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Geochemical and mineralogical evolution of the

McArthur River Zone 4 unconformity-related uranium
ore body and applicatio...
Outline of presentation

Modified after Jefferson et al. (2007) and
references therein

Study #1: McArthur River Zone 4 an...
Introduction to research: Sandstone-hosted
alteration systems
Fe3+/ΣFe?
Fe3+/ΣFe?

Fe3+/ΣFe?

Data from Percival
and Kodam...
Introduction to research: Sandstone-hosted
alteration systems

Data from Percival
and Kodama (1989),
Percival (1993),
Clou...
Research objectives and rationale
Study #1: McArthur River Zone 4 evolution and silicified zone






Mineralogical a...
Mineralogical and geochemical evolution of the

unconformity-related McArthur River Zone 4 ore
body in the Athabasca Basin...
McArthur River U deposit

Modified after Hoffmann (1989) and Ramaekers et al. (2007)

7
McArthur River Zone 4
 332.6 Mlbs U3O8, 20.7%
U3O8 (avg. grade)
 Basement-hosted and
sandstone-hosted ore
bodies

8
McArthur River Zone 4
 Zone 4: U hosted in
Manitou Falls Formation
sandstones and hanging
wall basement
(Wollaston Group)...
Evolution I: Mineral paragenesis

10
Evolution II: Origin of alteration fluids

Post-ore kaolinite:
recent meteoric waters

A single fluid
produced alteration
...
Genetic evolution of McArthur River Zone 4

12
Silicified zone I: Alteration pattern

 Spatial extent of
late pre- to syn-ore
chlorite alteration
limited by
silicified ...
Silicified zone II: Dispersion of radiogenic Pb
 Contours of 207Pb/206Pb
isotope ratios
 Silicified zone restricts
dispe...
Key Findings
Genetic evolution of McArthur
River Zone 4
 Silicified zone formed during early
stages of diagenesis
 Basin...
Oxidation state of iron in alteration minerals

associated with sandstone-hosted unconformityrelated uranium deposits and ...
57Fe

Mössbauer spectroscopy
Oct. Fe3+ phyllosilicate

Oct. Fe2+ phyllosilicate

Oct. Fe3+ hematite

Oct. Fe3+ phyllosilic...
McArthur River Zone 4 (mineralized)

 Fe3+/ΣFe ratios
 Outer illite and
illite-chlorite
mixed layer clay
zones are oxidi...
Wheeler River Zone K (apparently barren)

 Oxidizing illite
alteration
 Reducing sudoite
and clinochlore
alteration

19
...
Fe oxidation state vs. Pb isotope ratios
Mineralized alteration systems

 Decreasing Fe3+/ΣFe ratios in sudoite (more red...
Fe oxidation state vs. Pb isotope ratios
Barren alteration systems






Decreasing Fe3+/ΣFe ratios in chlorite at WR ...
Comparison of Fe3+/ΣFe ratios in chlorite
 Mineralized
systems:
higher Fe3+/ΣFe
ratios
 Barren systems:
lower Fe3+/ΣFe
r...
How clay alteration acquired their Fe3+/ΣFe
ratios?
(2) U6+(aq) + Fe2+(aq) + 2H2O = U4+O2(uraninite)
+ Fe3+(chlorite or he...
Key findings
 Critical geochemical factor for U mineralization
 U-bearing, oxidizing, basinal fluids must mix with reduc...
Summary
Redox conditions

Implications of
silicified zone

Source of Fe2+

Oxidation of Fe2+ to Fe3+

Evolution of
McArthu...
Acknowledgements
Special thanks to the following individuals:
Supervisors: Kurt Kyser, Paul Alexandre
QFIR staff: April Vu...
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Ronald Ng M.Sc. thesis presentation (Oct 2012)

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Ronald Ng M.Sc. thesis presentation (Oct 2012)

