Uranium

Uranium

Uranium in Alberta

Canada is the second-largest uranium producer in the world, with about 15% of total world production. Most uranium production comes from Saskatchewan in the uniquely rich deposits in the Proterozoic Athabasca Basin. Alberta has seen uranium exploration throughout the province in the past, and more recently, extensive staking is taking place in the Athabasca Basin and adjacent basement terrain in northeastern Alberta.

The Athabasca Basin, which straddles the Alberta-Saskatchewan border, contains some of the greatest uranium resources in the world. Athabasca-type, unconformity-related uranium deposits are unique in size and grade compared to similar deposits elsewhere. These deposits have uranium oxide pods, veins, and disseminations at or close to the unconformity at the base of the Athabasca Group.

The flat-lying Athabasca strata are mainly fluvial, pervasively altered, red to pale-tan quartz conglomerate, sandstone, siltstone, and mudstone and are about 1.7 to 1.8 billion years old. The underlying crystalline basement is made of reworked Archean and Early Proterozoic crust. The mines in the eastern part of the basin in Saskatchewan contain the richest uranium deposits in the world. The potential exists for similar unconformity-associated uranium deposits in the western part of the Athabasca Basin.

Unconformity-Related Uranium Deposits: Exploration Target in Northeastern Alberta

The Alberta portion of the basin was intensely explored in the 1970s and early 1980s, and uranium occurrences have been documented in drill core along the Maybelle structural trend south of Lake Athabasca and in a few outcrops north of the lake. Northeastern Alberta is favourable for uranium exploration because

  • the main stratigraphic units of the Athabasca Group associated with uranium deposits in Saskatchewan are also found in Alberta,
  • the crystalline basement underlying the Athabasca Group in Alberta is lithologically and geochemically similar to the basement units of Saskatchewan's highly prospective Wollaston domain,
  • there are ancient shear zones disrupted by faults, and
  • high-grade uranium ores occur in the Maybelle River shear zone.

In the Dragon Lake area, along the Maybelle River shear zone, steep, brittle fractures in the sandstone have disseminated to high-grade uraninite within a chlorite and illite-altered halo at the base of the Fair Point Formation of the Athabasca Group.

One intersection has 21% U3O8 over 5 metres, with thin intervals of pure uraninite. In 2006, an intersection of up to 54.5% U3O8 was reported. The alteration halo has numerous other metals, including nickel, arsenic, lead, molybdenum, and cobalt. This halo of complex mineralization and alteration extends at least 200 metres along the zone. This means the reactivated shear zone is permeable and was the main path for the upwelling of mineralizing fluids. Paragenetic and textural relationships indicate several phases of this mineralization and remobilization.

The northern rim of the Athabasca Basin is exposed on the north shore of Lake Athabasca. Exploration for uranium has documented several uraniferous outcrops with 10 000 counts per second and uraniferous boulder trails or individual boulders with up to 16 000 counts per second. This was done with scintillometer traverses, geological mapping, airborne and ground geophysics, and drilling. Near the Alberta-Saskatchewan border, uraniferous boulders showed geochemical characteristics consistent with a Saskatchewan source; whereas to the west, boulders have a distinct geochemical signal that suggests a local source in Alberta.


Sandstone-Hosted Uranium Deposits: Exploration Target in Southern Alberta

Southern Alberta has been targeted for sandstone-hosted epigenetic uranium deposits. Mesozoic to Tertiary formations in the Western Canada Sedimentary Basin are of similar age and lithological characteristics to formations in Wyoming, Colorado, Utah, New Mexico, and south Texas, which host many important sandstone-hosted uranium deposits.

In the United States, roll-front and peneconcordant tabular-type uranium deposits are hosted in organic-rich, reduced, porous fluvial and shallow-marine sandstones near regional oxidation/reduction fronts. Individual deposits commonly contain up to 50 000 tonnes U3O8 at average grades of 0.2% U3O8 and occur in districts that contain up to 300 000 tonnes U3O8 or more. Sandstone-hosted uranium deposits in the United States have been producing since the 1950s using conventional mining and in situ leach (ISL) methods.


Roll-front deposit model

During the uranium boom in the 1970s and early 1980s, exploration for sediment-hosted uranium deposits was conducted sporadically in Alberta. Several radioactive occurrences were discovered, but there was reportedly little detailed follow-up exploration. However, continued interest in uranium as fuel for nuclear energy, together with advances in ISL technology, rekindled exploration interest for uranium in Mesozoic and Tertiary fluvial to shallow-marine sandstones in southern Alberta. In 2006, the AGS studied the stratigraphy, lithology, alteration, structure, geochemistry, and anomalous radioactivity of and within favourable formations in southern Alberta and identified potential for sandstone-hosted uranium in the region.

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