black smoker

The concept of mining the seafloor for valuable mineral commodities is still in its early stages, so much so that to many observers the prospect seems closer to science fiction than science fact. Nevertheless, as the list of viable candidate sites for high-grade deposits grows ever shorter, interest in deep-sea mineral extraction from industry and academia is growing.

Blue Mining is a European Commission-funded consortium of research partners dedicated to exploring the potential for sustainably mining the seafloor. The group recently dispatched a team of scientists aboard the research vessel RRS James Cook, from Southampton to the Mid-Atlantic Ridge in the middle of the Atlantic Ocean.

The 57-day expedition’s scientific goal is to learn more about the fundamental processes that generate and preserve massive sulphide deposits on the seabed around hydrothermal vents, and the team has been testing a range of technologies developed by Blue Mining partners to explore these hydrothermal systems, and assess their mineral potential for commercial extraction.

The research cruise, which at the time of writing has finished its on-site work in waters 3.5km deep and begun its nine-day return voyage to Falmouth, follows closely after another Blue Mining expedition to the same region earlier in the year.

“[The previous expedition] deployed an autonomous underwater vehicle, which mapped the seabed in considerable detail,” says the current cruise’s chief scientist Dr Bramley Murton from onboard the James Cook. “We’ve been looking at those maps and determining which targets look the most promising, and we’ve been carrying out a combined geophysical and drilling campaign.”

Assessing the mineral potential of subsea hydrothermal vents

After nearly two months of study, what is Murton’s opinion of the mineral potential hidden within extinct hydrothermal vents on the seafloor? The good news is that compared to their active counterparts – the well-known ‘black smokers’ that play host to a range of unique wildlife – extinct hydrothermal systems are both more abundant and richer in metals, at least in the region that has been studied by Murton and his team.

“What we’ve found in this area is that the abundance of extinct deposits and the metal potential of these deposits is at least 10 times that of the nearby active field,” Murton says. “That will radically change our view of the resource potential for these deposits.”

"The abundance of extinct deposits and the metal potential of these deposits is at least 10 times that of the nearby active field."

Although the implications for the global supply of commodities such as copper, gold and rare earth elements is still unclear, the expedition has also seen evidence that extinct hydrothermal systems and their massive sulphide deposits contain higher-grades ores than can be found today on land. Murton uses copper to illustrate the point.

“If we think of terrestrial copper deposits operating at grades of less than 2%, those grades are relatively low,” he says. “We’re looking at grades here, and the average grades are 10%-15% copper. So they’re much more enriched. That means that although the volume of the deposits may appear to be small compared to terrestrial deposits, because of their higher grade, there’s a larger resource. And also the apparent abundance of the extinct deposits means that the potential is much higher than I think people have realised before.”

Testing new tech for deep-sea operations

So the potential is clear, but the billion-dollar question hanging over deep-sea mining remains unanswered: does the technology exist to identify mine and transport these deposits to the surface in an economical fashion?

Much of the RRS James Cook expedition’s work has been dedicated to testing the efficacy of various technologies – developed by Blue Mining research partners in the UK (University of Southampton), Germany (research institute GEOMAR), Norway (University of Trondheim) and elsewhere – to help answer this question.

For geophysical analysis the team has been deploying a technology called seismic reflection and refraction, while electromagnetic imaging techniques have been used to identify rock rich with metal.

“It’s a transmitter of a very high current, and we have instruments on the seafloor and towed behind the transmitters,” explains Murton. “The transmitter’s towed about 30m-40m off the seabed; we’re in 3,500m of water, so it’s quite a long way down. We tow that along slowly, and we transmit variable frequency currents, which image into the seabed and look for areas of metallic-rich rock, the ore bodies we’re looking for. We’re looking for massive sulphide deposits; they’re relatively conductive and they distort the electrical field in ways we can detect if we transmit these currents.”

Once potential targets were identified, the team used a remotely operated underwater vehicle (ROV) called HyBIS – invented by Murton himself – to survey the conical mounds around the extinct hydrothermal vents to sample the outcrop and place beacons for the expedition’s robotic drill rig RD2 – no relation to the chirping droid of Star Wars fame – which is on loan from the British Geological Survey and designed to operate in waters up to 4,000m deep.

“So we land a drill on the seabed where we’ve site-surveyed our landing spots, and drill holes deep into the mounds to try and find out what the distribution of the mineral deposit is at depth, what its structure is and what its metal contents are,” Murton says.

