| dc.description.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.
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