Rio said the landslip had been expected based on geo-technical monitoring at the mine, and all personnel had been removed from the area in advance to ensure safety.
Peru's presidential front-runner is taking aim at copper mining firms' coveted tax stability agreements that freeze tariffs, and the plan could have an outsized impact on Chinese miners.
Moscow has been keeping a close eye on rising raw materials costs in the construction sector as part of efforts to keep domestic commodity prices stable.
Sibanye reported a 78% increase in first-quarter core profit last month, on the back of higher prices for metals, including gold, platinum, palladium and rhodium.
The strike entered its fifth day on Monday, as the union awaited a decision by labor authorities over whether substitute workers the company called in are legal.
China plans to strengthen controls in industries such as steel and aluminum which involve high energy use and produce high emissions, in an effort to promote low-carbon developments.