Late Precambrian ash-flow tuffs and associated rocks of the Harbour Main Group near Colliers, eastern Newfoundland: chemistry and magmatic affinities
The Colliers Peninsula, a typical area in the western part of the Harbour Main Group in eastern Newfoundland, is underlain by three steeply-dipping sequences of ash-flow tuffs 250–500 m thick, separated by clastic sediments, conformably overlain by subaerial mafic flows and cut by small bodies of hi...
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crcansciencepubl:10.1139/e79-015 2024-04-28T08:28:48+00:00 Late Precambrian ash-flow tuffs and associated rocks of the Harbour Main Group near Colliers, eastern Newfoundland: chemistry and magmatic affinities Nixon, G. T. Papezik, V. S. 1979 http://dx.doi.org/10.1139/e79-015 http://www.nrcresearchpress.com/doi/pdf/10.1139/e79-015 en eng Canadian Science Publishing http://www.nrcresearchpress.com/page/about/CorporateTextAndDataMining Canadian Journal of Earth Sciences volume 16, issue 1, page 167-181 ISSN 0008-4077 1480-3313 General Earth and Planetary Sciences journal-article 1979 crcansciencepubl https://doi.org/10.1139/e79-015 2024-04-09T06:56:25Z The Colliers Peninsula, a typical area in the western part of the Harbour Main Group in eastern Newfoundland, is underlain by three steeply-dipping sequences of ash-flow tuffs 250–500 m thick, separated by clastic sediments, conformably overlain by subaerial mafic flows and cut by small bodies of high-level intrusive rocks rich in plagioclase phenocrysts. All rocks are of low metamorphic grade.The two lower pyroclastic sequences have a bulk composition of rhyolite and alkali rhyolite; they contain phenocrysts of albite, quartz, and biotite. Na/K ratios are highly variable; the albite crystals may be pseudomorphous after anorthociase. The upper sequence, rhyodacitic in bulk composition, has lower Si and higher Na; it lacks quartz and biotite phenocrysts but contains small amounts of calcic augite and altered olivine. The mafic flows (50% SiO 2 ) show high Al and alkalies and low Ca and Ti. The porphyritic intrusives have 60–65% SiO 2 , but their bulk chemistry is otherwise similar to that of the ash-flow tuffs.The present composition of the rocks reflects complex chemical adjustments, both contemporaneous with and subsequent to the magmatic event. However, mineralogical and chemical data and trends considered to be a part of the original magmatic heritage are consistent with suggestions that the western (probably lower) part of the Harbour Main volcanic pile was formed in a continental, extensional tectonic environment. Article in Journal/Newspaper Newfoundland Canadian Science Publishing Canadian Journal of Earth Sciences 16 1 167 181 |
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Open Polar |
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Canadian Science Publishing |
op_collection_id |
crcansciencepubl |
language |
English |
topic |
General Earth and Planetary Sciences |
spellingShingle |
General Earth and Planetary Sciences Nixon, G. T. Papezik, V. S. Late Precambrian ash-flow tuffs and associated rocks of the Harbour Main Group near Colliers, eastern Newfoundland: chemistry and magmatic affinities |
topic_facet |
General Earth and Planetary Sciences |
description |
The Colliers Peninsula, a typical area in the western part of the Harbour Main Group in eastern Newfoundland, is underlain by three steeply-dipping sequences of ash-flow tuffs 250–500 m thick, separated by clastic sediments, conformably overlain by subaerial mafic flows and cut by small bodies of high-level intrusive rocks rich in plagioclase phenocrysts. All rocks are of low metamorphic grade.The two lower pyroclastic sequences have a bulk composition of rhyolite and alkali rhyolite; they contain phenocrysts of albite, quartz, and biotite. Na/K ratios are highly variable; the albite crystals may be pseudomorphous after anorthociase. The upper sequence, rhyodacitic in bulk composition, has lower Si and higher Na; it lacks quartz and biotite phenocrysts but contains small amounts of calcic augite and altered olivine. The mafic flows (50% SiO 2 ) show high Al and alkalies and low Ca and Ti. The porphyritic intrusives have 60–65% SiO 2 , but their bulk chemistry is otherwise similar to that of the ash-flow tuffs.The present composition of the rocks reflects complex chemical adjustments, both contemporaneous with and subsequent to the magmatic event. However, mineralogical and chemical data and trends considered to be a part of the original magmatic heritage are consistent with suggestions that the western (probably lower) part of the Harbour Main volcanic pile was formed in a continental, extensional tectonic environment. |
format |
Article in Journal/Newspaper |
author |
Nixon, G. T. Papezik, V. S. |
author_facet |
Nixon, G. T. Papezik, V. S. |
author_sort |
Nixon, G. T. |
title |
Late Precambrian ash-flow tuffs and associated rocks of the Harbour Main Group near Colliers, eastern Newfoundland: chemistry and magmatic affinities |
title_short |
Late Precambrian ash-flow tuffs and associated rocks of the Harbour Main Group near Colliers, eastern Newfoundland: chemistry and magmatic affinities |
title_full |
Late Precambrian ash-flow tuffs and associated rocks of the Harbour Main Group near Colliers, eastern Newfoundland: chemistry and magmatic affinities |
title_fullStr |
Late Precambrian ash-flow tuffs and associated rocks of the Harbour Main Group near Colliers, eastern Newfoundland: chemistry and magmatic affinities |
title_full_unstemmed |
Late Precambrian ash-flow tuffs and associated rocks of the Harbour Main Group near Colliers, eastern Newfoundland: chemistry and magmatic affinities |
title_sort |
late precambrian ash-flow tuffs and associated rocks of the harbour main group near colliers, eastern newfoundland: chemistry and magmatic affinities |
publisher |
Canadian Science Publishing |
publishDate |
1979 |
url |
http://dx.doi.org/10.1139/e79-015 http://www.nrcresearchpress.com/doi/pdf/10.1139/e79-015 |
genre |
Newfoundland |
genre_facet |
Newfoundland |
op_source |
Canadian Journal of Earth Sciences volume 16, issue 1, page 167-181 ISSN 0008-4077 1480-3313 |
op_rights |
http://www.nrcresearchpress.com/page/about/CorporateTextAndDataMining |
op_doi |
https://doi.org/10.1139/e79-015 |
container_title |
Canadian Journal of Earth Sciences |
container_volume |
16 |
container_issue |
1 |
container_start_page |
167 |
op_container_end_page |
181 |
_version_ |
1797587217966694400 |