  1. 1. Geochemical and mineralogical evolution of the McArthur River Zone 4 unconformity-related uranium ore body and application of iron oxidation state in clay alteration as indicator of uranium mineralization Master of Science Ronald Ng Queen’s University with the assistance of Kurt Kyser1, Paul Alexandre1, Dan Jiricka2, Donald Wright3, Gary Witt2, Don Chipley1, Jonathan Cloutier5, Yassir A. Abdu4, Frank C. Hawthorne4, April Vuletich1, Steve Beyer1, 1Queen’s Facility for Isotope Research, 2Cameco Corp., 3Peridot Geoscience Ltd., of Manitoba, 5CSIRO Earth Science & Resource Engineering 4University 1 October 2012
  2. 2. Outline of presentation Modified after Jefferson et al. (2007) and references therein Study #1: McArthur River Zone 4 and silicified zone Study #2: Oxidation state of Fe in clay alteration from sandstone-hosted alteration systems 2
  3. 3. Introduction to research: Sandstone-hosted alteration systems Fe3+/ΣFe? Fe3+/ΣFe? Fe3+/ΣFe? Data from Percival and Kodama (1989), Percival (1993), Cloutier et al. (2010), Alexandre et al. (2009, 2012)  Major goal of thesis: Are there differences in the oxidation state of Fe in clay alteration between mineralized and barren systems?  Scientific and exploration implications? 3
  4. 4. Introduction to research: Sandstone-hosted alteration systems Data from Percival and Kodama (1989), Percival (1993), Cloutier et al. (2010), Alexandre et al. (2009, 2012)  Test site for Fe oxidation state study: McArthur River Zone 4  Mineralogy, geochemistry, and evolution?  Implications of overlying silicified zone? 4
  5. 5. Research objectives and rationale Study #1: McArthur River Zone 4 evolution and silicified zone      Mineralogical and geochemical evolution Spatial and temporal Role of silicified zone Sandstone-hosted ore bodies at McArthur River are not well understood Implications of the overlying silicified zone is unclear Study #2: Oxidation state of Fe in phyllosilicates from sandstone-hosted alteration systems      Spatial distribution of Fe oxidation state in alteration minerals Mineralized vs. barren systems Temporal evolution of Fe oxidation state in sandstone-hosted systems Fe oxidation state vs. geochemical pathfinders for U Can Fe oxidation state be used as an exploration tool? 5
  6. 6. Mineralogical and geochemical evolution of the unconformity-related McArthur River Zone 4 ore body in the Athabasca Basin, Canada: Implications of a silicified zone Submitted to Economic Geology Ronald Ng1, Paul Alexandre1, & Kurt Kyser1 Queen’s University 1Queen’s Facility for Isotope Research 6 October 2012
  7. 7. McArthur River U deposit Modified after Hoffmann (1989) and Ramaekers et al. (2007) 7
  8. 8. McArthur River Zone 4  332.6 Mlbs U3O8, 20.7% U3O8 (avg. grade)  Basement-hosted and sandstone-hosted ore bodies 8
  9. 9. McArthur River Zone 4  Zone 4: U hosted in Manitou Falls Formation sandstones and hanging wall basement (Wollaston Group)  200 m-thick silicified zone  Age of initial mineralization: ca. 1.6 Ga  Resetting ages: ca. 1268 Ma and 838 Ma 9
  10. 10. Evolution I: Mineral paragenesis 10
  11. 11. Evolution II: Origin of alteration fluids Post-ore kaolinite: recent meteoric waters A single fluid produced alteration in basement and sandstones: Basinal fluids 11
  12. 12. Genetic evolution of McArthur River Zone 4 12
  13. 13. Silicified zone I: Alteration pattern  Spatial extent of late pre- to syn-ore chlorite alteration limited by silicified zone 13
  14. 14. Silicified zone II: Dispersion of radiogenic Pb  Contours of 207Pb/206Pb isotope ratios  Silicified zone restricts dispersion of radiogenic Pb and U pathfinder elements  Silicified zone conceals surficial geochemical expression of the Zone 4 ore body 14
  15. 15. Key Findings Genetic evolution of McArthur River Zone 4  Silicified zone formed during early stages of diagenesis  Basinal fluids responsible for alteration in basin and basement – no significant contribution of a distinct basement-derived fluid  Reducing fluids generated when basinal fluids interacted with basement rocks  Affinity to genesis of basementhosted deposits Scientific and exploration implications of silicified zone  Focus U-bearing basinal fluids into fault zone  Enhance ore preservation  Limit spatial extent of chlorite alteration  Restrict dispersion of reducing fluids (e.g. Fe2+)  Limit dispersion of radiogenic Pb and U pathfinder elements 15
