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originating from the Athabasca Basin and descended downward along reactivated fracture
systems in the basement rocks. Interaction between the hydrothermal brine and the
metamorphic basement lithologies may have led to the deposition of the ±U 6 uranium
mineralization and Cal 10 -Chl 9 -Hem 8 -Py 7 mineral assemblage (Fig. 2.8). The 1620±4 Ma
Athabasca-related ±U 6 uranium mineralization is coincident with the age of the major
unconformity-related uranium mineralizing event in the Athabasca Basin (Alexandre et al.,
2007) and records tectonic reactivation during the 1.65-1.60 Ga Mazatzal Orogen in
southern Laurentia (Fig. 2.14) (Labrenze and Karlstrom, 1991; Eisele and Isachsen, 2001).
The Athabasca-related U 6 uranium mineralization age is also within the 1700-1500 Ma
intervals that Robinson (1955) originally suggested as the earliest uranium mineralization
in the Beaverlodge area.
From the Mesoproterozoic to recent time (Fig. 2.13H), far field tectonic events of
several orogenic episodes during the thermotectonic evolution of the Laurentian plate (e.g.
Hoffman, 1989; Evans and Pisarevsky, 2008) caused minor brittle fault reactivation in the
Beaverlodge area (Fig. 2.15). Post-mineralization alteration for all stages of uraninite
record a Mesoproterozoic tectonic event at ca. 1.4 Ga (Fig. 2.15), which corresponds to the
Granite Pluton event (1.55-1.35 Ga) along the southeastern margin of Laurentia (Fig. 2.14)
(Barinek et al., 1999; Thompson and Barnes, 1999). This event is subsequent to the final
breakup of the Nuna supercontinent (Hou et al., 2008; Evans et al., 2010) that culminated
at ca. 1.3 to 1.2 Ga (Ernst et al., 2008). The metasomatic-type U 3 uraninite in Gunnar
records this breakup event at ca. 1.27 Ga (Fig. 2.15), similar to the 1.27 Ga Mackenzie
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