Northern Territory uranium miner Energy Resources of Australia has healed relations with the Mirrar traditional landowners to the point where the Mirrar are open-minded about the prospect of supporting an extension of the Ranger mine lease past 2021.

The Rio Tinto-controlled miner is spending $120 million on an exploration tunnel at its Ranger 3 Deeps project in an attempt to access new sources of ore because the open pit must close later this year in accordance with its rehabilitation plan.

ERA will start construction of the tunnel in May but is unlikely to know whether it has an economic project until 2014 and would not start production until late 2015.

Gundjeihmi Aboriginal Corporation executive officer Justin O’Brien said an agreement struck yesterday with ERA for water studies at Ranger and rehabilitation of a water pond at the undeveloped Jabiluka deposit could “indeed bode well for further development of the Ranger project area”.

He wouldn’t say whether the Mirrar would support an extension to the mining lease but said it had now not been ruled out. “Let’s see what is proved up,” he said.

ERA chief executive Rob Atkinson said the agreement on the water studies was a “very significant step forward” in the company’s relationship with the Mirrar – so much so that the announcement was labelled as share price sensitive. “We don’t take this step for granted,” he said. “This is the first of many steps we hope.”

Mr O’Brien said the Mirrar remained opposed to the development of the Jabiluka project.

ERA has said it will not develop it without their consent.