Cambior a leading zinc producer in Quebec

Although production has already started, Cambior (CBJ-T) took time out recently to inaugurate the Gonzague Langlois zinc mine in northwestern Quebec.

The celebration, which took place in a large tent erected at the mine site, included 250 guests ranging from representatives of the federal, provincial and local governments, mining company executives and the news media to the company’s own directors and shareholders.

Although known as Grevet throughout its development, the name of the mine was changed to Gonzague Langlois, in honor of a deceased mining engineer who had been a long-time president of the Quebec Mining Association. He was also a Cambior director. On hand to accept the honor on his behalf was his widow, Therese.

Cambior has held an interest in the property since 1992, when it acquired 50% through a takeover of VSM Exploration. The following year, Cambior acquired SEREM-Quebec’s 50% interest for $7 million in Cambior shares, bringing the acquisition cost of the project to $18 million.

Cambior first began underground exploration there in late 1992, and the access road connecting the site to the Val d’Or-Chibougamau highway was completed then as well. The feasibility study for the Grevet project was completed in late 1994.

The three main zones, numbered 3, 4 and 97, extend along an axis of 2.2 km, and from surface to a depth of 1,000 metres. The zones vary in width from 1.5 to 8 metres.

As of Dec. 31, 1995, proven and probable reserves stood at 11 million tonnes grading 8.41% zinc, 0.46% copper, 37 grams silver and 0.1 gram gold per tonne.

The mine is expected to produce, per year, 62,000 tonnes zinc, 3,000 tonnes copper, 313,000 oz. silver and 700 oz. gold from 910,000 tonnes of ore.

Current reserves provide for a mine life of at least 12 years. Cambior senior vice-president, Henry Roy, said the mine’s annual revenue should be about $100 million, roughly the amount Cambior spent bringing the project into production. Annual production costs are estimated at $37 per tonne.

The deposit being mined at Gonzague Langlois, according to Chief Geologist Yves Michaud, consists of four polymetallic zones containing mainly zinc, copper and silver, with traces of gold. The massive sulphides of these zones are hosted in an Archean-age basaltic and rhyolitic volcanic sequence typical of volcanogenic massive sulphide deposits. In this case, however, the deposit has been squeezed by deformation associated with the regional Cameron shear zone, and is now tightly folded and highly schistose. The Cameron shear zone, which is 18 km long and 1-8 km wide, is 5 km wide at the mine site.

All of the minerals in the shear zone have been recrystallized by the deformation. Metal mineralization consists of fine grains of sphalerite (67% zinc as a sulphide), with associated pyrite and chalcopyrite (iron and copper-iron sulphide, respectively).

As a result of favorable geometry (the ore zones are nearly vertical), 80% of the deposit will be mined through the longhole method.

Cambior expects that mining 20-by-60-metre primary and secondary stopes, using paste backfill, will enable total recovery of the reserves.

The backfill, made of tailings, cement and water, is manufactured at an on-site plant, then returned underground through a network of pipes. The backfill will allow half of the mine’s waste to be returned underground.

The 1,800 tonnes per day currently being mined originate between the 5 and 6 levels (375 metres below surface), though production will increase to 2,500 tonnes per day later this summer, when ore from between the 10 and 11 levels (600 metres below surface) is mined.

Back on surface, the concentrator uses a conventional process of semi-autogenous grinding, sequential flotation and pressure filtration to produce zinc and copper concentrates in independent circuits. The zinc concentrate is 53-55% zinc metal, while the copper concentrate is 23-27% copper metal.

Metal concentrate is conveyed to the end of a spur line, where rail cars enter a small building to be filled with concentrate. The cars are then moved to a railway line less than a kilometre away, and on to smelters. Most of the zinc is refined at Canadian Electrolytic Zinc in Valleyfield, Que., while the copper concentrate, which includes silver and gold, is sent to Noranda’s Horne smelter in Rouyn-Noranda.

Gold at the operation is associated with chalcopyrite, sphalerite and pyrite, but only the gold associated with chalcopyrite (about 33%) is recovered, making it a minor byproduct. Zinc sales comprise 90% of the mine’s revenue.

Lo Ct, the mine’s manager, said once the zinc circuit is optimized, zinc recovery will rise to 95% from the current rate of 91%. Copper recovery stands at 82%.

The only notable metallurgical difficulty at the mine, according to mill superintendent Mario Courchesne, concerns the flotation of some very small (less than one micron) grains of zinc.

The mine will employ about 200 people once it enters full production later this year. Workers are currently bused to and from their homes in Lebel-sur-Quvillon, 45 km southwest of the mine, though some are being housed in a temporary mining camp because of a lack of housing in the town of 3,600. Included in the workforce are eight men from the local Cree population, with which, according to President Louis Gignac, Cambior has a strong relationship.

Gignac said he expects the opening of the Gonzague Langlois mine to be the beginning of Cambior’s base metal production in the area.

“We have a large land holding in the area, so with this mine up and running, we will be actively exploring and trying to add to it. I think we can increase capacity here at a fairly low cost.”