EXTECH IV ATHABASCA URANIUM DEPOSIT DATABASE
Geological Survey of Canada, Saskatchewan Industry and Resources, and Alberta Geological Survey


DEPNO COUNTRY LOCATION ALLNAMES COMMODITIES
40049 Canada (Nunavut) 66.35.31 N -- 108.00.04 W JCW; GBC; Twin Lakes Prospect; Twin Lakes U-Au Bearing Boulders U; Au; Se

Database name: Uranium Deposits, Athabasca Basin
Custodial agency: Geological Survey of Canada
Compilers: Sunil S. Gandhi
Release date: 2007-03-02
   
Deposit name(s): JCW (claim name); GBC (claim name); Twin Lakes Prospect (occurrence name); Twin Lakes U-Au Bearing Boulders (occurrence name)
Political location(s): Canada; Province or state: Nunavut; Nearest community: Bathurst Inlet Lodge (30 km 179°)
NTS map data: 076K09
Deposit clan (type): Unconformity-associated
Deposit (sub) types: Unconformity-associated - Proterozoic; source of mineralized clasts in glacial drift is unknown; it is postulated as a deposit located at the base of Tinney Cove Formation and mineralogically comparable with the D ore body at Cluff Lake; Reference: Roscoe, S. M.; Green, S.B.; Gandhi, S. S., 1986: Uranium, gold and selenide minerals locally concentrated in drift at 'Twin Lakes' near Bathurst Inlet, N.W.T.; Current Research - Geological Survey of Canada, Volume 86-1B, p. 47 - 56
Deposit status: drilled showing; Size category: unknown; Status comments: Trenches near the high grade clasts in glacial drift found some U and Au values in quartz-pyrite-chalcopyrite veins in bedrock beneath the drift, but drilling did not show their continuation at depth
Geologic province: Slave Craton
Geologic subprovince: Kilohigok Basin
Geologic district: Bathurst Inlet Fault Zone
Deposit object located: mineralized boulder field
Commodities: U; Au; Se
Mineralization styles: veinlets (mineralization zone); aggregates (mineralization zone); massive (mineralization zone); cavity - fill (mineralization zone); disseminated (mineralization zone); breccia - matrix (mineralization zone); breccia - clasts (mineralization zone)
Geological ages: Late Proterozoic (mineralization)
Tectonic setting: epicontinental basin-graben; divergent; Formal name: southwestern Elu Basin (country rocks)
Coincident features: lithological contact(s) (the host breccia is interpreted as fanglomerate at the base of Tinney Cove Formation deposited on the Goulburn Group); Coincident feature name: basal unconformity of Tinney Cove Formation
fault(s) (the east-side down Tub Fault is within 500 m east of the mineralized clasts; it is one of the brittle faults of the NW-trending Bathurst Fault Zone); Coincident feature name: Tub Fault
glacial transport (air photos suggest transport direction of mineralized float from around 200° and that of the widespread till from about 155°; source of float unknown); Coincident feature name: recent glaciofluvial stream
Regional tectonic structure: faults (two major parallel faults along Bathurst Inlet that trend 335°; a 40 km wide zone of subsidiary faults to the west in which the prospect is located) Tectonic structure name: Bathhurst Inlet Faults
Host rocks: (1) sedimentary; unclassified sedimentary rocks (sedimentary breccia or fanglomerate, possibly developed at the base of Mesoproterozoic sandstone later removed by erosion); Depositional setting: fluvial; Metamorphic grade: unmetamorphosed; Component: mineralization zone
External host rock forms:unknown
Host rock protoliths:sedimentary breccia (mineralized clasts in drift are possibly equivalent of fanglomerate of the Tinney Cove Formation deposited in fault-controlled basin); Host rock protolith name: Unnamed
Internal host rock structures:syn-sedimentary brecciation
Individual lithologies:sedimentary breccia (mineralized clasts in the drift comprise siltstone, vein quartz, hematitic quartzite, jasper and brown chert in a matrix of well sorted quartz grains)
Host rock stratigraphy:Tinny Cove Formation

