The metals we need for a low-carbon future

Publication date
Friday, 25 Mar 2022

Dr Mark Hoggard doesn’t seem like someone who would talk in favour of mining.

He’s a postdoctoral researcher with the ANU Research School of Earth Sciences who wants to “work on geoscience problems that are important to society”, such as how sea level responds to melting ice caps, and “share knowledge of this fascinating planet”. He loves rock climbing in the mountains and when he sits down to chat with me, he’s just finished making himself a cup of tea.

All things considered, I’m very curious to hear about another research interest of his: finding better ways to locate metal deposits to “support sustainable development and the transition to a low-carbon economy.”

In other words: showing mining companies the best places to dig. But … for a more sustainable future? How does that work? 

“We need to have some kind of roadmap to reduce the impacts of human-induced global warming,” he says.

“Changing our lifestyles to reduce our individual carbon footprints is a big part of handling the problem, but we also need technological change. We need to change the way we generate power, especially electricity.

“And if you want to shift your power generation away from fossil fuels to renewable resources, you need a lot more of certain kinds of metals: things like copper, nickel, lead and zinc.”

Those metals are used for a number of different applications, including renewable power and energy storage technologies.

They’re also used in electric cars: according to some estimates, we need to have around a billion electric vehicles on the road by 2050, and they use larger amounts of metals compared to conventional petrol-powered cars.

“One of the key sources of these metals is through recycling,” Mark says. “We’ll find more efficient methods for that as time goes on, and that will supply some of the shortfall – but not all of it.

“For example, over the next 25 years, humans are set to need as much copper again as we’ve ever used in human history until today. You’d need to recycle everything that has ever been made to meet that demand.

“These technologies need quantities of metals that are kind of astronomical to get your head around. And that inevitably means exploration for new sources of these critical minerals.”

Much of the exploration for metal deposits that are easy to access or easy to find has already happened.

“Halfway through the last century, people started using geophysical techniques to find deposits,” Mark says.

“For example, if you look at variations in the magnetic properties of rocks at the surface, those are linked to the processes responsible for forming metal deposits. 

“We got really good at finding giant deposits located at the surface of the Earth, but we remained less good at finding those that are buried beneath the surface.”

The search for new deposits has to go deeper – and that’s where Mark’s work comes into the picture.

A hand holding a chunk of grey rock.

A piece of galena (lead sulfide ore), one of the most common kinds of lead ore, which also sometimes contains other metals such as silver.

Mark never set out to create a ‘treasure map’ showing mining companies where to dig. He was initially researching a very different problem related to modelling sea level changes, working with a colleague to develop a tool for mapping variations in the thickness of the Earth’s tectonic plates across the globe. They used data from seismometers – instruments that measure seismic waves generated by earthquakes – to estimate their thickness.

They shared their work with Geoscience Australia, who noticed a pattern: there was a relationship between plate thickness and where large mineral deposits were forming.

“We suddenly realised we have this global map set up and all of these giant metal deposits are lining up with the boundary between thick and thin areas of the tectonic plates,” Mark says.

They weren’t the first researchers to figure out the underlying processes involved, but they were the first to show that if this could be demonstrated on a global scale, then “we can give you a map and tell you ‘there is X percent chance of finding deposits here if you go and look’”.

It complements a much larger research effort into critical metals led by Mark's colleagues at the Research School of Earth Sciences. They are developing geological models for understanding how metal deposits form in Australia, as well as newer, more environmentally sustainable technologies to extract metals from ore and reprocess waste rock from earlier mining operations.

There’s still a sense of unease that I can’t shake, stemming from every ‘bad news’ story I’ve ever heard about mining companies destroying the environment or displacing people from their homes. I ask Mark for his thoughts.

“There is a tendency to think of all mining as bad,” he acknowledges. “That is built on real examples of bad behaviour in mining, and those are very real problems and very real concerns.

“We absolutely need to hold these companies to account both in terms of the pollution produced by mining and in how they interact with local communities.”

Part of minimising some of that damage is finding high grade, high volume mineral deposits – which is exactly where a map of the Earth’s minerals can help. That means less digging, fewer waste products and lower carbon emissions associated with processing and extracting metals from the ore.

It’s also good news for Earth science as a whole. “Every time we find out a new piece of information we gain more insights into these surprisingly complicated deposits. They cover a huge range of Earth’s history – some of them are two and a half to three billion years old,” says Mark.

“That’s something we want to understand more. Earth science is really key to a lot of the solutions to the climate-related problems we’re facing.”

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