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the age when the concentrations of the secondary elements (e.g. Ca, Fe and Si) were
negligible (e.g. Alexandre and Kyser, 2005).
Mineral name abbreviations used in this chapter are those from Kretz (1983). The
superscript numerical value on mineral name abbreviations reflects mineral growth stages.
2.4. Results
2.4.1. The Main Ore shear zone
2.4.1.1. Geology of the Cinch Lake deposit
The Cinch Lake deposit is located 2.5 km south of Uranium City (Fig. 2.2). The
uranium mineralization is hosted in quartzo-feldspathic gneiss (Turek, 1962; Tortosa,
1983) and associated with a northeast-striking band of mylonite named the Main Ore shear
zone, which parallels the Black Bay fault (Bergeron, 2001). Three main lithological units
outcrop in the Cinch Lake area that generally strike northeast and dip southeast: a
leucocratic porphyroclastic metagranitoid, a hornblende-feldspar gneiss, and a
melanocratic porphyroclastic metagranitoid (Fig. 2.3).
The leucocratic porphyroclastic metagranitoid unit is exposed in the southeastern
part and occupies the hanging wall of the shear zone (Figs. 2.3A and 2.3B). The rock is
cataclasite-dominated (Fig. 2.4A) weakly foliated and comprises broken fragments of
plagioclase, quartz and feldspar embedded in a matrix composed of hematite, quartz,
chlorite, calcite, sericite, and pyrite (Fig. 2.4B).
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