The eclogite and granulite metamorphic Caledonian orogenic root of South Norway

Western Gneiss Region of South Norway has been famous for its eclogites since the first descriptions in 1921. Eclogites are metamorphic rocks formed at high temperature and pressures in the deep crust of orogenic root zones, while granulites are characterized as metamorphic rocks formed at high temperatures. The talk will give a brief introduction to the eclogites and the geology of Western Gneiss Region. It will give examples of eclogite, granulites and sillimanite gneisses from the high-pressure and ultra-high pressure regions with respect to its petrological evolution and tectonic implications. From the northwestern-most coastal area of South Norway the data support an evolution where the eclogite facies crust underwent decompression during heating into high-pressure granulite facies conditions. The host gneisses underwent migmatitisation, followed by amphibolitisation. Our investigation gives a regional petrological description in this area, and documents and illustrates an extensive high-temperature equilibration in the Caledonian root zone subsequent to the deep crustal burial.