SYDNEY--OZ Minerals Ltd. (OZL.AU) Monday cut forecasts for annual copper production for a second time this year after setbacks at its Prominent Hill mine in southern Australia. 

The Melbourne-based gold-and-copper miner said it now expects to produce just 70,000-75,000 metric tons of the industrial metal in 2013, down from a previous estimate of 82,000-88,000 tons. Earlier in the year, the company had been projecting output as high as 95,000 tons. 

OZ Minerals has faced disruptions due to a slippage in the overburden material--the rock that sits around the mineral deposit--at Prominent Hill's Malu open pit, which restricted access for mine workers. 

On Monday, the company said that while it had made "significant progress" in the three months through September, the ore that it had mined there during the period contained less of the mineral than expected. 

The company left its full-year guidance for gold output unchanged at 120,000-130,000 troy ounces--the guidance had been downgraded in July. 

OZ Minerals said it produced 28,177 ounces of gold last quarter, down 9.2% on the immediately preceding period. It also produced 17,390 tons of copper, down 0.1%.