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metamorphic origin of the main U 4 mineralizing event. Tremblay et al. (1972) suggested
that rocks of the Beaverlodge area may represent previously U-rich regions that were
leached during metamorphic-hydrothermal alteration during late Trans-Hudson
granitization processes and that the U mineralization was deposited along major fault
zones. Rees (1992) proposed a metamorphic origin for fluids associated with the lode-gold
quartz vein mineralization at the Nicholson deposit, which formed at ca. 1.85-1.84 Ga at
temperatures of ca. 300-400 o C. His results demonstrate that Au gold and U mineralization
likely formed from the same mineralizing event.
A strong structural control is reported in most metamorphic-related U systems, with
U commonly hosted by reactivated ductile to brittle-ductile fault zones (Cuney and Kyser,
2008). Skirrow et al. (2009) suggest that fluids in these systems are saline Na-Ca brines
that were F-rich and CO 2 -bearing. Such U deposits formed from fluids of metamorphicdehydration
origin and appear to be rare and of low grade and tonnage (Plant et al., 1999).
The relatively low oxidation state of such fluids may explain why these systems are not
associated with significant U mineralization. The Beaverlodge U deposits are therefore,
similar to these metamorphic-related U mineralization systems associated with Nametasomatism
(Cuney and Kyser, 2008). Examples include the Krivoy-Rog district in
Ukraine (Belevtsev and Koval, 1968), the Kurupung district in Guyana (Cinelu and
Cuney, 2007) and Skuppesavon in Sweden (Smellie and Laurikko, 1984). Therefore, these
deposits could be related to the global 1.9-1.75 Ga alkali-metasomatism associated with
the plate tectonic-scale collisional orogenesis culminating with the Nuna supercontinent
assembly (Cuney, 2010; Evans et al., 2010).
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