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TitleAnomalous abundances of He and mobile metals in surface media over the deeply buried Millennium U deposit, Athabasca Basin, Canada
AuthorPower, M J; Hattori, K; Pinti, D L; Potter, E GORCID logo
SourceGoldschmidt 2013 conference abstracts; Mineralogical Magazine vol. 77, no. 5, 2013 p. 1993, Open Access logo Open Access
Alt SeriesEarth Sciences Sector, Contribution Series 20130168
PublisherMineralogical Society
MeetingGoldschmidt 2013; Florence; IT; August 25-30, 2013
Mediapaper; on-line; digital
File formatpdf; html
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
Subjectseconomic geology; surficial geology/geomorphology; fossil fuels; uranium; uranium deposits; mineralization; mineral deposits; helium; gas geochemistry; soil gas geochemistry; soil geochemistry; Millennium Deposit
ProgramTargeted Geoscience Initiative (TGI-4) Uranium Ore Systems
AbstractWe examined soil and noble gas geochemistry over the Millennium uranium deposit, Athabasca Basin, SK, Canada. It has indicated resources of 68.2 million lbs U3O8 at ~750 m depth, along a major fault in granites & metamorphosed pelites of Archean to Paleoproterozoic age below the Athabasca sandstones.
110 soil samples along two transects 503 and 333 m long over the deposit yielded anomalous values in U (=0.6 ppm), Pb (=35 ppm) and Cu (=15 ppm) in aqua regia digestion of humus, when compared to the µ±2ox for metal values. Anomalous values were also detected for U (=102 ppb) Pb (=2100 ppb), and Cu (=220 ppb) in B-horizon soils leached by ammonium acetate compared to the µ±2ox of metal values. Most anomalies were directly above the ore zones and surface traces of major faults, including the ore-hosting Marker fault. Gas samples were collected in monitoring wells and drill holes by submerging diffusion samplers at 10 to 42 m below the surface for 3 days. The 4He, 22Ne, 36Ar, 40Ar, 84Kr and 132Xe were measured by quadrupole mass spectrometry at GEOTOP. Analytical uncertainties range from 1.5 to 4.6% of the measured amount. Measured 4He concentrations in water ranges from 6.89 x 10-8 to 4.23 x 10-5 ccSTP/g. The lower amount is identical to that expected by equilibration with the atmosphere (Air Satured Water value or ASW). The higher amount is clearly related to radiogenic 4He produced by the U ore and released in the water. Indeed, three samples yielded anomalous 4He/36Ar ratios, 715, 239 and 108 times the ASW value, clearly indicating the addition of radiogenic 4He. Ratios of 4He/22Ne (790, 340 and 130 times ASW value), 4He/84Kr (690, 240 and 110 times ASW), and 4He/132Xe (580, 210 and 95 ASW) were also observed, confirming the results.
Broad geochemical anomalies in soil and gas at the property show that fault-controlled redistribution of elements and gases possibly exists over the deposit. Our results suggest upward migration of metals and He to surface through these geological features - detectable by geochemical exploration methods for U using two different surface media.
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. Analysis of soils and gases dissolved in groundwater overlying deeply-buried uranium mineralization in the Athabasca Basin (Saskatchewan) has outlined the presence of certain elements in concentrations exceeding 'background' values. The presence of these geochemical anomalies in soil and gas indicate that fault-controlled redistribution of elements and radiogenic gases exists over the deposit and are detectable by geochemical exploration methods.

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