Deep in the Australian desert, an expedition in search of rare earth elements
As a professor and researcher and a geologist for over 20 years, I’ve had the opportunity to go on numerous field missions throughout my career. The expedition I’m about to tell you about was my last field mission—back in the days before the pandemic, during the 2019 Southern Hemisphere winter.
Bénédicte Cenki, University of Montpellier
As a professor and researcher and a geologist for over 20 years, I have had the opportunity to undertake numerous field missions throughout my career. Each time, I’ve been driven by the same passion to explore new territories—from the Peruvian Altiplano for my master’s thesis in 1997 (I traveled in the back of a truck filled with potatoes), to all those years surveying active quarries in South India for my dissertation in the early 2000s, to all those field missions in the mountains (including a via ferrata at over 3,000 meters on Mont Emilius in the Aosta Valley in 2007) or on idyllic Greek islands where metamorphic rocks (rocks transformed by tectonic processes such as mountain range formation) plunge into crystal-clear, Bahamas-green water.
The expedition I’m about to tell you about was my last field mission, back in the days before the pandemic, during the 2019 Antarctic winter.
The objective of this mission was to study rocks in an area near Nolans Bore, which in the coming years will become one of Australia’s largest rare-earth mines in the Northern Territory.
Rare earth elements such as lanthanum, cerium, praseodymium, neodymium, thulium, and ytterbium are chemical elements that are essential to new technologies (wind turbines, solar panels, electric vehicles).
These metals are considered critical because, in addition to their economic importance, their supply is heavily dependent on China.
Why mine rare earth elements in Central Australia?
In order to prevent future economic, geopolitical, and environmental problems, Western countries have been undertaking major research projects for the past decade or so with the goal of eventually diversifying their sources of supply and ensuring that extraction is carried out responsibly and with respect for people and the environment.
See also:
These metals, which are becoming scarce, pose a challenge for the societies of tomorrow
As a recipient of a European Marie Curie Horizon 2020 grant, I had the opportunity to spend 18 months on a research assignment at the University of Sydney to gain additional skills in numerical modeling. I took advantage of this opportunity to organize a field trip to the Australian outback—known as the bush—to assess the rare-earth potential of the pegmatites in the Entia Metamorphic Dome (a circular outcrop of partially melted rocks originating from the deep Earth’s crust during the formation of ancient mountain ranges) in Central Australia. Pegmatites are products of the melting of the continental crust, rich in quartz, feldspars, and micas, as well as rare metals.
To that end, I invited two colleagues: Patrice Rey, a tectonist and modeler from the University of Sydney, and Fleurice Parat, a magmatic petrologist from the University of Montpellier.
Organizing a completely self-sufficient expedition in the Australian bush
This meticulous planning begins several months in advance, because nothing can be left to chance (there will be enough uncertainties when the time comes, anyway). For this mission to be a success, I absolutely must find the GPS coordinates of the rare-earth deposits listed in the Northern Territory Geological Survey’s archives from the 1990s. In fact, after being intensively explored for uranium in the late20th century, this territory has shown significant interest in rare earths since the beginning ofthe 21st century (rare earth minerals are often radioactive as well, which further complicates their extraction).
Since we won’t have Internet access, I absolutely must prepare for this mission “the old-fashioned way”: select targets from reports that are over 30 years old, print out all the satellite images, any topographic or geological maps we might need, buy a solar charger for the GPS and iPad—which will help us navigate through the bush to reach the geological targets—and, of course, remember to bring the Géosciences Montpellier satellite phone and the emergency GPS beacon, which would allow us to be located in case of a serious problem (and make sure to register it properly before leaving civilization!).
I arrived in Alice Springs from Sydney on the morning of July 11, almost at the same time that my colleague Fleurice arrived from France after a 24-hour flight. Our colleague Patrice will join us two days later. So the two of us are in charge of planning the logistics and taking care of the essential errands. We’re setting out with just one 4×4, so we’ll have to stick to the trails visible on satellite images without risking straying off them.
