Dolomitization of the Lower Ordovician Aguathuna Formation carbonates, Port au Port Peninsula, western Newfoundland, Canada: implications for a hydrocarbon reservoir
The Lower Ordovician Aguathuna Formation (∼100 m thick) is formed of shallow-marine carbonates, which constitute the uppermost part of the St. George Group of western Newfoundland. Sedimentation was paused by a major subaerial exposure (St. George Unconformity), which likely developed a significant...
Published in: | Canadian Journal of Earth Sciences |
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Language: | English |
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NRC Research Press
2008
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Online Access: | https://research.library.mun.ca/11723/ https://research.library.mun.ca/11723/1/Azmy_et_al_2008_b_CJES.pdf https://doi.org/10.1139/E08-020 |
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ftmemorialuniv:oai:research.library.mun.ca:11723 2023-10-01T03:57:35+02:00 Dolomitization of the Lower Ordovician Aguathuna Formation carbonates, Port au Port Peninsula, western Newfoundland, Canada: implications for a hydrocarbon reservoir Azmy, Karem Lavoie, Denis Knight, I. (Ian) Chi, Guoxiang 2008-07 application/pdf https://research.library.mun.ca/11723/ https://research.library.mun.ca/11723/1/Azmy_et_al_2008_b_CJES.pdf https://doi.org/10.1139/E08-020 en eng NRC Research Press https://research.library.mun.ca/11723/1/Azmy_et_al_2008_b_CJES.pdf Azmy, Karem <https://research.library.mun.ca/view/creator_az/Azmy=3AKarem=3A=3A.html> and Lavoie, Denis <https://research.library.mun.ca/view/creator_az/Lavoie=3ADenis=3A=3A.html> and Knight, I. (Ian) <https://research.library.mun.ca/view/creator_az/Knight=3AI=2E_=28Ian=29=3A=3A.html> and Chi, Guoxiang <https://research.library.mun.ca/view/creator_az/Chi=3AGuoxiang=3A=3A.html> (2008) Dolomitization of the Lower Ordovician Aguathuna Formation carbonates, Port au Port Peninsula, western Newfoundland, Canada: implications for a hydrocarbon reservoir. Canadian Journal of Earth Sciences, 45 (7). pp. 795-813. ISSN 1480-3313 cc_by_nc Article PeerReviewed 2008 ftmemorialuniv https://doi.org/10.1139/E08-020 2023-09-03T06:48:25Z The Lower Ordovician Aguathuna Formation (∼100 m thick) is formed of shallow-marine carbonates, which constitute the uppermost part of the St. George Group of western Newfoundland. Sedimentation was paused by a major subaerial exposure (St. George Unconformity), which likely developed a significant pore system in the underlying carbonates by meteoric dissolution. The sequence has been affected by multiphase dolomitization that caused complex changes in the rock porosity. The Aguathuna dolomites are classified into three main generations ranging in crystal size between ∼4 µm and 2 mm. The occurrence of fabric-retentive dolomicrites implies that dolomitization likely started during the early stages of diagenesis. Although dolomitization is pervasive in the upper part of the formation and significantly occludes the pores, some intervals in the lower part have higher porosity. The development of lower permeable layers overlain by an impermeable (seal) cap suggests a possible potential diagenetic trap. Unlike sabkha deposits, the Aguathuna carbonates do not have evaporite interlayers. Furthermore, the low Sr contents (∼96 ppm) and the δ18O values of earlier dolomites (–3.3‰ to –6.9‰ VPDB (Vienna Pee Dee Belemnite)) are also difficult to reconcile with a brine origin. The Sr/Ca molar ratios (0.0067–0.0009), calculated for the earliest dolomitizing fluid, suggest a modified seawater origin, likely mixed sea and meteoric waters. The least radiogenic 87Sr/86Sr values of the earliest dolomite are consistent with those of early Ordovician seawater, which supports an early-stage diagenesis. Petrography, geochemistry, and fluid inclusions of the late dolomites suggest precipitation at higher temperatures (∼73–95 °C) in deeper burial environments from hydrothermal solutions. Article in Journal/Newspaper Newfoundland Memorial University of Newfoundland: Research Repository Canada Dee ENVELOPE(-59.767,-59.767,-62.433,-62.433) Canadian Journal of Earth Sciences 45 7 795 813 |
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Open Polar |
collection |
Memorial University of Newfoundland: Research Repository |
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ftmemorialuniv |
language |
English |
description |
