High-strain zones from mesoto macro-scale at different structural levels, Central Norwegian Caledonides

High-strain shear zones of diverse character, metamorphic grade and scale occur in different tectonic settings in the Caledonides of Central Norway. Three specific examples are described. Strain products range from high-PT granulite to amphibolite-facies, thrust-related, Scandian mylonites at deep structural levels, to ultracataclasites and mylonites generated in the ductile to ductile-brittle transition regimes along the multiply reactivated, orogen-oblique Mّre-Trّndelag Fault Complex. In another example, geochemical data from a transformation of granite to mylonite at an intermediate structural level indicate that the high-strain change-over probably occurred as an open, volume-gain system involving silicification. In the case of the Mّre-Trّndelag Fault Complex, a sinistral strike-slip regime during Devonian time was coeval with regionally extensive top-to-the-SW shear in the country rocks outside the fault zone. Later components of movement along the multiphase fault zone, from latest Palaeozoic to Cenozoic time, were mainly of brittle, dip-slip to dextral strike- or oblique-slip character.