Cantung

Overview

The Cantung Mine is located in the Nahanni area of western Northwest Territories, Canada, approximately 300 km by road northeast of Watson Lake, Yukon, close to the Yukon border.

The Cantung deposit was discovered by prospectors in 1954 while looking for copper in the area. The mine commenced production in 1962 from an open pit at the rate of 300 short tons per day. Supression of tungsten prices at various times over the mines history caused it to suspend operations and the mill was once destroyed by fire causing a complete shut down of acivities until a new one could be built. Underground mining began in 1974 having found the E-zone during deep drilling in 1971. 

The CanTung Mine is a primary producer of tungsten concentrates from underground operations. Major features and facilities associated with Cantung are: The Cantung deposits, consisting of the Open Pit resource near surface, and the E Zone, underground; The physical plant site including an underground mine, a small open pit, process plant, diesel power plant, workshops, warehouses, administration buildings, a town site and single status accommodation, and an airstrip; Waste rock storage facilities and a tailings storage facility.

The Cantung mine suspended operations in October 2009 and resumed production in October 2010.

Location

The Cantung Mine is located in the Nahanni area of western Northwest Territories, Canada, approximately 300 km by road northeast of Watson Lake, Yukon, close to the Yukon border.

The 1.3 million sq km Northwest Territories is one of the three federal territories of Canada. It was created in 1870 when Hudson Bay Company transferred Rupert's Land and the North-Western Territory to the government of Canada. Nowadays much of the Territory's economy is focused on minining and natural gas.

Geology and Mineralization

North American Tungsten holds 10 leases and 2 claims totalling 18,660 acres covering the mine and associated service areas. They have varying expiry dates ranging from November of 2012 to October of 2027. 

Southeastern Yukon and southwestern Northwest Territories are underlain by a thick sequence of late Precambrian and lower Paleozoic sedimentary strata, which are intruded by several Cretaceous granitic plutons. Basement rocks comprise upwards of 3,000 m of fine-grained Proterozoic clastic sediments, predominantly slate and phyllite, referred to as the Grit Unit.

In the mine workings, the lowest stratigraphic unit exposed is argillite of the Proterozoic Grit Unit, referred to as the Older or Lower Argillite. The overlying Swiss Cheese Limestone, or Chert Unit as it is referred to at the mine, is in the order of 40 m to 50 m thick. The Ore Limestone is approximately 30 m thick in the Open Pit, thickening to approximately 100 m in the underground E Zone. 

The Open Pit and E Zone orebodies lie on the west limb of the Flat River Syncline. This limb is steeply dipping and overturned in the west, but becomes flat to the east, where in the area around the two mined deposits it forms a recumbent anticlinal fold that trends east to west. The Open Pit lies on the flat lying upper limb of this fold and the E Zone on the lower limb.

Two of the deposits at Cantung have been mined. These are the original Open Pit orebody, which was mined from 1962 to 1973, and the E Zone, which was mined between 1973 and 1986, again between January 2002 and December 2003, and is currently in production. Both deposits are in calc-silicate skarn zones that replace the Ore Limestone.

Mining & Operation

The Cantung Mine produces ore at a rate of 1,160 short tons per day ("stpd"). Mineral Reserves support a mine life ending in Q4 2014. Primary mining methods include, longhole stoping and pillar-remnant ore recovery using different techniques. Currently, longhole methods are planned for mining the majority of the remaining reserves, both for pillar recovery and for primary mining in areas with favourable geometry.

The open pit mine is located west of the main underground ore body, at the 4900 level and contains the Open Pit and PUG Zones. Access is limited to the summer months, as the steep road is prone to icing and avalanche danger during the winter. 

Mining is carried out by use of conventional open pit methods. The pit utilizes a triple bench with the bench height being 20 ft, 25 ft safety berm, and 12% grade for the haul road. 

Pit ore is hauled over a three mile haulage road to a stockpile located in the vicinity of the primary crusher, directly above the mill. The ore, grading approximately 0.5% WO3, is occasionally blended with underground feed whenever underground production lags below planned levels.

Underground, the majority of remaining reserves are mined using longhole methods. Access drifts are driven under the old workings, providing drill locations for upholes into remnant pillars above. 

Cut and fill methods are used in areas with narrower ore widths, such as the West Extension, and for a few primary stopes in other areas. Mining widths for cut and fill are approximately 15 ft. Waste rock is used as backfill for the working areas. Backfill material comes from waste development.

From both the open pit and underground sections of the mine, ore is either taken from a stockpile by a loader or directly dumped from haulage truck into a 30 ton receiving bin equipped with 42 in x 10 ft apron feeder, which, in turn, feeds a 42 in x 48 in jaw crusher reducing the ore to a nominal five inch crushed product. A vibratory feeder and a conveyor then feed a 4¼ ft (secondary) standard head cone crusher, which produces a minus 1½ inch product. Any oversize remaining is fed into a tertiary short head cone crusher. Finally, 5/8 inch marerial is screened out and conveyed to grinding mills in the concentrator.

Processing

Processing is carried out by gravity and flotation circuits. Final products include a premium gravity concentrate (G1), containing 65% WO3 and a flotation concentrate containing 45% WO3.

Environment & Community

N.A.