Midwest partners try out borehole mining

Partners Cogema Resources and Denison Mines (DEN-T) got mixed results from a test of two borehole mining systems at the McClean Lake uranium project in northern Saskatchewan this summer. The results were good enough, though, for the companies to agree on a budget for further testing in the 2006 field season.

The program tested two separate remote mining methods. In jet boring, a pilot hole is drilled into the orebody. Once the hole is through the orebody, the drill rods are replaced by a water jet cutting head, which mines out a cylindrical bore around the pilot hole with a high-pressure stream of water. The resulting slurry of water and ore runs out the pilot hole and is pumped to storage.

The second method, blind boring, starts from a similar pilot hole, but reams the ore around the borehole with a cutting head. A high-pressure water supply or air jet flushes cuttings to the surface.

In practice, the companies found the drill rig to be underpowered for the job, progressing slowly through the sandstone overlying the uranium deposit. The hole also deviated enough that the driller could not set casing in it.

The partners believe modifications to the system will allow successful test mining next season, and plan 15 further test holes to mine about 450 tonnes U₃O₈.

Denison also is close to approving a $5-million exploration budget for its five major Saskatchewan projects next year, up from $3.5 million in 2005. At Midwest, where it owns a 25% interest, Denison tested along strike from an isolated drill intersection north of the known orebody. Three holes intersected uranium mineralization at the base of the Athabasca sandstone, with one cutting 7.1 metres grading 6.25% U₃O₈, a second cutting 7.7 metres grading 11.67%, and a third cutting 17.7 metres grading 1.14%.

The Midwest partners (Cogema, with 69%, Denison, and OURD Canada, a consortium of Japanese power utilities, with 6%) plan a 5,000-metre drill program on the zone in an attempt to mark out a resource. Four other drill holes will test metamorphic basement rocks below the sandstone, where some drill intersections were identified in the late 1970s and early 1980s.

At the McClean property, where Cogema owns 70%, Denison 22.5% and OURD Canada 7.5%, the partners plan testing in basement rocks at the McClean South prospect, another area untested since the 1980s. There are also plans to test strike extensions of the known JEB deposit and a new prospect at Bena Lake, west of the known Sue E zone.

Cogema is a subsidiary of French power utility Areva (ARVCF-O).

Denison also has plans for a 13,500-metre drill program on the Wheeler River project, near the present McArthur River mine. Denison, which is funding a $7-million program to earn a 60% interest from McArthur operator Cameco (CCO-T, CCO-N) and from Japan-Canada Uranium, will be testing targets along the strike of a basement quartzite ridge that extends on to the property from McArthur River.