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TitleHigh-temperature alteration and porosity generation in Upper Ordovician microbial reefs, Hudson Bay intracratonic basin, Arctic Canada
AuthorLavoie, DORCID logo; Castagner, A; Haghnazar-Liseroudi, M; Ardakani, O HORCID logo; Desrochers, A
SourceSedimentary Geology vol. 374, 2018 p. 1-16,
Alt SeriesNatural Resources Canada, Contribution Series 20170298
PublisherElsevier BV
Mediapaper; on-line; digital
File formatpdf; html
NTS24N; 24O; 24P; 25; 33M; 33N; 34C; 34D; 34E; 34F; 34I; 34J; 34K; 34L; 34M; 34N; 34O; 34P; 36A; 36B; 36C; 36D; 36E; 36F; 36G; 36H; 36I; 36J; 36K; 36L; 43M; 43N; 43O; 43P; 44; 45; 46; 54A; 54F; 54G; 54H; 54I; 54J; 54K; 54L; 54M; 54N; 54O; 54P; 55A; 55B; 55C; 55D; 55E; 55F; 55G; 55H; 55I; 55J; 55K; 55O; 55P; 56A
AreaCanadian Arctic; Hudson Bay; Hudson Strait; Foxe Basin
Lat/Long WENS -95.0000 -64.0000 68.0000 55.0000
Subjectsfossil fuels; sedimentology; geochemistry; geochronology; geophysics; reefs; bioherms; alteration; porosity; fractures; cementation; isotopic studies; oxygen isotopes; carbon isotopes; fluid inclusions; thermal history; marine environments; fission-track dates; fluid dynamics; petrographic analyses; salinity; burial history; recrystallization; aragonite; calcite; source rocks; bedrock geology; lithology; sedimentary rocks; shales; sandstones; geophysical interpretations; seismic interpretations; diagenesis; paragenesis; hydrothermal alteration; Upper Ordovician; Hudson Bay Basin; Red Head Rapids River Formation; Sponges; Phanerozoic; Paleozoic; Ordovician
Illustrationslocation maps; geoscientific sketch maps; cross-sections; stratigraphic columns; photographs; photomicrographs; geochronological charts; tables; plots; bar graphs; histograms
ProgramGEM2: Geo-mapping for Energy and Minerals Hudson/Ungava Hydrocarbon source rocks
Released2018 07 19
AbstractUpper Ordovician biohermal mounds of the Red Head Rapids River Formation in the Hudson Bay Basin consist of microbial and sponge boundstone and cementstone. The cementstone is made up of isopachous layers and botryoids of former aragonite now calcite. Secondary dissolution porosity and small fractures are cutting through the bioherm. Secondary pore-fillings consist of drusy calcite cement and subsequent bitumen. The delta-18O(VPDB) and delta-13C(VPDB) values of late cements are invariably more negative than those of the marine cements. Fluid inclusion microthermometry documents the presence of two distinct populations of homogenization temperatures, one in secondary pore-filling burial calcite cement (Th average 93±10 °C) and a second one in recrystallized marine calcite cements (Th average 118 ± 25 °C). The combined delta-18O(VPDB) and Th data suggest that burial cements precipitated from a fluid having delta-18O(SMOW) values between +0.5 and ±2 per mille,whereas the marine cement data indicate resetting of the fluid inclusions in the presence of a high temperature, delta-18O(SMOW) heavy brine (+2.5 to +12 per mille). The lower temperature fluid inclusions of the late pore-filling cement agree with recent Apatite Fission Track data suggesting early oil window temperature at maximum burial. The higher Th values recorded in the marine cement represent resetting of initial or entrapment of new fluid inclusions from fracture-controlled circulation of basement-derived fluids. The petrographic and geochemical data suggest that fracture-controlled high temperature brine circulation occurred after the inception of burial and recrystallization of original marine aragonite to calcite, which resulted in the generation of significant secondary porosity that was later filled by lower temperature burial cements and hydrocarbons.
Summary(Plain Language Summary, not published)
Upper Ordovician reefs in the Hudson Bay Basin are large structures that are porous and locally filled with bitumen and dead oil. The detailed study of one of these reefs on Southampton Island led to the proposition of a complex evolution of pore space with the first recognition of early hydrothermal alteration leading to the formation of secondary porosity later filled by hydrocarbons. The results of this study indicate that these reefs are potential significant hydrocarbon reservoirs in the subsurface.

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