Production at Codelco Norte's Chuquicamata copper operations in northern Chile was stopped for six hours by workers who opposed its decision to shut down its copper smelter.
The closure brings further trouble to Chile’s troubled copper industry, which has seen strikes at the embattled Spence copper mine owned by BHP.
Strikes there have seen production reduced to a minimum due to safety concerns.
The protesters expressed their dissent against the decision by preventing access to operations, which caused the company to lose about $5m.
The copper smelter, which employed 50 people, was shut down as the operation was considered too costly compared to the rest of the industry, Codelco Norte manager Juan Carlos Canales said.
"We use technology based on gas and we do not have that resource today, and if we did have it, the costs would still not be competitive," Canales said.
Chuquicamata is a large open-pit copper mine located in northern Chile.