Abstract
The geometry and field relationships of the gneisses and their associated rocks in the area immediately north-west of the Frederikshåbs Isblink reflect a complex intrusive, metamorphic and deformational history. All the rocks have been affected to a greater or lesser extent by amphibolite facies metamorphism and they comprise predominantly dark grey biotite and hornblende gneiss, together with thin anorthosites (mostly brecciated to white agmatites), intercalated striped green and dark grey amphibolite (sometimes garnetiferous), black hornblendites, gamet-kyanitesillimanite gneisses, sillimanite quartzites and pegmatitic pale creamy brown marbles and calc-silicate gneiss and fine-grained leucocratic gneisses. Early discordant layers include hornblendites, amphibolites, peridotites, silico-carbonatites and aplitic rocks.
Highlights
Discordant bodies late in the deformational sequence of the complex appear to be confined to veins and dykes of quartz, quartzo-feldspathic pegmatite and aplite
In some amphibolites gamet homblendite relics of such structures have a tadpole-like appearance and bear a slight resemblance to structures in the Ravns Storø metavolcanics (Windley et al, 1966, p.9). The relationships between these folds and a second set of isoclinal folds are well displayed in three dimensions in the thin quartzofeldspathic layers weathered from within the marbles where small scale examples of both fold sets are well developed
The F2 folded aplite veins which cross cut the carbonatite dykes are sometimes symmetrically zoned and rarely may contain scattered garnet. In the field they resemble the garnet 'rhyolitic' sheets of the Ravns Storø belt (Windley, 1968, p. 29) and mayaiso be equivalent to the gamet aplite noted by Williams
Summary
Discordant bodies late in the deformational sequence of the complex appear to be confined to veins and dykes of quartz, quartzo-feldspathic pegmatite and aplite. This foliation which is parallel to the axial planes of the F2 isoclinally folded aplite veins lies at a high angle to the contact between the dyke and the host amphibolite.
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