Coal projects planned by some of Australia's biggest mining magnates and port developments backed by the federal government may be delayed or become unviable because of sagging demand for the resources from China, an Oxford University study has found.

Clive Palmer's China First mine and Gina Rinehart's 21 per cent-owned Alpha Coal Project - both in Queensland's Galilee Basin - are likely to have production costs well above the current price for thermal coal of about $94 a tonne, according to the Stranded Down Under? report.

Expansion can be a minefield: Clive Palmer. Credit:Glenn Hunt

Doubts about the projects come after Environment Minister Greg Hunt last week approved the expansion of Abbot Point port that will serve the Galilee Basin mines.