Sinkhole at Lundin's Chilean mine to impact copper output

The suspension of mining operations at Canadian firm Lundin Mining’s Alcaparrosa mine in northern Chile, due to the appearance of a 60m sinkhole, will impact the company's copper production this year by 2%, according to a release.

The large, cylindrical sinkhole opened up in July near the underground mine, operated by Minera Ojos de Salado, forcing the company to isolate the area and halt mining operations. 

Lundin is supporting the ongoing investigation with regulatory authorities to determine how its mining operations caused the problem. 

In early October, construction was completed to seal and isolate the Gaby area of the mine to control the flow of groundwater into the hole, with the company focused on trying to minimize the impact on operations after the suspension, Lundin said in a corporate presentation.

“The Gaby area, which is directly related to the subsidence, is definitively closed and can never be operated again,” mining minister Marcela Hernando said earlier this month.

Studies on the sinkhole are being carried out by a regional technical group and the results are expected to be released in December. The area is only a few hundred meters from the town of Tierra Amarilla. 

In mid-October, environmental regulator SMA filed four charges against Minera Ojos del Salado related to the over-extraction of ore from Alcaparrosa and unauthorized modifications to mine infrastructure, which are alleged to have affected the Copiapó River aquifer, reducing its flow from the normal 500l/s to just 300l/s.

“What they were authorized to excavate in that unit [Gaby] … was exceeded,” Hernando told radio station ADN.

According to her, the stoppage at Alcaparrosa means Lundin will lose around US$13mn per month, in addition to the environmental fines for the damage caused. 

Mining and geological service Sernageomin is also studying the case and checking whether there will be other sanctions against the company. Works are currently being carried out in an effort to restore the flow of the aquifer water and halt any further impacts to the groundwater.

Lundin produced 37,192t of copper and around 21,000oz of gold at its Candelaria complex in Q3, which was an increase compared with the same period of last year, due to higher ore grades. 

Candelaria comprises two adjacent copper mining operations, Candelaria and Ojos del Salado, which produce copper concentrates from open pit and underground operations, including Alcaparrosa. The complex is controlled by Lundin Mining (80%) and Sumitomo (20%).