(2) sedimentary; siltstone (bedrock host of a 30 cm thick steep quartz vein trending north, with pyrite, chalco pyrite and weak radioactivity beneath the uraniferous drift); Depositional setting: fluvial; Metamorphic grade: unmetamorphosed; Component: mineralization zone
External host rock forms:tabular sedimentary body
Host rock protoliths:siltstone-shale (beds in outcrops and subcrop near the trenches are mainly grey siltstone and pyritic shale dipping gently to the east, underlain by varicoloured beds); Host rock protolith name: Mara Formation of Goulburn Group

(3) sedimentary; mudstone-siltstone (host of a quartz vein explored by trenching); Depositional setting: shallow marine; Metamorphic grade: unmetamorphosed; Component: mineralization zone
External host rock forms:tabular sedimentary body
Host rock protoliths:siltstone-shale; Host rock protolith name: Mara Formation of Goulburn Group
Internal host rock structures:thick to thin bedding
Individual lithologies:siltstone (mainly grey siltstone with minor shale)
Host rock stratigraphy:Mara Formation
Country rocks: (1) siltstone; (grey siltstones with pyritic shale beds, gentle dip to the east; overlying varicouloured siltstones with thin red beds); Country rock name: Mara Formation; Metamorphic grade: unmetamorphosed
Country rock protoliths:siltstone-shale (Lower part of the late Paleoproterozoic Goulburn Group of the Kilohigok Basin; overlain by stromatolitic carbonates); Country rock protolith name: Mara Formation
Individual lithologies:sandstone-siltstone-shale (mainly siltstones with minor sandstone, hematitic ironstone and pisolitic dolomite; in lower part of platform-shelf sequence)

(2) carbonate; (stromatolitic Quadyuk Formation, mudstone rhythmites of peacock Hills Formation Kuuvik Formation and ); Country rock name: Quadyuk and Peacock Hills Formations; Metamorphic grade: unmetamorphosed
Country rock protoliths:carbonates (stromatolitic carbonate of Quadyuk Formation and mudstone rhythmites of Peacock Formation overly Mara Formation to the east); Country rock protolith name: Quadyuk and Peacock Hills Formations
Individual lithologies:carbonate-mudstone

(3) sandstone; (Mesoproterozoic sandstone-conglomerate unconformably overlying Goulburn Group 12 km east of Twin Lakes); Country rock name: Tinney Cove and Ellis Formations; Metamorphic grade: unmetamorphosed
Country rock protoliths:sandstone (conglomerate-sandstone deposited in fault-controlled basins, with local basal fanglomerate, in the Bathurst fault zone); Country rock protolith name: Tinney Cove and Ellis Formations
Individual lithologies:conglomerate-sandstone (arkose, quartz arenite and polymictic conglomerate; local fanglomerate)
Metallogenic signatures: U-Au-Se-Bi-Cu-Co-Ni-Pb
Alteration signatures: sericite/muscovite alteration: sericitization; What was altered: clasts and matrix of host breccia; Component: mineralization zone
oxidation: hematization; What was altered: iron oxides and pyrite in host breccia; Component: mineralization zone
oxidation: limonite; What was altered: iron oxides and sulphides; Component: alteration halo
Mineralogy: (mineralization / mineralization zone): pitchblende - botryoidal, pitchblende - sooty, brannerite, clausthalite, clausthalite - cobaltian, tiemannite, paraguanajuatite, carrollite, gold
(mineralization / alteration halo): limonite, hematite
(mineralization - vein / mineralization zone): quartz, chalcopyrite, pyrite
Radiometric ages: Object dated: mineralization(1); Age - Ma: 901; Dating method: U-Pb; Concentrate: pitchblende; Source rock: mineralized breccia; Formal name: clast in glacial drift; Event dated: mineralization; Interpretive comment: 207Pb/206Pb ratio date is the minimum age; 207Pb/235U = 770 Ma, 206Pb/238U = 726 Ma; Reference: Roscoe, S. M.; Green, S.B.; Gandhi, S. S., 1986: Uranium, gold and selenide minerals locally concentrated in drift at 'Twin Lakes' near Bathurst Inlet, N.W.T.; Current Research - Geological Survey of Canada, Volume 86-1B, p. 47 - 56
Qualified comments: (Applies to: discovery and development) Initial uranium discoveries in the Bathurst Inlet area were during 1975-1976, and included the POMIE and JCW prospects by Cominco Limited and YON prospect by Noranda Exploration Co. Ltd. The discoveries resulted from airborne radiometric surveys and ground follow-up. At the JCW prospect small pebble size (a few mm to 2 cm in diameter) pitchblende-gold aggregates and similar mineralization as veins and open space fillings in clasts of breccia comprising siltstone fragments in matrix of sorted quartz grains. The float occurs in glacial drift up to 1 m thick, in the vicinity of a quartz-pyrite-chalcopyrite vein cutting gently dipping siltstones of the Goulburn Group. The vein was exposed by several pits and trenches for a strike length of 100 m in northeasterly direction during 1976-1978. In 1979, 424 m of drilling was done in 6 holes spread over 725 m along the strike. The drilling showed that the vein is vertical and the uranium values are at the surface beneath the drift containing the mineralized detritus. Cominco Limited allowed the claims to lapse, which were restaked in 1984 as GBC group by Glen Warner of Yellowknife. Source of the detritus is unknown.

