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. 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. 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. 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. 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. 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. McArthur River U deposit
Modified after Hoffmann (1989) and Ramaekers et al. (2007)
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8. McArthur River Zone 4
 332.6 Mlbs U3O8, 20.7%
U3O8 (avg. grade)
 Basement-hosted and
sandstone-hosted ore
bodies
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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
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10. Evolution I: Mineral paragenesis
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11. Evolution II: Origin of alteration fluids
Post-ore kaolinite:
recent meteoric waters
A single fluid
produced alteration
in basement and
sandstones:
Basinal fluids
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12. Genetic evolution of McArthur River Zone 4
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13. Silicified zone I: Alteration pattern
 Spatial extent of
late pre- to syn-ore
chlorite alteration
limited by
silicified zone
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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
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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. 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. 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)
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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. Wheeler River Zone K (apparently barren)
 Oxidizing illite
alteration
 Reducing sudoite
and clinochlore
alteration
19
Modified after Cloutier et al. (2010)

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. 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
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mineralization

22. Comparison of Fe3+/ΣFe ratios in chlorite
 Mineralized
systems:
higher Fe3+/ΣFe
ratios
 Barren systems:
lower Fe3+/ΣFe
ratios
22

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
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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)
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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
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(1993), Cloutier et al. (2010),
Alexandre et al. (2009, 2012)

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.
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