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How interest in the deep sea is resurfacing

“Marine exploration of mineral resources is more about sovereignty than economics”

Anaïs Marechal, science journalist
On June 8th, 2022 |
4 min reading time
Ewan Pelleter
Ewan Pelleter
Researcher in Marine Geosciences at Ifremer
Key takeaways
  • The seabed contains very interesting geological resources contained in three strata: polymetallic nodules, crusts, and sulphide clusters.
  • This concern for marine mining began in 2001 with the first exploration contracts and then with the increase in metal prices.
  • Estimates around the geological value of the seabed are uncertain but the Clarion- Clipperton zone could contain up to 340 million tonnes of nickel and 275 million tonnes of copper.
  • Many grey areas remain, however. Like the ecological footprint of such exploitation, which remains unknown and could be dramatic.

What are the known deep-sea mineral resources?

There are three geo­log­i­cal objects con­tain­ing resources of inter­est: poly­metal­lic nod­ules enriched in man­ganese, iron, cobalt, nick­el, and cop­per; crusts con­tain­ing man­ganese, iron, cobalt and plat­inum; and sul­phide clus­ters rich in cop­per, zinc and some­times gold and sil­ver. Nod­ules and crusts are dis­trib­uted over large areas, unlike sul­phide clusters.

All may also con­tain so-called rare met­als such as cer­tain rare ele­ments, tel­luri­um, zir­co­ni­um, indi­um, ger­ma­ni­um, etc. These resources are wide­ly used in new tech­nolo­gies such as smart­phones and tech­nolo­gies for the ener­gy tran­si­tion. For exam­ple, neodymi­um is used in per­ma­nent mag­nets for wind tur­bines, and cobalt in batteries. 

Three con­texts rich in min­er­al resources

Dif­fer­ent envi­ron­men­tal and geo­log­i­cal con­di­tions lead to the for­ma­tion of met­al-rich objects on the seabed.

Sul­phide clus­ters are formed by the cir­cu­la­tion of water at depth with­in rocks from the earth’s man­tle. On con­tact with them, the water becomes enriched with dis­solved min­er­als. When it ris­es to the bot­tom of the ocean, the min­er­als pre­cip­i­tate out in the form of sul­phide clus­ters. They are found spo­rad­i­cal­ly at depths of 800 to 5,000 metres, at ridges or at the edges of sub­ma­rine vol­ca­noes in the inte­ri­or of plates.

Crusts are rocky clus­ters cov­er­ing square kilo­me­tres of the seabed, from 400 to 4,000 metres depth. They form where envi­ron­men­tal con­di­tions – ocean cur­rents, oxy­gen con­tent, etc. – lim­it the depo­si­tion of sed­i­ment. They form where envi­ron­men­tal con­di­tions – sea cur­rents, oxy­gen lev­els, etc. – lim­it the depo­si­tion of sed­i­ment on the seabed. Grad­u­al­ly, var­i­ous met­als con­tained in the sea­wa­ter pre­cip­i­tate to the bot­tom and aggre­gate to form the crusts. They grow at a rate of a few mil­lime­tres per mil­lion years.

Poly­metal­lic nod­ules are dark balls 5 to 10 cen­time­tres in diam­e­ter, found on the abyssal plains (3000 to 5500 metres deep). At this depth, numer­ous small par­ti­cles of “waste” (pieces of erod­ed rock, remains of ani­mal skele­tons, etc.) sed­i­ment on the bot­tom of the water. They serve as a sup­port on which the met­als con­tained in the sea water accu­mu­late, as in the case of crusts.

Aren’t these minerals already being exploited on land?

Yes. At present, the known resources of met­als on land are much high­er than at sea. And for some of them, such as man­ganese, nick­el, cop­per and cobalt, the onshore deposits will not be used up for sev­er­al decades. Lit­tle is known about marine resources. The known sul­phide deposits on the ocean floor rep­re­sent only 0.5% of the ton­nage of their land-based equiv­a­lents. This is still very lit­tle! In the case of poly­metal­lic nod­ules, the cobalt resource in the explo­ration con­tract held by France would rep­re­sent at most 4% of the cobalt resources avail­able on land 1, despite its dis­tri­b­u­tion over an area equiv­a­lent to that of the Occ­i­tanie region (~75,000 km2). 

