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

most dominant factors controlling U 4 uranium deposition. The style of the mineralization process is similar to U deposits in northern Sweden, Ukraine, Brazil and Guyana, all of which contain high grade U mineralization in zones of brecciation related to the global 1.9-1.75 Ga alkali-metasomatism during plate tectonic-scale collisional orogenesis culminating with the Nuna supercontinent assembly. In the Beaverlodge area, brittle reactivated ductile shear zones represent an exploration target for U mineralization. However, the metamorphic origin of the main U mineralization with fluids incapable of transporting significant amounts of U may indicate that these deposits have only marginal potential to host economic U mineralization, and certainly they would be relatively lowgrade. These U mineralization events are older than the unconformity-related U mineralization in the overlying Athabasca Basin. Therefore, U mineralization in this older successor basin would have been one potential source of U for the Athabasca Basin. 131
CHAPTER 4 FLUID EVOLUTION AND GENESIS OF URANIUM MINERALIZATION IN THE SOUTH ALLIGATOR VALLEY AREA, NORTHERN TERRITORIES, AUSTRALIA Abstract Uranium deposits in the South Alligator Valley Mineral Field, Northern Territories, Australia, are hosted in deformed and metamorphosed volcanoclastic rocks and calcareous and carbonaceous sedimentary units of the Koolpin Formation, at the unconformity with overlying El Sherana Basin sandstones. The ore is confined to greenschist facies host rocks that are cut by the El Sherana-Palette fault, a northwest-striking, southwest dipping and dextral strike-slip fault system. Petrographic studies on polished thin sections combined with electron microprobe analysis, stable isotope geochemistry, and geochronology of uranium-bearing minerals at the El Sherana and Coronation Hill deposits have identified a multistage fluid history, involving hydrothermal alteration and uranium mineralization. The pre-ore stage mineralogy consists of sericite, quartz, chlorite, and calcite alteration at temperatures at ca. 300°C, interpreted to result from regional greenschist metamorphism of the basement rocks during the ca. 1860-1840 Ma Nimbuwah event and prior to deposition of the ca. 1840-1830 Ma El Sherana Basin. The basement pre-ore alteration is followed by diagenesis of the El Sherana Basin sediments by oxidizing low latitude basinal brines that produced a kaolinite+quartz+hematite assemblage. The ore stage of uranium, gold, and galena formed at ca. 1820 Ma from evolved basinal brines that originated from the El Sherana Basin and descended downward into basement rocks along 132
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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
Page 99 and 100: CHAPTER 3 GENESIS OF MULTIFARIOUS U
Page 101 and 102: eccia-type. The other styles of min
Page 103 and 104: The basement consist of Neoarchean
Page 105 and 106: of essentially unmetamorphosed arko
Page 107 and 108: WDX X-ray spectrometers at Carleton
Page 109 and 110: 3.4. Results 3.4.1. Paragenesis of
Page 111 and 112: are derived from their chlorite cry
Page 113 and 114: Figure 3.4. Photomicrographs of typ
Page 115 and 116: 3.4J). Py 6 Pyrite and Cpy 5 chalco
Page 117 and 118: mineralization varies from 25.70 to
Page 119 and 120: 6137APt71 60.67 13.73 4.59 6.48 0.0
Page 121 and 122: Fig. 3.6A). The Ca may result from
Page 123 and 124: Sample ID 1 ± 2 ± 3.a ± 4 ± 5.a
Page 125 and 126: Stable isotopic O and C composition
Page 127 and 128: Sample ID Deposit Mineral Mineral v
Page 129 and 130: equilibrium with a fluid having δ
Page 131 and 132: Syn-ore Chl 8 chlorite sampled from
Page 133 and 134: Figure 3.9. Binary diagrams showing
Page 135 and 136: Figure 3.10. Chondrite-normalized R
Page 137 and 138: Retrograde metamorphism Early vein
Page 139 and 140: contents in syn-ore Chl 4 chlorite
Page 141 and 142: decompression and hydration reactio
Page 143 and 144: mineralizations, which upgraded the
Page 145 and 146: metamorphic origin of the main U 4
Page 147 and 148: y the abundance of Ap 1 apatite and
Page 149: of late fluid events that have affe
Page 153 and 154: 1990, 1991; Wyborn et al., 1990). H
Page 155 and 156: stable isotope geochemistry, U-Pb g
Page 157 and 158: coincident with the initiation of s
Page 159 and 160: plasma mass spectrometry (LA-HR-ICP
Page 161 and 162: The Coronation Hill deposit occupie
Page 163 and 164: arsenides, nickel selenide and copp
Page 165 and 166: No corrections were made to the 238
Page 167 and 168: which was interpreted as being asso
Page 169 and 170: porphyry and coated by Chl 1 formin
Page 171 and 172: Mineralized breccias showing quartz
Page 173 and 174: SOUTH ALLIGATOR RIVER GROUP EL SHER
Page 175 and 176: 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
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at ca. 1820 Ma, approximately 40 My
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culminating with the formation of R
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deposits is related to fluids deriv
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CHAPTER 5 GENERAL DISCUSSION 5.1. I
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ed-bed strata and associated volcan
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character of the fluid that formed
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5.2.1.2. Metamorphic-related uraniu
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during brecciation or reduction as
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ca. 1820 Ma that triggered reactiva
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Plutons Event at 1.4 Ga (Barinek et
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Kolari-Kittila Province Kuusamo Pro
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The uranium deposits in various pro
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Fig. 5.6. Distribution of the Rorai
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Roraima Basin, similar to what is o
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etween ca. 2.3 Ga and 1.9 Ga. Later
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REFERENCES Adams, J., 1989. Postgla
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Ashton, K.E., 2010. The Gunnar Mine
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Bowles, J.F.W., 1990. Age dating of
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Cuney, M.L., 2005. World-class unco
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deposits in the Athabasca Basin, Sa
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Hartlaub, R.P., Heaman, L.M., Chack
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Saskatchewan Geological Survey, Sas
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Kyser, K., and Cuney, M., 2008. Geo
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two-sided oblique-slip collisional
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Creek Geosyncline: in ‘The minera
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Piper, J.D.A., 2004. Discussion on
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99.Sheppard SMF and Gilg HA 1996. S
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Proceedings Darwin Conference 1984
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Wingate, M.T.D, Pisarevsky SA, Evan
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Sample Deposit 207 Pb/ 206 Pb ±2σ
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APPENDIX B REE contents of various
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Sample Y Zr Cs Ba Th La Ce Pr Nd Sm
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Sample ΣREE TLREE THREE LREE/HREE
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SAMPLE ID. SiO 2 TiO 2 AL 2O 3 CR 2
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SAMPLE ID. SiO 2 TiO 2 AL 2O 3 CR 2
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APPENDIX E Electron microprobe data
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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
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Mineralized veins Quartz veins 276
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