Zinc recycling in the North (October 30, 2006)

Doubtless helped by the price of zinc, two former Arctic zinc producers, both operated by Cominco, are getting second looks by junior explorers bent on showing that resources left behind when the mines were closed are economically feasible.

London-based explorer Angus & Ross (AGU-L) has one new discovery and one showing-turned-resource at the Black Angel property in western Greenland, where Cominco — now Teck Cominco (TCK.B-T, TCK-N) — mined between 1973 and 1990.

Angus & Ross’s new discovery is the South Lakes Glacier zone, a stratabound lead-zinc deposit uncovered by glacial retreat. That Cominco missed it doesn’t reflect badly on the former owners, who would have had to melt 60 metres of ice to find the surface showings. Time has given Angus & Ross substantially better access.

This past field season, drill holes over a 500-metre strike length established that the new zone extends to 170 metres vertical depth, over core lengths of 1 to 3 metres. Zinc grades were mostly 4% to 12% and lead grades 2% to 8%, with 10 to 30 grams silver.

Later drilling has confirmed earlier results, as well as revealing a couple of wide intersections. A 6.5-metre interval near the southwestern end of the zone averaged 6.1% zinc and 2.6% lead, with 49 grams silver per tonne, and a 6.3-metre interval near the middle of the zone ran 8.8% zinc and 3% lead, with 29 grams silver per tonne.

It also appears that the zone may have zinc-rich subzones; a narrow 0.3-metre intersection in the west-central part of the deposit had negligible lead and only 2 grams silver, but ran 25% zinc.

The showing-turned-resource is at Ark, which Cominco discovered in the 1980s but never developed. Ark is about 7.5 metres wide at its thickest, with zinc grades around 5% to 7% and lead grades from 0.3% to just over 4%. Silver grades are low.

The topography around Black Angel fits the old phrase about Greenland’s icy mountains; the old mine hauled ore via an aerial tramway from an adit in the side of a mountain — at 600 metres elevation — down to the port at Maarmorilik. The tramway is now gone, but for vehicle access there is a 6-km tunnel from Maarmorilik up to a portal at plateau level. The company is getting quotes on construction of a system of surface roads up on the plateau.

Prefeasibility work this year established that the remnant resource in the Black Angel mine itself amounted to 2.2 million tonnes grading 9.7% zinc and 3% lead. Early costing exercises concluded that production from the remnant resource would be economic at prices of US$1,950 per tonne for zinc and US$1,100 per tonne for lead. Consultants for the company also concluded that disposing of tailings as a paste fill in empty stopes will allow a new operator to remove at least 80% of the remnant resource safely.

The field season is now over, but Angus & Ross expects to have a revised resource estimate from its consultants, Wardell Armstrong International, in November.

At Pine Point on the south shore of Great Slave Lake in the Northwest Territories, Tamerlane Ventures (TAM-V, TMLVF-O) is working on the R-190 deposit, the highest-grade of the resources left on the old Pine Point property. Cominco’s mining holdings had all lapsed by 2001, and former Royal Oak Mines executives Ross Burns and Margaret Kent, now president and chairman of Tamerlane, picked up a 38-claim block plus eight claims held by Pine Point Mines to put together a 222-sq.-km land package. Tamerlane met work commitments of $1.25 million to earn a 60% interest and bought out its executives for another $1 million to get full control of the project. Burns and Kent retain a 3% net smelter return.

There is no current resource on the R-190 deposit, which is only to say that old resource estimates do not comply with current securities regulations. The historical figure is 1 million tonnes grading 12.1% zinc and 6.3% lead.

The project is well under way, with environmental assessment under review by the territorial government and with mine design already largely specified. Tamerlane is looking into freeze-ring technology — drill holes with pipes containing a refrigerant, forming a cutoff wall around the mine — to limit water infiltration, which had plagued earlier operations and ultimately forced early closure of the mine in the late 1980s.

Another planned innovation is a dense-medium separation plant, to process fine mineralization (a crushed fraction below 0.6 mm in size). Early testing is under way.