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Figure 2.12. Plot of element contents in uraninite as a function of chemical Pb ages. A: Early
tensional vein type ±U 2 uraninite (Sample 6122BV-Cat, Ace deposit) . B: Breccia-type U 4
uraninite (Sample B5812, Ace-Fay deposit). C: Volcanic-type ±U 5 uraninite (Sample B6120,
Ace-Fay deposit). D: Athabasca-related ±U 6 uraninite (Sample B3705, Ace-Fay deposit).
2.5. DISCUSSION
2.5.1. Interpretation of the Main Ore shear zone and Saint Louis fault
Structural and textural relationships along the Main Ore shear zone and the Saint
Louis fault indicate a sequential development of early ductile and ductile-brittle, to late
brittle episodes of movement (Fig. 2.13). The Main Ore shear zone and the Saint Louis fault
display a spatial distribution of deformed rocks that is consistent with a dominant
extensional normal sense of movement (Sibson, 1977). Therefore, the Main Ore shear zone
is interpreted as an oblique-normal and dextral listric fault. The sense of movement along
the Saint Louis fault is contentious due to paucity of shear sense indicators. Allen (1963)
described the Saint Louis fault as a dextral normal fault with multiple slip events. However,
the footwall-dominated mylonite and the hanging wall-dominated cataclasite, which is
capped by the Martin Lake basal conglomerate, suggest a significant normal sense of
movement.
Metamorphic relationships indicate that mylonitization was initiated in the ductile
environment (Fig. 2.13B) at amphibolite metamorphic conditions and that retrogression to
lower greenschist facies is concomitant with exhumation to shallower crustal depths. The
host mylonites are overprinted by ductile-brittle and brittle faults, reflecting progressive
unroofing of the shear zones to shallower crustal levels. The ductile shear zones
experienced reactivated slip movement in the ductile-brittle zone associated with cataclasite
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