U-Pb ages and tectono-magmatic evolution of Middle Ordovician volcanic rocks of the Wild Bight Group, Newfoundland Appalachians
The Wild Bight Group and spatially associated South Lake Igneous Complex form one of the Ordovician oceanic terranes of the central mobile belt of the Newfoundland Appalachians. An integrated study of these rocks, involving detailed mapping, geochemistry, Sm-Nd isotopic analyses and U-Pb geochronolo...
Published in: | Canadian Journal of Earth Sciences |
---|---|
Main Authors: | , |
Format: | Article in Journal/Newspaper |
Language: | English |
Published: |
Canadian Science Publishing
1998
|
Subjects: | |
Online Access: | http://dx.doi.org/10.1139/e98-050 http://www.nrcresearchpress.com/doi/pdf/10.1139/e98-050 |
id |
crcansciencepubl:10.1139/e98-050 |
---|---|
record_format |
openpolar |
spelling |
crcansciencepubl:10.1139/e98-050 2023-12-17T10:44:48+01:00 U-Pb ages and tectono-magmatic evolution of Middle Ordovician volcanic rocks of the Wild Bight Group, Newfoundland Appalachians MacLachlan, Kate Dunning, Greg 1998 http://dx.doi.org/10.1139/e98-050 http://www.nrcresearchpress.com/doi/pdf/10.1139/e98-050 en eng Canadian Science Publishing http://www.nrcresearchpress.com/page/about/CorporateTextAndDataMining Canadian Journal of Earth Sciences volume 35, issue 9, page 998-1017 ISSN 0008-4077 1480-3313 General Earth and Planetary Sciences journal-article 1998 crcansciencepubl https://doi.org/10.1139/e98-050 2023-11-19T13:38:19Z The Wild Bight Group and spatially associated South Lake Igneous Complex form one of the Ordovician oceanic terranes of the central mobile belt of the Newfoundland Appalachians. An integrated study of these rocks, involving detailed mapping, geochemistry, Sm-Nd isotopic analyses and U-Pb geochronology, has shown that there are two temporally and genetically distinct volcanic sequences within the Wild Bight Group. The younger sequence comprises a lower volcanic succession associated with coarse volcaniclastic rocks and an upper volcanic succession interbedded with argillite, chert, and minor greywacke. The lower volcanic succession has calc-alkaline affinties, and isotopic evidence for minor crustal contamination. It is interpreted to represent a volcanic arc formed in proximity to the Gondwanan margin, above an east-dipping subduction zone. The age of this volcanic sequence is confined to 472 ± 3 Ma by felsic tuffs which occur stratigraphically above and below it. The upper volcanic unit has predominantly enriched tholeiitic to alkaline geochemical characteristics with isotopic signatures indicative of little or no crustal contamination, and is interpreted to represent arc rifting. The age of this sequence was determined indirectly by dating two geochemically related gabbro sills (472 +2 -9 Ma and 471 ± 4 Ma). This work shows that despite different lithologies and stratigraphic and structural relationships between Early and Middle Ordovician sequences in the northern and southern Exploits Subzone, they have undergone essentially the same tectono-magmatic events. The age constraints on the magmatic events in the Wild Bight Group provide evidence for the timing of "obduction" of Early Ordovician oceanic sequences and the reversal of subduction polarity along the Gondwanan margin, suggested by previous workers. Article in Journal/Newspaper Newfoundland Canadian Science Publishing (via Crossref) Wild Bight ENVELOPE(-54.831,-54.831,49.600,49.600) Canadian Journal of Earth Sciences 35 9 998 1017 |
institution |
Open Polar |
collection |
Canadian Science Publishing (via Crossref) |
op_collection_id |
crcansciencepubl |
language |
English |
topic |
General Earth and Planetary Sciences |
spellingShingle |