Source: Author provided
Alice Springs is a small town of about 20,000 people in central Australia, tucked away several thousand kilometers from civilization (1,500 km north of Darwin and south of Adelaide). The local supermarket is a far cry from the extravagance of our European hypermarkets or the posh Pacific Coast! But it has the essentials: water for 15 days (there are no water sources where we’re going), pasta, canned vegetables, freeze-dried soups, tea, muesli, spreads, vitamin powder (like spirulina), a table, folding chairs, and dishes (which we’ll leave for the locals after the mission), shovels (for digging daily, individual latrines), sunscreen, wide-brimmed hats, and… fly nets! We’re heading out completely self-sufficient, but traveling light and minimalist (what reassures me is that my colleague Patrice has plenty of missions in the bush under his belt): cooking over an open fire (a fire pit dug into the sand at the cove), no generator, no fridge—so we’re only bringing food that keeps at room temperature—and, of course, a first-aid kit.
The Entia metamorphic dome is located on private land at Ambalindum Station, a vast cattle ranch spanning several thousandkm². My requests for permission to access the site, sent to the corporate headquarters in Brisbane, have gone unanswered, so we’ll have to negotiate access on-site with the ranchers when the time comes. That means a 300-km detour—and we’re not even sure they’ll let us in!
So we spend our first three nights acclimatizing at the Hale River Homestead campground in Old Ambalindum (150 km east of Alice Springs). After a quick phone call to the farm owner on the second night, she tells me to stop by the next day at 7 a.m., after their morning debriefing. The sun rises through a veil of dry, red dust; I spot the farmers’ helicopter, its spinning blades breaking the icy morning silence. We park in front of the small, single-story shack where the morning meeting is being held. We aren’t invited inside, even though the temperature is only a few degrees. We wait for the farmer’s wife to arrive with some maps, which we spread out on the hood of the car. She hesitates to grant us access, and we repeat that we’re not a mining company but academics; in the end, the key to getting in was the name of a colleague from the University of Adelaide who had visited the previous year and made a good impression. Phew, the mission is saved. We set off on a six-hour drive to enter the Entia Dome via a passable and secure track, with just a single vehicle. Our last stop to fill up the diesel tank before leaving civilization behind: the Atitjere Aboriginal community, remote and so far removed from our Western worldview.
Our daily life for 10 days in the heart of the Entia Dome
We arrive at our campsite in the late afternoon, right in the heart of the dome—which will allow us to explore the area daily—in a dry creek bed that Patrice recognizes from having been here several times before: this rocky spot is the kitchen area (magnificent migmatites!), over there the sand is the most comfortable spot for the tents, and over there are the restrooms. Once our camp is set up, we cook our first dinner (pasta with ratatouille!) under the stars over a campfire dug into the sand. With a bowl of tea warming our hands—it’s only a few degrees—we enjoy our first evening beneath the vast expanse of a magnificent starry sky, enveloped in a reassuring silence. The second day begins just like the ones that follow, with the morning ritual at sunrise around 6:30 a.m.: Patrice and Fleurice stoke the fire, prepare tea and breakfast, while I check that the electronic devices are charged, map out our itinerary for the day, and determine the order of the geological sites to visit. Very quickly, everyone naturally finds their role in this type of mission, and everything runs smoothly and simply.
Source: Author provided
The days go by, one much like the next: we drive our 4x4s as close as possible to our target sites, following the trails visible on Google Earth. Then we set off on foot with water, our hammers, field notebooks, and GPS devices to reach the selected outcrop. Fortunately, the vegetation is sparse and scant, and the elevation gain is minimal, allowing us to navigate in a straight line by sight: pegmatites are very light-colored rocks and therefore clearly visible against the monotonous brown-ochre landscape. Once we reach the outcrop, Fleurice and I take out our magnifying glasses to try to spot rare minerals with obscure names like samarskite, fergussonite, or monazite, while Patrice takes out his compass to take measurements and compare the strike of the pegmatites with that of the surrounding rocks. A well-coordinated and efficient team! These minerals contain heavy rare earth elements such as thulium and ytterbium (used in superconductors, radiation therapy, and infrared lasers), as well as niobium and tantalum (used primarily in alloys for the aerospace industry).
