Geology of the Dawn Lake uranium deposits northern Saskatchewan

Clarke, P. J. ; Fogwill, W. D.
Organization: Canadian Institute of Mining, Metallurgy and Petroleum
Pages: 9
Publication Date: Jan 1, 1986
"The Dawn Lake uranium deposits are located 340 km north of La Ronge, Saskatchewan, in the Athabasca Basin between the Midwest Lake and Rabbit Lake deposits. Four zones of uranium mineralization, called the ""11, 14, 11A and 11B Zones,"" lie within the Athabasca Sandstone, at the sub-Athabasca unconformity and in the basement.At Dawn Lake, approximately 100 metres of Helikian Athabasca Group clastic sediments overlie Aphebian Wollaston Group pelitic and calcareous metasediments and pegmatites. Uranium with some nickel, cobalt and copper, occurs near the sheared stratigraphic contact between calc-silicate gneiss and graphitic, pyritic pelite. The mineralization lies in an area of low magnetic susceptibility which is thought to represent a rock sequence lying stratigraphically high within the Wollaston Group. There is no obvious vertical displacement of the unconformity by faulting, despite considerable brecciation, shearing and slickensides seen in the basement rocks. This suggests horizontal displacement on steeply dipping wrench faults as the main tectonic control along the 11, 11A and 11B trend.Below the Athabasca unconformity, the Wollaston Group rocks are altered to fine-grained mixtures of clays, chlorite and silica commonly called regolith. Along the mineralized trend post-Athabasca fracturing and (or) compaction have occurred through this clay-rich alteration zone, causing the steeply-dipping primary foliation to become contorted. This ""crenulated"" horizon can reach depths of 35 metres below the unconformity and is thickest along fault zones in the calc-silicate rocks. The ""crenulite"" is a distinctive unit which at Dawn Lake is commonly found above pods of ore located deep below the unconformity.Much of the mineralization in the 11A and 11B Zones occurs above, beside and below the thickest part of the crenulated zone, although the crenulated rock itself contains negligible amounts of carbonate, pyrite and uranium. Intense vuggy alteration and collapse breccias are found in calc-silicate rocks deeper and to the west of the 11A and 11B mineralization. There are at least two ages of uranium deposition in the basement zones, shown by small bright cubes of ""pitchblende /"" overgrown and replaced by duller botryoidal ""pitchblende II. ""Sooty pitchblende and yellow secondary minerals are the result of still younger reworking.The geological setting of mineralization, along the contact between carbonate-rich calc-silicate rock and pyritic pelite, suggests that the uranium was concentrated at a pH/Eh boundary located between deeply weathered, carbonate-rich and sulphide-rich basement rocks."
Full Article Download:
(1660 kb)


Additional chapters/articles from the CIM book CIM Special Volume 33

Uranium exploration in Canada
Huronian geology and the Blind River (Elliot Lake) uranium d
Uranium deposits South Limb of the Quirke syncline Elliot La
The Pronto Mine
Geology of the Agnew Lake Mine
Other conglomerate-hosted deposits
Uranium deposits* of the Bancroft area, Ontario
Geology of Madawaska Mines Limited, Bancroft, Ontario
Uranium in Early Proterozoic Aillik Group, Labrador
General geology and uranium deposits of the Beaverlodge Dist
Geology of the Beaverlodge operation Eldorado Nuclear Limite
The geology of the Cenex uranium deposit Beaverlodge, Saskat
Geology of the Athabasca Basin
The Geology of the Rabbit Lake urnnium deposit, Saskatchewan
Uranium deposits in the Rabbit Lake-Collins Bay area, Saskat
Uranium deposits of the Carswell structure
Geology of the Key Lake deposits
Geology of the Midwest uranium deposit northern Saskatchewan
Geology of the Dawn Lake uranium deposits northern Saskatche
The geology of the McClean uranium deposits, northern Saskat
The Cigar Lake uranium deposit: discovery and general charac
North Rim deposits Athabasca Basin
Geology and lithogeochemistry of the Maurice Bay uranium dep
The Gunnar uranium deposit
Uranium deposits and prospects of the Baker Lake Basin and s
Geology and exploration history of the Lone Gull property
Mountain Lake deposit, Northwest Territories
PEC uranium deposit Hornby Bay Basin, Northwest Territories
The Rexspar fluorite and uranium deposits
Basal type uranium deposits in south-central British Columbi