Database name: |
Uranium Deposits, Athabasca Basin |
Custodial agency: |
Geological Survey of Canada |
Compilers: |
Sunil S. Gandhi |
Release date: |
2007-03-02 |
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Deposit name(s): |
Nisto Uranium Mine (mine name); Nisto Uranium Mine Adit (mine name); Nisto Zones 1 to 8 and A to J (occurrence name); Nisto North Uranium Showing (occurrence name); Nisto South Uranium Showing (occurrence name) |
Political location(s): |
Canada; Province or state: Saskatchewan; Nearest community: La Ronge (455 km N) |
NTS map data: |
074P03 (Fir Island) |
Deposit clan (type): |
Unconformity-associated |
Deposit (sub) types: |
Veins - fracture filling and veinlets; Main quartz-pitchblende veins trend northeast parallel to the Black lake shear zone 75 m to the southeast; subsidiary veins trend NW to NNW; host rocks are mylonitized metasediments and amphibolites; Reference: Homeniuk, L. A.; Clark, R. J. M., 1986: North Rim Deposits, Athabasca Basin; Chapter 4, Section Saskatchewan Unconformity-associated and Sedimentary-hosted Deposits of Helikian Age, In Uranium Deposits of Canada, Edited by Evans, E. L., Special Volume, The Canadian Institute of Mining and Metallurgy, The Canadian Institute of Mining and Metallurgy, 33, 323 p., p. 230 - 240 |
Deposit status: |
past producer; Size category: small |
Geologic province: |
Churchill - Rae Craton |
Geologic subprovince: |
Tantato Domain / East Athabasca Mylonite Triangle |
Geologic district: |
Black Lake Shear Zone / Snowbird Tectonic Zone |
Deposit object located: |
deposit centre (surface proj.) |
Commodities: |
U; Cu; Co; Sb |
Mineralization styles: |
vein (mineralization zone); zoned (main mineralization zone); fracture fill (mineralization zone) |
Geological ages: |
Late Archean - Late Paleoproterozoic (host rocks) Late Paleoproterozoic - Early Mesoproterozoic (mineralization) |
Tectonic setting: |
continental marginal deformation zone-intracratonic; multiple regimes; Formal name: East Athabasca Mylonite Triangle (host rocks) |
Coincident features: |
shear zone(s) (Part of the NE-trending Snowbird Tectonic Zone that marks boundary between the Rae and Hearne cratons; dip steep to NW; west-side up; sinistral fault ); Coincident feature name: Black Lake Shear Zone shear zone(s) (parallel shears subsidiary to the Black Lake Shear Zone on the northwest side; host to some uranium mineralization; steeply dipping); Coincident feature name: subsidiary parallel shears fracture(s) (subsidiary tensional fractures at high angle to, and on northwest side of the Black Lake Shear Zone; host to uranium mineralization; steeply dipping); Coincident feature name: tensional fractures |
Host rocks: |
(1) metamorphic; paragneiss (fine banded gray sediments and pink granitized gneisses ); Metamorphic grade: granulite; Component: host rocksExternal host rock forms: | batholith | Host rock protoliths: | sandstone (fine banded gray sediments and pink granitized gneisses of older literature are equivalent of the 'straight gneiss' derived from Chipman tonalite); Host rock protolith name: Chipman Granite | Internal host rock structures: | banding | Individual lithologies: | tonalite (banded character due to strong shearing at the eastern fault boundary of the Striding-Athabasca mylonite zone trending northeast ) | Host rock stratigraphy: | Chipman Batholith |
(2) intrusive; gabbro suite (swarm of sheared gabbro sills and dykes on west side of Black Lake shear zone); Metamorphic grade: granulite; Component: host rocksExternal host rock forms: | dyke | Host rock protoliths: | basalt (subconcordant mafic dykes and sills in the tonalitic straight gneiss; up to 100 m wide, with chilled margins; some with feldspar phenocrysts); Host rock protolith name: Chipman Dyke Swarm | Internal host rock structures: | massive to weakly foliated | Individual lithologies: | amphibolite ( of the dykes) |
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Metallogenic signatures: |
U-Cu |
Alteration signatures: |
hematization: hematite; What was altered: mylonitized granitic and gabbroic intrusions; Component: wall rocks |
Mineralogy: |
(alteration - undifferentiated / wall rocks): hematite (alteration - undifferentiated / mineralization zone): hematite, chlorite (gangue / mineralization zone): quartz (mineralization / mineralization zone): pitchblende, chalcopyrite, pyrite, galena, stibnite |
Qualified comments: |
(Applies to: discovery and development) Pitchblende veins on the west shore of Black Lake were discovered in 1948 by prospectors Roy Tobey and John Albrecht, working under the Saskatchewan Prospectors' Assistance Program. The showings area, namely the Nisto Concession, was acquired later that year by Transcontinental Resources Ltd. Its subsidiary, Nisto Mines Ltd., carried out prospecting and trenching in 1949, which located a number of radioactive veins in an area about 800x150 m with 43 m relief above the lake level. They were grouped in to 8 zones, and tested by 51 drill holes totalling 2663 m. During 1950-'51 two adits 200 m apart were driven from the lake side, with lateral work totalling 518 m. A raise was driven 45 m in the western (# 2) adit. By 1953 underground drilling amounted to 3749 m. In 1959 the property was leased to Haymac Mines for high grading ore. A total of 500 tons of ore was mined from the western adit, with one shipment of 106 tons (96.16 tonnes) of ore grading 1.63 % U3O8 (1.382 % U) to the Lorado mill near Uranium City. In 1966 Mokta Canada Ltd. conducted an airborne scintillometer survey in the area, and located a showing 2.4 km to the southwest, referred to as the South Showing. In 1968 a hole was drilled by Amok Ltd. near the Nisto or North showing on the east side of the Black Lake Fault. It was drilled at azimuth 306° and inclination of 69°, and intersected the Sub-Athabasca Group unconformity at 140 m. No radioactivity was encountered in the hole. Another hole near it was drilled by Eldorado Nuclear Ltd. and SMDC in 1979, on the south shore of the lake, but again no mineralization was intersected. Further geophysical surveys in 1980 along the Black Lake fault were also not encouraging. In 1996 the mine site was rehabilitated by placing radioactive rock, rails and ore cars in the adit. Adit portals and the stope at surface were sealed. A Geotem-EM survey was carried out over region in 1996 by JNR Resources Inc. The follow-up surface work was not encouraging.
