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Athabasca Basin Overview - McArthur River, Key Lake, Cigar Lake, Cluff Lake, Dawn Lake, Carswell, Amok, Rabbit Lake, Eagle Point, Collins Bay

Saskatchewan, Canada

Main commodities: U Ni Au
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The Athabasca Basin covers an oval shaped area of some 400x200 km, elongated in a general east-west direction in northern Saskatchewan, Canada.   A series of major uranium deposits are developed at the unconformity at the base of the basin with the underlying Palaeoproterozoic metamorphics.   These include the Key Lake, Cigar Lake, Cluff Lake, Dawn Lake, Amok/Carswell, McArthur River and Rabbit Lake Operations,

The Athabasca Basin straddles both the Rae and Hearne Archaean Provinces and section of the Palaeoroterozoic Trans-Hudson Mobile Belt which separates the Hearne and the Superior Archaean Province to the east. With the exception of the deposits of the Carswell Structure, all of the large orebodies are in the western section of the basin, within a north-east trending strip coincident with the overlap of the Athabasca Basin and the underlying Wollaston Domain of the basement. The Wollaston Domain is a north-east trending zone of more intense metamorphism on the north-western margin of the Trans-Hudson Mobile Belt. It is composed of interlayered biotite-cordierite gneiss, biotite gneiss±garnet, arkosic meta-conglomerate and meta-arkose, and minor hornblende-biotite rocks, amphibolite, meta-pelites, and calc-silicates with marble and graphitic meta-pelite units. More specifically, the majority of the Athabasca Basin orebodies are hosted within, and immediately above Palaeoproterozoic (pre 1800 Ma) graphitic meta-pelites of this suite, underlying the Mesoproterozoic (1450 to 1500 Ma) Athabasca Group sandstones with an angular unconformity. These ore deposits are widespread, being distributed over an inteval of around 150 km in a north-east direction. The deposits of the circular Carswell Structure to the west are approximately 300 km from the main belt.

The Athabasca Group comprises a sequence of mature, fluviatile quartzose sandstones and conglomerates which have red bed characteristics. The sandstones are primarily composed of quartz and clay with no remaining feldspar. Approximately 1000 m above its base is a marine unit, overlain again by further sandstones and another marine unit of organic shales and stromatolitic dolomites. The group is approximately 2200 m thick, although fluid inclusion data from minerals at its base suggests a depth of burial of as much as 4 to 5 km.

The basement metamorphics are reduced and grey to green in colour, while the Athabasca sandstones are hematitic and red. The sub Athabasca unconformity is underlain by a kaolinite rich, locally diaspore bearing, palaeo weathering profile of lateritic character. This zone is from 1 to more than 100 m thick.

In all deposits the mineralisation is at or close to the sub-Athabasca unconformity. The ore is structurally controlled by steeply dipping faults that are several kilometres long and offset the unconformity by up to 50 m. The faults commonly follow graphitic meta-pelites in the basin floor, while the deposits are elongate bodies which straddle or flank the graphitic meta-pelites at the unconformity. The graphitic metamorphic units associated with the various deposits are at different stratigraphic levels within the basement sequence. The ore bodies consist of a high grade core, at or just below the unconformity, with a low grade envelope extending a few hundred metres into the overlying sandstone and/or downwards into the basement. The alteration halo which is characterised by abundant illite or chlorite, quartz dissolution and the destruction of graphite extends further into the basement when the deposits are associated with carbonates, in contrast to more meta-pelitic hosts, where the alteration halo is funnel shaped, converging downward into the associated fault zone.

Pitchblende is the main uraniferous mineral, although many deposits contain as much Ni and Co as U and some contain significant Au.

The total production and known and resources within the Athabasca basin, in 2005 (Jefferson, et al., 2005) amounted to:
    28.81 Mt @ 2.27% U3O8 for 653 040 t U3O8.

Ore deposit sizes include:

 McArthur River - 0.727 Mt @ 24.28% U
3O8 = 177 200 t U3O8 (proven + probable reserve).
 Key Lake - 4.1 Mt @ 20 kg/t U
3O8 = 82 875 tonnes U3O8
 Cigar Lake - 1.5 Mt @ 120 kg/t U
3O8 = 175 000 tonnes U3O8
 Cluff Lake - 3.8 Mt @ 5 kg/t U
3O8 = 19 125 tonnes U3O8
 Dawn Lake - 0.7 Mt @ 20 kg/t U
3O8 = 13 660 tonnes U3O8
 Amok/Carswell - 4 deposits, totalling 3.15 Mt@ 5.2 kg/t U
3O8 = 16 360 tonnes U3O8
 Rabbit Lake Operations - 195 000 tonnes U
3O8, including:
       Rabbit Lake - 5.6 Mt @ 3.4 kg/t U
3O8
       Eagle Point - 1.9 Mt @ 18 kg/t U
3O8
       Collins Bay A - 0.067 Mt @ 96.8 kg/t U
3O8
       Collins Bay B - 7 Mt @ 8 kg/t U
3O8.

See the individual records for most of these deposits for more detail.