The Lower Ordovician Aguathuna Formation (∼100 m thick) is formed of shallow-marine carbonates, which constitute the uppermost part of the St. George Group of western Newfoundland. Sedimentation was paused by a major subaerial exposure (St. George Unconformity), which likely developed a significant pore system in the underlying carbonates by meteoric dissolution. The sequence has been affected by multiphase dolomitization that caused complex changes in the rock porosity. The Aguathuna dolomites are classified into three main generations ranging in crystal size between ∼4 µm and 2 mm. The occurrence of fabric-retentive dolomicrites implies that dolomitization likely started during the early stages of diagenesis. Although dolomitization is pervasive in the upper part of the formation and significantly occludes the pores, some intervals in the lower part have higher porosity. The development of lower permeable layers overlain by an impermeable (seal) cap suggests a possible potential diagenetic trap. Unlike sabkha deposits, the Aguathuna carbonates do not have evaporite interlayers. Furthermore, the low Sr contents (∼96 ppm) and the δ18O values of earlier dolomites (–3.3‰ to –6.9‰ VPDB (Vienna Pee Dee Belemnite)) are also difficult to reconcile with a brine origin. The Sr/Ca molar ratios (0.0067–0.0009), calculated for the earliest dolomitizing fluid, suggest a modified seawater origin, likely mixed sea and meteoric waters. The least radiogenic 87Sr/86Sr values of the earliest dolomite are consistent with those of early Ordovician seawater, which supports an early-stage diagenesis. Petrography, geochemistry, and fluid inclusions of the late dolomites suggest precipitation at higher temperatures (∼73–95 °C) in deeper burial environments from hydrothermal solutions. |
format |
Article in Journal/Newspaper |
author |
Azmy, Karem Lavoie, Denis Knight, I. (Ian) Chi, Guoxiang |
spellingShingle |
Azmy, Karem Lavoie, Denis Knight, I. (Ian) Chi, Guoxiang Dolomitization of the Lower Ordovician Aguathuna Formation carbonates, Port au Port Peninsula, western Newfoundland, Canada: implications for a hydrocarbon reservoir |
author_facet |
Azmy, Karem Lavoie, Denis Knight, I. (Ian) Chi, Guoxiang |
author_sort |
Azmy, Karem |
title |
Dolomitization of the Lower Ordovician Aguathuna Formation carbonates, Port au Port Peninsula, western Newfoundland, Canada: implications for a hydrocarbon reservoir |
title_short |
Dolomitization of the Lower Ordovician Aguathuna Formation carbonates, Port au Port Peninsula, western Newfoundland, Canada: implications for a hydrocarbon reservoir |
title_full |
Dolomitization of the Lower Ordovician Aguathuna Formation carbonates, Port au Port Peninsula, western Newfoundland, Canada: implications for a hydrocarbon reservoir |
title_fullStr |
Dolomitization of the Lower Ordovician Aguathuna Formation carbonates, Port au Port Peninsula, western Newfoundland, Canada: implications for a hydrocarbon reservoir |
title_full_unstemmed |
Dolomitization of the Lower Ordovician Aguathuna Formation carbonates, Port au Port Peninsula, western Newfoundland, Canada: implications for a hydrocarbon reservoir |
title_sort |
dolomitization of the lower ordovician aguathuna formation carbonates, port au port peninsula, western newfoundland, canada: implications for a hydrocarbon reservoir |
publisher |
NRC Research Press |
publishDate |
2008 |
url |
https://research.library.mun.ca/11723/ https://research.library.mun.ca/11723/1/Azmy_et_al_2008_b_CJES.pdf https://doi.org/10.1139/E08-020 |
long_lat |
ENVELOPE(-59.767,-59.767,-62.433,-62.433) |
geographic |
Canada Dee |
geographic_facet |
Canada Dee |
genre |
Newfoundland |
genre_facet |
Newfoundland |
op_relation |
https://research.library.mun.ca/11723/1/Azmy_et_al_2008_b_CJES.pdf Azmy, Karem <https://research.library.mun.ca/view/creator_az/Azmy=3AKarem=3A=3A.html> and Lavoie, Denis <https://research.library.mun.ca/view/creator_az/Lavoie=3ADenis=3A=3A.html> and Knight, I. (Ian) <https://research.library.mun.ca/view/creator_az/Knight=3AI=2E_=28Ian=29=3A=3A.html> and Chi, Guoxiang <https://research.library.mun.ca/view/creator_az/Chi=3AGuoxiang=3A=3A.html> (2008) Dolomitization of the Lower Ordovician Aguathuna Formation carbonates, Port au Port Peninsula, western Newfoundland, Canada: implications for a hydrocarbon reservoir. Canadian Journal of Earth Sciences, 45 (7). pp. 795-813. ISSN 1480-3313 |
op_rights |
cc_by_nc |
op_doi |
https://doi.org/10.1139/E08-020 |
container_title |
Canadian Journal of Earth Sciences |
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45 |
container_issue |
7 |
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795 |
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813 |
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