Proposed Title 1: - Queen's University

5.2.1.2. Metamorphic-related uranium mineralization
5.2.1.2.1. Early-vein and cataclasite-type uranium mineralization
Minor U mineralization associated with early veins and cataclasite in the Beaverlodge
area formed at ca. 2.29 Ga during late stages of the ca. 2.35 Ga Arrowsmith Orogen and
was triggered by reactivation of basement-rooted shear zones during exhumation, resulting
in overprinting of mylonite by cataclasite and early tensional veins (Fig. 5.3; Dieng et al.,
2011). The δ 13 C and δ 18 O values and chlorite crystal chemistry of syn-ore minerals are
consistent with formation of Ca-F-Mg-rich fluids at ca. 310 o C derived from retrograde
metamorphic processes during exhumation and erosion of the supracrustal rocks. Hydraulic
fracturing and hydration during decompression and exhumation is interpreted as the main
mechanism for the early tensional vein formation. The associated pressure decrease and
fluid decompression during fracturing changed the stability of the U-carbonate complexes,
decreased the temperature of the fluids, and likely promoted U precipitation into fractures.
Although this style of U mineralization is limited, it indicates that the Beaverlodge area
probably had elevated reserves of leachable U.
5.2.1.2.2. Breccia-type uranium mineralization
The major event of U mineralization in the Beaverlodge area coincided with massive
brecciation at ca. 1850 Ma triggered by reactivation of fault zones that breached the host
rock (Fig, 5.3) during the early stages of the Trans-Hudson Orogen. The δ 18 O, δ 13 C and δ 2 H
values and chlorite crystal chemistry of syn-ore minerals indicate that the ore-forming
brines originated from a ca. 330 o C, Ca-Na-F-containing metamorphic-hydrothermal fluid.
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