  16. 16. Oxidation state of iron in alteration minerals associated with sandstone-hosted unconformityrelated uranium deposits and apparently barren alteration systems in the Athabasca Basin, Canada: Implications for exploration Submitted to Journal of Geochemical Exploration Ronald Ng1, Paul Alexandre1, Kurt Kyser1, Jonathan Cloutier2, Yassir A. Abdu3, and Frank C. Hawthorne3 Queen’s University 1Queen’s Facility for Isotope Research, 2CSIRO Earth Science & Resource Engineering, 3University of Manitoba 16 October 2012
  17. 17. 57Fe Mössbauer spectroscopy Oct. Fe3+ phyllosilicate Oct. Fe2+ phyllosilicate Oct. Fe3+ hematite Oct. Fe3+ phyllosilicate McArthur River Zone 4 illite Centennial (Virgin River) sudoite Δ = quadrupole splitting (mm/s) δ = isomer shift (mm/s) 17
  18. 18. McArthur River Zone 4 (mineralized)  Fe3+/ΣFe ratios  Outer illite and illite-chlorite mixed layer clay zones are oxidizing  Inner chlorite alteration zone is reducing 18
  19. 19. Wheeler River Zone K (apparently barren)  Oxidizing illite alteration  Reducing sudoite and clinochlore alteration 19 Modified after Cloutier et al. (2010)
  20. 20. Fe oxidation state vs. Pb isotope ratios Mineralized alteration systems  Decreasing Fe3+/ΣFe ratios in sudoite (more reducing) and 207Pb/206Pb ratios in drill core (more radiogenic) towards U mineralization 20
  21. 21. Fe oxidation state vs. Pb isotope ratios Barren alteration systems     Decreasing Fe3+/ΣFe ratios in chlorite at WR Zone K; uniform at Spring Point No trend in 207Pb/206Pb ratios with proximity to fault zone Decrease in Fe3+/ΣFe ratios in both mineralized and barren systems Implication: Fe3+/ΣFe ratios reflects proximity to reducing fluid and not to U 21 mineralization
  22. 22. Comparison of Fe3+/ΣFe ratios in chlorite  Mineralized systems: higher Fe3+/ΣFe ratios  Barren systems: lower Fe3+/ΣFe ratios 22
  23. 23. How clay alteration acquired their Fe3+/ΣFe ratios? (2) U6+(aq) + Fe2+(aq) + 2H2O = U4+O2(uraninite) + Fe3+(chlorite or hematite) + 4H+(aq) Basin Oxidizing basinal fluids Illite Fe3+ Fe3+ U 4Fe2+(aq) + Basement Fe2+ 4H+(aq) (1) O2(aq) + = 4Fe3+(chlorite or hematite) + 2H2O Chlorite Fe2+ Reducing basement fluids 23
  24. 24. Key findings  Critical geochemical factor for U mineralization  U-bearing, oxidizing, basinal fluids must mix with reducing Fe2+-bearing basement fluids: (1) basinal fluids must be available (2) right timing  Implications to U exploration  Fe3+/ΣFe ratios in chlorite reflect fluid-mixing process  Predict whether new alteration systems are potentially mineralized  Spatial distribution of Fe3+/ΣFe ratios vector to reducing fluids  Validate 207Pb/206Pb isotope ratio trends  Structural Fe in chlorites  Oxidizing conditions favour formation of di-trioctahedral chlorites (e.g. sudoite) in Athabasca Basin U deposits Fe2+ + Fe3+ + □ (vacancy) = 3 octahedral Mg2+ (Billault et al., 2002) 24
  25. 25. Summary Redox conditions Implications of silicified zone Source of Fe2+ Oxidation of Fe2+ to Fe3+ Evolution of McArthur River Zone 4 Data from Percival and Kodama (1989) , Percival 25 (1993), Cloutier et al. (2010), Alexandre et al. (2009, 2012)
  26. 26. Acknowledgements Special thanks to the following individuals: Supervisors: Kurt Kyser, Paul Alexandre QFIR staff: April Vuletich, Don Chipley, Evelyne Leduc, Kristen Feige Former QFIR staff: Kerry Klassen, Allison Laidlow, Bill McFarlane QFIR pdfs and students: Steve Beyer, Jonathan Cloutier, Yulia Uvarova, Majdi Geagea, Sandeep Banerjee, Urmidola Raye, Serigne Dieng, Vivian Wasiuta, Paul Stewart, Phillip Adene, Claudio Munoz, Alexi Li, Valeria Li, Sara Rice, John Burns, and the many undergraduate students over these years Queen’s Geology: Brian Joy, Alan Grant University of Manitoba: Yassir A. Abdu, Frank C. Hawthorne Cameco Corporation: Gary Witt, Dan Juricka, Donald Wright Office mates: Ehsan Ghazvinian, Matt Perras Others: Eric Hiatt, Mostafa Fayek, James Brenan, Ed Spooner Thank you for your attention. 26

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