Expectations of copper restocking in the West have prompted Canaccord Adams to lift its rating on Antofagasta, the South America-focused miner of the red metal.'The low average cash costs and extremely strong balance sheet provide positive optionality with regard to future corporate activity, as well as downside protection in the event of a market pullback,' the broker said.'However, we believe it is also prudent for investors to recognise the doubling of the share price since the start of Q2 and uncertainty surrounding the sustainability of Chinese import demand.'