Earth's mantle may contain a wealth of "green metals"

In the global pursuit of sustainable energy solutions, the availability of essential metals plays a pivotal role. The components of batteries, solar panels, electric vehicles, and other ‘green’ technologies rely heavily on these critical elements.

Yet, as demand for these metals soars, traditional methods of mineral exploration are increasingly strained to meet such needs.

A recent study led by Dr. Isra Ezad at Macquarie University offers new hope, suggesting that the Earth’s mantle could hold a wealth of “green metals.”

Carbonate melts

Earth’s mantle, the vast layer beneath the crust, is predominantly composed of silicate rocks. However, in certain regions, trace amounts of carbon and water induce melting at lower temperatures.

These specialized molten mixtures, termed carbonate melts, possess distinct chemical properties that make them unexpectedly effective at concentrating valuable metals.

Dr. Ezad’s team sought to understand exactly how carbonate melts extract and transport metals from the surrounding mantle rocks. The researchers precisely replicated the Earth’s deep, high-pressure, and high-temperature conditions. They observed that under these conditions, carbonate melts become exceptional solvents.

Discovering green metals

The researchers mimicked the mantle environment using specialized experimental apparatus designed to generate immense pressures. They started with two types of natural mantle compositions: mica pyroxenite, a rock type rich in mica minerals from western Uganda, and fertile spinel lherzolite, characterized by the mineral spinel from Cameroon.

“We knew that carbonate melts carried rare earth elements, but this research goes further,” said Dr. Ezad. “We show this molten rock contains carbon takes up sulfur in its oxidized form, while also dissolving precious and base metals — ‘green’ metals of the future — extracted from the mantle.”

The team stumbled upon an unexpected finding. Initially, they found that sulfur, especially in its oxidized state, is key to the process. This form of sulfur significantly improves how carbonate melts can gather metals.

These melts become more efficient at dissolving and holding onto various metals. This includes metals that are critical for green technology. Thus, sulfur’s role is essential in sourcing materials for sustainable innovations.

Implications for Ore Deposits

These findings have profound implications for the field of ore deposit formation. As carbonate melts enriched with metals ascend from the mantle towards the Earth’s crust, geological processes can lead to cooling and crystallization.

This can result in the localized concentration of metals, forming the valuable ore deposits that mining companies pursue.

“This study indicates that tracking carbonate melts could give us a better understanding of large-scale metal redistribution and ore formation processes over Earth’s history,” noted Dr. Ezad.

These processes occur over vast geological time scales, but the results can produce different types of ore deposits relevant to modern mining.

The future of green metals

The research has the potential to transform exploration strategies as we seek to secure sustainable sources of metals for renewable energy technologies.

“As the world transitions away from fossil fuels to battery, wind and solar technology, the demand for these essential metals is skyrocketing, and it’s becoming harder to find reliable sources,” said Dr. Ezad.

“This new data provides us with a mineral exploration space previously not considered for base and precious metals — deposits from carbonate melts.”

This is particularly important because metals like nickel and cobalt are crucial for large-scale batteries, and the renewable power sector will require massive amounts of these elements.

Potential hidden within the Earth’s interior

Though traditional mineral exploration often focuses on near-surface deposits, the study underscores the potential hidden within the Earth’s interior.

Understanding the dynamics of carbonate melts and their role in transporting metals could pave the way for targeted, more efficient exploration strategies.

The findings serve as a reminder of the complex and interconnected processes at play within our planet, and how unraveling these secrets may be essential in ensuring a sustainable future.

More about green metals

In the quest for sustainability and environmental preservation, the spotlight has turned towards “green metals.” As discussed above, these metals, essential for the advancement of green technologies, play a pivotal role in reducing our carbon footprint and fostering a sustainable future.

Defining green metals

Green metals refer to metals and minerals used extensively in renewable energy technologies, electric vehicles (EVs), and other applications that contribute to a lower carbon economy. These include, but are not limited to, copper, lithium, cobalt, nickel, and rare earth elements.

The ‘green’ in green metals signifies their critical role in environmentally friendly and sustainable applications, rather than their actual color or extraction methods being inherently green.

Key roles of copper and nickel

Copper stands out as a cornerstone of green metals due to its excellent electrical conductivity. It is crucial in the production of wind turbines, solar panels, and the infrastructure required for transmitting renewable energy. As the demand for renewable energy sources skyrockets, so does the need for copper, making its role in the green transition indispensable.

Nickel, with its high energy density, is becoming increasingly important for battery production, especially for electric vehicles and large storage systems. Its role in the battery industry is crucial for enhancing the performance and capacity of lithium-ion batteries, making EVs more efficient and competitive with traditional vehicles.

Lithium, cobalt and Rare Earth Elements (REEs)

The surge in electric vehicle production has escalated the demand for lithium and cobalt, essential components of lithium-ion batteries. These batteries power not only EVs but also storage solutions for renewable energy, making lithium and cobalt critical in reducing reliance on fossil fuels and cutting down CO2 emissions.

Rare Earth Elements (REEs) are key components in the manufacture of magnets used in wind turbines and electric motors. Despite their name, REEs are relatively abundant but require complex processing to be extracted and used, making their supply chain a critical consideration for green technology industries.

Challenges and solutions for the future of green metals

While the demand for green metals is a positive sign of a shift towards a more sustainable future, it also brings challenges, including the environmental impact of mining and the need for responsible sourcing.

Innovations in recycling green metals from used technology and developing more sustainable mining practices are crucial steps towards mitigating these challenges.

In summary, green metals are at the heart of the transition to a more sustainable and environmentally friendly future. Their role in renewable energy, electric vehicles, and other green technologies is undeniable.

As we advance, the focus must be on increasing the supply of these essential materials while also ensuring their production and use are as sustainable as the technologies they support. Through innovation, responsible sourcing, and recycling, the path to a sustainable future becomes clearer and more attainable.

The study is published in the journal Science Advances.

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