisses issued from deeper parts of the Hellenic edifi ce. Shortening perpendicular to stretching has produced the extension-parallel folds that are also observed in b-type domes but to a lesser extent. The formation of b-type and then a-type domes during extension is discussed in terms of crustal collapse during slab retreat.

A field study in the coesite province, the deepest unit of the Norwegian Caledonides, gives new constraints on the rheological behaviour of the continental crust during exhumation. Lithological heterogeneities and differential retrogression led to crustal‐scale boudinage during the late‐orogenic intense E–W stretching event in the footwall of the Nordfjord‐Sogn Detachment. The main gneissic lithologies display a modest but widespread syn‐exhumation migmatization. Textural criteria allow estimation of a 30% fusion rate. Partial melting mostly post‐dates eclogitization and is synchronous with ductile stretching and top‐to‐west shearing. Presented observations suggest that the melt reactions and migmatization resulted in a soft rheology. During subduction to ~ 100 km depth and subsequent exhumation, crustal viscosity can be reduced by up to four orders of magnitude. Models are discussed that consider a transition from a small internal strain of the crust to viscous flow during exhumation.

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