Neptune’s Ocean Floor Exploration

While the possibility of ocean floor mining opens up a new world to explore, this unique environment needs to be protected.

International exploration company Neptune Minerals explained how, as their exploration programme was commissioned at Mount Maunganui in mid May.

The company is exploring an area in the Kermadec volcanic arc using high resolution seafloor mapping and remote sampling of sulphide targets – Seafloor Massive Sulphides (SMS). The company is interested in gold, silver, lead, zinc and copper that is found near ‘cold’ ‘black smokers’. Black smokers are hydrothermal vents on the ocean floor that follow the “Pacific Rim of Fire’ to the northeast of the North Island. They expel large amounts of hot mineral-rich fluid into the sea, building up small stalagmite-like ‘mini volcanoes’ in the process. A ‘cold’ black smoker is one that is no longer active.

Black smoker systems have been researched for several decades, but it is only recently that their commercial potential has been recognised. SMS mounds cover areas the size of a few football fields on the sea floor. The commercial attraction comes from the possibility of finding multiple mounds, with recovered chimney samples being values at over $1000 a tonne at today’s prices.

above: Dr. John Feenan with the Sub Atlantic Comanche ROV capable of operating to a depth of 3000 metres.

Dr John Feenan is in charge of the expedition. He describes finding their target as being something like being in a hot air balloon high above an area the size of Wellington Harbour and trying to pick up a sample sitting on a car trailer in the middle of the Cake Tin.

‘We are looking for cold chimneys and the mound of sediment that surrounds them. We will be targeting rigid, fallen and buried chimneys to provide samples to assist us in defining the resource’.

Fortunately John has technology more sophisticated than a hot air balloon to help him and his team. The Geosounder is capable of remaining on station through satellite tracking and its sophisticated system of bow and stern thrusters.

To get down to the ocean floor some two and a half kilometres below the team use a Sub Atlantic Comanche ROV capable of operating to a depth of 3000 metres.

The ROV is housed in a steel framed ‘garage’ and lowered to the sea floor. Once there, it is deployed on a 300 metre tether. An array of video cameras, lights and controls allow the ship-based team to control the vehicle and deploy its the exploration sensors housed in a sled slung under the main body.

It will take about 40 minutes to reach the sea floor, and the same amount of time for the ROV to be winched back to the surface once it has returned to the garage.

The expedition will first video map and survey areas of interest, then during the second phase of the project they will grab samples in a 100 metre grid pattern. The small clamshell grab will take a sediment sample in areas of between one and two square metres.

above: One of the robotic arms on the Comanche ROV.

John is confident that if the resource is defined, then technology will follow. He sees the very real possibility of a future operation ‘cherry picking’ cold chimneys and sediment with average metal contents of 11 grams per tonne of gold and 122 grams per tonne of silver. Such an operation, he believes, would be economic and meet environmental criteria.

Also on board are NIWA scientists, keen to use the opportunity to continue their research in the area. ‘We openly share information with each other, there is a regular flow of data between us’, says John. ‘ In many ways our objectives complement each other’.