110,000 oz in ’88 Detour underground

It’s official. The Detour Lake gold mine northeast of Timmins, Ont., will go into underground production, with full production at the rate of 2,000 tons per day expected to be achieved by mid-1988.

The go-ahead decision by 50/50 partners Campbell Red Lake Mines and Amoco Canada Petroleum means that by about mid-1987 the open pit with which Detour Lake started life a little over three years ago will be shut down, and Detour will become a totally underground operation.

Cost of phase two of the underground mine development program at Detour will be in the order of $48,600,000, split equally between the two partners, Campbell President Henry Brehaut tells The Northern Miner.

“In 1988,” Mr Brehaut said, “it’s anticipated that Detour will produce 112,000 oz of gold.”

That will be almost double the 60,000 oz the mine will produce this year, but as the Campbell president explains, a lot of the gold produced in 1987 will come from a low-grade stockpile,

Of just over 800,000 tonnes to be milled this year, 453,000 tonnes or more than half the total, will come from that stockpile, he said. Underground development ore will provide some 166,000 tonnes in the year.

The possibility is also being investigated of mining additional ore from the walls of the pit. And, Mr Brehaut said, it is hoped to advance the underground schedule, to get more of the high grade underground ore during 1987.

Proven and probable reserves for the underground mine are 8,201,000 tons at an average grade of 0.15 oz gold per ton.

Production cost per oz for the underground operation will be in the order of $260(US), he said.

The shaft is now completed down to 660 m, 100 m below the lowest exploration level. The $48- million phase two development program will consist primarily of development of stoping blocks and installation of mine services.

There will be no additions to the mill, Mr Brehaut said, but a tailings treatment plant will have to be added, for effluent control.

Exclusive of contractor’s personnel, there are currently 170 employees at Detour Lake, but this number is expected to build to at least 320 by year-end.

Mr Brehaut noted that while 60,000 oz gold is the production expectation this year, in 1986 the mine produced 86,000 oz, well above plan, and resulting from availability of more and higher grade pit ore than anticipated, as well as higher grades from underground development ore.

“General manager John Rogers and his staff have done an excellent job over the past few years in responding to current economic conditions,” he said, adding that the 1986 results provide a “good illustration of what they ‘ve been able to achieve.”

The feasibility study for the Detour underground operation was “extremely well done”, producing a scheme that’s economical, and which also enables Detour to keep the mill running while developing underground, the Campbell president commented.