Athabasca Basin - Dawn Lake

Saskatchewan, Canada

Main commodities: U
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The Dawn Lake unconformity hosted uranium deposit is located close to the eastern margin of the Athabasca Basin, some 20 km north-west of the Rabbit Lake deposit, around 10 km north-east and north-west of the Midwest and McClean Lake deposits respectively, and approximately 700 km north of Saskatoon, in northern Saskatchewan, Canada (#Location: 58° 20' 12"N, 103° 55' 41"W).

The Dawn Lake orebody is located in early Paleoproterozoic metasedimentary rocks of the Wollaston litho-structural domain, immediately below the unconformity with the overlying late Paleo- to Mesoproterozoic Athabasca Basin sequence. The Athabasca Basin straddles both the Rae and Hearne Archaean Provinces and section of the Paleoproterozoic Trans-Hudson Mobile Belt which separates the Hearne and the Superior Archaean Province to the east. The Wollaston Domain is a north-east trending zone of more intense metamorphism on the north-western margin of the Trans-Hudson Mobile Belt, and comprises metasediments of an early Paleoproterozoic supracrustal succession overlying a remobilised 2.47 Ga and older granitoid Archaean basement, which forms the cores of doubly plunging domal inliers.

The Wollaston Domain metasediments, the Wollaston Group, include 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.

The late Paleo- to Mesoproterozoic (1.63 to 1.45 Ga) 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. At the base of the sequence, immediately above the unconformity, there are approximately 60 m of non-marine fluvial sandstone and conglomerate of the Manitou Falls Formation. Around 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 unconformity surface between the Wollaston Group and the basal Athabasca Group is marked by a kaolinite rich, locally diaspore bearing, palaeo-weathering or regolith profile of lateritic character. This zone varies from 1 to more than 100 m in thickness and has a characteristic vertical zonation, with a lower green zone (chloritic), an upper red zone (hematitic and kaolinitic) and a narrow "bleached zone" very close to, or along, the unconformity surface (Harvey and Bethune, 2000).

The Dawn Lake deposit consists of four zones, 11, 11A, 11B and 14, the two most important being 11 A and B. Each zone comprises several NE-SW elongated, cigar shaped orebodies warying from 100 to 190 m in length and 20 to 45 m in width. There are four and three such bodies each in the 11A and 11B zones respectively.

The mineralisation is hosted by graphitic meta-pelites, calc-silicate rocks, biotite gneiss and pegmatite of the Wollastonite Group, immediately below the unconformity with the overlying Athabasca Basin, mostly within the palaeo-regolith zone. The location of ore is controlled by steeply west dipping strike-slip fault set with apparent horizontal movement, but no obvious vertical displacement of the unconformity, despite the presence of significant shearing in both the basement and overlying sandstone.

Alteration surrounding the ore in the basement is characterised bychlorite and illite.

The total resource of the deposits (after Ghandi, 2005) at Dawn Lake are:

    0.685 Mt @ 1.97% U3O8 containing 13 500 t U3O8.

Indicated resources in 2005 (Cameco Annual Report) were:

    0.347 Mt @ 1.69% U
3O8 containing 5 875 t U3O8.

The most recent source geological information used to prepare this summary was dated: 2006.    
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

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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