Underground expansion in the cards at Campbell mine?

Officials of Placer Dome (TSE) are seriously considering extending the life of the Campbell gold mine in Balmerton, Ont. The estimated price tag: $40 million.

“We are assessing various options for developing a resource below the 27 level, our deepest working level,” Mine Manager Tim Mann told The Northern Miner. “We expect to complete a recommendation and seek board approval for one of the options by year-end, or early next year.”

Mann said one option would be to re-sink the existing shaft to the 39 level from the 27 (roughly 1,800 ft). The other options being evaluated include a vertical conveyor system, as well as a ramp along which ore would be hauled by all-electric, trolley-driven Kiruna trucks.

“We are still at the study stage,” Mann stressed, “and have yet to submit a proposal to the board.”

The feasibility study is nearing completion, however, and a formal decision for the go-ahead is expected sometime in early 1994. If the expansion is given the green light, it would be the fifth time the mine’s depth has been increased since production began in 1949.

The operation produced 298,829 oz. gold in 1992, and about 8 million oz. since 1949. The 1992 cash cost of production was US$156 per oz. of gold produced, while the total cost was US$175 per oz.

At the end of 1992, proven and probable reserves stood at 4.7 million tons grading 0.55 oz. gold per ton, for a total of 2.6 million contained ounces. The ore occurs in gold-bearing, quartz-carbonate veins, and in sulphide replacement zones.

The mine has additional resources in the measured, indicated and inferred categories. These include the resource below existing workings, to which the company hopes to gain access.

In 1990, a decision was made to begin outlining ore below 4,000 ft., which led to the launching of a 3-year, 132,000-ft. drill program. Extensions of existing ore zones to depth have been confirmed by deep drilling, begun in 1991 and continuing this year.

“We also are exploring the mine above the 27 level, in the vicinity of the known workings, which seems to be paying off,” Mann said. “This ongoing effort is focused on zones which, for one reason or another, were not mined between certain levels, or were bypassed in the early stages of development because the geological knowledge of the deposit was not as extensive as it is now. We are quite excited about the potential of the upper levels.” In recent years, several improvements have been made at the mine: roasting was replaced by autoclaving with the startup of a pressure oxidation plant in July, 1991; the conventional flotation circuit was switched to column flotation in late 1991; and a hoisting system was upgraded in 1992. The Campbell mill is the first in Canada to use Sherritt Gordon’s pressure oxidation technology for the recovery of gold from refractory ore. (A similar process was started in the summer of 1991 at Placer Dome’s Porgera mine joint venture in Papua New Guinea.)

Mann said Campbell broke its milling record successively in recent months. The budgeted target was 1,430 tons per day, compared with the 1,485 and 1,606 tons per day achieved in September and October respectively. “The increase reflects improvements made to the surface crushing and screening system,” Mann said. “Also, the sulphur grade of the ore has been relatively low, so no restrictions were placed on us through excessive volumes of concentrate.”