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$Fayek & Kyser 2000 uraninite fractionations.pdf - Queen's University$

CHAPTER 6 CONCLUSIONS An integrated multidisciplinary geological study, including structural geology, geochronology, petrographic and geochemistry approaches, was used to detail the structural and fluid evolution of uranium deposits in successor basins in the Beaverlodge area in Canada, and the South Alligator River area in Australia. The results presented in this research demonstrate that: a) The Beaverlodge area in Canada and the South Alligator River area in Australia record ore-forming systems that resulted from multistage deformation, hydrothermal alteration, U mineralization, and late fluid processes during protracted tectonic evolution that spans over 2.3 Gyr. b) The main breccia-type U mineralizing event that affected all deposits in the Beaverlodge area formed at ca. 1850 Ma from Ca-Na-dominated metamorphic fluids at ca. 330 o C linked to metasomatism accompanying regional metamorphism of the Trans- Hudson Orogen. The ore-forming fluids were likely derived from metamorphic remobilization of pre-existing U-rich basement rocks, and ascended upward along deep fracture systems that resulted from brittle reactivation of early ductile shear zones. U precipitated when decompression during brecciation decrease the solubility of the U- carbonates complexes and the temperature of the fluid. c) Early minor stages of U mineralization in the Beaverlodge area are hosted in cataclasite and veins at ca. 2.29 Ga and in albitized granite in the Gunnar deposit 209
etween ca. 2.3 Ga and 1.9 Ga. Later stages are related to minor U veins at ca. 1.82 Ga linked to Martin Lake mafic dikes and to minor late veins at ca. 1.62 Ga corresponding to the timing of unconformity-type U mineralization in the Athabasca Basin. d) The main event of U mineralization in the South Alligator River area formed at ca. 1820 Ma, subsequent to deposition of the El Sherana Group at 1840-1830 Ma. The formation of these deposits is related to fluids derived from diagenetic processes in sandstone of the El Sherana Group. The source of the ore was likely U-bearing minerals in the sandstone and volcanic rocks of the El Sherana Group and the source of metals such as Au and PGE are from basement rocks, similar to some of the multielement deposits (i.e. Nicholson) in the Beaverlodge area of Canada. These deposits can be classified as a variation on unconformity-related U mineralization similar to those in the overlying Kombolgie Basin. Tectonic reactivation of the El Sherana- Palette fault during the Nimbuwah event would have provided structural conduits for hydrothermal basinal brines that descended downward into the metamorphic basement rocks. Interaction between the oxidizing U-bearing basinal brines and the reducing carbonaceous shale of the Koolpin Formation would have led to U precipitation. Uranium deposits in the Beaverlodge and South Alligator River areas record late alteration fluid events related to both near and far-field tectonic events. These late events represent circulation of meteoric water through fault zones. e) Uraninite in major structures is greatly sensitive to fluid events stimulated by both near- and far-field tectonic events. It can serve as vehicle to understand the complex 210
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FLUID EVOLUTION AND STRUCTURAL CONT
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Abstract Uranium deposits associate
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Co-Authorship This thesis and the m
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Sarah Rice and Jonathan Cloutier, a
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TABLE OF CONTENTS Abstract………
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2.5.2. Temporal relationships of fa
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4.5.3. Isotopic compositions of min
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List of Figures Figure 1.1. General
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Figure 4.16. Distribution of 207 Pb
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Table 4.4. Isotopic data of the U-P
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processes by which these deposits f
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Figure 1.1. Generalized geological
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which is the equivalent of the Mill
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dolostone and carbonaceous shale (L
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Mineral Field (Figure 1.2). Many de
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2005). U mineralization is controll
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Figure 1.4. Schematic representatio
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In particular, the key issues to be
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genetic model for the U mineralizat
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fourth and most significant uranium
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The Beaverlodge area is part of the
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1998; Hartlaub and Ashton, 1998). R
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(D 1 ) produced a regional migmatit
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These previous age models do not ta
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the age when the concentrations of
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Figure 2.3. A: Detailed geologic ma
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hornblende-feldspar gneiss showing
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east-west striking en-échelon quar
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and broken Kfs 1 and Qtz 1 embedded
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A Meters LEGEND B Figure 2.6. A: De
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Figure 2.7. Microphotograph of vari
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eplaces Kfs 1 feldspars (Fig. 2.7A)
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the Qtz 1 quartz dissolution result
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Figure 2.9. Microphotograph of typi
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uraninite (Fig. 2.10). The errors o
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Figure 2.10. Backscattered Electron
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post-mineralization alteration duri
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Post-mineralization alteration even
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Volcanic-type ±U 5 (Sample 6139, G
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6134 pt8a 2 Gunnar 82.92 2.92 5.30
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Regression to zero content of the s
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faults (Fig. 2.13C). The breccias w
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Figure 2.13. Schematic cross-sectio
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Mylonites were then reactivated at
