DEPNO | COUNTRY | LOCATION | ALLNAMES | COMMODITIES |
40016 | Canada (Saskatchewan) | 58.18.11 N -- 104.05.11 W | Midwest Lake Uranium Deposit; Mink Arm Main, A, B and C Zones; South McMahon Lake Deposit | U; Ni; Ag; Co; As |
Database name: | Uranium Deposits, Athabasca Basin | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Custodial agency: | Geological Survey of Canada | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Compilers: | Sunil S. Gandhi | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Release date: | 2007-03-02 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Deposit name(s): | Midwest Lake Uranium Deposit; Mink Arm Main, A, B and C Zones; South McMahon Lake Deposit | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Political location(s): | Canada; Province or state: Saskatchewan; Nearest community: Key Lake mine-mill complex (100 km NE) | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
NTS map data: | 074I08 (Henday Lake) | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Deposit clan (type): | Unconformity-associated | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Deposit (sub) types: | Unconformity-associated - Proterozoic - clay-bound; most of the ore at unconformity; some ore in the basement and some in Athabasca sandstone; polymetallic, contains nearly as much Ni as U; Reference: Wray, E. M.; Ayres, D. E.; Ibrahim, H. J., 1985: Geology of the Midwest Uranium Deposit, Northern Saskatchewan; Chapter 2, Section Unconformity-type Deposits in Saskatchewan, In Geology of Uranium Deposits, Edited by Sibbald, T. I. I.; Petruk, W., Special Volume, The Canadian Institute of Mining and Metallurgy, The Canadian Institute of Mining and Metallurgy, 32, 268 p., p. 54 - 66 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Deposit status: | test producer; Size category: large; Status comments: 1.2 Mt ore | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Geologic province: | Churchill - Hearne Craton | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Geologic subprovince: | Wollaston Domain (Fold Belt) | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Geologic district: | Eastern Athabasca Basin | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Deposit object located: | drillhole | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Commodities: | U; Ni; Ag; Co; As | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Mineralization styles: | radial-textured colloform ore; pitchblende nodules; fracture-filling and dissemination; breccia - matrix; remobilized ore; cavity - fill; coating | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Geological ages: | Early Mesoproterozoic - Middle Mesoproterozoic (mineralization) | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Tectonic setting: | continental marginal deformation zone-basement reactivation; convergent; Formal name: Mudjatik Domain, east boundary (country rocks) continental marginal deformation zone-fold belt; convergent; Formal name: linear outliers of Wollaston Group metasediments (country rocks) continental surficial-intracratonic; stable; Formal name: sub-Athabasca Group regolith (country rocks) continental basin-intracratonic; stable; Formal name: Athabasca Basin (country rocks) | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Coincident features: | lithology (over 80 % of mineralization above the graphitic horizons; rest within it to a depth of 100 m); Coincident feature name: Pelitic gneiss fault(s) (coincident with the graphitic metapelite horizons; mineralization at fault intersection with the sub-Athabasca unconformity); Coincident feature name: Basement faults with post-Athabasca reactivation unconformity (most of the high grade ore, up to 10 % U, is in clay masses in altered regolith at the sub-Athabasca unconformity; grades are lower above and below it); Coincident feature name: Sub-Athabasca unconformity cross-faults (high grade ore appears to be controlled in part by west-northwest trending cross faults); Coincident feature