(Applies to: regional stratigraphy) Regional stratigraphy of the Mara and Tinney Cove formations are relevant to the possible Unconformity-associated mineralization seen in glaciofluvial detritus at the JCW property. Maps and reports in the 1970s described the bedrock siltstones there as the uppermost part of the Burnside River Formation, which is a dominantly siliciclastic unit in the lower part of Goulburn Group. Later Campbell and Cecile (1981, p. 115) distinguished the siltstone dominated strata as the Mara Formation. It includes granular hematite-ironstone at the top, which is regarded as paleosol. The type section of the formation at the junction of Mara and Burnside rivers is 200 m thick. At East Twin Lake it and the overlying Quadyuk Formation of stromatolitic carbonates are truncated by the Tub Fault that trends northwest and has juxtaposed them with mudstone rhythmites of the Peacock Hills Formation. Tinney Cove and Ellis formations are preserved in grabens formed by the Bathurst Fault system 10 to 18 km to the northeast. Ellis Formation is a sandstone unit correlated with the basal unit 11 of the Dismal Lakes Group in Coppermine Homocline to the west (Kerans et al., 1981), which hosts the sandstone-type Mountain Lake (PEC-YUK) uranium deposit. The host unit unconformably overlies the Hornby Bay Group, which includes Narakay volcanics dated at 1663 ± 8 Ma (Bowring and Ross, 1985). Tinney Cove Formation is older as it accumulated along syn-depositionally active Bathurst faults related to the terminal collision phase of Wopmay Orogen ca. 1880 Ma.

