Dr. Boen Tan and Rick Mazur of Forum Development

Unconformity-type uranium deposits are among the richest and largest in comparison to other uranium deposit types. Those found in the Athabasca Basin in northern Saskatchewan, Canada are unique, as they are much higher grade than other deposits of this type found elsewhere in the world. One-third of the world's uranium, with ore grades ranging from 1 percent (20 lbs. per ton) to over 20 percent (400 lbs. per ton) uranium is produced in Saskatchewan from unconformity-type deposits. For this reason, the Athabasca Basin is an attractive place to explore for uranium.

The original sources of uranium were derived from various types of basement rocks such as granites of Archean age (greater than 2 billion years old) and black shale and arkosic rocks of Proterozoic age (1.8 to 2 billion years old). Further uranium enrichment occurred 1.8 billion years ago during the Hudsonian orogeny, an event that created mountains higher than the Himalayas. Uranium mineralization containing a few hundred ppm (parts per million) to a few percent uranium were formed at this time in pegmatites and metasomatic deposits.

The Athabasca Basin is a thick accumulation of sandstone deposited around 1.7 billion years ago, during an extended period of river systems following this long period of erosion. The contact between the Athabasca sediments and the altered basement rocks is the 'Unconformity' surface that marks the position where these uranium deposits were formed. During the time of deposition of the Athabasca sediments, uranium, which travels in solution under oxidizing conditions, was transported along with the sediments.

Unconformity-type uranium deposits within the Athabasca Basin were formed after the deposition of the Athabasca sediments, or 'Post- Athabasca'. Uranium was concentrated and mobilized via hot, percolating hydrothermal solutions (around 250 degrees Celsius or 480 degrees Fahrenheit) into 'structural traps'. The uranium precipitated from solution when the oxidizing solutions from the Athabasca Basin came into contact and reacted with reducing solutions from the underlying basement rocks. The Athabasca sediments and the basement rocks were also affected by alteration from these hydrothermal solutions.

There are currently three uranium mines operating in the Athabasca Basin of northern Saskatchewan. The McArthur River Mine/Key Lake Mill, operated by Cameco Corporation and AREVA is an underground operation being mined at a grade of 24% U3O8 and at a depth of approximately 500 to 650 metres. The Eagle Point Mine/Rabbit Lake Mill, operated by Cameco Corporation is an underground operation being mined at a grade of 1.3% U3O8 to a depth of 400 metres. The McClean Lake Mill, operated by AREVA, Denison and OURD is currently processing stockpiled ore from an open pit, but will be processing ore grading 19% U3O8 at a depth of 430 metres from the Cigar Lake underground mine, scheduled for production in 2007.