Correlation of gravity anomalies with Yellowknife Supergroup rocks, North Arm, Great Slave Lake
A gravity map compiled from observations made on the frozen surface of Great Slave Lake shows that the positive gravity anomaly associated with the Yellowknife greenstone belt extends offshore into the North Arm of the lake. On the western shore of Yellowknife Bay the axis of the anomaly coincides w...
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1980
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Online Access: | http://dx.doi.org/10.1139/e80-158 http://www.nrcresearchpress.com/doi/pdf/10.1139/e80-158 |
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crcansciencepubl:10.1139/e80-158 2023-12-17T10:30:38+01:00 Correlation of gravity anomalies with Yellowknife Supergroup rocks, North Arm, Great Slave Lake Gibb, R. A. Thomas, M. D. 1980 http://dx.doi.org/10.1139/e80-158 http://www.nrcresearchpress.com/doi/pdf/10.1139/e80-158 en eng Canadian Science Publishing http://www.nrcresearchpress.com/page/about/CorporateTextAndDataMining Canadian Journal of Earth Sciences volume 17, issue 11, page 1506-1516 ISSN 0008-4077 1480-3313 General Earth and Planetary Sciences journal-article 1980 crcansciencepubl https://doi.org/10.1139/e80-158 2023-11-19T13:39:08Z A gravity map compiled from observations made on the frozen surface of Great Slave Lake shows that the positive gravity anomaly associated with the Yellowknife greenstone belt extends offshore into the North Arm of the lake. On the western shore of Yellowknife Bay the axis of the anomaly coincides with mafic volcanic rocks of the Kam Formation. Offshore the axis continues southwards for about 10 km to the West Mirage Islands where it takes a dramatic turn to the southeast and continues for a further 60 km to the Outer Whaleback Rocks. Using the geology and rock density determinations on land for control, a three-dimensional geological model comprising a large number of prismatic blocks was derived from the gravity anomalies. In the model the simplifying assumption has been made that the greenstone belt is everywhere floored by granodiorite similar to the adjacent Western and South-east granodiorites. According to the model, mafic volcanic rocks of the Kam Formation are generally 1–3 km thick with a maximum thickness of 7 km at the mouth of Yellowknife Bay. Greywacke and mudstone of the Burwash Formation vary in thickness from 1 to 3 km. Locally these sedimentary rocks attain a thickness of 8 km but this is probably an overestimated value as they may very well be underlain by volcanic rocks of the Kam Formation. The presence of a third pluton of granodiorite flanking the belt to the southwest is also inferred from the gravity data. Previous seismic work indicated a greenstone basin with an average thickness of about 10 km. However, reexamination of the seismic records suggests that weak arrivals interpreted as originating from the base of the greenstone belt are more likely to be pulses associated with earlier arrivals. Article in Journal/Newspaper Great Slave Lake North Arm Yellowknife Canadian Science Publishing (via Crossref) Yellowknife Great Slave Lake ENVELOPE(-114.001,-114.001,61.500,61.500) Yellowknife Bay ENVELOPE(-114.336,-114.336,62.367,62.367) Mirage Islands ENVELOPE(-91.700,-91.700,62.617,62.617) West Mirage Islands ENVELOPE(-114.486,-114.486,62.275,62.275) Outer Whaleback Rocks ENVELOPE(-113.975,-113.975,61.880,61.880) Whaleback Rocks ENVELOPE(-59.078,-59.078,-63.654,-63.654) Canadian Journal of Earth Sciences 17 11 1506 1516 |
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 Gibb, R. A. Thomas, M. D. Correlation of gravity anomalies with Yellowknife Supergroup rocks, North Arm, Great Slave Lake |
topic_facet |
General Earth and Planetary Sciences |
description |
