Plans to open the world's first mine in the deep ocean have moved significantly closer to becoming reality.
A Canadian mining company has finalised an agreement with Papua New Guinea to start digging up an area of seabed.
The controversial project aims to extract ores of copper, gold and other valuable metals from a depth of 1,500m.
However, environmental campaigners say mining the ocean floor will prove devastating, causing lasting damage to marine life.
The company, Nautilus Minerals, has been eyeing the seabed minerals off Papua New Guinea (PNG) since the 1990s but then became locked in a lengthy dispute with the PNG government over the terms of the operation.
Under the agreement just reached, PNG will take a 15% stake in the mine by contributing $120m towards the costs of the operation.
Mike Johnston, chief executive of Nautilus Minerals, told BBC News: "It's a taken a long time but everybody is very happy."
"There's always been a lot of support for this project and it's very appealing that it will generate a significant amount of revenue in a region that wouldn't ordinarily expect that to happen."
The mine will target an area of hydrothermal vents where superheated, highly acidic water emerges from the seabed, where it encounters far colder and more alkaline seawater, forcing it to deposit high concentrations of minerals.
The result is that the seabed is formed of ores that are far richer in gold and copper than ores found on land.
Mr Johnston said that a temperature probe left in place for 18 months was found to have "high grade copper all over it".
For decades, the idea of mining these deposits – and mineral-rich nodules on the seabed – was dismissed as unfeasible because of the engineering challenge and high cost.
But the boom in offshore oil and gas operations in recent years has seen the development of a host of advanced deep sea technologies at a time when intense demand for valuable metals has pushed up global prices.
The mine, known as Solwara-1, will be excavated by a fleet of robotic machines steered from a ship at the surface.
The construction of the largest machine, a Bulk Cutter weighing 310 tonnes, has just been completed by an underwater specialist manufacturer, Soil Machine Dynamics (SMD), based in Newcastle, UK.
The plan is to break up the top layer of the seabed so that the ore can be pumped up as a slurry.
Written By: David Shukman
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