The Iceland Research Drilling Project crustal section: stable remagnetization below 3 km crustal depth
A section at below 3.1 km depth in Icelandic crust, sampled in the 1978 Icelandic Research Drilling Project drill hole, contains a number of subaerially deposited lava flows showing both downwards and probably original upwards inclinations of cleaned, stable remanent magnetization. Such "mixed...
Published in: | Canadian Journal of Earth Sciences |
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Language: | English |
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Canadian Science Publishing
1988
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Online Access: | http://dx.doi.org/10.1139/e88-125 http://www.nrcresearchpress.com/doi/pdf/10.1139/e88-125 |
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crcansciencepubl:10.1139/e88-125 2023-12-17T10:32:18+01:00 The Iceland Research Drilling Project crustal section: stable remagnetization below 3 km crustal depth Hall, James M. Fisher, Brian E. 1988 http://dx.doi.org/10.1139/e88-125 http://www.nrcresearchpress.com/doi/pdf/10.1139/e88-125 en eng Canadian Science Publishing http://www.nrcresearchpress.com/page/about/CorporateTextAndDataMining Canadian Journal of Earth Sciences volume 25, issue 8, page 1304-1315 ISSN 0008-4077 1480-3313 General Earth and Planetary Sciences journal-article 1988 crcansciencepubl https://doi.org/10.1139/e88-125 2023-11-19T13:38:54Z A section at below 3.1 km depth in Icelandic crust, sampled in the 1978 Icelandic Research Drilling Project drill hole, contains a number of subaerially deposited lava flows showing both downwards and probably original upwards inclinations of cleaned, stable remanent magnetization. Such "mixed polarities" are inconsistent with an initial cooling thermoremanent origin for the magnetization. An attempt is made to identify the factors involved in producing these mixed polarities and to consider the possible wider importance of the results. The mixed-polarity flows have experienced intense hydrothermal alteration, followed by the widespread deposition of secondary magnetite. Secondary magnetite, which is formed in relatively anhydrous conditions associated with dike intrusion, dominates primary magnetite volumetrically where dike density locally exceeds about 30%.Where secondary magnetite is very dominant or is the only type of magnetite present, directional remagnetization appears to be uniform and complete. Where secondary and primary magnetite are both important, relatively high remanence and saturation magnetizations, total magnetite and primary magnetite grain size, and low deuteric oxidation state of primary magnetite are all associated with downwards directional remagnetization. It appears that a complex balance of the properties and history of primary and secondary magnetite, in addition to the relative abundances of these phases, controls the final stable polarity of samples.If the narrow transition zones between little-altered extrusives, greenschist-facies flows and dikes of the Troodos (Cyprus) ophiolite, and DSDP hole 504B are typical of oceanic crust, a narrow ~0.2 km interval of mixed polarities may be underlain in some locations by an intermediate crustal layer in polarity opposition with the uppermost, little-altered, extrusive layer. Article in Journal/Newspaper Iceland Canadian Science Publishing (via Crossref) Canadian Journal of Earth Sciences 25 8 1304 1315 |
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Open Polar |
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Canadian Science Publishing (via Crossref) |
op_collection_id |
crcansciencepubl |
language |
English |
topic |
General Earth and Planetary Sciences |
spellingShingle |
General Earth and Planetary Sciences Hall, James M. Fisher, Brian E. The Iceland Research Drilling Project crustal section: stable remagnetization below 3 km crustal depth |
topic_facet |
General Earth and Planetary Sciences |
description |
A section at below 3.1 km depth in Icelandic crust, sampled in the 1978 Icelandic Research Drilling Project drill hole, contains a number of subaerially deposited lava flows showing both downwards and probably original upwards inclinations of cleaned, stable remanent magnetization. Such "mixed polarities" are inconsistent with an initial cooling thermoremanent origin for the magnetization. An attempt is made to identify the factors involved in producing these mixed polarities and to consider the possible wider importance of the results. The mixed-polarity flows have experienced intense hydrothermal alteration, followed by the widespread deposition of secondary magnetite. Secondary magnetite, which is formed in relatively anhydrous conditions associated with dike intrusion, dominates primary magnetite volumetrically where dike density locally exceeds about 30%.Where secondary magnetite is very dominant or is the only type of magnetite present, directional remagnetization appears to be uniform and complete. Where secondary and primary magnetite are both important, relatively high remanence and saturation magnetizations, total magnetite and primary magnetite grain size, and low deuteric oxidation state of primary magnetite are all associated with downwards directional remagnetization. It appears that a complex balance of the properties and history of primary and secondary magnetite, in addition to the relative abundances of these phases, controls the final stable polarity of samples.If the narrow transition zones between little-altered extrusives, greenschist-facies flows and dikes of the Troodos (Cyprus) ophiolite, and DSDP hole 504B are typical of oceanic crust, a narrow ~0.2 km interval of mixed polarities may be underlain in some locations by an intermediate crustal layer in polarity opposition with the uppermost, little-altered, extrusive layer. |
format |
Article in Journal/Newspaper |
author |
Hall, James M. Fisher, Brian E. |
author_facet |
Hall, James M. Fisher, Brian E. |
author_sort |
Hall, James M. |
title |
The Iceland Research Drilling Project crustal section: stable remagnetization below 3 km crustal depth |
title_short |
The Iceland Research Drilling Project crustal section: stable remagnetization below 3 km crustal depth |
title_full |
The Iceland Research Drilling Project crustal section: stable remagnetization below 3 km crustal depth |
title_fullStr |
The Iceland Research Drilling Project crustal section: stable remagnetization below 3 km crustal depth |
title_full_unstemmed |
The Iceland Research Drilling Project crustal section: stable remagnetization below 3 km crustal depth |
title_sort |
iceland research drilling project crustal section: stable remagnetization below 3 km crustal depth |
publisher |
Canadian Science Publishing |
publishDate |
1988 |
url |
http://dx.doi.org/10.1139/e88-125 http://www.nrcresearchpress.com/doi/pdf/10.1139/e88-125 |
genre |
Iceland |
genre_facet |
Iceland |
op_source |
Canadian Journal of Earth Sciences volume 25, issue 8, page 1304-1315 ISSN 0008-4077 1480-3313 |
op_rights |
http://www.nrcresearchpress.com/page/about/CorporateTextAndDataMining |
op_doi |
https://doi.org/10.1139/e88-125 |
container_title |
Canadian Journal of Earth Sciences |
container_volume |
25 |
container_issue |
8 |
container_start_page |
1304 |
op_container_end_page |
1315 |
_version_ |
1785585873268506624 |