In a statement sent to Reuters, the company said the job cuts represented less than 2 percent of the operation's workforce, including an unspecified number of voluntary early retirement offered to other staff.

"Lundin Mining has created over 1,000 employee and contractor positions at the Candelaria Mining Complex since acquisition in 2014 and continues to make significant investments to improve and increase productivity the operation," it said. "There are currently approximately 5,900 people working at site."

Lundin has operations in Chile, Portugal, Sweden and the United States.

In September, its incoming chief executive officer told Reuters in an interview that the company was looking for copper mines and projects and willing to spend up to $3 billion on mergers and acquisitions.

An 80 percent, $1.85 billion purchase of Freeport-McMoRan's stake in Candelaria in 2014 was the company's last major acquisition.

The company said in October that planned lower ore grades had led to lower production in the third quarter. The company is also in the process of upgrading its milling and underground mining operations.

Nelson Araya, a trade union leader at Candelaria, told Chile's Radio Cooperativa that workers would strike for 48 hours from Friday over the cutting of 40 jobs from the union.

He criticized the company's poor communication, adding: "There have been many more complex times, from the point of view of the price of copper, the business itself and the management of the company, and the workers through the unions always kept channels of communication open."

Up until September, the mine had produced 77,800 tonnes of copper.

(This story corrects to reflect that job cuts would be under 2 percent of workforce including voluntary retirements.)

(Reporting by Susan Taylot and Aislinn Laing; Editing by David Gregorio)

By Susan Taylor and Aislinn Laing