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TitleNew constraints on genesis of the polymetallic veins at Port Radium, Great Bear Lake, northwest Canadian Shield
AuthorGandhi, S S; Potter, E G; Fayek, M
SourceOre Geology Reviews vol. 96, 2018 p. 28-47,
Alt SeriesEarth Sciences Sector, Contribution Series 20140404
PublisherElsevier BV
Mediapaper; on-line; digital
File formatpdf
ProvinceNorthwest Territories
NTS86E; 86F; 86K; 86L; 86M/01; 86M/08; 86N/01; 86N/02; 86N/03; 86N/04; 86N/05; 86N/06; 86N/07; 86N/08
AreaGreat Bear Lake; Dismal Lake; Coppermine River; Hottah Lake
Lat/Long WENS-120.0000 -116.0000 67.5000 65.0000
Subjectseconomic geology; geochronology; tectonics; geochemistry; mineral deposits; vein deposits; polymetallic ores; unconformity-type deposit; uranium; cobalt; nickel; copper; silver; base metals; ore mineral genesis; ore controls; structural controls; mineral occurrences; bedrock geology; structural features; fault zones; faults; fractures; unconformities; lithology; igneous rocks; intrusive rocks; diabases; granites; granodiorites; monzonites; porphyries; volcanic rocks; basalts; rhyolites; dacites; rhyodacites; volcaniclastics; andesites; sedimentary rocks; dolomites; siltstones; mudstones; sandstones; breccias; metamorphic rocks; paragneisses; metavolcanic rocks; basement geology; tectonic history; tectonic setting; precipitation; intrusions; dykes; veins; plutons; mineralization; uraninite; alteration; isotopic studies; oxygen isotopes; radiometric dating; uranium lead dating; geochemical analyses; geochemical anomalies; metallogeny; Archean; Canadian Shield; Port Radium Mine; Terra Mine; Great Bear Magmatic Zone; Hornby Bay Group; Western Channel Diabase; Laurentia; Rapakivi Granite; Sloan Group; Cameron Bay Formation; Dumas Group; LaBine Group; Echo Bay Formation; Surprise Lake Member; Port Radium Formation; Faber Group; Dismal Lakes Group; Cleaver Diabase; Hepburn Intrusive Suite; Akaitcho Group; Hottah Terrane; Rainy Lake Intrusive Complex; Narakay Volcanic Complex; rare earth element analyses; geochemical signatures; syenogranites; siliciclastics; Precambrian; Proterozoic
Illustrationsgeoscientific sketch maps; tables; stratigraphic columns; photographs; autoradiographs; aerial photographs; cross-sections; plots; histograms; photomicrographs; Concordia diagrams; geochronological charts
ProgramGEM2: Geo-mapping for Energy and Minerals, South Rae Province Bedrock/Surficial geology
ProgramTargeted Geoscience Initiative (TGI-5)
ProgramNSERC Natural Sciences and Engineering Research Council of Canada
Released2018 04 04
AbstractThe historic Eldorado U-Co-Ni-Cu-Ag veins at Port Radium are hosted by one of the arrays of northeast-trending quartz-filled brittle fault zones in the 1875-1855 Ma Great Bear magmatic zone. The veins formed in a lensoid segment of the fault, which underwent repeated reactivation that created subsidiary fractures, tensional openings, and breccia zones that were favorable for precipitation of multiple stages of ore minerals. The timing of ore precipitation is constrained by two swarms of diabase intrusions. The older ca. 1740 Ma Cleaver dikes predate the polymetallic mineralization and deposition of Mesoproterozoic strata of Hornby Bay Group. The ca. 1590 Ma Western Channel sheets postdate the main ore stages in the veins and intrude the lower strata of the Hornby Bay Group.
While diabase intrusions constrain ore precipitation to 1740-1590 Ma, in situ U-Pb analyses of fine-grained uraninite record isotopic resetting at 1453 ± 18 Ma. The delta-18O compositions of all uraninite stages range from -35.0 to -27.4 per mil, and reflect an overprint by late meteoric fluids. Chondrite-normalized rare earth element data for uraninite produce bell-shaped patterns centered on Sm-Dy, with slight negative Eu anomalies. The age constraints imposed by the dikes, delta-18O values and REE signatures of the early U and Co-Ni sulfarsenide stages indicate that the U and base metal mineralization at Port Radium is akin to the basement-hosted, polymetallic unconformity-related U deposits in the coeval Athabasca and Thelon basins. The 1453 Ma isotopic resetting builds to the growing body of evidence for a major event in Laurentia at 1.4 Ga while the youngest Ag-Bi stage at Port Radium was likely related to intrusion of the Western Channel diabase.
Summary(Plain Language Summary, not published)
Despite being one of Canada's first uranium mines, the origin and classification of the uranium-bearing veins at Port Radium remains contentious. This study, started under the GEM I uranium project, used unpublished historical maps and recently published age determinations combined with application of modern analytical tools on archival materials to refine the origin of the veins. These field relationships, age determinations and geochemical signatures all highlight that the veins are best classified as basement-hosted expressions of unconformity-type uranium mineralization related to the Hornby Bay Basin, akin to the Athabasca Basin uranium deposits. These findings significantly increase the potential for high-grade uranium mineralization of the region.