Intrusion history of the Portrush Sill, County Antrim, Northern Ireland : evidence for rapid emplacement and high-temperature contact metamorphism
The gabbroic Portrush Sill in Northern Ireland, part of the North Atlantic Igneous Province, intruded Lower Jurassic mudstones and siltstones about 55 Ma ago. We used petrologic observations and geochemical analyses to study how the sill interacted with the sedimentary rocks. Field relationships sho...
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2012
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ftnerc:oai:nora.nerc.ac.uk:16214 2023-05-15T17:34:05+02:00 Intrusion history of the Portrush Sill, County Antrim, Northern Ireland : evidence for rapid emplacement and high-temperature contact metamorphism Ledevin, Morgane Arndt, Nicholas Cooper, Mark R. Earls, Garth Lyle, Paul Aubourg, Charles Lewin, Eric 2012 text http://nora.nerc.ac.uk/id/eprint/16214/ https://nora.nerc.ac.uk/id/eprint/16214/1/PortrushSill.pdf http://geolmag.geoscienceworld.org/content/149/1.toc en eng Cambridge University Press https://nora.nerc.ac.uk/id/eprint/16214/1/PortrushSill.pdf Ledevin, Morgane; Arndt, Nicholas; Cooper, Mark R.; Earls, Garth; Lyle, Paul; Aubourg, Charles; Lewin, Eric. 2012 Intrusion history of the Portrush Sill, County Antrim, Northern Ireland : evidence for rapid emplacement and high-temperature contact metamorphism. Geological Magazine, 149 (1). 67-79. https://doi.org/10.1017/S0016756811000537 <https://doi.org/10.1017/S0016756811000537> Publication - Article PeerReviewed 2012 ftnerc https://doi.org/10.1017/S0016756811000537 2023-02-04T19:30:22Z The gabbroic Portrush Sill in Northern Ireland, part of the North Atlantic Igneous Province, intruded Lower Jurassic mudstones and siltstones about 55 Ma ago. We used petrologic observations and geochemical analyses to study how the sill interacted with the sedimentary rocks. Field relationships show that an Upper Sill and numerous associated Minor Intrusions were emplaced in the sedimentary host rocks before intrusion of the Main Sill, some 10 m above its upper contact. Geochemical analyses reveal two magma contamination processes: Nb and Ta anomalies, coupled with incompatible element enrichment, record contamination by deep crustal rocks, whereas Li, Pb and Ba anomalies reveal a superficial contamination through fluid circulation at the contact between magmatic and sedimentary rocks. Analysis of mineral assemblages and geochemical data from the contact aureole demonstrate uniform metamorphic conditions between the two main intrusions and an absence of a thermal gradient. The identification of pyrrhotite by magnetization analyses and of orthopyroxene by microprobe analyses indicates very high temperatures, up to 660°C. Thermal modelling explains these temperatures as the coupled effects of the Main Sill and the earlier intruded Upper Sill and Minor Intrusions. Even though the chemical composition of the Main Sill suggests another type of parental liquid, all three units were emplaced in a very short time, certainly less than five years. Article in Journal/Newspaper North Atlantic Natural Environment Research Council: NERC Open Research Archive Geological Magazine 149 1 67 79 |
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Open Polar |
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Natural Environment Research Council: NERC Open Research Archive |
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ftnerc |
language |
English |
description |
The gabbroic Portrush Sill in Northern Ireland, part of the North Atlantic Igneous Province, intruded Lower Jurassic mudstones and siltstones about 55 Ma ago. We used petrologic observations and geochemical analyses to study how the sill interacted with the sedimentary rocks. Field relationships show that an Upper Sill and numerous associated Minor Intrusions were emplaced in the sedimentary host rocks before intrusion of the Main Sill, some 10 m above its upper contact. Geochemical analyses reveal two magma contamination processes: Nb and Ta anomalies, coupled with incompatible element enrichment, record contamination by deep crustal rocks, whereas Li, Pb and Ba anomalies reveal a superficial contamination through fluid circulation at the contact between magmatic and sedimentary rocks. Analysis of mineral assemblages and geochemical data from the contact aureole demonstrate uniform metamorphic conditions between the two main intrusions and an absence of a thermal gradient. The identification of pyrrhotite by magnetization analyses and of orthopyroxene by microprobe analyses indicates very high temperatures, up to 660°C. Thermal modelling explains these temperatures as the coupled effects of the Main Sill and the earlier intruded Upper Sill and Minor Intrusions. Even though the chemical composition of the Main Sill suggests another type of parental liquid, all three units were emplaced in a very short time, certainly less than five years. |
format |
Article in Journal/Newspaper |
author |
Ledevin, Morgane Arndt, Nicholas Cooper, Mark R. Earls, Garth Lyle, Paul Aubourg, Charles Lewin, Eric |
spellingShingle |
Ledevin, Morgane Arndt, Nicholas Cooper, Mark R. Earls, Garth Lyle, Paul Aubourg, Charles Lewin, Eric Intrusion history of the Portrush Sill, County Antrim, Northern Ireland : evidence for rapid emplacement and high-temperature contact metamorphism |
author_facet |
Ledevin, Morgane Arndt, Nicholas Cooper, Mark R. Earls, Garth Lyle, Paul Aubourg, Charles Lewin, Eric |
author_sort |
Ledevin, Morgane |
title |
Intrusion history of the Portrush Sill, County Antrim, Northern Ireland : evidence for rapid emplacement and high-temperature contact metamorphism |
title_short |
Intrusion history of the Portrush Sill, County Antrim, Northern Ireland : evidence for rapid emplacement and high-temperature contact metamorphism |
title_full |
Intrusion history of the Portrush Sill, County Antrim, Northern Ireland : evidence for rapid emplacement and high-temperature contact metamorphism |
title_fullStr |
Intrusion history of the Portrush Sill, County Antrim, Northern Ireland : evidence for rapid emplacement and high-temperature contact metamorphism |
title_full_unstemmed |
Intrusion history of the Portrush Sill, County Antrim, Northern Ireland : evidence for rapid emplacement and high-temperature contact metamorphism |
title_sort |
intrusion history of the portrush sill, county antrim, northern ireland : evidence for rapid emplacement and high-temperature contact metamorphism |
publisher |
Cambridge University Press |
publishDate |
2012 |
url |
http://nora.nerc.ac.uk/id/eprint/16214/ https://nora.nerc.ac.uk/id/eprint/16214/1/PortrushSill.pdf http://geolmag.geoscienceworld.org/content/149/1.toc |
genre |
North Atlantic |
genre_facet |
North Atlantic |
op_relation |
https://nora.nerc.ac.uk/id/eprint/16214/1/PortrushSill.pdf Ledevin, Morgane; Arndt, Nicholas; Cooper, Mark R.; Earls, Garth; Lyle, Paul; Aubourg, Charles; Lewin, Eric. 2012 Intrusion history of the Portrush Sill, County Antrim, Northern Ireland : evidence for rapid emplacement and high-temperature contact metamorphism. Geological Magazine, 149 (1). 67-79. https://doi.org/10.1017/S0016756811000537 <https://doi.org/10.1017/S0016756811000537> |
op_doi |
https://doi.org/10.1017/S0016756811000537 |
container_title |
Geological Magazine |
container_volume |
149 |
container_issue |
1 |
container_start_page |
67 |
op_container_end_page |
79 |
_version_ |
1766132804144332800 |