(Applies to: mineralization) The mineralized float includes massive pitchblende as pebbles and as veinlets cutting the breccia clasts in glacial drift. Some samples contain visible gold in colloform pitchblende, up to 10.5 oz Au/t (at 16 m S, 95 m W in local grid). Paraguanajuatite, clausthalite and carrolite are commonly associated with them and form rosette-like clusters, with irregular gold grains at core, surrounded by cobaltian clausthalite. These are followed by a chain of colloform pitchblende grains connected by veinlets of clausthalite, pitchblende and carrollite. Clausthalite also forms the outer ring or shell. Tiemannite occurs in lieu of gold in some rosettes. Chalcopyrite occurs locally as angular grains interstitial to coarse grained, late, open-space filling quartz. It likely represents quartz-pyrite veins that were broken up and incorporated in breccia or conglomerate, which became the host of the exotic suite of minerals, then itself was broken up to form the clasts seen in the drift. Bedrock beneath the drift contains some uranium as seen from the trenches on the quartz-pyrite-chalcopyrite veins, but drill holes were mostly barren or nearly so, indicating downward uranium migration from the drift. A channel sample from Trench T1 at 42 m S and 15 m W, included 16 ft of siltstone and 1 ft of quartz vein, and averaged 0.065 % U3O8/t. The quartz vein assayed 0.22 % U3O8/t. A channel sample from Trench 2, located about 18 m northeast of the Trench 1, of 8.5 feet of siltstone and 0.5 feet of quartz vein, averaged 0.005 % U3O8/t. The quartz vein assayed 0.035 % U3O8/t. Gold values in trench samples are quite erratic but a few are notable. Grab samples from quartz vein material assayed 4.5 to 14.5 oz Au/t, 7.7 to 11.0 oz Ag/t and 26 to 111 lbs U3O8/t. Source of the mineralized float is probably an unconformity-associated deposit, like the D ore body at Cluff Lake, formed at the base of Tinney Cove Formation, and is not exposed or is eroded away (Roscoe, 1984; Roscoe et al., 1986).
Links to other databases: NUMIN; Key value: 076KNE0001
Geophysical-chemical signature: Signature type: Airborne Radiometrics; Response type: positive (strong)
References:
Campbell, F. H. A.; Cecile, M. P., 1976
Geology of the Kilohigok Basin, Goulburn Group, Bathurst Inlet (76-1AP369)
Report of Activities - Geological Survey of Canada, Volume 76-1A, p. 369 - 377

Campbell, F. H. A., 1979
Stratigraphy and Sedimentation in the Helikian Elu Basin and Hiukitak Platform, Bathurst Inlet-Melville Sound, N.W.T. (79-8)
Paper, Geological Survey of Canada, Geological Survey of Canada, Publication code 79-8, 18 p..

Cecile, M. P.; Campbell, F. H. A., 1977
Large Scale Stratiform and Intrusive Sedimentary Breccias of the Lower Proterozoic Goulburn Group, Bathurst Inlet, N.W.T.
Canadian Journal of Earth Sciences, Volume 14, p. 2364 - 2387

Gandhi, S. S., 1995
An Overview of the Exploration History and Genesis of Proterozoic Uranium Deposits in the Canadian Shield
Exploration and Research for Atomic Minerals, Department of Atomic Energy, India, Volume 8, p. 1 - 48

Kerans, C.; Ross, G. M.; Donaldson, J. A.; Geldsetzer, H. J., 1981
Tectonism and Depositional History of the Helikian Hornby Bay and Dismal Lakes Groups, District of Mackenzie
In Proterozoic Basins of Canada, Edited by Campbell, F. H. A., Paper, Geological Survey of Canada, Geological Survey of Canada, 81-10, 444 p., p. 157 - 182

Roscoe, S. M., 1984
Assessment of Mineral Resource Potential in the Bathurst Inlet Area, NTS 76J,K,N,O including the Proposed Bathurst Inlet National Park (788)
Open File, Geological Survey of Canada, Geological Survey of Canada, Publication code 788, 75 p., 1 maps.

Roscoe, S. M.; Green, S.B.; Gandhi, S. S., 1986
Uranium, gold and selenide minerals locally concentrated in drift at 'Twin Lakes' near Bathurst Inlet, N.W.T.
Current Research - Geological Survey of Canada, Volume 86-1B, p. 47 - 56

Wright, R. L., 1976
Year End Report on the TUB Property, Bathurst Inlet Area, Mackenzie (061591)
Mineral Assessment Report, Cominco Ltd, Indian and Northern Affairs Canada, Publication code 061591

Wright, R. L., 1976
JCW Group: Geology, Ground Track Etch and Radiometric Survey Report; Bathurst Inlet Area, District of mackenzie (061590)
Mineral Assessment Report, Cominco Ltd, Indian and Northern Affairs Canada, Publication code 061590

Wright, R. L., 1976
Airborne Geophysical Survey of the Bathurst Inlet Area, N.W.T. (080557)
Mineral Assessment Report, Cominco Ltd, Indian and Northern Affairs Canada, Publication code 080557


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