"We see[the Carmichael mine] as being economic - but only just,"Mr Simington said,adding his firm estimates thermal coal prices in five years'time will also be in the $US80 range.
While coal proponents hailed Thursday's granting by the Queensland government of the final environmental approval for Adani as opening the way for other Galilee Basin mines,their prospects are arguably dimmer.
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"We think a fair bit of infrastructure is needed for a second player to come in there,which is going to discourage people,"Mr Simington said.
Tim Buckley,an analyst with the Institute for Energy Economics and Financial Analysis (IEEFA),said the Carmichael mine has advantages over other prospective Galilee mines because Adani owns the Abbot Point port which will export the coal,and power plants in its home nation of India that will burn it.
Mr Buckley noted Adani's huge Mundra plant had recently been granted a 30 per cent tariff increase for its power,while its new Godda plant in north-east Jarkhand state - set up to supply neighbouring Bangladesh - enjoys tax relief and other incentives in a special economic zone.
"If you give enough subsidies to anything,it becomes viable,"Mr Buckley said,noting the Carmichael mine itself has unlimited access to groundwater and other fuel and royalty inducements in Australia.