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Athabasca Basin Uranium by Darren Smith


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Athabasca Basin Uranium by Darren Smith

  1. 1. Darren L. Smith, M.Sc., P.Geol. Nov 2013 1
  2. 2. o Actinide element o 3 ppm average abundance in crust • Cu = 68 ppm • Ni = 90 ppm • Fe = 63,000 ppm o Mobile element o Uranium is a radioactive element ◦ Unstable, must decay to stable element ◦ Five times more radioactive than thorium o Main use is fuel in nuclear reactors (power) Pitchblende (uraninite) • Dominant ore mineral 2
  3. 3. o 85 natural occurring RA elements and isotopes exist ◦ Th-232, U-238, and K-40 are the most common ◦ Also cosmological RA → C-14, H-3 (Tritium) Drum of yellowcake o RA is everywhere ◦ Its all relative and a matter of perception ◦ A banana is radioactive (K-40) o RA elements have an unstable nucleus • Isotopes are atoms that have the same number of protons but a different number of neutrons • Elements may have many isotopes, each with ◦ 14 elements in uranium decay series different properties ◦ (U-238 decays to stable Pb-206) ◦ Daughter products with short half-lives are problem o Yellowcake concentrate end-product ◦ Not RA as daughter products stripped away ◦ 70-90% U3O8, +UO2 and UO3 3
  4. 4. o Three isotopes of uranium ◦ Abundance in nature = U-238 (99.27%), U-235 (0.72%), and U-234 (0.006%) Nuclear Power Plant • Requires enrichment to ~1-5% U-235 • Complex and difficult process Weapons Grade • Requires enrichment to +85% U-235 • Extremely complex and difficult process • If one person’s power needs for their entire life were satisfied by nuclear energy, the waste produced would fit into a single pop can 4
  5. 5. o Regulated Canadian allowed dosage is max 20 millisievert (mSv) per year ◦ Average Canadian receives 1.8 mSv per year (range up to 4.0 depending on latitude) ◦ India, Brazil range from 20 to 50+ mSv per year with no ill effects ever reported o o o Uranium mine workers in Canada receive a dosage of ~1 to 5 mSv per year RA exposure from uranium exploration and mining is well managed and not hazardous to a workers health when set protocols are followed Remember, RA is everywhere ◦ RA is source of heat and is critical to the earth as we know it ◦ Without it the Outer Core would be solid, the earth would cool, and plate tectonics would not occur *Dosage information source: D. Grant Feasby, COM2013 Presentation 5
  6. 6. o o o Highest grade deposits are found in the Athabasca Basin, Northern Saskatchewan, Canada Average world grade is 0.14 % U3O8 Average Basin grade is 2% U3O8 ◦ Several deposits/mines with ore grade over 15%  MacArthur River, Cigar Lake, Phoenix o Largely underexplored and low geopolitical risk 6
  7. 7. o For Athabasca Basin uranium deposits to form, they require: 1. URANIUM BEARING FLUIDS (U6+), 2. STRUCTURES to act as conduits for fluid flow, 3. GRAPHITIC CONDUCTORS (or other reductant) to facilitate uranium deposition (U4+), and 4. TIME (millions of years) o Two main end-member deposit types o Unconformity-sandstone hosted o E.g. Cigar Lake o Basement hosted o Patterson Lake South (PLS), Roughrider, Millennium 7
  8. 8. o o Paleoproterozoic (1740 Ma) Sedimentary Basin Two main uranium mineralizing events ◦ 1500 and 1350 Ma ◦ Further alteration and uranium remobilization at 1176, 900, and 300 Ma Athabasca Basin formation begins 8
  9. 9. *From Jefferson et. al. 2007 9
  10. 10. Carswell Structure formed by meteorite impact @ ~115 Ma (Lower Cretaceous) *From Jefferson et. al. 2007 10