A gravity map compiled from observations made on the frozen surface of Great Slave Lake shows that the positive gravity anomaly associated with the Yellowknife greenstone belt extends offshore into the North Arm of the lake. On the western shore of Yellowknife Bay the axis of the anomaly coincides with mafic volcanic rocks of the Kam Formation. Offshore the axis continues southwards for about 10 km to the West Mirage Islands where it takes a dramatic turn to the southeast and continues for a further 60 km to the Outer Whaleback Rocks. Using the geology and rock density determinations on land for control, a three-dimensional geological model comprising a large number of prismatic blocks was derived from the gravity anomalies. In the model the simplifying assumption has been made that the greenstone belt is everywhere floored by granodiorite similar to the adjacent Western and South-east granodiorites. According to the model, mafic volcanic rocks of the Kam Formation are generally 1–3 km thick with a maximum thickness of 7 km at the mouth of Yellowknife Bay. Greywacke and mudstone of the Burwash Formation vary in thickness from 1 to 3 km. Locally these sedimentary rocks attain a thickness of 8 km but this is probably an overestimated value as they may very well be underlain by volcanic rocks of the Kam Formation. The presence of a third pluton of granodiorite flanking the belt to the southwest is also inferred from the gravity data. Previous seismic work indicated a greenstone basin with an average thickness of about 10 km. However, reexamination of the seismic records suggests that weak arrivals interpreted as originating from the base of the greenstone belt are more likely to be pulses associated with earlier arrivals. |
format |
Article in Journal/Newspaper |
author |
Gibb, R. A. Thomas, M. D. |
author_facet |
Gibb, R. A. Thomas, M. D. |
author_sort |
Gibb, R. A. |
title |
Correlation of gravity anomalies with Yellowknife Supergroup rocks, North Arm, Great Slave Lake |
title_short |
Correlation of gravity anomalies with Yellowknife Supergroup rocks, North Arm, Great Slave Lake |
title_full |
Correlation of gravity anomalies with Yellowknife Supergroup rocks, North Arm, Great Slave Lake |
title_fullStr |
Correlation of gravity anomalies with Yellowknife Supergroup rocks, North Arm, Great Slave Lake |
title_full_unstemmed |
Correlation of gravity anomalies with Yellowknife Supergroup rocks, North Arm, Great Slave Lake |
title_sort |
correlation of gravity anomalies with yellowknife supergroup rocks, north arm, great slave lake |
publisher |
Canadian Science Publishing |
publishDate |
1980 |
url |
http://dx.doi.org/10.1139/e80-158 http://www.nrcresearchpress.com/doi/pdf/10.1139/e80-158 |
long_lat |
ENVELOPE(-114.001,-114.001,61.500,61.500) ENVELOPE(-114.336,-114.336,62.367,62.367) ENVELOPE(-91.700,-91.700,62.617,62.617) ENVELOPE(-114.486,-114.486,62.275,62.275) ENVELOPE(-113.975,-113.975,61.880,61.880) ENVELOPE(-59.078,-59.078,-63.654,-63.654) |
geographic |
Yellowknife Great Slave Lake Yellowknife Bay Mirage Islands West Mirage Islands Outer Whaleback Rocks Whaleback Rocks |
geographic_facet |
Yellowknife Great Slave Lake Yellowknife Bay Mirage Islands West Mirage Islands Outer Whaleback Rocks Whaleback Rocks |
genre |
Great Slave Lake North Arm Yellowknife |
genre_facet |
Great Slave Lake North Arm Yellowknife |
op_source |
Canadian Journal of Earth Sciences volume 17, issue 11, page 1506-1516 ISSN 0008-4077 1480-3313 |
op_rights |
http://www.nrcresearchpress.com/page/about/CorporateTextAndDataMining |
op_doi |
https://doi.org/10.1139/e80-158 |
container_title |
Canadian Journal of Earth Sciences |
container_volume |
17 |
container_issue |
11 |
container_start_page |
1506 |
op_container_end_page |
1516 |
_version_ |
1785583632783507456 |