Kinross opens QR gold mine in B.C.

The recent opening of the QR gold mine, 70 km southeast of this timber-mining town, marks a first for Kinross Gold (TSE). While the company already has six other operating mines, QR is the first that was developed from the ground up.

“Before now, we have essentially taken orphaned mines and rebuilt or reworked them”, explains President Robert Buchan, who likens the startup to the birth of a first child.

On an extensive site visit, The Northern Miner learned that the QR is expected to produce 37,000 oz. per year over a mine life of about five years.

With reserves of 1.3 million tonnes grading 4.68 grams gold per tonne, the operation is decidedly small and low-grade. And Arthur Ditto, chief operating officer, stresses that keeping capital and operating costs down represents a challenge.

The final capital cost of the operation (including completion of another $800,000 in tailings dam work) is expected to be $21 million, while operating cash costs are projected at US$220 per oz.

North American Construction Group of Edmonton, Alta., holds the mining contact. Its fleet at the property includes four 45-tonne haulage trucks and two hydraulic backhoes.

Open-pit mining will be seasonal, ending in mid-December and resuming in mid-February.

Initially, miners will focus on the Main zone pit, which contains an estimated 680,000 tonnes grading 4.4 grams gold with a stripping ratio of 5.5-to-1. This zone, which dips at 40-70!, measures about 250 metres in strike, up to 35 metres in thickness and extends from surface to a vertical depth of about 100 metres. Kinross expects the zone to be depleted at the end of 1996.

The QR also hosts two other known deposits: the Midwest and West.

In 1996, Kinross will drive a ramp from the pit wall of the Main zone to the hangingwall of the Midwest zone, a few hundred metres to the west.

The Midwest, which dips at 45-80!, is 300 metres long and up to 17 metres thick. It extends from within 50 metres of surface to a vertical depth of about 200 metres.

Sublevel mining

Underground mining will involve driving crosscut drifts to the zone from the ramp every 15 vertical metres. Sublevels will then be established along the strike of the zone, so that sublevel retreat mining methods can be employed.

Production from the zone is expected to get under way in October of next year. The Midwest hosts probable reserves of 486,000 tonnes grading 4.32 grams gold, compared with the West zone, which contains about 186,000 tonnes grading 6.64 grams.

The latter is a synclinal body, consisting of a relatively flat middle with steepening limbs at each end. It measures roughly 400 metres long, 50-75 metres wide and up to 9 metres thick.

Mining of the West zone will be carried out using room-and-pillar methods on the flat-lying areas, combined with shrinkage stoping on the steep limbs.

The three QR deposits lie within a volcanic belt along the eastern edge of what is known as the Quesnel Trough.

Strata in the area are composed of up to 850 metres of hornblende and augite-bearing porphyritic alkali basalt, which is overlain by up to 300 metres of argillite and siltstone.

These rocks are intruded by numerous calc-alkalic and alkalic stocks related to a dioritic intrusion known as the QR stock, 200 metres south of the known deposits.

Gold mineralization, which is contained within propylitized basaltic tuff and breccias, is associated with a pyritic zone conformable to the enclosing volcanic and sedimentary strata.

There is no visual marker for ore, so all blastholes are assayed for gold content, as well as for acid-generating potential. With pyrite content varying between 2% and 5% and the presence of lenses that contain up to 80% pyrite, acid generation is a concern.

Acid generation

The amount of acid-generating waste in the Main zone is estimated at 1.2 million tonnes, slightly less than half of which will be used in the dam construction, while the balance will be submerged within the tailings impoundment itself.

On assaying for grade, the material is split into four categories: ore grade at a 1.5-gram cutoff; low grade at a 1-gram cutoff; very low grade at a 0.3-gram cutoff; and material grading less than 0.3 gram, which is considered waste.

Low-grade material is being stockpiled for potential milling at a later date, while the very low-grade ore is stockpiled for potential heap-leaching.

Jason McKenzie, general manager, says leaching tests are under way, and preliminary tests are returning encouraging results. The final results of these leaching tests could have an impact on mining plans.

All the zones, particularly the Midwest, have lower-grade haloes around the mill-grade cores. As a result, if heap leaching proves viable, it may be more economic to mine both the Midwest and the West zones by open-pit methods.

“If I had my druthers, I’d open-pit them all,” says McKenzie.

Plans call for contract mining to begin on the Midwest before Christmas, with collaring of the portal scheduled to begin in the new year.

The QR’s carbon-in-leach mill, while sized to handle 800 tonnes per day, is currently operating at about 1,150 tonnes, with no appreciable negative affect.

For calender 1995, Kinross expects the QR to spin off about 24,000 oz. gold.