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A systematic geochronological study was conducted on the Cigar Lake uranium deposit. U–Pb and Pb–Pb systematics were applied to different types of uranium ore, and various associated sheet silicates were dated by the K–Ar method. These two approaches define a widespread retrograde metamorphic event in the basement, which occurred at about 1780 Ma during the Hudsonian orogeny, and a four-stage evolutionary model for the ore deposit. This model is compatible with the history of other unconformity-type, uranium deposits in the Athabasca Basin.The first stage in the evolution of the Cigar Lake uranium deposit is marked by uraninite crystallization at 1341 ± 17 Ma, which, in association with arsenides and sulpharsenides, constitutes the mineralization of economic interest (main orebody). The second stage, characterized by a Fe-kaolinite and Fe-illite paragenesis, occurred locally at about 900 Ma. The third stage involved uranium mobilization at about 325 Ma and is characterized by (i) preferential loss of radiogenic lead from primary uraninite and crystallization of pitchblende at the rims of uraninite grains and (ii) formation of pitchblende associated with Fe-sulphides or hematite in the main and perched orebodies. The last stage is characterized by recent alteration and coffinitization which have affected all ore types.

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