name: West-northwest Cross Faults | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Regional tectonic structure: | synform in host metasedimentary sequence (interpreted synclinal structure trending 035° and with axis about a kilometre east of the Midwest deposit) Tectonic structure name: syncline mylonitic zone (a mylonite zone along the west limb of the syncline indicated by ribbon-textured porphyritic metapelitic gneiss) Tectonic structure name: west margin fault zone fault zone (a steep main fault along the deposit and subsidiary faults, show a 30 m down drop of the sub-Athabasca unconformity to the west) Tectonic structure name: Post-Athabasca fault zone | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Host rocks: | (1) metamorphic; metasedimentary schist (metapelites-metasemipelites); Depositional setting: platform-shelf; Metamorphic grade: amphibolite (upper) - granulite
(2) metamorphic; migmatite (anatectic and younger pegmatites); Depositional setting: katazonal; Metamorphic grade: amphibolite (upper) - granulite
(3) surficial; laterite (weathered basement; profile ~50 m deep); Host series: paleoregolith; Depositional setting: subaerial; Metamorphic grade: unmetamorphosed
(4) sedimentary; sandstone-siltstone-conglomerate; Depositional setting: fluviatile; Metamorphic grade: unmetamorphosed; Component: mineralization zone
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Related igneous rocks: | (1) intrusive; gabbro suite (dykes and sill-like intrusions); Initials: Diabase Intrusives; Magma series: calc-alkaline
(2) intrusive; gabbro suite (northwest-trending dyke); Initials: Mackenzie diabase dyke; Magma series: calc-alkaline
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Country rocks: | (1) granitic gneisses; (reactivated Archean granites); Country rock name: Midwest Granitoid Dome; Metamorphic grade: amphibolite (upper) - granulite
(2) metapelites-metasemipelite; (pelitic gneisses); Country rock name: graphitic metapelite; Metamorphic grade: amphibolite (upper) - granulite
(3) quartzo-feldspathic paragneiss; (folded and metamorphosed); Country rock name: unit of Lower Wollaston Group ; Metamorphic grade: amphibolite (upper) - granulite
(4) paleo-regolith; (up to 50 m thick lateritic profile); Country rock name: sub-Athabasca regolith; Metamorphic grade: unmetamorphosed
(5) conglomerate-sandstone; (flat-lying, undeformed); Country rock name: Athabasca Group; Metamorphic grade: unmetamorphosed
(6) diabase dykes; (Mesoproterozoic dykes and sills); Country rock name: Mackenzie and Moore Lakes intrusions; Metamorphic grade: unmetamorphosed
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Metallogenic signatures: | U-Ni-Co-Cu-As | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Alteration signatures: | retrograde metamorphism: sericitization and chloritization along faults; What was altered: paragneisses and graniitc gneisses paleoweathering: upper oxidized zone; lower reduced zone; What was altered: sub-Athabasca basement diagenetic alteration: illite, dominant in and around high grade ore; What was altered: Athabasca strata and basement diagenetic alteration: hematitic beds and layers; What was altered: mafic silicates argillic alteration: clay minerals, hematite coating, secondary silica; What was altered: metapelites and metasemipelites; Component: mineralization sericitization: sericitization; What was altered: feldspar; Component: mineralization sericitization: sercitization of pre-existing clay minerals; What was altered: sub-Athabasca regolith; Component: mineralization chlorite alteration: chlorite, new generation; What was altered: sub-Athabasca regolith tourmalinization; What was altered: sun-Athabasca regolith; Component: mineralization desilication: quartz depletion; What was altered: sub-Athabasca regolith; Component: mineralization graphite depletion: removal of graphite; What was altered: sub-Athabasca regolith; Component: mineralization bleaching: bleaching of red oxidized zone; What was altered: sub-Athabasca