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Drift Prospecting for Uranium: Emphasis on Athabasca Basin, Saskatchewan

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DriftDrift ProspectingProspecting forfor Uranium:Uranium: emphasisemphasis onon AthabascaAthabasca Basin,Basin, SaskatchewanSaskatchewan J.E. Campbell Geological Survey of Canada OutlineOutline •• AthabascaAthabasca Basin:Basin: RegionalRegional QuaternaryQuaternary geologygeology andand glacialglacial historyhistory -- Ice flow history -- Nature and distribution of sediments -- Till composition and provenance •• DriftDrift prospectingprospecting forfor uraniumuranium -- Geological considerations -- Surficial geochemical techniques •• ApplicationApplication toto northernnorthern ManitobaManitoba AthabascaAthabasca Basin,Basin, SaskatchewanSaskatchewan 110° 60° 102° NOLAN 60° ENA ZEM LAK TRAIN AY DODGE K B FO RC IE AC BL NEVINS BEAVERLO D GE TANTATO MUDJATIK C ARSWELL STRUC TURE AthabascaATHABASCA BASIN E K A L ER ET Basin P WESTERN GRANULITE ER IV R IN RG VI N A K N TI M H A TO A IT J S TH L D A A O U LL H M W T O BA W EW E YN N SE O E IS ST G K N N TE O T R EW RO LA N EY SS KI IE N N LE G N LO F N LI F Ê Ê NEA-IAEA 49° 110° 49° 102° test area Ê Ê Ê Ê Ê RegionalRegional QuaternaryQuaternary SettingSetting Extent of ice cover – Middle Wisconsinan (27-30 C14 ka BP) •• Multiple glaciations -- extensive drift cover - complex glacial history - •• Likely ice covered entire Canadian Shield for last 115k to 8k years •• Present day landscape primarily result of last glaciation –Late Wisconsinan (after Dyke et al., 2002) LateLate WisconsinanWisconsinan GlaciationGlaciation andand DeglaciationDeglaciation Last Glacial Maximum, 20-23 C14 ka BP Queen Elizabeth Islands Glacier Complex Greenland Ice Sheet Foxe-Baffin C Sector S h o e r d Keewatin e i t l l Sector e r a Laurentide Ice Sheet n I c Hudson Newfoundland Ice e Ice Cap Labrador Sector Appalachian Glacier Complex Late Wisconsinan RegionalRegional IceIce FlowFlow AthabascaAthabasca Basin ––SurficialSurficial GeologGeologyy (After Schreiner, 1984) TillTill DepositsDeposits andand LandformLandformss Drumlins Cross-section of a drumlin ~ 30 m A Hummocky moraine Ground moraine (till plain) EskerEsker SystemsSystems andand OutwashOutwash PlainPlainss • Regional esker systems -Subglacial Esker meltwater drainage systems • Generally structurally controlled • Associated ice-contact features • Extensive proglacial outwash plains Outwash plain Large deposits of sand and gravel MultipleMultiple DriftDrift UnitsUnits andand ThickThick DrifDriftt HindersHinders explorationsexplorations ReducesReduces chancechance ofof surfacesurface expressionexpression ASSOCIATED STRATIGRAPHIC SUB UNIT, DISTRIBUTION ICE FLOW GLACIATION UNIT MATERIALS DIRECTION RECENT Peat, Lacustrine, - Throughout DEPOSITS Eolian UPPER Sand, Gravel; - Sporadic, STRATIFIED minor silt and throughout SEDIMENTS clay - Eskerine complexes, outwash plains Ablation (Flow) - Related to re- 190-200° Till3 TILL 3 Till advance dominantly (UPPER TILL) west of Subglacial unconformity LATE - Discontinuous READVANCE - Hummocky, drift, thin veneer, small Till 2 drumlins MIDDLE Sand, Gravel; - Uncommon, Mixed STRATIFIED minor silt and with Upper Till SEDIMENTS clay TILL 2 Ablation - Throughout 210-220° Subglacial - Most common unit (MIDDLE TILL; LATE - Melt-out - Associated with Geddes LOWER WISCONSIN - Lodgement drumlins, fluted and TILL) featureless till plains LOWER Clay and silt; - Rare STRATIFIED Sand - No surface PRE –LATE SEDIMENTS Gravel expression WINSCONSIN (LOWER GRAVELS) Till - Very rare, Unknown TILL 1 5 preserved in (230-240°) ? PRE –LATE (LOWER TILL; bedrock lows WINSCONSIN Geddes OLD DRIFT) JebJeb Pit,Pit, McCleanMcClean LkLk BEDROCK Athabasca Group Sandstone; Basement Rock (modified after Geddes, 1980b) TillTill CompositionComposition andand ProvenanceProvenance Sandstone-rich • Very sandy to silty-sand texture; Low clay content (<1%) Mixed provenance • Sandstone (intra-basinal) versus basement derived (extra- basinal) • Proportion and type of basement material is indicator of transport distance and direction •Relative proportions of sandstone to basement related to: • till deposit type, • the till unit and • the thickness of the drift BasementBasement clastsclasts SandstoneSandstone tilltill MultipleMultiple tilltill unitsunits ExoticExotic componentcomponent Till3 Crystalline clasts Till 2 Sandstone clasts ThinThin DriftDrift CoverCover Locally Derived Material Silty-sand Sandstone-rich till Sandstone-rich till BedrockBedrock Ternary Plot of K, eTh and eU 2001 -reprocessed and leveled 5 km spacing NATGAM data for the entire Basin eTh 1 K eU Ternary 10 0 50 KM TillTill CompositionComposition ImplicationsImplications forfor uraniumuranium explorationexploration •• IndicatorIndicator ofof provenance,provenance, transporttransport distancesdistances andand