Lower recovery rates and lower grades have led to lower production figures at Imperial Metals' Red Chris mine in British Columbia.
Copper grades were down 24% from 2020 levels, while gold grades decreased 21% in the same period.
Recovery for copper had declined 2% year-on-year to 79%. Gold recovery increased 3% to 56% this year.
Red Chris' total production for the December quarter amounted to 14.7 million pounds of copper and 13,600 ounces of gold, down from 17.2 million pounds of copper and 15,200 ounces of gold in the September quarter.
The decline was largely due to lower mill throughput. Mill throughput in the December quarter totaled 2,124,732 tonnes, compared to 2,543,495 tonnes in the September quarter.
Throughput was down due to the processing of clay-rich ores early in the December quarter, which decreased the availability of the primary crusher.
Poor weather in British Columbia also led to several power outages. Red Chris is powered by hydropower from BC Hydro.
Imperial Metals owns 30% of Red Chris, and its share of production for 2021 was 19.6 million pounds of copper and 18,000 ounces of gold.
Newcrest Mining acquired 70% of the mine in August 2019.
It said in October 2021 that it was advancing the Red Chris block cave to the feasibility stage.