The precambrian metamorphic rocks around the lake Vegår (Aust-Agder, southern Norway).
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An area about 2000 km between the Skagerak coast (Tvedestrand - Risør) and the Southern part of the Telemark province (Tjønefoss - Neslandvatn) has been investigated and is considered to be a genetically homogenous migmatitic complex. The evolution of the rocks is supposed to represent an orogenic development in which 3 fundamental phases have been recognized: 1) Deposition of geosynclinal supracrustals (mainly detrital or peltic sediments and basic intrusions). 2) Widespread migmarization as a consequence of deformation and intermediate pressure regional metamorphism (Caledonian type). The grade of metamorphism is essentially controlled by theavailable amount of water as a free gazeous phase and decreases regularly from the Skagerak coast (hornblende granulite subfacies) towards the Telemark (low ampholite facies). 3) Local retrograde metamorphism in elongated zones which have remained mobile well after the end regional migmatization. In connection with this late diapthoresis important movements brought in contact areas at different stages of migmatitic evolution, particularly the catazonal and deep catazonal Bamble and the mesozonal Telemark domains.