Age of the Brookville Gneiss and associated rocks, southeastern New Brunswick
The Brookville Gneiss is a medium- to high-grade quartz–feldspar–biotite and hornblende–quartz–feldspar–biotite gneiss found north and northeast of Saint John, New Brunswick. The Green Head Group, a sequence of low-grade metasediments, surrounds the Brookville Gneiss. Analyses of zircons with euhedr...
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Canadian Science Publishing
1982
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crcansciencepubl:10.1139/e82-190 2023-12-17T10:28:23+01:00 Age of the Brookville Gneiss and associated rocks, southeastern New Brunswick Olszewski Jr., William J. Gaudette, Henri E. 1982 http://dx.doi.org/10.1139/e82-190 http://www.nrcresearchpress.com/doi/pdf/10.1139/e82-190 en eng Canadian Science Publishing http://www.nrcresearchpress.com/page/about/CorporateTextAndDataMining Canadian Journal of Earth Sciences volume 19, issue 11, page 2158-2166 ISSN 0008-4077 1480-3313 General Earth and Planetary Sciences journal-article 1982 crcansciencepubl https://doi.org/10.1139/e82-190 2023-11-19T13:39:11Z The Brookville Gneiss is a medium- to high-grade quartz–feldspar–biotite and hornblende–quartz–feldspar–biotite gneiss found north and northeast of Saint John, New Brunswick. The Green Head Group, a sequence of low-grade metasediments, surrounds the Brookville Gneiss. Analyses of zircons with euhedral to subhedral overgrowths and rounded to subrounded cores from the Brookville Gneiss yield an upper intercept age on concordia of 1641 Ma, considered to be the age of the source area for the zircons. The zircon analyses also indicate two Pb-loss events at approximately 780 and 370 Ma. These ages are confirmed by zircon analyses of a quartz diorite gneiss from Green Head Island, which yields ages of 827 and 333 Ma. A small euhedral single zircon from the Brookville Gneiss, believed to be formed during metamorphism, gives a concordant age of 814 Ma corresponding to the first Pb-loss event. Rb–Sr whole-rock analyses of a granite from the east side of Musquash Harbour southwest of Saint John give an age of 392 Ma and an initial Sr ratio of 0.7187 substantiating the second Pb-loss event.The results indicate that the Brookville Gneiss and Green Head Group are older than 800 Ma and probably younger than 1200 Ma. The zircon source area age (1641 Ma) and first Pb-loss event (800 Ma) are similar to ages found in rocks of the eastern margin of the Appalachian orogen from Massachusetts and Cape Breton Island, respectively. They suggest a setting and tectonic event correlated in time for the Late Precambrian of the eastern margin distinct from the younger so-called "Avalonian." Article in Journal/Newspaper Breton Island Head Island Canadian Science Publishing (via Crossref) Breton Island ENVELOPE(141.383,141.383,-66.800,-66.800) Head Island ENVELOPE(-62.917,-62.917,-64.517,-64.517) Green Head ENVELOPE(-55.881,-55.881,49.767,49.767) Canadian Journal of Earth Sciences 19 11 2158 2166 |
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 Olszewski Jr., William J. Gaudette, Henri E. Age of the Brookville Gneiss and associated rocks, southeastern New Brunswick |
topic_facet |
General Earth and Planetary Sciences |
description |
The Brookville Gneiss is a medium- to high-grade quartz–feldspar–biotite and hornblende–quartz–feldspar–biotite gneiss found north and northeast of Saint John, New Brunswick. The Green Head Group, a sequence of low-grade metasediments, surrounds the Brookville Gneiss. Analyses of zircons with euhedral to subhedral overgrowths and rounded to subrounded cores from the Brookville Gneiss yield an upper intercept age on concordia of 1641 Ma, considered to be the age of the source area for the zircons. The zircon analyses also indicate two Pb-loss events at approximately 780 and 370 Ma. These ages are confirmed by zircon analyses of a quartz diorite gneiss from Green Head Island, which yields ages of 827 and 333 Ma. A small euhedral single zircon from the Brookville Gneiss, believed to be formed during metamorphism, gives a concordant age of 814 Ma corresponding to the first Pb-loss event. Rb–Sr whole-rock analyses of a granite from the east side of Musquash Harbour southwest of Saint John give an age of 392 Ma and an initial Sr ratio of 0.7187 substantiating the second Pb-loss event.The results indicate that the Brookville Gneiss and Green Head Group are older than 800 Ma and probably younger than 1200 Ma. The zircon source area age (1641 Ma) and first Pb-loss event (800 Ma) are similar to ages found in rocks of the eastern margin of the Appalachian orogen from Massachusetts and Cape Breton Island, respectively. They suggest a setting and tectonic event correlated in time for the Late Precambrian of the eastern margin distinct from the younger so-called "Avalonian." |
format |
Article in Journal/Newspaper |
author |
Olszewski Jr., William J. Gaudette, Henri E. |
author_facet |
Olszewski Jr., William J. Gaudette, Henri E. |
author_sort |
Olszewski Jr., William J. |
title |
Age of the Brookville Gneiss and associated rocks, southeastern New Brunswick |
title_short |
Age of the Brookville Gneiss and associated rocks, southeastern New Brunswick |
title_full |
Age of the Brookville Gneiss and associated rocks, southeastern New Brunswick |
title_fullStr |
Age of the Brookville Gneiss and associated rocks, southeastern New Brunswick |
title_full_unstemmed |
Age of the Brookville Gneiss and associated rocks, southeastern New Brunswick |
title_sort |
age of the brookville gneiss and associated rocks, southeastern new brunswick |
publisher |
Canadian Science Publishing |
publishDate |
1982 |
url |
http://dx.doi.org/10.1139/e82-190 http://www.nrcresearchpress.com/doi/pdf/10.1139/e82-190 |
long_lat |
ENVELOPE(141.383,141.383,-66.800,-66.800) ENVELOPE(-62.917,-62.917,-64.517,-64.517) ENVELOPE(-55.881,-55.881,49.767,49.767) |
geographic |
Breton Island Head Island Green Head |
geographic_facet |
Breton Island Head Island Green Head |
genre |
Breton Island Head Island |
genre_facet |
Breton Island Head Island |
op_source |
Canadian Journal of Earth Sciences volume 19, issue 11, page 2158-2166 ISSN 0008-4077 1480-3313 |
op_rights |
http://www.nrcresearchpress.com/page/about/CorporateTextAndDataMining |
op_doi |
https://doi.org/10.1139/e82-190 |
container_title |
Canadian Journal of Earth Sciences |
container_volume |
19 |
container_issue |
11 |
container_start_page |
2158 |
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2166 |
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