A study of some uranium mineralization in Athabasca sandstone, near Stony Rapids, Northern Saskatchewan, Canada

Abstract

The deposits were studied in the field by the writer in 1952. Later laboratory work was directed towards determining more or the nature, origin, and mode of deposition of this unique mineralization. The chief uranium mineral is autunite, a calcium uranyl phosphate which occurs locally as a cementing material in nearly flat-lying beds of Athabasca sandstone, and disseminated in a clay-like regolith lying immediately below the unconformity at the base of the sandstone. The autunite occurs as aggregates of tiny, greasy-looking, platy, lemon-yellow crystals, which fluoresce a bright yellow green under ultra-violet light. All known showings of this type, in the Hiddle Lake area are located along prominent scarps marking the eastern and northern limits of Athabasca rocks in the area. Usually the greatest concentration of uranium is on the unconformity, although it may occur in the sandstone anywhere to the top of the scarp, a vertical distance up to 70 or 80 feet. Limited diamond drilling and surface sampling indicate that the grade is low; i.e. probably less than 0.05% U308 equivalent except in selected samples. The origin is still much in doubt but results suggest that the uranium was derived from primary pitchblende deposits in pre-Athabasca rocks. Pre-Athabasca weathering of the pitchblende resulted in the accumulation of secondary deposits on the ancient surface of erosion. Following deposition of the Athabasca series, groundwaters reworked some of these deposits and reprecipitated some of the uranium in the overlying sandstone. Regardless of the origin, the unconformity at the base of the Athabasca appears to have had a major effect on localization of the autunite. Note:This thesis contains maps that have been sized to fit the viewing area. Use the zoom in tool to view the maps in detail or to enlarge the text.