General Earth and Planetary Sciences MacLachlan, Kate Dunning, Greg U-Pb ages and tectono-magmatic evolution of Middle Ordovician volcanic rocks of the Wild Bight Group, Newfoundland Appalachians |
topic_facet |
General Earth and Planetary Sciences |
description |
The Wild Bight Group and spatially associated South Lake Igneous Complex form one of the Ordovician oceanic terranes of the central mobile belt of the Newfoundland Appalachians. An integrated study of these rocks, involving detailed mapping, geochemistry, Sm-Nd isotopic analyses and U-Pb geochronology, has shown that there are two temporally and genetically distinct volcanic sequences within the Wild Bight Group. The younger sequence comprises a lower volcanic succession associated with coarse volcaniclastic rocks and an upper volcanic succession interbedded with argillite, chert, and minor greywacke. The lower volcanic succession has calc-alkaline affinties, and isotopic evidence for minor crustal contamination. It is interpreted to represent a volcanic arc formed in proximity to the Gondwanan margin, above an east-dipping subduction zone. The age of this volcanic sequence is confined to 472 ± 3 Ma by felsic tuffs which occur stratigraphically above and below it. The upper volcanic unit has predominantly enriched tholeiitic to alkaline geochemical characteristics with isotopic signatures indicative of little or no crustal contamination, and is interpreted to represent arc rifting. The age of this sequence was determined indirectly by dating two geochemically related gabbro sills (472 +2 -9 Ma and 471 ± 4 Ma). This work shows that despite different lithologies and stratigraphic and structural relationships between Early and Middle Ordovician sequences in the northern and southern Exploits Subzone, they have undergone essentially the same tectono-magmatic events. The age constraints on the magmatic events in the Wild Bight Group provide evidence for the timing of "obduction" of Early Ordovician oceanic sequences and the reversal of subduction polarity along the Gondwanan margin, suggested by previous workers. |
format |
Article in Journal/Newspaper |
author |
MacLachlan, Kate Dunning, Greg |
author_facet |
MacLachlan, Kate Dunning, Greg |
author_sort |
MacLachlan, Kate |
title |
U-Pb ages and tectono-magmatic evolution of Middle Ordovician volcanic rocks of the Wild Bight Group, Newfoundland Appalachians |
title_short |
U-Pb ages and tectono-magmatic evolution of Middle Ordovician volcanic rocks of the Wild Bight Group, Newfoundland Appalachians |
title_full |
U-Pb ages and tectono-magmatic evolution of Middle Ordovician volcanic rocks of the Wild Bight Group, Newfoundland Appalachians |
title_fullStr |
U-Pb ages and tectono-magmatic evolution of Middle Ordovician volcanic rocks of the Wild Bight Group, Newfoundland Appalachians |
title_full_unstemmed |
U-Pb ages and tectono-magmatic evolution of Middle Ordovician volcanic rocks of the Wild Bight Group, Newfoundland Appalachians |
title_sort |
u-pb ages and tectono-magmatic evolution of middle ordovician volcanic rocks of the wild bight group, newfoundland appalachians |
publisher |
Canadian Science Publishing |
publishDate |
1998 |
url |
http://dx.doi.org/10.1139/e98-050 http://www.nrcresearchpress.com/doi/pdf/10.1139/e98-050 |
long_lat |
ENVELOPE(-54.831,-54.831,49.600,49.600) |
geographic |
Wild Bight |
geographic_facet |
Wild Bight |
genre |
Newfoundland |
genre_facet |
Newfoundland |
op_source |
Canadian Journal of Earth Sciences volume 35, issue 9, page 998-1017 ISSN 0008-4077 1480-3313 |
op_rights |
http://www.nrcresearchpress.com/page/about/CorporateTextAndDataMining |
op_doi |
https://doi.org/10.1139/e98-050 |
container_title |
Canadian Journal of Earth Sciences |
container_volume |
35 |
container_issue |
9 |
container_start_page |
998 |
op_container_end_page |
1017 |
_version_ |
1785563963803566080 |