Geological investigations in the Bamble sector of the Fennoscandian Shield South Norway. I. The geology of eastern Bamble.
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- Artikler 
This paper, based upon a recent survey on a scale of 1:15 000, constitutes a description of the geology and broad structural aspects of the E. Bamble regiom, S. Norway. Two principle groups of Precambrian metamorphics and intrusives are recognized, namely: (1) those exhibiting only localized, minor cataclasis and (2) characterized by cataclasis. The latter group occupies a 4-5 km wide zone in the north of the region. All of these rocks have undergone regional metamorphism under the P-T conditions of the almandine-amphibolite facies. Assemblages diagnostic of both the sillimanite-almandine-orthoclase subfacies and the sillimanite-almandine-muscovite subfacies of the almandine-amphibolite facies are common. Occasionally assemblages suggestive of the hornblende-granulite- or the pyroxene-granulite-subfacies of the granulite facies were noted. Retrograde metamorphism or distinct, lowergrade thermal regimes are indicated by the presence of epidote, chlorite and prehnite. A group of metasediments, representing pre-existing sandstones, arkoses and argillaceous rocks, has been partially mobilized and affected by injection of syntectonic granitic and gabbroic rocks. Granitic, granodioritic and quartz-dioritic gneisses are common throughout the region and are thought to have been derived by anatexis within a meta-sedimentary-metavolcanic sequence.