The palaeomagnetism of the central zone of the Lewisian foreland, north-west Scotland
Three principal directions of magnetization are recognized in the central part of the Lewisian metamorphic terrain of north-west Scotland. The first (‘A’) magnetization is a high blocking temperature component residing in magnetite and imposed during post-Laxfordian uplift and cooling. Fifty sites y...
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Oxford University Press
1979
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fthighwire:oai:open-archive.highwire.org:gji:59/1/101 2023-05-15T17:35:33+02:00 The palaeomagnetism of the central zone of the Lewisian foreland, north-west Scotland Piper, J. D. A. 1979-10-01 00:00:00.0 text/html http://gji.oxfordjournals.org/cgi/content/short/59/1/101 https://doi.org/10.1111/j.1365-246X.1979.tb02554.x en eng Oxford University Press http://gji.oxfordjournals.org/cgi/content/short/59/1/101 http://dx.doi.org/10.1111/j.1365-246X.1979.tb02554.x Copyright (C) 1979, Oxford University Press Articles TEXT 1979 fthighwire https://doi.org/10.1111/j.1365-246X.1979.tb02554.x 2013-05-27T00:18:19Z Three principal directions of magnetization are recognized in the central part of the Lewisian metamorphic terrain of north-west Scotland. The first (‘A’) magnetization is a high blocking temperature component residing in magnetite and imposed during post-Laxfordian uplift and cooling. Fifty sites yield an overall mean D = 285.9°, I = 54.9° and palaeomagnetic pole at 273.2° E, 37.6° N ( dp = 3.7°, dm = 5.2°); this magnetization was probably acquired at crustal depths of 6–10 km and is linked to K—Ar uplift ages averaging 1650–1625 Ma. The second (‘B’) magnetizations are defined by E—W directions and also reside in high blocking temperature components; they are, however, dipolar, have some properties distinct from the ‘A’ magnetizations, and are correlated with late stages in the history of the complex at 1400–1200 Ma. The third (‘C’) NE directed magnetizations reside predominantly in low blocking temperature components in pyrrhotite and possibly maghemite, and were probably acquired at a late stage of the regional uplift; they do not correlate with post-1450 Ma magnetizations from the Laurentian Shield and probably relate to the as yet undefined interval 1600–1450 Ma. The collective palaeomagnetic data and certain geologic data suggest that the Lewisian foreland should be rotated by 30° clockwise about a local axis of rotation on the conventional reconstruction of the North Atlantic continents; this rotation is associated with Lower Palaeozoic trans-current movements and may be related to a fourth (‘D’) magnetization of viscous origin. A collective assessment of 1850–1600 Ma palaeomagnetic data for the Laurentian Shield defines a large apw loop; there is widespread agreement between data from the constituent structural provinces of the Shield although different metamorphic regions define complementary segments of the loop related to uplift over different intervals of time. Text North Atlantic HighWire Press (Stanford University) Geophysical Journal International 59 1 101 122 |
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Articles Piper, J. D. A. The palaeomagnetism of the central zone of the Lewisian foreland, north-west Scotland |
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Three principal directions of magnetization are recognized in the central part of the Lewisian metamorphic terrain of north-west Scotland. The first (‘A’) magnetization is a high blocking temperature component residing in magnetite and imposed during post-Laxfordian uplift and cooling. Fifty sites yield an overall mean D = 285.9°, I = 54.9° and palaeomagnetic pole at 273.2° E, 37.6° N ( dp = 3.7°, dm = 5.2°); this magnetization was probably acquired at crustal depths of 6–10 km and is linked to K—Ar uplift ages averaging 1650–1625 Ma. The second (‘B’) magnetizations are defined by E—W directions and also reside in high blocking temperature components; they are, however, dipolar, have some properties distinct from the ‘A’ magnetizations, and are correlated with late stages in the history of the complex at 1400–1200 Ma. The third (‘C’) NE directed magnetizations reside predominantly in low blocking temperature components in pyrrhotite and possibly maghemite, and were probably acquired at a late stage of the regional uplift; they do not correlate with post-1450 Ma magnetizations from the Laurentian Shield and probably relate to the as yet undefined interval 1600–1450 Ma. The collective palaeomagnetic data and certain geologic data suggest that the Lewisian foreland should be rotated by 30° clockwise about a local axis of rotation on the conventional reconstruction of the North Atlantic continents; this rotation is associated with Lower Palaeozoic trans-current movements and may be related to a fourth (‘D’) magnetization of viscous origin. A collective assessment of 1850–1600 Ma palaeomagnetic data for the Laurentian Shield defines a large apw loop; there is widespread agreement between data from the constituent structural provinces of the Shield although different metamorphic regions define complementary segments of the loop related to uplift over different intervals of time. |
format |
Text |
author |
Piper, J. D. A. |
author_facet |
Piper, J. D. A. |
author_sort |
Piper, J. D. A. |
title |
The palaeomagnetism of the central zone of the Lewisian foreland, north-west Scotland |
title_short |
The palaeomagnetism of the central zone of the Lewisian foreland, north-west Scotland |
title_full |
The palaeomagnetism of the central zone of the Lewisian foreland, north-west Scotland |
title_fullStr |
The palaeomagnetism of the central zone of the Lewisian foreland, north-west Scotland |
title_full_unstemmed |
The palaeomagnetism of the central zone of the Lewisian foreland, north-west Scotland |
title_sort |
palaeomagnetism of the central zone of the lewisian foreland, north-west scotland |
publisher |
Oxford University Press |
publishDate |
1979 |
url |
http://gji.oxfordjournals.org/cgi/content/short/59/1/101 https://doi.org/10.1111/j.1365-246X.1979.tb02554.x |
genre |
North Atlantic |
genre_facet |
North Atlantic |
op_relation |
http://gji.oxfordjournals.org/cgi/content/short/59/1/101 http://dx.doi.org/10.1111/j.1365-246X.1979.tb02554.x |
op_rights |
Copyright (C) 1979, Oxford University Press |
op_doi |
https://doi.org/10.1111/j.1365-246X.1979.tb02554.x |
container_title |
Geophysical Journal International |
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59 |
container_issue |
1 |
container_start_page |
101 |
op_container_end_page |
122 |
_version_ |
1766134747265761280 |