regolith; Component: mineralization potassic alteration: illitization or sericitization; K enrichment; What was altered: Athabasca sandstones; Component: mineralization mineralization-related: strong illitization in and around high grade ore; What was altered: Athabasca sandstones chlorite alteration: green coloration due to chlorite; What was altered: Athabasca sandstones; Component: mineralization bleaching: bleaching of red diagenetic hematitic layers; What was altered: Athabasca sandstones; Component: mineralization hematization: irregular rehematization of bleached zones; What was altered: Athabasca sandstone bleached zones; Component: mineralization carbonation: carbonaceous sooty material and blebs; What was altered: Athabasca sandstone; Component: mineralization uranium remobilization: remobilization of uranium by diabase intrusion; What was altered: ore deposit; Component: mineralization | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Mineralogy: | (fracture fillings, coatings, disseminations): pitchblende - sooty, coffinite, marcasite, gersdorffite, Ni-Co sulpharsenide, safflorite, galena, sphalerite, maucherite, hematite, kaolinite, chlorite, sericite, quartz (nodular ore): pitchblende - massive, pitchblende - colloform, pitchblende - sooty, pitchblende - colloform/radial textured, coffinite, niccolite, gersdorffite, rammelsbergite, millerite, galena, pyrite, chalcopyrite, sericite, hematite | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Radiometric ages: | Object dated: Mineralization Style(1); Age - Ma: 1,331; +13; -13; Dating method: U-Pb; Concentrate: pitchblende; Source rock: uranium ore; Formal name: First Generation Pitchblende; Event dated: mineralization; Interpretive comment: upper intersept from 9 samples that are less than 10% discordant; lower intercept: 334 ± 26 Ma; Reference: Cumming, G. L.; Krstic, D., 1992: The Age of Unconformity-Related Uranium Mineralization in the Athabasca Basin, Northern Saskatchewan; Canadian Journal of Earth Sciences, Volume 29, p. 1623 - 1639 Object dated: Mineralization Style(2); Age - Ma: 1,094; +27; -27; Dating method: U-Pb; Concentrate: pitchblende and coffinite; Source rock: uranium ore; Formal name: Second Generation Mineralization; Event dated: mineralization; Interpretive comment: 10 data points form a poorly defined line, which passes through concordia origin; Reference: Worden, J. M.; Cumming, G. L.; Baadsgaard, H., 1985: Geochronology of the Host Rocks and Mineralization of the Midwest Uranium Deposits, Northern Saskatchewan; Chapter 2, Section Unconformity-type Deposits in Saskatchewan, In Geology of Uranium Deposits, Edited by Sibbald, T. I. I.; Petruk, W., Special Volume, The Canadian Institute of Mining and Metallurgy, The Canadian Institute of Mining and Metallurgy, 32, 268 p., p. 67 - 72 Object dated: Related Magmatic Rx(1); Age - Ma: 1,084; +54; -54; Dating method: K-Ar; Concentrate: whole rock; Source rock: diabase intrusion; Formal name: intrusion-related remobization of ore; Event dated: post-mineralization (intrusion); Interpretive comment: average of 3 K-Ar ages: 1062, 1085 and 1105 Ma; close to 1094 ± 27 Ma old remobilized pitchblende ; Reference: Worden, J. M.; Cumming, G. L.; Baadsgaard, H., 1985: Geochronology of the Host Rocks and Mineralization of the Midwest Uranium Deposits, Northern Saskatchewan; Chapter 2, Section Unconformity-type Deposits in Saskatchewan, In Geology of Uranium Deposits, Edited by Sibbald, T. I. I.; Petruk, W., Special Volume, The Canadian Institute of Mining and Metallurgy, The Canadian Institute of Mining and Metallurgy, 32, 268 p., p. 67 - 72 Object dated: Related Magmatic Rx(2); Age - Ma: 1,267; +2; -2; Dating method: U-Pb; Concentrate: baddeleyite; Source rock: diabase intrusion; Formal name: intrusion-related remobiliztion of ore; Event dated: post-mineralization (intrusion); Interpretive comment: a northwest-trending dyke at south end of Midwest Lake deposit belongs to the Mackenzie dyke swarm; Reference: LeCheminant, A. N.; Heaman, L. M., 