Tackling the challenges of the deep

One potential advantage of mining in the marine environment is that there’s no need for fixed infrastructure such as one would find in terrestrial mining operations. Deep-sea mining will be carried out by vessels adapted to become mobile mining plants, meaning that such vessels could work on one deposit before moving on to another, minimising the issue of ore distribution density that is a large factor for land-based mine development.

“All your infrastructure is mobile, so even if the distribution was every 20 miles, it doesn’t really matter because you can just move,” Murton says.

That does not, however, mean that deep-sea mining will be a simple task. Far from it, in fact. There are a host of challenges, many of which Murton’s team have experienced during the expedition.

"The main obstacle is the water,” says Murton with a wry laugh.

“The main obstacle is the water,” says Murton with a wry laugh. “There’s an irony that hasn’t gone amiss here, which is that we work for oceanographic institutes either in Germany or in the UK, and it’s the water that gets in the way for us, because we’re geologists!”

The robotic drilling system used by the team had to be deployed on the seabed with an astonishing degree of precision – “we have to position it within a few tens of centimetres,” says Murton – made possible only with the James Cook’s dynamic positioning capabilities, which have allowed the crew to make minute alterations to the vessel’s position and thus tweak the course of the drill tethered beneath it. Positioning of the drill is important not only from a mining perspective, but also because of the topography of the mounds targeted by the team.

“They’ve got very steep angles – they’re conical-shaped mounds with a few flat areas near the top,” Murton says. “So the topography is quite challenging to operate on if you’re trying to land anything. So that’s been more surprisingly challenging than we had appreciated originally.”

Another dilemma for subsea miners is transporting mined slurry from the seabed up to the surface, which is something Murton believes would require a riser system and mid-water pumping stations to pull off. Here, lessons could be learned from the offshore oil and gas industry, with its expertise in pumping gas and liquids from thousands of metres underwater, but sulphide slurry is far more abrasive than the offshore sector’s usual product, so that would be another obstacle with which deep-sea miners would need to contend.

Nevertheless, the subsea mining vehicles built for Nautilus Minerals – the company that aims to establish the world’s first deep-sea mining operation at Solwara 1 in the territorial waters of Papua New Guinea – show the value that other industries can bring to the endeavour.

“SMD, the company that made those mining machines for Nautilus – they basically cut their teeth on providing ROV solutions to the offshore industry,” says Murton. “I think there are lot of translatable skills and engineering capability that could be brought to bear.”

Better together: looking to the future

Looking ahead, there are still many uncertainties surrounding seafloor mining that the Blue Mining project and other public and private organisations will need to tackle over the coming years. Environmentally, Murton believes that the impact would be relatively low if miners stick to extinct hydrothermal systems, which don’t play host to the array of fauna seen around active vents. But more environmental research is required to verify this; MIDAS, an EC-funded sister project to Blue Mining, is dedicated to measuring and managing the environmental effects.

“The work that our MIDAS partners are doing will most definitely feed into the regulatory framework in the future,” Murton says. “Understanding what the mineral deposits look like in three dimensions, what their structure is, what their compositions are, what their distribution is – all of these sorts of things will hopefully feed into informing regulators about how to maximise the environmental sustainability of these deposits.”

Murton also emphasises the technical difficulty and financial risk involved in taking on the challenge of mining underwater at these kinds of depths. He points to Nautilus as an example – even though the waters of the Solwara 1 site are far shallower than those studied by the expedition, the company has still reported difficulties securing financing to continue the exploration of the area, and according to a June report by the Maritime Executive, will consider suspending or even terminating the copper-gold project if it can’t get more financial backing soon. Certainly, Nautilus’s original target date of early 2018 to start testing its seafloor production system now looks unlikely.

For Murton, such is the complexity of the task ahead that the only viable way to safely and sustainably make it happen is through multinational cooperation on the scale of Blue Mining.

“This is an EU-funded project,” he says. “I don’t know what will happen in the future for the UK’s involvement in these sorts of programmes, with Brexit and all of that. But at the moment, I would say it’s beyond the capability of one single nation to do this sort of work alone. We’re deploying equipment that has been developed by Germans, by Norwegians, by French. It’s the entire European continent that is throwing its technological resources at this project right now, and [the UK] couldn’t mount this kind of operation on its own, and nor could any other single European country. It requires a considerable and sustained effort to make this work.”