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TitleSurface media expressions above buried uranium: The Phoenix & Millennium deposits, Athabasca Basin
AuthorPower, M J; Hattori, K H; Sorba, C; Kotzer, T; Pinti, D L; Potter, E GORCID logo
SourceGeological Association of Canada-Mineralogical Association of Canada, Joint Annual Meeting, Programs with Abstracts vol. 36, 2013 p. 166
LinksOnline - En ligne
Alt SeriesEarth Sciences Sector, Contribution Series 20130169
PublisherGeological Association of Canada and the Mineralogical Association of Canada (GAC-MAC)
MeetingGeological Association of Canada - Mineralogical Association of Canada Joint Annual Meeting; Winnipeg; CA; May 22-24, 2013
File formatpdf
NTS64E; 64L; 64M; 74E; 74F; 74G; 74H; 74I; 74J; 74K; 74L; 74M; 74N; 74O; 74P
AreaAthabasca Basin; northern Saskatchewan
Lat/Long WENS-112.0000 -102.0000 60.0000 57.0000
Subjectssurficial geology/geomorphology; geochemistry; glacial landforms; glacial deposits; uranium; uranium deposits; geochemical analyses; lithology; tills; till geochemistry; soil samples; soil geochemistry; Athabasca Basin; Phoenix Deposit; Millennium Deposit; Cenozoic; Quaternary
ProgramTargeted Geoscience Initiative (TGI-4) Uranium Ore Systems
AbstractIn order to evaluate surficial geochemical anomalies over deeply-buried unconformity-related uranium deposits, we selected two deposits with no apparent surface expression of mineralization: The Phoenix and Millennium deposits. The Phoenix deposit, owned by Denison Mines Corporation, has currently defined indicated resources of 52.3 million lbs U3O8 situated ~400 m below the surface, whereas Cameco Corporation¿s basement-hosted Millennium deposit has indicated resources of 46.8 million lbs U3O8, at a depth of ~750 m. Both are located in the southeastern margin of the Athabasca Basin in northern Saskatchewan. The area is covered by 25-100 m thick glacial tills comprised of moraine plains, streamlined moraines and subordinate eskers. Whole rock compositions of till samples from both properties suggest that the glacial sediments were sourced from a mixture of granitic basement rocks and Athabasca sandstones.
2011 field sampling above the Phoenix deposit yielded anomalous concentrations of U, Ni, Cu, Mo, Ag and W in humus, B-horizon soil and C-horizon glacial till in the areas directly above the A and B deposits and the WS Shear zone. 2012 sampling reproduced similar geochemical anomalies in soil samples (2-17 ppm U, 10-27 ppm Cu, 4-7 ppm Ni, 1000-1500 ppb As). Furthermore, leaching of humus samples in H2O, HBr, HNO3 and HF-HBr solutions show that these metals are not simply adsorbed on the surface; instead, they are tightly held in organics. Finally, analyses of the uppermost Manitou Falls ¿D¿ Formation sandstones with partial HF-HNO3-HCl digestion above the ore zones contain anomalous U (up to 2 ppm).
Following the successes at Phoenix, soil sampling was carried out along the transects over the Millennium deposit in the summer of 2012, and yielded anomalies in U (0.4-0.6 ppm), Pb (15-35 ppm) and Cu (5-15 ppm) in aqua regia digestion of humus as well as anomalies in ammonium acetate leach of B horizon soils again above the ore zones and surface traces of B1 and Marker faults. Broad surficial geochemical anomalies in the property likely reflect abundant faults and fault-bound mineralization. Gas samples placed in water-filled drill holes at depths of several m yielded anomalously high radiogenic 4He as indicated by 4He/36Ar ratios up to 700 times the atmospheric one, confirming the upward migration of 4He from the Millennium deposit. The combined results suggest upward migration of both mobile metal ions and uranium decay products from the ore zones to the surface.
Summary(Plain Language Summary, not published)
The Targeted Geoscience Initiative (TGI-4) is a collaborative federal geoscience program that provides industry with the next generation of geoscience knowledge and innovative techniques to better detect buried mineral deposits, thereby reducing some of the risks of exploration. Geochemical analysis of soils and the uppermost rock units overlying deeply-buried uranium mineralization in the Athabasca Basin (Saskatchewan) has outlined the presence of certain elements in concentrations exceeding 'background' values using a variety of geochemical digestion methods. The geochemical results from the uppermost rock units indicate that elevated concentrations in the humus and B soil horizons reflect those in the siliciclastic rock units. Leaching results from humus samples also indicates that the metals are not adsorbed on the surface but rather tighly bound within the organics.

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