Uranium in Alberta

Recent increase in uranium prices prompted the almost complete restaking of the Alberta portion of the Athabasca Basin and adjacent basement, as well as of large areas in central and southern Alberta. Therefore, Alberta Geological Survey (AGS) initiated a systematic re-evaluation of the uranium potential to

support renewed exploration for uranium in Alberta;
enhance knowledge about the uranium potential needed by government agencies for informed decision-making; and
raise public awareness of possible issues regarding uranium exploration and development.

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 quartzose conglomerate, sandstone, siltstone and mudstone about 1.7 to 1.8 billion years old. The underlying crystalline basement is made of reworked Archean and Early Proterozoic crust. The majority of mines and prospects are in the eastern part of the basin in Saskatchewan. However, the potential exists for similar unconformity-associated uranium deposits in the western part of the Athabasca Basin. These significant mined deposits and prospects are near Cluff Lake in the Carswell Structure and new prospects intersected by drilling at Shea Creek, Saskatchewan and Dragon Lake, Alberta.

The Alberta portion of the basin has been intensely explored in the 1970s and early 1980s, and uranium occurrences have been documented in drillcore along the Maybelle structural trend south of Lake Athabasca and in a few outcrops north of the lake. 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; and
of the presence of ancient shear zones disrupted by faults.

In the Dragon Lake area, along the Maybelle River shear zone (MRSZ), steep brittle fractures in the sandstone host disseminated to high-grade uraninite within a chlorite and illite-altered halo at the base of Fair Point Formation of the Athabasca Group. One intersection has 21% U3O8 over 5 metres, with thin intervals of pure uraninite. The alteration halo also contains numerous other metals, including nickel, arsenic, lead, molybdenum and cobalt. This halo of complex mineralization and alteration extends at least 200 metres along the MRSZ, indicating that the reactivated shear zone is permeable and was the main path for upwelling mineralizing fluids. Paragenetic and textural relationships indicate several phases of the mineralization’s deposition and remobilization consistent with intermittent basement reactivation and release of metalliferous brine. grades

The northern rim of the Athabasca Basin is exposed on the north shore of Lake Athabasca. Exploration for uranium, including scintillometer traverses, geological mapping, airborne and ground geophysics and drilling, 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. Near the Alberta-Saskatchewan border, uraniferous boulders showed geochemical characteristics consistent with a Saskatchewan source, while to the west boulders have a distinct geochemical signal that suggests a local source in Alberta.

AGS is compiling uranium exploration data from industry and government geological reports for the northern edge of the Athabasca Basin and the adjacent crystalline basement. The digital dataset will contain

locations of diamond drillholes;
locations of uranium boulders and uranium boulder trains along the northern shore of Lake Athabasca in Alberta;
uranium mineralization outcrops from detailed industry mapping in the 1970s;
sites of uranium mineral stains and/or radioactivity discovered during the 1957 to 1975 mapping of the Alberta Shield by the Alberta Research Council and ‘mineralized zones’ identified by the Geological Survey of Canada during the early 1990s remapping of the Alberta Shield; and
metallic mineral showings re-examined and new sites identified by AGS during the Canada-Alberta Mineral Development Agreement in the early 1990s.

Southern Alberta has recently re-emerged as having potential 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 that host many important sandstone-hosted uranium deposits. In the U.S.A., 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 t U3O8 at average grades of 0.2% U3O8, and occur in districts that contain up to 300,000 t U3O8 or more. Sandstone-hosted uranium deposits in the U.S.A. have been producing since the 1950s using conventional mining and in-situ leach (ISL) methods. Understanding of the geology and especially the alteration were major factors in focusing exploration efforts, but drilling has been the most important exploration tool for these deposits. For example, in 1968, at the peak of the uranium rush, 12 million feet of exploratory drilling were done in Wyoming alone.

In Alberta, during the last ‘uranium boom’ in the 1970s and early 1980s, exploration for sediment-hosted uranium deposits was conducted sporadically. Several radioactive occurrences were discovered, but there was reportedly little detailed follow-up exploration of anomalous areas. However, the recent sharp increase in uranium prices, together with advances in ISL technology, have rekindled exploration interest for sandstone-hosted uranium deposits in Mesozoic and Tertiary fluvial to shallow marine sandstones in southern Alberta. An overview of some of the formations with potential for sandstone-hosted uranium deposits in Alberta follow.

Sandy clastic sediments of Campanian (81.5-81 Ma) Milk River Formation in southeastern Alberta contain a weakly anomalous (up to 200 counts per second) radioactive occurrence, associated with rusty altered sandstone, within massive sandstone unit in the banks of Police Creek.

The dominantly fluvial Campanian (80-75 Ma) Belly River clastic wedge includes Foremost, Oldman and Dinosaur Park formations that were deposited as the Laramide Orogeny began. In the Basal Belly River wedge conglomeratic fluvial sandstone channel complexes reach thicknesses up to 30 metres and some exceed 1 km in width in at least one area.

Fluvial sandstone channels of Campanian-Maastrichtian age (72-66 Ma) St. Mary River Formation are generally reduced, friable and sometimes contain abundant organic material. The upper part of the St. Mary River Formation, called Whitemud member, is represented by a regional oxidation of the upper beds that formed during a significant break in sedimentation, before deposition of the organic-rich Battle shale and Kneehills tuff zone. A radioactive occurrence (up to 350 cps) is associated with folded and faulted beds of St. Mary River Formation near the village of Kimball (photo).

Reduced, friable fluvial sandstones of Maastrichtian–Paleocene (66-64 Ma) Willow Creek Formation (some with abundant organic material) were reported in the 1994 Alberta Geological Survey’s Metallogenic Report to host “...four radioactive occurrences (with maximum radioactivity of 2000, 900, 300 and 200 cps…) along the Waterton River over about 7 km.” More recently, industry reported a rock grab sample with 0.9% U3O8 in Willow Creek Formation on the banks of Waterton River.

Massive cross-bedded fluvial sandstones of Paleocene (64-60 Ma) Porcupine Hills and Paskapoo formations in southwestern and central Alberta were staked for uranium in 2005, based reportedly on anomalous (4-6 parts per million) concentrations of uranium in stream sediments.

Paleocene (65-62 Ma) Ravenscrag Formation comprises fluvial and estuarine immature sandstones, mudstones and lignites, and reportedly is being explored for uranium in both southwestern Saskatchewan and southeastern Alberta. It has been suggested that uranium was mobilized by groundwaters and deposited under reducing conditions, particularly by coals lower in the stratigraphic sequence. Concentrations up to 0.2% U3O8 have been reported from previous exploration.

During 2006, the Alberta Geological Survey evaluated the regional potential for sandstone-hosted uranium in southern Alberta. Studies of stratigraphy, lithology, alteration, structure, geochemistry and anomalous radioactivity of and within favourable formations will yield a better understanding of the potential for sandstone-hosted uranium deposits. Because little geoscience information and especially drilling exist for sandstone-hosted uranium deposits in southern Alberta, exploration is in the early stages.

The growing energy demands fuelling exploration around the world have put Alberta on the map, not only as a major fossil fuel supplier, but as a potential uranium province as well.

Last modified: May 8, 2008