| Summary: | The rocks exposed on the eastern part of the island of Seiland are the metasedimentary envelope to the large basic and ultrabasic plutons that make up the western part of the island and the neighbouring island of Stjernoy. These metasediments have been intensely deformed and metamorphosed, thus all sedimentary structures have been obliterated. The metasedimentary sequence is, therefore, a structural one. The lowest group is the psammitic Komagnes Group. This is followed by the Eidvageid Schist Group which is followed by the relatively thin psammitic Trollvann Group. Structurally above this is the pelitic Olderbugten Group and finally the dominantly psammitic Olderfjord Group. Broadly speaking two major fold-forming deformations have been recognised; F.1 and F.2. The latter part of the first phase, which was responsible for tight isoclinal folds and a penetrative schistosity, was accompanied by intrusion of sheets of basic material parallel to the axial planes of the early folds. During the static interval separating the two deformations the maximum grade of metamorphism was achieved, this, however, varies across the area and a sequence of metamorphic isograds have been recognised. The highest grade occurs in the west and is marked by a kyanite-sillimanite porphyroblastesis, migmatisation and intrusion of adamellitic sheets. The lowest grade in the east is characterised by albite, biotite, epidote, hornblende assemblages in the psammites of the Lower Komagnes Group. These isograds reflect a contemporaneous lateral change in metamorphic grade. Following the development of these high grade assemblages in the west, there was a phase of intense flattening leading to the development of mylonitic textures in the rocks. It is suggested that this deformation phase is related to a rising basic asthenolith. The majority of folds on the area are attributed to F.2.By the onset of F.2. the metamorphic grade appears to have waned to sub-garnet grade conditions. The folds have a very variable style. In the east, they have ...
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