TECK CORP Newfoundland Zinc: Ready to Go

With the drop in the price of zinc and declining ore grades, Teck has no immediate plans to re-open the Newfoundland Zinc mine although an improvement in price could trigger a production decision. The mine was closed in April, 1986, but is being maintained on a care- and-maintenance basis. The property is on the west side of Newfoundland’s Great Northern Peninsula, about 135 miles north of Deer Lake. In the early 1960s some companies conducting geochemical work began picking up high values in the area of the mine. Their efforts alerted Leitch Gold Mines and Mastodon- Highland Bell. They, along with an affiliate of Amax, began exploration in 1963. Prospectors Charlie Pegg and Mike Labchuck, working under the direction of J. T. Meagher, discovered zinc mineralization in float and in place. This discovery was followed up by some preliminary drilling and the property was then farmed out to Cominco. This arrangement remained in effect until 1972.

Teck Corp. purchased a controlling share position in Leitch and Highland Bell in 1969; and when the Cominco option expired in 1972, Teck and Amax elected to proceed with an intensive drilling program. This program established a mineable reserve of 4.5 million tons at 8.9% zinc.

A feasibility study was completed in 1974 and construction started in July. The mine, rated at 1,500 tons per day, was in production by June of 1975 and operated continuously until April, 1986, when production was suspended because of a sharp reduction in zinc prices. Reserves are now placed at 813,000 tons containing 7.9% zinc. Teck is the mine operator and the property is a joint venture with Teck holding a 64% interest and Amax, 36%.

Ore occurs in a carbonate sediment of Ordovician age and is similar to zinc mines in the Mississippi Valley. Mineralization is related to a collapsed breccia which consists of a rectangular body of oligomictic breccia with margins marked by vertically dipping and cross-cutting zones of polymictic fine rock matrix breccia. The zinc occurs in pseudobreccia beds adjacent to th e collapsed breccias in an area where the beds are cut by linear vein systems that run roughly parallel to the long axis of the collapsed breccia.

The main L zone plunges gently from surface for a distance of 13,000 ft before reaching a depth of 1,000 ft. Access to this zone was gained with a 20×15-ft decline. Trackless mining has been employed. The more massive ore zones were mined using room and pillar techniques. Drifting and slashing are used on narrow veins.

Trackless underground equipment includes 3-boom drill jumbos, 5-yd scooptrams, 4-yd front-end loaders and 30-ton rear-dump haulage trucks. The ore is truck-hauled from underground to a primary crusher on surface. Mine ventilation is provided by two exhaust raises, supplying about 200,000 cu ft per min. Auxiliary fans are used to divert fresh air to operating faces. There are four main dewatering pump stations. Eight 300-hp and five 150-hp deep-well turbine pumps are used to discharge between 6,000 and 20,000 gallons per minute. Auxiliary pumping, to the main stations, includes 20 88-hp and eight 30-hp units.

In addition to the main underground mine, a number of small surface pits have been developed. Underground equipment is used in these pits, except that an airtrack is used for all surface drilling. The pits are relatively small and often the mineralization continues beyond the economic limits of the pit. In these situations it is possible to follow the vein from the pit by going underground.

Mine ore is dumped into a 125-ton coarse ore bin which feeds a 36×46-in jaw crusher through a 4×16-ft reciprocating feeder. The ore is crushed to five inches, fed to a 5×12-ft screen and the oversize is conveyed to a surge bin ahead of a 5 1/2 -ft cone crusher. The cone and screen undersize products are combined and conveyed to a 4,000-ton capacity fine ore bin.

Fine ore is conveyed to the grinding circuit, which consists of a 9×12-ft rod mill and a 10 1/2 x10-ft ball mill. The ball mill is in closed circuit with cyclone classifiers. The cyclone overflow is gravity-fed to two conditioners which prepare the feed for the flotation circuit. Scavenger tails are pumped directly to the tailings pond. The concentrate from the flotation cells is thickened, filtered and dried to 6% moisture.

The mill can produce a 62% zinc concentrate and achieves a 98% recovery. The concentrate is held in a storage shed on site and is moved to the port as required. Front-end loaders load highway trucks, which transport the concentrate 40 miles to the saltwater port at Hawkes Bay. The shed at the wharf has a storage capacity of 30,000 tons. A conveyor system is used to move this concentrate to 6,000-ton vessels for delivery, mainly to European and U.S. markets.