Athabasca Basin uranium deposits are of the Unconformity type. They are developed at, and below, the unconformity that is developed at the base of the shallow dipping, Proterozoic Athabasca sandstone, either at its contact with the underlying metamorphosed gneiss sequence, or within the gneiss for up to 500 metres below the unconformity. Both styles of mineralization are frequently associated with graphitic gneiss units in basement rocks, and faults associated with these lithologies, which together form conductive geophysical anomalies that can be traced using electromagnetic surveys. Deposits occur in a variety of forms ranging from cigar shaped pods of massive to disseminated pitchblende developed along the unconformity above faults and graphitic units, to pitchblendebearing veins and replacement zones developed in basement rocks beneath the unconformity. Mineralization occurs within mineralogically and chemically zoned alteration haloes that may extend for several hundred meters above and laterally from deposits, forming a larger target than the deposits themselves, and a means of vectoring drill holes.

Zoned alteration developed in the sandstone column above unconformity type deposits commonly forms chimneys in cross section that surround, and extend upward for several hundred meters from the deposits through the Athabasca sandstone column. These provide a much larger footprint that the deposits themselves, and an important tool in targeting drill holes. Two common end members of alteration are depicted at left.

Deposit Economics

Deposit economics are controlled principally by depth of the overlying Athabasca sandstone. At the eastern margin of the Athabasca Basin in the vicinity of UEX's Hidden Bay property, and at Cluff Lake, where sandstone cover is thin (less than 100 metres) or absent, relatively low grade deposits of 0.3% to 1% U₃O₈ (US$585 to US$1,980 per tonne at US$90.00 per pound U₃O₈) are mineable by standard open pit and near surface underground, decline access, operations. In deeper parts of the basin (>400 metres sandstone), only high grade large deposits are economic due to the significantly higher mining costs induced by the need to freeze the sandstone to prevent water influx and improve ground conditions, and the costs associated with remote mining of the highly radioactive ore in confined areas.

Deposits at the eastern side of the Athabasca Basin and at Cluff Lake, while smaller than the giant McArthur River and Cigar Lake deposits, have significant gross contained values and high grades when compared to other mineral deposit types. For example, the Eagle Point deposit, a narrow vein underground uranium mine in the Wollaston Lake area, has production and resources of approximately 70 million pounds U₃O₈ at grades of approximately 1.3%. At a market price of US$91.00 per pound U₃O₈ this is equivalent to a gross value of approximately US$6.37 billion, and a value per tonne of approximately US$2,602. Basement hosted deposits in this area can be profitably mined to depths of 400 metres or more at grades of less than 1% U₃O₈, due to the competent, relatively impermeable nature of the metamorphic host rocks, in contrast to the mining problems encountered under deep Athabasca sandstone cover.

UEX's Hidden Bay Project is located in the productive Wollaston Belt of the eastern Athabasca Basin, while the Riou Lake and Black Lake projects are located in a highly prospective, but relatively under-explored area near the northern rim of the basin. These 100%-owned UEX projects represent a balance between easily accessible, near-surface deposits of 5 to 70 million pounds U₃O₈ potential in an area of well-developed mining infrastructure at Hidden Bay, to grassroots potential for giant, world-class McArthur River and Cigar Lake-type deposits at Riou Lake and Black Lake.