One evening, on his way back to camp, Patrice pulled the 4×4 over near a livestock water trough, climbed the few rungs of the ladder, and discovered that the hatch covering it was open: from now on, we’d be able to fill a jerry can with water every evening for washing dishes (and the occasional shower with a cup—what a luxury!).
Every evening we return shortly before nightfall, around 6 p.m., so we can make the most of the southern winter’s roughly ten hours of daylight out in the field. So our evening routine often takes place by headlamp: gathering some dry grass to rekindle the fire, cooking, washing dishes with a trickle of water, sorting through the day’s samples, and updating our field notebooks while trying to synthesize all the information and formulate and discuss scientific hypotheses to test later. One last glance at the Milky Way and the Southern Cross while sipping some tea, before we each retreat to our tents around 9 p.m.
Source: Author provided
The days pass peacefully, one much like the next. It is only on the last afternoon that a surprise awaits us: our first (and last) encounter with the dingo, that famous wild dog and icon of the Australian bush. We are at the final outcrop, in the heart of the Inkamulla sub-dome. We’re engaged in a lively discussion about the significance of these folded structures and are carefully using a chisel and hammer to chip away rock samples from layers with folds that are crucial to understanding how this geological structure formed. The evening light makes the red-ochre hue of the rock—with its rounded, inviting, and timeless contours—even more intense.
In fact, this looks like an Aboriginal cave, sheltered from wild animals, just a few meters up a climb that’s easy to scale. A few Aboriginal artifacts found in the dust bear witness to this. The shadows of the eucalyptus trees—with their mottled white trunks and light-green leaves—grow longer with each passing minute. It is in this peaceful, surreal moment that a dingo nonchalantly approaches our group, which is deep in a geological discussion about our sampling technique for these small shear zones that we need to date. Curious, the dingo circles around us a few meters away and then sits down on a rock to continue watching us.
What now?
Before flying back to civilization, we stop by the post office in Alice Springs to mail the four barrels of samples—which we had carefully cataloged and packed the previous evening in the parking lot of the Alice Springs motel—to France.
Since my return to France in August 2020, I have carefully sawn each sample to produce thin sections 30 micrometers thick that can be examined under an optical microscope, followed by a scanning electron microscope, an electron probe, and a laser ablation mass spectrometer, in order to quantify the mineral contents of major chemical elements and rare earth elements.
Jonas Nollo, a second-year master’s student in the “Exploration and Reservoir Geology” program, is providing us with invaluable assistance on the analytical aspect of the study. If borders reopen, I sincerely hope he secures a doctoral fellowship in Australia so he can continue this work exploring critical metals, which include rare earth elements: it’s a field with a bright future, because the ecological transition must be led by geologists! The initial results of our study will be presented in early July 2021 at the annual Goldschmidt International Conference, scheduled to take place (virtually) in Lyon. Through meticulous analysis, Jonas has identified four families of pegmatites with different mineralogical compositions that may have very distinct depths and ages of formation—and thus varying potentials for rare earth elements. He will quantify the chemical composition of major and critical elements using an electron microprobe and a mass spectrometer in early May.
Unfortunately, so far, microscopic analysis has not allowed us to identify the rare minerals we were hoping to find, but we have found many garnet pegmatites (which contain heavy rare earth elements, though in lower concentrations). However, Jonas has confirmed the presence of allanite pegmatites containing light rare earth elements southwest of the Entia dome (lanthanum, cerium, neodymium, praseodymium). Science often advances in small steps. Major discoveries are always preceded and driven by a multitude of fundamental studies conducted by numerous researchers collaborating around the world. To be continued…
Bénédicte Cenki, Associate Professor at the University of Montpellier, EU H2020 MSCA visiting researcher at the University of Sydney, University of Montpellier
This article is republished from The Conversation under a Creative Commons license. Readthe original article.