If exploita­tion is envis­aged in the com­ing decades, it will not be because of a lack of avail­abil­i­ty on land but rather for a ques­tion of sovereignty. 

Exploitation of the seabed therefore has important geopolitical interests… Which states are involved in this race?

The Chal­lenger explo­ration cam­paign led by the British at the end of the 19th Cen­tu­ry marked the begin­ning of oceano­graph­ic explo­ration. It was dur­ing this cam­paign that poly­metal­lic nod­ules and crusts were described for the first time. Numer­ous explo­ration mis­sions focus­ing on nod­ules fol­lowed from the 1960s onwards, enabling the iden­ti­fi­ca­tion of the Clar­i­on-Clip­per­ton zone (east­ern Pacif­ic), which is rich in poly­metal­lic nod­ules. Inter­est waned in the 1980s due to the fall in met­al prices.

But since the mid-2000s, the surge in met­al prices has revived deep-sea explo­ration. The first inter­na­tion­al explo­ration con­tracts were award­ed in 2001 to Rus­sia, Chi­na, Japan, France, India, and an inter­na­tion­al con­sor­tium 2. Since then, 25 new con­tracts – 23 of them after 2011 – have been award­ed on the three dif­fer­ent marine min­er­al resources. This craze is marked by geopo­lit­i­cal and strate­gic issues: in 2011, Chi­na pro­duced 95% of rare ele­ments and gal­li­um, 68% of ger­ma­ni­um and 57% of indi­um, met­als used in high tech­nol­o­gy and green ener­gy. In Papua New Guinea, the for­mer Cana­di­an com­pa­ny Nau­tilus Min­er­als was the first to obtain a min­ing licence (for sul­phide deposits). Min­ing nev­er start­ed and the com­pa­ny is no longer in activity.

Do we have any idea of the economic potential of the deep sea?

There is no assess­ment of exploitable marine resources at present. Some work has been done to esti­mate the poten­tial amount of met­al avail­able: for exam­ple, the Clar­i­on-Clip­per­ton zone could con­tain up to 340 mil­lion tonnes of nick­el and 275 mil­lion tonnes of cop­per. But these esti­mates are high­ly uncer­tain. At best, they indi­cate a max­i­mum poten­tial because not all of this resource is exploitable! The exploitable por­tion depends on met­al prices, oper­at­ing and envi­ron­men­tal costs and legal, social, and gov­ern­men­tal fac­tors. If all these para­me­ters are con­sid­ered, it can very quick­ly be reduced to zero.

The envi­ron­men­tal cost remains a big unknown. We imag­ine that it could prove to be very sig­nif­i­cant: the Clar­i­on-Clip­per­ton zone cov­ers an area larg­er than the Euro­pean Union! Explo­ration remains essen­tial to char­ac­terise the avail­able resources in greater detail and to make a bet­ter inven­to­ry of the asso­ci­at­ed fau­na. This will take sev­er­al more years for the nod­ules. For crusts and sul­phide clus­ters, knowl­edge of the resource is even more limited. 

Are we already technically capable of exploiting deep-sea minerals?

No, not yet. This is one of the oth­er chal­lenges: indus­tri­al­ists are focused on poly­metal­lic nod­ules in the hope of devel­op­ing an extrac­tion tech­nol­o­gy that would enable them to posi­tion them­selves on the gear mar­ket if it were to open up. 

Last year, the Bel­gian com­pa­ny Glob­al Sea Min­er­al Resources test­ed a pro­to­type nod­ule extrac­tor on a 1/4 scale. But they are still far from hav­ing a com­plete min­ing sys­tem: they have yet to devel­op the ris­er (a tube that allows mate­r­i­al to be brought up from the seabed) and the sup­port ves­sel that oper­ates the col­lec­tor, recov­ers the min­er­als and man­ages the waste. All of this is adapt­ed to depths of 5,000 metres, where­as cer­tain tech­nolo­gies well mas­tered by oil tankers do not exceed 2,000 metres. No com­plete or scaled sys­tem has ever been test­ed in real con­di­tions. For ink­ing, it will be a mat­ter of recov­er­ing a fair­ly thin plate from a hard sub­strate and no pro­to­type exists to date.

2 Regroupant la Bul­gar­ie, la République Tchèque, la Pologne, la Slo­vaquie, Cuba et la Russie.

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