directiondirection •• ProportionProportion ofof basementbasement versusversus sandstonesandstone detritusdetritus isis keykey •• GeochemicalGeochemical signaturesignature –– basementbasement componentcomponent masksmasks sandstonesandstone componentcomponent •• AvoidAvoid basementbasement--richrich tillstills DriftDrift ProspectingProspecting forfor UraniumUranium Tracing of mineralization indicators in glacial sediments to their bedrock source Traditional methods Lake sediment sampling Boulder prospecting •• -- Radioactive boulder prospecting -- Lake sediments -- Soils -- Radon, Track-etch -- Vegetation -- Heavy minerals –RC drilling Pitchblende boulder •• Led to many of early uranium discoveries •• Effective in areas of thin drift and thin sandstone cover Soil or Till sampling DriftDrift ProspectingProspecting forfor UraniumUranium GeologicalGeological considerationsconsiderations •• Distribution of mineralized material at surface largely dependent on nature and composition of the glacial drift and the sub-cropping expression of uranium mineralization •• The applicability of drift prospecting and choice of type of technique(s) are dependent on: -- Thickness of sandstone cover-subcropping mineralization Type of mineralization: ingress vs egress -- Type of alteration – silification vs desilification -- -- Quaternary geological conditions (surficial geology, thickness and stratigraphy) -- Till composition and provenance UnconformityUnconformity typetype IngressIngress EgressEgress Pathfinder suite of elements including U, B, Pb, Ni, Cu, As, Co, Mo, Zn, V and REE) CurrentCurrent SurficialSurficial GeochemicalGeochemical ExplorationExploration TechniquesTechniques CompositeComposite boulderboulder samplingsampling (Earle et al, 1989; Earle & Sopuck, 1989; Earle, 2001) Focus on recognition/detection of the subtle alteration and geochemical enrichment halos in sandstone Al2O3, MgO, K2O, and B analyses – normative clay calculations of kaolin, chlorite and illite TillTill geochemistrygeochemistry (Simpson & Sopuck, 1983; Campbell et.al., 2007) Not widely used but gaining interest CompositeComposite BoulderBoulder SamplingSampling ProsPros •• Sample sandstone component- avoid basement component of till •• Quick, cost effective method – especially if PIMA used in field •• Minimal training needed for sampling •• Detects subtle hydrothermal alteration products not generally detected by geochemical analyses of the till fine fraction CompositeComposite BoulderBoulder SamplingSampling ConsCons •• TransportTransport directionsdirections andand distancesdistances oftenoften unknownunknown –– silicifiedsilicified sandstonesandstone moremore resistantresistant •• PoorPoor preservationpreservation ofof alteredaltered oror geochemicallygeochemically-- enrichedenriched bouldersboulders inin glacialglacial driftdrift derivedderived fromfrom desilificationdesilification typetype ofof alterationalteration UraniumUranium inin tilltill T ill 3 0.05% U Bleached sandstone till Hematite-rich 2% U T ill 2 0.008% U 0.02% U (82ppm) TillTill GeochemistryGeochemistry && MineralogyMineralogy •• Application of fine fraction and bulk till sampling - Major and trace element geochemistry - ICP-AES or MS; U partial (HNO3:HCl – 8:1) by fluorimetry or ICP-MS; B by ICP- AES- NaOH fusion - U is best indicator ; also associated pathfinders (Ni, Cu, Pb, Co, As, V, REE etc) - Bleached sandstone - depleted Fe2O3, MgO, CaO & K2O; elevated Al2O, TiO2, Zr and REEs, % clay normalize for basement component – Na O ratio - 2 - Pebble fraction – sandstone clasts –signs of hydrothermal alteration, mineralized clasts - Clay-size fraction/clay mineralogy – XRD- Sandstone derived clay content – kaolin, illite, chlorite - Heavy minerals – (Geddes, 1982) defines provenance sandstone vs basement (eg. hemitite, zircon and rutile vs garnets, amph, pyrox., pyrite) - U-bearing and pathfinder minerals (eg, coffinite, ramberzite, uraninite, pitchblende; sulphides-niccolite, AsPy, CuPy, Sphalerite ) TillTill GeochemistryGeochemistry (Simpson & Sopuck, 1983) Major and trace element geochemistry <2 µm (clay-size) element geochemistry <63 µm Heavy Minerals 180-63 µm (sand) -- <2 µm size fraction best background to peak ratio Midwest Lk logarithmic Boulder train area -- <63 µm size fraction most economical Uranium ppm Sample No. along line 92N TillTill GeochemistryGeochemistry NormalizeNormalize forfor basementbasement componentcomponent (Na(Na O)O) 103°30” 104°25” 2 58°30’ 56°07’30” Partial Uranium_ppm <63µm Size Fraction Till Geochemistry Normalized Partial Uranium (U:Na2 O) 0.25 - 0.86 0.124 - 0.255 10 Km 0.87 - 2.10 0.256 - 0.473 2.11 - 4.06 0.474 - 1.169 4.07 - 14.00 Athabasca Basin Margin 1.170 - 4.965 14.01 - 29.90 4.966 - 19.865 Drift Prospecting for Uranium Multiple Drift Units and Thick Drift •• New techniques: Surficial geochemical
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