Summary:
The Roughrider deposits are interpreted to be Athabasca unconformity-associated uranium deposits, or some variant thereof. Two end-members of the unconformity-associated uranium deposit model have been defined (Quirt, 2003). A sandstone hosted egress-type model (one example is the Midwest A deposit south of the Project) involves the mixing of oxidizing sandstone-hosted brine with relatively reduced fluids from the basement in the sandstone. Basement-hosted, ingress-type deposits (one example is the Rabbit Lake deposit) formed by fluid-rock reactions between an oxidizing sandstone brine and the local wall rock of a basement fault zone. Both types of mineralization and associated host-rock alteration occur at sites of basement–sandstone fluid interaction where a spatially stable redox gradient, or front, was present. Although either type of deposit can result in high grade pitchblende mineralization with up to 20% pitchblende, they are not physically large.
Egress-type deposits tend to be polymetallic (uranium-nickel-cobalt-copper-arsenic) and typically follow the trace of the underlying graphitic pelites and associated faults along the unconformity. Ingress-type, tend to be monomineralic uranium deposits, and can have more irregular, structurally controlled geometry.
The Project comprises the Roughrider West Zone (“RRW”), the Roughrider East Zone (“RRE”) and Roughrider Far East Zone (“RRFE”) unconformityrelated uranium deposits. The deposits occur at, and below, the unconformity between the overlying Athabasca group sandstones and conglomerates, and the Wollaston group orthogneisses.
Uranium mineralization is localized by structures, adjacent to, and within graphitic meta-pelites. The mineralization is characterized by uraninite and lesser amounts of uranophane, and red to orange coloured oxy-hydroxillized iron oxides. Uranium mineralization in the Athabasca basin, and the Project, is interpreted to form where oxidized uranium bearing fluids, presumably sourced from the Athabasca group, mix, at or near the unconformity with reduced fluids, or rock masses of the basement, Wollaston group. Uranium is reduced at the redox front where these conditions exist.
The RRW, RRE, and RRFE deposits occur in the basal part of the Wollaston Group of the WMTZ. The basement is structurally complex, comprising steeply dipping Wollaston Group rocks dominated by garnet- and cordieritebearing pelitic gneisses with subordinate amounts of graphitic pelitic gneisses and psammopelitic to psammitic gneisses, and rare garnetites. The pelitic gneiss varies from equigranular to porphyroblastic in texture. The porphyroblasts vary in size up to centimetre-scale and normally comprise red almandine rich garnets when fresh. The gneisses have been intruded by syn- to post-peak metamorphic felsic pegmatites, granites, and microgranites of Hudsonian age. These rocks locally contain up to 400 parts per million (“ppm”) of primary uranium and unconformably overlie the basal Archean aged granitic gneiss.
Proximal to mineralization, graphite in graphitic pelitic gneisses has been consumed by alteration and mineralization; distal to mineralization, the graphite appears to be discontinuous. These two features may help explain the absence of basement-hosted graphitic conductors at the Project.
Hydrothermal calc-silicate alteration of the orthogneisses is present locally. The alteration is interpreted to be postpeak metamorphism in age and is probably related to the introduction of the Hudsonian felsic rocks. The sandstone and basement rocks have been subjected to several episodes of brittle deformation, including the brittle reactivation of older ductile shear zones.
Macro-scale geophysical, geological and structural modelling suggests that the Property is crosscut by a large number of structures. The two main structures to note are:
- An east-west striking, north-dipping fault (approximately 75°/010°) with a reverse sense of slip and a maximum throw of approximately 20 m.
- A north-east striking, northwest-dipping fault (approximately 55°/295°) with ambiguous throw, possibly suggesting strike-slip movement. This is locally referred to as the ‘Midwest Trend’, that hosts the Midwest and Midwest A uranium deposits on the adjacent mineral leases, to the south of the Property.
Mineralization
Uranium deposits in the Athabasca Basin can be broadly subdivided into two styles: unconformity-hosted (occurring at or above the unconformity) and basement-hosted. The Project is characterized by basement hosted mineralization, which is typically hosted in faults (often referred to as veins when hosting mineralization) which must have been open to hydrothermal fluid flow at the time of mineralization and thus were likely active at some stage post basin formation.
Uranium mineralization is highly variable in thickness and style in all zones. High grade uranium mineralization occurs primarily as structurally controlled, medium- to coarse-grained, semi-massive to massive pitchblende with what has been termed worm-rock texture, and texturally complex redox controlled mineralization. This high-grade uranium mineralization is intimately associated locally with lesser amounts of red-to-orange coloured oxyhydroxillized iron oxides. Yellow secondary uranium minerals, probably uranophane, are present locally as veinlets or void-filling masses within the high-grade primary mineralization.
Lower grade mineralization occurs as either disseminated grains of pitchblende, fracture-lining, or veins of pitchblende. Galena occurs in a number of habits and is variably present in the uranium mineralization. The lead is presumed to have formed from the radioactive decay of uranium. Veinlets of galena are up to 5 mm thick and either crosscut massive pitchblende, as anhedral masses (less than 1 mm in size) interstitial to the massive pitchblende, or as fine- grained, sub-millimetre-scale disseminated flecks of galena omnipresent throughout mineralized drill core. In all cases, the galena appears to have formed later than the uranium mineralization.
Mineralization is in general terms, mono-metallic (uraninite) in composition. In the RRW deposit, visible, crystalline nickel-cobalt sulf-arsenides are present locally. At the RRE and RRFE deposits, the presence of nickel-cobalt sulfarsenides is rare. The exact relationship of these elements to uranium is variable and still unclear at this time. However, unlike many unconformity-type uranium deposits in the Athabasca Basin, variable amounts of copper mineralization are present within the deposits.
The zones of uranium mineralization at the Project vary in size and depth below the unconformity:
• RRW - is 200 m long and up to 50 m wide, and occurs at the unconformity down to approximately 50 m below the unconformity;
• RRE - is 100 m long and up to 50 m wide, and occurs from 20 m below the unconformity down to approximately 120 m below the unconformity; and
• RRFE - is 75 m long and up to 50 m wide, and occurs from 100 m below the unconformity down to approximately 220 m below the unconformity.