1989: Mackenzie Igneous Events, Canada: Middle Proterozoic Hotspot Magmatism Associated with Ocean Opening; Earth and Planetary Science Letters, Volume 96, p. 38 Object dated: Country Rocks(1); Age - Ma: 2,613; +93; -93; Dating method: Rb-Sr; Concentrate: whole rock; Source rock: granitic gneiss; Formal name: emplacement age of western gneiss; Event dated: remobilized Archean granitoid; Interpretive comment: 5 of the 12 samples analyzed are collinear; rest indicative of incomplete response to younger events; Reference: Worden, J. M.; Cumming, G. L.; Baadsgaard, H., 1985: Geochronology of the Host Rocks and Mineralization of the Midwest Uranium Deposits, Northern Saskatchewan; Chapter 2, Section Unconformity-type Deposits in Saskatchewan, In Geology of Uranium Deposits, Edited by Sibbald, T. I. I.; Petruk, W., Special Volume, The Canadian Institute of Mining and Metallurgy, The Canadian Institute of Mining and Metallurgy, 32, 268 p., p. 67 - 72 Object dated: Country Rocks(2); Age - Ma: 1,711; +8; -8; Dating method: Rb-Sr; Concentrate: biotite; Source rock: biotitic paragneiss; Formal name: Hudsonian metamorphism; Event dated: cooling; Interpretive comment: 8 samples of metapelitic and biotite-quartz gneiss define isochron and indicate end of metamorphism ; Reference: Worden, J. M.; Cumming, G. L.; Baadsgaard, H., 1985: Geochronology of the Host Rocks and Mineralization of the Midwest Uranium Deposits, Northern Saskatchewan; Chapter 2, Section Unconformity-type Deposits in Saskatchewan, In Geology of Uranium Deposits, Edited by Sibbald, T. I. I.; Petruk, W., Special Volume, The Canadian Institute of Mining and Metallurgy, The Canadian Institute of Mining and Metallurgy, 32, 268 p., p. 67 - 72 Object dated: Alteration Signature(6); Age - Ma: 1,337; +11; -11; Dating method: Rb-Sr; Concentrate: sericite - pearly young; Source rock: wallrock; Formal name: main mineralization event; Event dated: alteration (hypogene); Interpretive comment: 9 of 11 data points define an isocron indicative of a relatively lower temperature alteration event; Reference: Worden, J. M.; Cumming, G. L.; Baadsgaard, H., 1985: Geochronology of the Host Rocks and Mineralization of the Midwest Uranium Deposits, Northern Saskatchewan; Chapter 2, Section Unconformity-type Deposits in Saskatchewan, In Geology of Uranium Deposits, Edited by Sibbald, T. I. I.; Petruk, W., Special Volume, The Canadian Institute of Mining and Metallurgy, The Canadian Institute of Mining and Metallurgy, 32, 268 p., p. 67 - 72 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Deposit shape: | cigar-shaped
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Qualified comments: | (Applies to: discovery and development) A glacial bounder train led to discovery in 1978; outlined by 488 drill holes; min-able resources in 1981: 19300 t U in 1.2 Mt of ore averaging 1.6 % U and 1.59 % Ni; plus 2300 t U in lower grade ore. in 1988-1989 test mining from a 185 m shaft; revised estimate of mine-able reserves in 1990: 13850 t U in 0.363 Mt of ore averaging 3.816 % U at cut-off grade of 0.424 % U; same figures reported in 2001. Most of the high grade ore occurs at northeast end of the deposit, where ore zone is as much as 150 m wide and occurs at the sub-Athabasca unconformity; basement ore extends for minimum 100 m below it. The main zone is under water at southwest end of Mink Arm of Midwest Lake; subsidiary discontinuous small zones, referred to as A, B and C zones, occur to the northeast along Mink Arm over 2.5 km strike zone. It has been dormant since 1995. | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Links to other databases: | SMDI; Key value: 1720 GSC U-Th File (Prasad); Key value: 2714 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
References: |
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Resource data: |
Percent weights allocated to deposit: 100.0% Associated mine(s): |
Midwest Uranium Mine (40019) | Generated 2007-03-02 2:36:34 PM with GQuery -- 3.7 ADO (3.19/3.20/3.21 -- 2006-02-24) |