This review of the geology, geophysics, and origin of the unconformity-associated uranium deposit type is focused on the Athabasca Basin. Pods, veins, and semimassive replacements of uraninite (var. pitchblende) are located close to unconformities between late Paleo-to Mesoproterozoic conglomeratic sandstone basins and metamorphosed basement rocks. The thin, overall flat-lying, and apparently unmetamorphosed but pervasively altered, mainly fluvial strata include red to pale tan quartzose conglomerate, sandstone, and mudstone. Beneath the basal unconformity, red hematitic and bleached clay-altered regolith grades down through chloritic altered to fresh basement gneiss. The highly metamorphosed interleaved Archean to Paleoproterozoic granitoid and supracrustal basement gneiss includes graphitic metapelitic that preferentially hosts reactivated shear zones and many deposits. A broad variety of deposit shapes, sizes and compositions ranges from monometallic and generally basement-hosted veins to polymetallic lenses located just above or straddling the unconformity, with variable Ni, Co, As, Pb and traces of Au, Pt, Cu, REEs, and Fe. Résumé Cet examen de la géologie, de la géophysique et de l'origine des gîtes d'uranium associés à des discordances est focalisé sur le bassin d'Athabasca. Les minéralisations d'uraninite (variété pechblende) qui prennent la forme de lentilles, de filons ou de corps semi-massifs de remplacement se situent près de la discordance entre des grès conglomératiques de bassin du Paléoprotérozoïque tardif au Mésoprotérozoïque et les roches du socle métamorphisées. La succession sédimentaire de bassin est mince, repose dans l'ensemble à plat, est apparemment non métamorphisée, mais profondément altérée, et se compose principalement d'unités fluviatiles constituées de conglomérats quartzeux, de grès et de mudstones de couleur rouge à chamois pâle. Sous la discordance marquant la base de la succession sédimentaire, un régolite hématitique rouge, décoloré par endroits par une altération argileuse, passe progressivement vers les profondeurs du socle à des gneiss chloritisés puis à des gneiss non altérés. Les roches très métamorphisées du socle, formées d'une intercalation de gneiss granitoïdes et de gneiss supracrustaux de l'Archéen au Paléoprotérozoïque, incluent des métapélites graphitiques qui renferment de manière préférentielle des zones de cisaillement réactivées et un grand nombre de gîtes. Les gîtes sont de formes, de dimensions et de compositions très variées, passant de minéralisations monométalliques, généralement sous forme de filons encaissés dans le socle, à des lentilles polymétalliques présentant des concentrations variables de Ni, Co, As, Pb et des traces de Au, Pt, Cu, de terres rares et de Fe, qui se situent à cheval sur la discordance ou à peu de distance au-dessus. Definition Unconformity-associated uranium deposits are pods, veins, and semimassive replacements consisting of mainly uraninite dated mostly 1600 to 1350 Ma, and located close to basal unconformities between Proterozoi...

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Eight new U-Pb zircon ages are reported for volcanic and plutonic rocks from the Paleoproterozoic Flin Flon Domain. The shoshonitic Vick Lake tuff crystallized at 1885 +/- 3 Ma, marking a late phase of arc-related volcanism. Synvolcanic diabase of the Ocean Floor Assemblage at Athapapuskow Lake is poorly dated at ca. 1.9 Ga, but nevertheless is the first direct age constraint on mafic rocks of the Ocean Floor Assemblage. Tonalite from the West Arm of Athapapuskow Lake crystallized at 1903 +6/-4 Ma, an age that supports a correlation with the dated Mystic Lake tonalite to the northwest, places a minimum age on the volcanic rocks it intrudes, and a maximum age for its deformation. Porphyritic granodiorite and marginal gabbro from the Reynard Lake pluton crystallized at 1850 +/- 3 Ma and 1849 +3/-2 Ma, respectively. As the pluton is larely undeformed, these results place a minimum age on an early foliation that we attribute to amalgamation of the Ocean Floor, Mystic Lake, and Arc assemblages. A felsic dyke, interpreted as having intruded during terrane amalgamation, crystallized at 1869 +/- 1 Ma. Thus, deformation associated with terrane accretion commenced after 1903 Ma, was in progress by 1869 Ma, and was complete by 1850 Ma. Amphibolite-facies quartz diorite from the sub-Paleozoic Namew Gneiss Complex crystallized at 1880 +/- 2 Ma. An improved age of 1831 +5/-4 Ma was obtained for the Cormorant Batholith, marking the last major phase of plutonism in the Flin Flon Domain.

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