Marble dykes emanating from marble layers in an amphibolite-facies, multiply-deformed carbonate succession, Troms, northern Norway
In one of the higher nappes of the Caledonides of Troms, northern Norway, rare thin dykes of calcite marble lie subparallel to the axial surfaces of folds in multilayered marble beds. The dykes emanate from pure calcite marble layers mostly in or close to the hinge zones of these flat-lying, tight t...
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Cambridge University Press (CUP)
2007
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Online Access: | http://dx.doi.org/10.1017/s0016756807003810 https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0016756807003810 |
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crcambridgeupr:10.1017/s0016756807003810 2024-09-15T18:25:49+00:00 Marble dykes emanating from marble layers in an amphibolite-facies, multiply-deformed carbonate succession, Troms, northern Norway ROBERTS, DAVID BOUKE ZWAAN, KLAAS 2007 http://dx.doi.org/10.1017/s0016756807003810 https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0016756807003810 en eng Cambridge University Press (CUP) https://www.cambridge.org/core/terms Geological Magazine volume 144, issue 5, page 883-888 ISSN 0016-7568 1469-5081 journal-article 2007 crcambridgeupr https://doi.org/10.1017/s0016756807003810 2024-07-17T04:03:00Z In one of the higher nappes of the Caledonides of Troms, northern Norway, rare thin dykes of calcite marble lie subparallel to the axial surfaces of folds in multilayered marble beds. The dykes emanate from pure calcite marble layers mostly in or close to the hinge zones of these flat-lying, tight to sub-isoclinal, F3 folds. In many cases, they appear to penetrate along the axial surfaces of these same folds, and there is an up to 10° angular disparity between dyke orientation and axial surfaces. The dykes are considered to have originated, and been expelled, from parent calcite marble layers either at or shortly after the peak of amphibolite-facies metamorphism between the D2 and D3 deformation phases of the Scandian orogeny. The dykes display a dyke-parallel, dark grey to white, colour banding, the origin of which is uncertain at present. In thin-section, an equigranular texture is dominated by 2–3 mm, equant, unstrained, calcite grains with straight boundaries and low- T twin lamellae, denoting a late-stage recrystallization. A weak, oblique, calcite grain-shape orientation fabric curves into a dyke-parallel alignment along the finer-grained margins, reflecting the simple-shear deformation imposed on the host rock. Regarding the initiation of these marble dykes, it seems likely that a combination of P–T conditions and possibly partial melting processes was conducive to generating extreme ductility/superplasticity, at least locally, and that this led to the sudden expulsion of a partially molten carbonate aggregate which had momentarily attained a critical pressure and intruded preferentially along available, transient fractures prior to the imposition of the D3 simple-shear regime. Article in Journal/Newspaper Northern Norway Troms Cambridge University Press Geological Magazine 144 5 883 888 |
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Cambridge University Press |
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English |
description |
In one of the higher nappes of the Caledonides of Troms, northern Norway, rare thin dykes of calcite marble lie subparallel to the axial surfaces of folds in multilayered marble beds. The dykes emanate from pure calcite marble layers mostly in or close to the hinge zones of these flat-lying, tight to sub-isoclinal, F3 folds. In many cases, they appear to penetrate along the axial surfaces of these same folds, and there is an up to 10° angular disparity between dyke orientation and axial surfaces. The dykes are considered to have originated, and been expelled, from parent calcite marble layers either at or shortly after the peak of amphibolite-facies metamorphism between the D2 and D3 deformation phases of the Scandian orogeny. The dykes display a dyke-parallel, dark grey to white, colour banding, the origin of which is uncertain at present. In thin-section, an equigranular texture is dominated by 2–3 mm, equant, unstrained, calcite grains with straight boundaries and low- T twin lamellae, denoting a late-stage recrystallization. A weak, oblique, calcite grain-shape orientation fabric curves into a dyke-parallel alignment along the finer-grained margins, reflecting the simple-shear deformation imposed on the host rock. Regarding the initiation of these marble dykes, it seems likely that a combination of P–T conditions and possibly partial melting processes was conducive to generating extreme ductility/superplasticity, at least locally, and that this led to the sudden expulsion of a partially molten carbonate aggregate which had momentarily attained a critical pressure and intruded preferentially along available, transient fractures prior to the imposition of the D3 simple-shear regime. |
format |
Article in Journal/Newspaper |
author |
ROBERTS, DAVID BOUKE ZWAAN, KLAAS |
spellingShingle |
ROBERTS, DAVID BOUKE ZWAAN, KLAAS Marble dykes emanating from marble layers in an amphibolite-facies, multiply-deformed carbonate succession, Troms, northern Norway |
author_facet |
ROBERTS, DAVID BOUKE ZWAAN, KLAAS |
author_sort |
ROBERTS, DAVID |
title |
Marble dykes emanating from marble layers in an amphibolite-facies, multiply-deformed carbonate succession, Troms, northern Norway |
title_short |
Marble dykes emanating from marble layers in an amphibolite-facies, multiply-deformed carbonate succession, Troms, northern Norway |
title_full |
Marble dykes emanating from marble layers in an amphibolite-facies, multiply-deformed carbonate succession, Troms, northern Norway |
title_fullStr |
Marble dykes emanating from marble layers in an amphibolite-facies, multiply-deformed carbonate succession, Troms, northern Norway |
title_full_unstemmed |
Marble dykes emanating from marble layers in an amphibolite-facies, multiply-deformed carbonate succession, Troms, northern Norway |
title_sort |
marble dykes emanating from marble layers in an amphibolite-facies, multiply-deformed carbonate succession, troms, northern norway |
publisher |
Cambridge University Press (CUP) |
publishDate |
2007 |
url |
http://dx.doi.org/10.1017/s0016756807003810 https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0016756807003810 |
genre |
Northern Norway Troms |
genre_facet |
Northern Norway Troms |
op_source |
Geological Magazine volume 144, issue 5, page 883-888 ISSN 0016-7568 1469-5081 |
op_rights |
https://www.cambridge.org/core/terms |
op_doi |
https://doi.org/10.1017/s0016756807003810 |
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Geological Magazine |
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144 |
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5 |
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883 |
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