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...

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Published in:Canadian Journal of Earth Sciences
Main Authors: Azmy, Karem, Lavoie, Denis, Knight, Ian, Chi, Guoxiang
Other Authors: Jin, Jisuo
Format: Article in Journal/Newspaper
Language:English
Published: Canadian Science Publishing 2008
Subjects:
Dee
Online Access:http://dx.doi.org/10.1139/e08-020
http://www.nrcresearchpress.com/doi/full-xml/10.1139/E08-020
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spelling crcansciencepubl:10.1139/e08-020 2024-06-23T07:54:45+00:00 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, Ian Chi, Guoxiang Jin, Jisuo 2008 http://dx.doi.org/10.1139/e08-020 http://www.nrcresearchpress.com/doi/full-xml/10.1139/E08-020 http://www.nrcresearchpress.com/doi/pdf/10.1139/E08-020 en eng Canadian Science Publishing http://www.nrcresearchpress.com/page/about/CorporateTextAndDataMining Canadian Journal of Earth Sciences volume 45, issue 7, page 795-813 ISSN 0008-4077 1480-3313 journal-article 2008 crcansciencepubl https://doi.org/10.1139/e08-020 2024-06-13T04:10:51Z 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 δ 18 O 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 87 Sr/ 86 Sr 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 Canadian Science Publishing Canada Dee ENVELOPE(-59.767,-59.767,-62.433,-62.433) Canadian Journal of Earth Sciences 45 7 795 813
institution Open Polar
collection Canadian Science Publishing
op_collection_id crcansciencepubl
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 δ 18 O 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 87 Sr/ 86 Sr 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.
author2 Jin, Jisuo
format Article in Journal/Newspaper
author Azmy, Karem
Lavoie, Denis
Knight, Ian
Chi, Guoxiang
spellingShingle Azmy, Karem
Lavoie, Denis
Knight, 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, 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 Canadian Science Publishing
publishDate 2008
url http://dx.doi.org/10.1139/e08-020
http://www.nrcresearchpress.com/doi/full-xml/10.1139/E08-020
http://www.nrcresearchpress.com/doi/pdf/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_source Canadian Journal of Earth Sciences
volume 45, issue 7, page 795-813
ISSN 0008-4077 1480-3313
op_rights http://www.nrcresearchpress.com/page/about/CorporateTextAndDataMining
op_doi https://doi.org/10.1139/e08-020
container_title Canadian Journal of Earth Sciences
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