The most recent source geological information used to prepare this summary was dated: 2005.    
This description is a summary from published sources, the chief of which are listed below.
© Copyright Porter GeoConsultancy Pty Ltd.   Unauthorised copying, reproduction, storage or dissemination prohibited.


  References & Additional Information
   Selected References:
Alexandre P, Kyser K and Jiricka D,  2009 - Critical Geochemical and Mineralogical Factors for the Formation of Unconformity-Related Uranium Deposits: Comparison between Barren and Mineralized Systems in the Athabasca Basin, Canada: in    Econ. Geol.   v104 pp 413-435
Alexandre P, Kyser K, Polito P and Thomas D  2005 - Alteration Mineralogy and Stable Isotope Geochemistry of Paleoproterozoic Basement-Hosted Unconformity-Type Uranium Deposits in the Athabasca Basin, Canada: in    Econ. Geol.   v100 pp 1547-1563
Alexandre P, Kyser K, Thomas D, Polito P and Marlat J,  2009 - Geochronology of unconformity-related uranium deposits in the Athabasca Basin, Saskatchewan, Canada and their integration in the evolution of the basin: in    Mineralium Deposita   v.44 pp. 41-59
Baudemont D, Fedorowich J  1996 - Structural control of Uranium mineralization at the Dominique-Peter deposit, Saskatchewan, Canada: in    Econ. Geol.   v91 pp 855-874
Chen, S., Hattori, K. and Grunsky, E.C.,  2018 - Multielement statistical evidence for uraniferous hydrothermal activity in sandstones overlying the Phoenix uranium deposit, Athabasca Basin, Canada: in    Mineralium Deposita   v.53, pp. 493-508.
Chi, G., Li, Z., Chu, H., Bethune, K.M., Quirt, D.H., Ledru, P., Normand, C., Card, C., Bosman, S., Davis, W.J. and Potter, E.G.,  2018 - A shallow-burial mineralization model for the unconformity-related uranium deposits in the Athabasca Basin: in    Econ. Geol.   v.113, pp. 1209-1217.
Gaboreau S, Cuney M, Quirt D, Beaufort D, Patrier P and Mathieu R,  2007 - Significance of aluminum phosphate-sulfate minerals associated with U unconformity-type deposits: The Athabasca basin, Canada : in    American Mineralogist   v92 pp 267-280
Hoeve J and Sibbald I T,  1978 - On the genesis of Rabbit Lake and other unconformity-type uranium deposits in northern Saskatchewan, Canada: in    Econ. Geol.   v73 pp 1450-1473
Leventhal J S, Grauch R I, Threlkeld, Lichte F E  1987 - Unusual organic matter associated with Uranium from the Claude deposit, Cluff Lake, Canada: in    Econ. Geol.   v82 pp 1169-1176
Li, Z, Chi, G., Bethune, K.M., Thomas, D. and Zaluski, G.,  2017 - Structural Controls on Fluid Flow During Compressional Reactivation of Basement Faults: Insights from Numerical Modeling for the Formation of Unconformity-Related Uranium Deposits in the Athabasca Basin, Canada: in    Econ. Geol.   v.112, pp. 451-466.
Lorilleux G, Cuney M, Jebrak M, Rippert J C, Portella P  2003 - Chemical brecciation processes in the Sue unconformity-type uranium deposits, Eastern Athabasca Basin (Canada): in    J. of Geochemical Exploration   v80 pp 241-258
Ng R, Alexandre P and Kyser K,  2013 - Mineralogical and Geochemical Evolution of the Unconformity-Related McArthur River Zone 4 Orebody in the Athabasca Basin, Canada: Implications of a Silicified Zone : in    Econ. Geol.   v.108 pp. 1657-1689
Pascal, M., Boiron, M.-C., Ansdell, K., Annesley, I.R., Kotzer, T., Jiricka, D. and Cuney, M.,  2016 - Fluids preserved in variably altered graphitic pelitic schists in Dufferin Lake Zone, south-central Athabasca Basin, Canada: implications for graphite loss and uranium deposition: in    Mineralium Deposita   v.51, pp. 619-636.
Richard, A., Cathelineau, M., Boiron, M.C., Mercadier, J., Banks, D.A. and Cuney, M.,  2016 - Metal-rich fluid inclusions provide new insights into unconformity-related U deposits (Athabasca Basin and Basement, Canada): in    Mineralium Deposita   v.51 pp. 249-270
Trocki L K  1984 - Ages of major Uranium mineralization and Lead loss in the Key Lake Uranium deposit, northern Saskatchewan, Canada: in    Econ. Geol.   v79 pp 1378-1386
Wilson M R, Kyser T K  1987 - Stable isotope geochemistry of alteration associated with the Key Lake Uranium deposit, Canada: in    Econ. Geol.   v82 pp 1540-1557


Porter GeoConsultancy Pty Ltd (PorterGeo) provides access to this database at no charge.   It is largely based on scientific papers and reports in the public domain, and was current when the sources consulted were published.   While PorterGeo endeavour to ensure the information was accurate at the time of compilation and subsequent updating, PorterGeo takes no responsibility what-so-ever for inaccurate or out of date data, information or interpretations.

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