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The mine near Bathurst is being put into care and maintenance, with no potential restart date defined.

"These market conditions, combined with high concentrate treatment charges, make mine operations at Caribou uneconomic at this time," officials said, adding that the company's Bathurst operations centre would remain open to serve the balance of its global portfolio.

While the mine is closed, president and CEO Ricus Grimbeek said it would be looking at "a multitude of options in the Bathurst region to maximise value" and reduce the cost structure of Caribou. This could include supplementing the feed from ore deposits from within trucking distance.

"[These are] metallurgical opportunities which may lead to commercial benefits around copper and gold, and potential for joint ventures with third parties," he said.

He also said the mine had been on a positive path the last 12 months.

"During the past year we demonstrated that the Caribou mill can achieve higher throughput than nameplate capacity while at the same time increasing metallurgical recoveries leading to higher production; however, the significant recent drop in the zinc price limits our ability to generate positive cash flow."

Trevali will be aiding its impacted workforce with transitional opportunities as well as severance options. The cost of closure for the underground operation, it estimated, could exceed US$5 million for April and May.