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and thrusting during the 1.94-1.92
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Beaverlodge area (Morelli et al., 2
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dikes (Ernst and Buchan, 2001b) and
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Figure 2.15: Distribution of 207 Pb
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CHAPTER 3 GENESIS OF MULTIFARIOUS U
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eccia-type. The other styles of min
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The basement consist of Neoarchean
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of essentially unmetamorphosed arko
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WDX X-ray spectrometers at Carleton
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3.4. Results 3.4.1. Paragenesis of
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are derived from their chlorite cry
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Figure 3.4. Photomicrographs of typ
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3.4J). Py 6 Pyrite and Cpy 5 chalco
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mineralization varies from 25.70 to
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6137APt71 60.67 13.73 4.59 6.48 0.0
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Fig. 3.6A). The Ca may result from
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Sample ID 1 ± 2 ± 3.a ± 4 ± 5.a
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Stable isotopic O and C composition
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Sample ID Deposit Mineral Mineral v
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equilibrium with a fluid having δ
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Syn-ore Chl 8 chlorite sampled from
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Figure 3.9. Binary diagrams showing
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Figure 3.10. Chondrite-normalized R
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Retrograde metamorphism Early vein
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contents in syn-ore Chl 4 chlorite
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decompression and hydration reactio
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mineralizations, which upgraded the
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metamorphic origin of the main U 4
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y the abundance of Ap 1 apatite and
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of late fluid events that have affe
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CHAPTER 4 FLUID EVOLUTION AND GENES
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1990, 1991; Wyborn et al., 1990). H
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stable isotope geochemistry, U-Pb g
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coincident with the initiation of s
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plasma mass spectrometry (LA-HR-ICP
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The Coronation Hill deposit occupie
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arsenides, nickel selenide and copp
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No corrections were made to the 238
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which was interpreted as being asso
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porphyry and coated by Chl 1 formin
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Mineralized breccias showing quartz
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SOUTH ALLIGATOR RIVER GROUP EL SHER
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A Carbonaceous Shale B Src 1 Qtz 1
Page 177 and 178: A Granite Qtz 0 fragments Qtz 0 B M
Page 179 and 180: chemical composition as a result of
Page 181 and 182: Sample I.D SiO 2 CaO FeO ThO 2 MnO
Page 183 and 184: site occupancy (Cathelineau, 1988).
Page 185 and 186: Mineral values Temperature Fluid va
Page 187 and 188: Corrected ratios Apparent ages ( ±
Page 189 and 190: G H Figure 4.12. U-Pb concordia dia
Page 191 and 192: Figure 4.13. Pb-Pb isochron diagram
Page 193 and 194: and 4.12B), and to 207 Pb/ 206 Pb a
Page 195 and 196: 160 o C at Coronation Hill. The tem
Page 197 and 198: Figure 4.15. Conceptual genetic mod
Page 199 and 200: of the Koolpin Formation, while dep
Page 201 and 202: at ca. 1820 Ma, approximately 40 My
Page 203 and 204: culminating with the formation of R
Page 205 and 206: deposits is related to fluids deriv
Page 207 and 208: CHAPTER 5 GENERAL DISCUSSION 5.1. I
Page 209 and 210: ed-bed strata and associated volcan
Page 211 and 212: character of the fluid that formed
Page 213 and 214: 5.2.1.2. Metamorphic-related uraniu
Page 215 and 216: during brecciation or reduction as
Page 217 and 218: ca. 1820 Ma that triggered reactiva
Page 219 and 220: Plutons Event at 1.4 Ga (Barinek et
Page 221 and 222: Kolari-Kittila Province Kuusamo Pro
Page 223 and 224: The uranium deposits in various pro
Page 225 and 226: Fig. 5.6. Distribution of the Rorai
Page 227: Roraima Basin, similar to what is o
Page 231 and 232: REFERENCES Adams, J., 1989. Postgla
Page 233 and 234: Ashton, K.E., 2010. The Gunnar Mine
Page 235 and 236: Bowles, J.F.W., 1990. Age dating of
Page 237 and 238: Cuney, M.L., 2005. World-class unco
Page 239 and 240: deposits in the Athabasca Basin, Sa
Page 241 and 242: Hartlaub, R.P., Heaman, L.M., Chack
Page 243 and 244: Saskatchewan Geological Survey, Sas
Page 245 and 246: Kyser, K., and Cuney, M., 2008. Geo
Page 247 and 248: two-sided oblique-slip collisional
Page 249 and 250: Creek Geosyncline: in ‘The minera
Page 251 and 252: Piper, J.D.A., 2004. Discussion on
Page 253 and 254: 99.Sheppard SMF and Gilg HA 1996. S
Page 255 and 256: Proceedings Darwin Conference 1984
Page 257 and 258: Wingate, M.T.D, Pisarevsky SA, Evan
Page 259 and 260: Sample Deposit 207 Pb/ 206 Pb ±2σ
Page 265 and 266: APPENDIX B REE contents of various
Page 267 and 268: Sample Y Zr Cs Ba Th La Ce Pr Nd Sm
Page 269 and 270: Sample ΣREE TLREE THREE LREE/HREE
Page 271 and 272: SAMPLE ID. SiO 2 TiO 2 AL 2O 3 CR 2
Page 273 and 274: SAMPLE ID. SiO 2 TiO 2 AL 2O 3 CR 2
Page 275 and 276: APPENDIX E Electron microprobe data
Page 277 and 278: SAMPLE Si 4+ AL 4+ Total AL 6+ Ti 4
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SAMPLE Si 4+ AL 4+ Total AL 6+ Ti 4
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Sample ID. Deposit UO 2 SiO 2 CaO F
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Sample ID. Deposit UO 2 SiO 2 CaO F
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Corrected ratios Apparent ages ( ±
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Corrected ratios Apparent ages ( ±
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Sample ID. Al 2O 3 CaO FeO K2O MgO
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Sample ID. Al 2O 3 CaO FeO K2O MgO
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250 85 330 40 145 70 25 65 30 30 27
Page 295 and 296:
Mineralized veins Quartz veins 276
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