Deep-sea mineral crusts, a hidden treasure to be explored by science

Oceanographic research collaborations funded by FAPESP in partnership with UK research council begin to survey the South Atlantic's mineral potential.

By Diego Freire  |  Agência FAPESP – The Rio Grande Rise, a 3,000 sq. km. mountainous rock formation at the bottom of the Atlantic Ocean approximately 1,500 km off the coast of Rio Grande do Sul in Brazil, holds a veritable trove of minerals and chemical elements that are becoming increasingly scarce on land – and science is starting to explore this treasure.

A group of researchers supported by FAPESP and the Natural Environment Research Council (NERC), one of the United Kingdom’s seven research councils, have begun work on a project entitled “Marine ferromanganese deposits – a major resource of E-tech elements (Marine E-Tech)”, a multidisciplinary effort to study metal deposits at the bottom of the Atlantic. In addition to the Rio Grande Rise, on which the Brazilian researchers will focus, the project also involves studies of the Madeira abyssal plain in the North Atlantic.

The project was presented on December 8 at FAPESP’s headquarters in the city of São Paulo during a workshop on “Research in E-Tech Elements and Submarine Ferromanganese Crusts”, attended by researchers from institutions in Brazil, the UK and the United States who are working on oceanographic projects in the region.

“The ocean floor is the new frontier for mineral and biotechnological exploration, but the potential of this region must be sustainably developed,” said Frederico Brandini, Head of the University of São Paulo’s Oceanographic Institute (IO-USP) and the Marine E-Tech project’s principal investigator in Brazil.

“Scientific knowledge plays a key role in this,” he went on. “Brazil has 8,500 km of coastline with a wealth of available natural resources and still relies heavily on rare earths for technological development purposes. The Rio Grande Rise is a potential source of resources, but so little is known about it scientifically in terms of oceanography and mining that a profound understanding of its potential and sustainable development is impossible. Our research will contribute to a solution to this problem.”

The researchers want to answer some of the questions posed by the international scientific community about such formations in different ocean areas, especially how they emerged, grew and are maintained. “It’s necessary to determine whether the nodules found there are biogenic or the result of chemical reactions that caused the precipitation of metals,” Brandini said. “For example, lithotrophic bacteria use oxidation/reduction of chemical elements to precipitate metals.”

Submerged treasure

Their survey of the Rio Grande Rise also aims to study the compositions of polymetallic nodules found on the ocean bottom: these are golf ball- to potato-sized lumps of mineral precipitates formed of concentric layers of iron and manganese hydroxides around a core. 

“These nodules are about 10 cm in diameter on average, and in certain areas the ocean floor is full of them,” Brandini said. “They’re mostly iron and manganese, but they also include other chemical elements that can be extracted with relative ease. However, all this mineral treasure lies at depths of at least 1,000 m and in some cases 5,000 m, so that a lot of highly specific scientific knowledge and technological expertise is required to develop it.”

Some of the elements of interest, typically byproducts from the extraction of common metals, are essential to the green economy and the technology needed to produce cleaner and more efficient energy, such as batteries for electric vehicles, wind turbines and solar panels, among other applications. They include tellurium, cobalt and selenium, sometimes referred to as “e-tech” elements.

“Some of these elements are highly concentrated in deposits on the sea bed. They’re the most important marine metal resource for future extraction and development. For example, the highest concentrations of tellurium are found in the ocean depths, in ferromanganese crusts on seamounts,” said Paul Lusty, ore deposits and commodities team leader with the British Geological Survey (BGS).

Tellurium, a critical ingredient of thin-film photovoltaic cells, is found in minute quantities, equivalent to an average abundance of approximately 1 µg/kg, and in only 0.0000001% of the Earth’s crust, making it three times scarcer than gold. 

“It’s not a gold rush but an option for the future,” Lusty said. “What with population growth and rising patterns of consumption in the BRICS [Brazil, Russia, India, China and South Africa], as well as other African countries, alongside the development of new technologies, demand is surging for rare earth metals that are increasingly scarce, for geological reasons or owing to economic and political factors. China controls over 95% of world rare earth production. The world needs alternative sources.” 

“Living stones”

Despite the region’s considerable economic potential, the project will not focus on mining but on understanding polymetallic nodules from an environmental standpoint, said Luigi Jovane, a professor at IO-USP.

“We’re doing oceanographic research to unveil the history of these nodules, which are organisms with unique properties. They grow like living stones. Their chemical composition is very unusual, and there are many unanswered scientific questions about them. That’s why the project is multidisciplinary, involving researchers in biology, geology and physics, as well as professionals with expertise in certain technologies and the methodologies of the international groups associated with them,” Jovane said.

An understanding of how these organisms formed over time may also furnish more general information on key aspects of the ocean floor, such as variations in water mass, current and temperature, absorption of CO2 and organic matter, and the benthic biota of deep-sea ecosystems.

The researchers are also interested in the geology of these rock formations. They will study such aspects as geochemical properties and geomicrobiology, researching the bacteria that live on top of the structures and symbiotically make them grow.

Vivian Pellizari, also a professor at IO-USP, addressed the workshop on the role of lithotrophic bacteria, which use inorganic energy sources, in the formation of polymetallic nodules.

“Cores from drilling in these structures have already shown that their subsurface biosphere is widespread, extensive, and genetically and geochemically diverse,” Pellizari said. “These deep-sea microbial communities play an important role in global biogeochemical cycles, mineral alteration, and hydrocarbon production and destruction.” 

The researchers will also study the role of microbes in concentrating e-tech elements, their lifecycles, and the implications for bioprocessing using living cells or components of them to synthesize products and produce energy, among other goals. “These studies may also create opportunities for the development of biomining processes to recover useful metals from manganese nodules,” Pellizari said.

For Brandini, “only an understanding of the environmental forces that explain the emergence of these nodules there can lead to the best techniques for extracting them”.

He added, “Mining is notorious for its highly negative environmental impact. On land, it’s possible to exert a degree of control despite all the well-known difficulties. You can reforest degraded areas, for example. The marine ecosystem is more fragile, and currently its resilience is badly impaired, so it doesn’t recover rapidly. A great deal of research will be needed before deep-sea mining can be allowed.”

Other speakers on multidisciplinary research strategies at the marine e-tech workshop included Ilson Silveira, Paulo Sumida and Alexander Turra from IO-USP; José Angel Alvarez Perez from Itajaí Valley University (UNIVALI); Bramley Murton from the UK’s National Oceanography Center (NOC); and Jim Hein from the US Geological Survey.

The researchers who are participating in the project plan to make four scientific expeditions. Three expeditions lasting up to 30 days will be conducted by the Brazilian team to investigate the deep-sea environment in and around the Rio Grande Rise. The fourth expedition will be conducted by researchers from the UK to investigate the Madeira abyssal plain. In the South Atlantic expeditions, the Brazilian researchers will be on board the Alpha Crucis, an oceanographic research vessel bought by FAPESP for IO-USP in 2012. 

Marine E-Tech is part of a program called SoS Minerals (Security of Supply of Mineral Resources), an interdisciplinary research program funded by NERC and the UK’s Engineering & Physical Sciences Research Council (EPSRC). The project is supported by FAPESP under a cooperation agreement signed in September 2009 with Research Councils UK (RCUK).