Rio Tinto has sold more than 300 million tonnes of iron ore in a year for the first time but a 33 per cent price plunge has raised doubts about its promised higher shareholder returns.

The world’s second largest miner beat its own guidance but missed some analysts’ forecasts in lifting 2014 iron ore sales by 17 per cent to 302.6 million tonnes. However the fall in its average realised price was far more dramatic: down 33 per cent from $US126 a tonne in 2013…