  11. 11. o o Pitchblende first discovered in 1935 on north shore of Lake Athabasca, now known as Beaverlodge District Beaverlodge District Production from 1953 to 1982 ◦ >60 million pounds (Mlbs) uranium produced ◦ Production from 16 deposits, milled at 3 facilities o o Mineralization hosted in veins By 1964 only one mine remained in operation in Beaverlodge Area ◦ Last mine closed in 1982 Pitchblende (uraninite) 11
  12. 12. o Rabbit Lake Deposit discovered in 1968 ◦ Incited staking rush and extensive exploration o Rabbit Lake New deposit models developed ◦ Unconformity-Associated Deposits o o Prolific Eastern Athabasca Trend revealed and focus of exploration Eastern Athabasca Trend Patterson Lake South (PLS) Deposit discovered in 2012 within southcentral Basin o New staking rush in emerging district 12
  13. 13. o McArthur River (production) ◦ Reserves of 1.05 Mt @ 16.4% U3O8 (378.9 Mlbs) o Rabbit Lake (production) ◦ Reserves of 1.47 Mt @ 0.70% U3O8 (22.8 Mlbs) o Key Lake (mined out*) ◦ *(stockpiled low grade ore used to dilute McArthur River ore) o Cluff Lake (mined out) ◦ Produced ~63 Mlbs at ore grade of 0.93% U3O8 o Cigar Lake (near-term producer) ◦ Reserves of 0.57 Mt @ 18.3% U3O8 (216.7 Mlbs) o 3 processing mills located on eastern side of Basin ◦ Key Lake, Rabbit Lake, McClean Lake (JEB) Basin deposits are in the range of Kt, not Mt, focused in 10’s of metres wide, cigar shaped pods with 100 m strike lengths 13
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  16. 16. Sandstone ± Basement Hosted Basement ± Sandstone Hosted Basement hosted *From Jefferson et. al. 2007 16
  17. 17. Quartz Dissolution Egress Style (E.g. Cigar Lake, Midwest) Silicification Egress Style (E.g. MacArthur River, Key Lake) *From Jefferson et. al. 2007 o Deposits often termed ‘blind deposits’ as cannot be detected directly o Therefore, must use indirect methods (e.g. map clay alteration) 17
  18. 18. Evolution of Midwest Deposit Idealized Basin Deposit Model o Midwest Deposit discovered in 1978 o Located on northern end of Eastern Athabasca Trend o Indicated resource of 43 Mlbs @ 5.50% U3O8 *From Sibbald et. al. 1991 18
  19. 19. o We are trending towards looking deeper to find deposits than before o o o o o o o o Key Lake discovered in 1975 McClean Lake discovered in 1979 Midwest discovered in 1978 Cigar Lake discovered in 1981 McArthur River discovered in 1988 Millennium discovered in 2000 Phoenix discovered in 2008 Roughrider discovered in 2008 19
  20. 20. Boulder Prospecting o o o Method of tracing back mineralized boulder fields to source based on knowledge of glacial advances Very powerful indicator of proximal mineralization Deposits found via this method ◦ Cluff Lake ◦ Rabbit Lake ◦ Patterson Lake South ◦ Maurice Bay ◦ Collins Bay ◦ Several others 20
  21. 21. Radon Sampling o o o o Grid based collection of radon gas at surface Radon (Rn) is product of uranium decay series and will migrate to surface through rock fractures and porosity Radon gas migrates to surface One the closest methods to direct detection of a uranium ore body there is Credited with final targeting and discovery at PLS in Nov 2012 21
  22. 22. Lake Sediment Sampling o o o Utilizes helicopter or boat to sample lake bottom May also collect water sample (less valuable) Pathfinder geochemistry important ◦ (Ni, Cu, B, As, Pb, Co) o Good tool for regional evaluation Soil sampling o o o o Grid based ground sampling Must keep in mind glacial influences Pathfinder geochemistry important ◦ (Ni, Cu, B, As, Pb) Good tool to systematically evaluate smaller area Other o o Helicopter support lake sampling Biogeochemical sampling Biogeochemical Mobile Metal Ion (MMI) 22
