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These previous age models do not take into account the various styles of uranium
mineralization and associated deformation, and their spatial and relative temporal
relationships (Collins et al., 1954; Robinson, 1955a; Koeppel, 1969). Most of these models
have been limited to a single deposit (Russel et al., 1957; Bell, 1981; Dudar, 1982; Rees,
1992) that cannot provide a regional picture of the timing of uranium mineralization and
fluid events and their relationship to deformational history.
In this chapter, structural, petrographic and metamorphic relationships along the
Main Ore shear zone at the Cinch Lake deposit and the Saint Louis fault at the Ace-Fay-
Verna deposits (Fig. 2.2) are used to constrain the timing of deformation and fluid events.
Paragenetically constrained uraninite grains collected from five uranium deposits (Fig. 2.2)
are dated to determine the timing of the uranium mineralization and alteration events.
2.3. Methodology
2.3.1. U-Pb dating of uranium-rich minerals by LA-HR-ICP-MS
U-Pb isotope ratios were determined by laser ablation-high resolution inductivelycoupled
plasma mass spectrometry (LA-HR-ICP-MS) (Chipley et al., 2007) using a
Finnigan MAT ELEMENT XR HR-ICP-MS and a NEPTUNE HR-MC-ICP-MS, both
equipped with a high-performance Nd:YAG New Wave UP-213 laser ablation system at
the Queen’s Facility for Isotope Research. Ablation of uraninites was achieved on polished
thin sections using a 30 to 40μm spot size with 35% to 40% laser power at a frequency of
2Hz. The argon gas flows were as follows: cooling gas, 1.5l/min; auxiliary gas, 1.0l/min;
and sample carrier gas, 1.0 l/min. A low resolution of 350 (defined as the ratio of mass
over peak width mass at 5% of the signal height) was used. For each sample, 204 Pb, 206 Pb,
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