(Applies to: mineralization) Uranium at Nisto deposit occurs in quartz veins and as fractures fillings in mylonitized granitic rocks and diabase dykes and sills. Hriskevitch (1949) described pitchblende distribution as coatings along planes in shear zones and along fractures adjacent to shears, and as fracture filling and replacement veinlets in quartz. Pitchblende veins as wide as 5 cm were noted, but narrower ones as more common. Reddish amorphous hematite is abundant in the pitchblende-bearing shears and adjacent wall rock. The mere presence of hematite however is no positive indication of the presence of pitchblende. Paragenetic relation of pitchblende with the sulphides is not clear. Carbonate, common in the pitchblende deposits of the Martin Lake and Goldfields areas of Saskatchewan, and of Great Bear Lake, is conspicuously absent or rare in the Black Lake area. Mafic host rocks show a marked bleaching, as much as a foot-wide on both sides of the pitchblende veins, which occupy tensional fractures, whereas the felsic wall rock show little or no alteration. Petrographic examination revealed that the bleaching is due to decolouration of biotite and alteration of biotite to chlorite. Mafic rocks appear to be more favourable hosts for pitchblende deposition than the felsic rocks. Since the Black Lake fault, to which the mineralized fractures are related, displaces the Athabasca Group, the mineralization post-dates the group. Homeniuk and Clark (1986, p. 238) suggested the possibility that this basement-hosted pitchblende deposit is the 'root' of an eroded unconformity-associated deposit. This possibility must be weighed against the upward displacement of the west side of the Black Lake fault, which must be significantly more than the 140 m depth of the sub-Athabasca Group unconformity encountered in a drill hole on the east side. |
Links to other databases: |
SMDI; Key value: 1621 GSC U-Th File (Prasad); Key value: 2890 |
References: |
Anonymous, 2000 |
The Nisto Story - Report to Communities 1999-2000 |
Annual Report to Communities, Northern Saskatchewan's Environmental Quality Committees and Northern Mine Monitoring Secretariat, 2 p.. |
Beck, L. S., 1969 |
Uranium Deposits of the Athabasca Region, Saskatchewan |
Report, Department of Mineral Resources, Province of Saskatchewan, Department of Mineral Resources, Province of Saskatchewan, Publication code 126, 140 p., 4 maps. |
Hanmer, S.; Parrish, R.; Williams, M.; Kopf, C., 1994 |
Striding-Athabasca Mylonite Zone: Complex Archean Deep-crustal Deformation in the East Athabasca Mylonite Triangle, Northern Saskatchewan |
Canadian Journal of Earth Sciences, Volume 31, p. 1287 - 1300 |
Hanmer, S., 1994 |
Geology, East Athabasca Mylonite Triangle, Saskatchewan |
Geological Survey of Canada, 1859A, Scale 1:100000 |
Hanmer, S., 1997 |
Geology of the Striding-Athabasca Mylonite Zone, Northern Saskatchewan and Southeastern District of Mackenzie, Northwest Territories |
Bulletin, Geological Survey of Canada, Publication code 501, 92 p.. |
Homeniuk, L. A.; Clark, R. J. M., 1986 |
North Rim Deposits, Athabasca Basin |
Chapter 4, Section Saskatchewan Unconformity-associated and Sedimentary-hosted Deposits of Helikian Age, In Uranium Deposits of Canada, Edited by Evans, E. L., Special Volume, The Canadian Institute of Mining and Metallurgy, The Canadian Institute of Mining and Metallurgy, 33, 323 p., p. 230 - 240 |
Hriskevich, M. E., 1949 |
Radioactive Occurrences in the Black Lake Area, Athabasca Mining Division, Saskatchewan |
Precambrian Geology, Department of Natural Resources, Province of Saskatchewan, Publication code Report 2, 31 p.. |
Lang, A. H., 1952 |
Canadian Deposits of Uranium and Thorium (First Edition) (16ED1) |
Economic Geology Series, Geological Survey of Canada, Department of Mines and Technical Surveys, Publication code 16ED1, 173 p.. |
Lang, A. H.; Griffith, J. W.; Steacy, H. R., 1962 |
Canadian Deposits of Uranium and Thorium (Second Edition) (16ED2) |
Economic Geology Series, Geological Survey of Canada, Department of Mines and Technical Surveys, Publication code 16ED2, 310 p.. |
Saskatchewan Geological Survey, 2003 |
Geology, and Mineral and Petroleum Resources of Saskatchewan |
Miscellaneous Report, Saskatchewan Industry and Resources, Publication code 2003-7, 173 p., 4 maps. |
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