  23. 23. Airborne Methods o Helicopter borne VTEM plus survey Electromagnetic (EM) Survey ◦ Locates conductors associated with deposits o Magnetic Survey ◦ Helps define geology (mag low may be prospective meta-sediments), and structure o Eastern Athabasca Trend Radiometric Survey ◦ Measures RA (Th, U, and K) within ~ top 30 cm of surface ◦ Look for hot spots representing boulder fields etc. 23
  24. 24. Ground Methods o Electromagnetic (EM) Survey ◦ Better defines conductors than airborne data o Gravity Survey ◦ Maps alteration through density contrast ◦ Gravity lows are targets (alteration destroys host rock) o Electromagnetic principle DC Resistivity ◦ Maps clay alteration within sandstone ◦ Very common within basin o Other ◦ Magnetic Survey, Seismic Gravity anomaly principle 24
  25. 25. *From Jefferson et. al. 2007 25
  26. 26. Within Basin (<100 m to 800 m sandstone cover) 1. Airborne EM, RA, and Magnetics 2. Prospecting and ground sampling 3. Ground DC Resistivity/ Gravity, EM, and Radon surveys 4. Drill Outside Basin (no sandstone cover) 1. Airborne EM, RA, and Magnetics 2. Prospecting and ground sampling 3. Ground Gravity, EM, and Radon surveys 4. Drill o Mineralized core (Roughrider Deposit) Approach is very similar within and outside of Basin with Gravity – DC Resistivity the main difference 26
  27. 27. Patterson Lake South (PLS) o o o o o o 1977-81 – PLS corridor discovered, ground radon anomaly defined, and drilling reveals favourable geologic setting Fall 2009 –Airborne RA survey confirms historic RA anomaly, radon surveys completed Summer 2011 – Prospecting discovers mineralized boulder train coincident with RA anomaly Fall 2011 – Drill program intersects favorable geology and alteration Winter/Spring 2012 – Airborne VTEM, Ground DC-Resistivity, and SMLTEM Surveys November 5, 2012 – Discovery drill hole released ‘PLS12-022’ (8.5 m of 1.07% U3O8) No resource yet defined One of the best intersections is: PLS13-075’ (54.05 m of 9.08% U3O8) Mineralization is near-surface (<200 m) making deposit even more attractive 27
  28. 28. Patterson Lake South – DC Resistivity *From Fission Uranium Corp. website 28
  29. 29. Patterson Lake South – Radon Survey *From Fission Uranium Corp. website 29
  30. 30. Roughrider - discovered in 2008 ~100 m Indicated: 0.39 Mt @ 1.98% U3O8 (17.2 Mlbs) Inferred: 0.16 Mt @ 11.43% U3O8 (40.7 Mlbs) 30
  31. 31. J-Zone and Roughrider – almost discovered prior ~100 m o Historic drilling came close to discovering the deposits o Deposits are cigar shaped and may be only 10’s of metres across making them very difficult to find. Therefore, must put all clues together to find o alteration, chemistry, geophysics, favourable geologic setting 31
  32. 32. Jefferson et. al. (2007) Empirical Models for Canadian Unconformity-Associated Uranium Deposits, In “Proceedings of Exploration 07: Fifth Decennial International Conference of Mineral Exploration, edited by B. Milkereit, p. 741-769 Jefferson et. al. (2007?) Unconformity Associated Uranium Deposits (DRAFT) Sibbald et. al. (1991) Uranium Deposits of the Athabasca Basin, Saskatchewan (Field Trip 11) , Open File 2166 Ford et al. (2007) Overview of Geophysical Signatures Associated with Canadian Ore Deposits, in Goodfellow, W.D., ed. Mineral Deposits of Canada: A of Major Deposit-Types, District Metallogeny, the Evolution of Geological Provinces, and Exploration Methods: Geological Association of Canada, Mineral Deposits Division, Special Publication No 5. 5, p. 939-970 32