Critical raw materials used to make many high-tech products are found all over the world, yet just 3% of the supply comes from Europe, according to a 2014 report by the European Commission. Still, experts believe there is a wealth of unexplored deposits across the continent, and so are developing ways to locate them.
Researchers from the University of Exeter and geologists from the Camborne School of Mines are collaborating to uncover rare earths and essential raw materials, such as tantalum, niobium, indium, tungsten and fluorspar, which are associated with alkaline rocks and carbonatites; two types of igneous rocks. The $5.4m project will be carried out under the European Union’s Horizon 2020 research and innovation programme.
Why these particular rocks?
The research focuses on carbonatites and alkaline rocks. There are only about 500 known occurrences of carbonatites in the world – there are lots of places with alkaline rocks that don’t have carbonatites, although the latter usually occur within alkaline rocks. The particular metal ores the team are looking for can be found in both the rock types, but they don’t both have to be present.
"We know the kind of places where carbonatites and alkaline rocks occur," says lead researcher Professor Frances Wall, who has worked on carbonatites and alkaline rocks for nearly 30 years. "They tend to be in the middle of the continent…not really where [tectonic] plates have already broken apart."
Wall says that the African Rift Valley is one example where they are found, and also at Kaiserstuhl which is on the border between Germany and France, near the Rhine River, where the team is conducting its research.
"You can see the volcanic rocks and you can also see the rocks that crystallised under the ground," Wall says. "That’s what we call the intrusive rock, and when we’re looking for ore deposits, it’s always the intrusive rocks that we’re looking for."
For geologists, carbonatite is one of the most economically important rocks to find, due to its rarity. If carbonatite is found anywhere, Wall says there is a one in ten chance of it turning into a mine.
"If you compare that with another igneous rock such as basalt which makes up a huge proportion of the ocean floor, it’s a huge contrast in the two," Wall adds. "It’s one of the most prospective rock types to actually find."
It also has a very unusual chemistry. Carbonatite rocks are made of carbonate, so they’re different to every other igneous rock in the world, which mainly consist of silicate minerals.
"It’s the bizarre chemistry that gives rise to deposits of some of these high-tech minerals," says Wall. The problem though, she continues, is that this exploration area is very niche and isn’t as well-developed as research into iron ore or copper deposits, for example.
"There’s a huge opportunity here to improve our knowledge of what actual ore deposits of these high-tech minerals look like," Wall says. "That’s what we mean by a geo-model."
Tools and techniques
A geo-model is where the team tries to understand the architecture and the structure of what sits underneath a carbonatite volcano, and work out the most prospective area to find the ore deposits they’re interested in. They will analyse areas to create advanced exploration maps and computerised representations of portions of the Earth’s crust.
"If you see a particular rock type at the surface, does that mean that it’s likely that there’s something of economic interest below or does that mean that you don’t need to look anymore because it’s very unlikely?" Wall explains. "The way that you find out about what’s under the ground when you can’t see it, before you drill a hole, is to use geophysics and do geophysical exploration."
One of the geophysical techniques is to fly some kind of aircraft over the area of interest and pick up any magnetic or radiometric signals. These signals can be processed and reveal what lies under the ground, revealing major intrusion structures as well as smaller ones that are a meter or so across, which are called dikes and veins (carbonatites).
Wall says that, eventually, a hole has to be drilled to see what the rocks are like under the ground, but that’s very expensive, so it is avoided for as long as possible. She adds that cameras and geophysical tools can be lowered down a borehole to construct what the researchers call a ‘natural laboratory’.
The project started at the beginning of February and the team will be collecting data over the next four years. There are 12 partners and five universities involved from all over the world. For example, Mkango Resources which is a Canadian exploration company, GeoAfrica, the British Geological Survey, and the Universities of Tübingen, St Andrews, G. d’Annunzio and Mendel in Brno.
According to Wall, there are important deposits in Greenland, as well as carbonatite and alkaline rocks in the volcanic areas of Italy and Spain, but it is unclear whether it is worth exploring for ore deposits underneath those.
"This is what we hope to learn from this project," she says. "By improving the geo-models and the understanding of how these systems work, then we should be able to tell people whether they should go and explore in places like Italy."
The team believes the results will be directly useful for exploration at prospective deposits anywhere in the world. Wall says the findings are being made public, so any research group can get hold of them once the study is completed.
"If we could see our model being used by exploration companies and academics in exploring in the future, that would be a really big success for us," she says. "If somebody actually found an economic deposit in Europe because of this research that we will do over the next four years that would be extremely exciting."
Wall explains that it is very high risk strategy, as it takes around ten years to develop a mine, and nature cannot be controlled.
"We don’t actually know what’s under these Italian volcanoes; we can only do the research to push the science and understanding forward," she says.
It’s high risk, but it would be worth the time and the money to build mines for these metals as they are so important to many industries. Metals such as tantalum are used in electronics like smartphones and laptops, fluorspar is used to make hydrofluoric acid, and niobium is often used in pipeline construction.
The team believes this is the largest ever research project on carbonatites and alkaline rocks. Wall says there is a good mix of experts that each partner brings to the table; scientists with decades of knowledge in the field, and consultants that keep them ‘grounded in reality’.
"We knew some other people we had worked with over previous years; some are project partners on other research projects, some people are new to the consortium brought in for particular expertise," she says. "So it’s a nice mix of people who’ve known each other for a long time, and people who are just meeting now for the first time."