Oz Minerals Ltd has flagged a significant hit to its first-half profit due to falls in copper and gold prices.
In a statement to the Australian Securities Exchange, the company said it estimates a non-cash charge for asset impairment of between $200 million and $240 million after tax.
The estimate will be finalised pending board approval and an auditors' review, the company said.
The group made the announcement after impairment testing of its Prominent Hill operations which also flagged the impact of a lower exchange rate that OZ Minerals said has had a beneficial effect.
Oz Minerals also blamed the impairment on higher asset values as a result of capitalisation of work towards developing the new Malu Underground mine.
As the company has no drawn debt, the impairment will have no impact on its gearing level.