The annual fall meeting of the American Geophysical Union (AGU) is a comprehensive expression of the latest fundamental geophysical research. In 2019, through talks, poster sessions and town-hall style meetings, some 30,000 scientists descended on the Moscone Center in San Francisco to share research with each other on a global variety of topics to broadly include atmospheric science, oceans, geology, hydrology and other planets in our solar system.

Anthropomorphic climate change reverberates through almost every area of Earth studies represented at AGU. In response to the dramatic increase in demand for lithium carbonate used in low-emission vehicle batteries, stationary electric storage devices and personal electronic devices, more scientists are studying how and where economically viable lithium deposits occur.

In 2018, the fall AGU meeting featured a special session on lithium exploration where as many as 30 researchers presented their findings. Other than last year, 2019 marks the biggest year for lithium exploration research science presentation in AGU history.

The AGU poster sessions occupy the entire underground hall in the Moscone Center South in San Francisco, a city-block-sized cement cavern with a 100 foot ceiling. Hundreds of vertical, grey cloth-covered bulletin boards were positioned end-to-end to form 10 foot wide rows that striped across the entire exhibit hall. Scientists tacked big, roughly five foot wide by three foot tall posters to the boards. The giant documents were vibrant with large images, text, graphics and mathematical formulas.

Over five days of the conference, an elaborate time schedule prompted a topical changeover in posters every four hours or so. An international cast of presenters stood next to their posters while scientists mulled about in the crowded rows to consider the science and ask questions, and thus, research was presented and duly scrutinized.

The buzz inside the huge room was constant, the reverberating sound of scientific dialectic.

I first learned about the work of Tom Benson when researching the lithium mine proposed for the Thacker Pass area some 70 miles north of Winnemucca, Nevada. Benson wrote his PhD. dissertation at Stanford on the Thacker Pass deposit and now works for the company developing a mine at the site, Lithium Americas and its subsidiary Lithium Nevada. I was surprised and excited to see Dr. Benson presenting his research at AGU and stopped by his poster during the few hours it was on display.

Benson’s poster was part of a session titled, Critical Mineral Resources and the Green Tech Revolution: Criticality and Critical Materials in the Next Generation of Renewable Energy and Energy Storage Technologies.

Benson is a volcanologist and a seasoned veteran of the AGU fall meeting having done his graduate work at nearby Stanford. He looked comfortable standing next to his poster titled, From Supervolcanoes to Salars: The Role of Volcanism in Forming the Largest Lithium Deposits in the World. The poster bearing text, images and math transports the reader to South America and the Lithium Triangle as it’s known, an exotic area in the high Andes Mountains.

More than half of the world’s lithium metal is mined in what is known as the Lithium Triangle. The high, arid region of the Andes includes parts of Bolivia, Chile and Argentina. There are no fewer than 20 companies currently producing or seeking lithium within the Triangle. Lithium Americas is a Canadian corporation developing a lithium brine mine at the Cauchari-Olaroz salar. According to the company, the mine will begin operation in 2020.

A mine nearby the Lithium Americas facility has been producing roughly 17,5000 tons of lithium carbonate a year since 2014, the Orocobre corporation Olaroz facility. Roughly 60 miles west of the Cauchari-Olaroz salar is the Salar de Atacama in Chile, the world’s largest single source of lithium metal and third largest salt flat on the planet. 200 miles to the north of the Atacama in Bolivia is the gigantic salt flat, the Salar de Uyuni, another vast lithium deposit.

Use the map’s zoom tool for details. The Lithium Triangle:

What is a salt flat and how is lithium mined from brine?

Dr. Benson’s poster answers a critical question for lithium metal exploration. The concentrations of lithium in South American salt flats is well-documented, but where did it come from and how much more is in the watershed entrained in volcanic rock?

Benson sampled shards of volcanic tuffs in the catchment watershed of the three largest lithium producing salars in the Lithium Triangle. The samples were taken near calderas or the remains of ancient super volcanoes.

Benson analyzed the samples using the Sensitive High Resolution Ion Microprobe – Reverse Geometry or SHRIMP-RG instrument at Stanford University. The results show that there is a lot of lithium metal in the rock around the salars and that it came from volcanism. Benson’s analysis reveals that there are several orders of magnitude more lithium metal in the rock adjacent to the salars than is in the salt flats.

A salt flat is a remnant of a desiccated ancient lake. The Bonneville Salt Flat in Utah is what remains of a lake as large as Lake Michigan. Salt flats are typically hydrologically closed basins where minerals are concentrated in the salts that have evaporated out of the water and eroded from the local rock over tens of thousands to millions of years.

The combination of soft lithium-bearing rock, weather forces, and the salt flat can be considered a continuous dynamic system that functions over long-term geologic time scales. Water continually interacts with lithium-heavy rocks and concentrates the metal in the salar.


A graphic from Tom Benson’s 2019 fall AGU poster titled From Supervolcanoes to Salars: The Role of Volcanism in Forming the Largest Lithium Deposits in the World – image – Lithium Americas Corporation.

Depending on the location, the water level in a salt flat basin varies with precipitation and other factors. The expression of surface water on the salts can be ephemeral, and though a salt flat may sometimes appear dry and cracked on the surface, mineral rich brine can extend several kilometers deep into the salts. Water and salts mix to form a brine laden with lithium and other minerals. The brine is pumped to the surface and spread out into giant, shallow evaporation ponds.

In the arid, high elevations of the Triangle, water evaporates quickly and increases lithium concentration by a factor of 10. The enhanced brine is then processed to remove a variety of other minerals. Using proprietary chemical and mechanical means, companies create lithium carbonate, a chemical manufactured to the particular specifications of end users, primarily battery makers.

The only active lithium mine in North America is a brine mine in Nevada’s Clayton Valley. Lithium Nevada is planning to develop a mine some 80 miles north of Winnemucca. The carbon neutral Thacker Pass mine and processing facility is expected to begin construction as soon as 2021 and operate for nearly 50 years to develop a known reserve in sedimentary clay-like material. The soft clay of the McDermitt Caldera is the remnant of a volcanic lake. A different processing method than is used in a brine mine is required, but according to Dr. Benson’s research, both Thacker Pass and the deposits in Argentina came from ancient, giant volcanoes.

Super volcanoes in Nevada and South America 

It has long been known that concentrations of lithium metal are associated with volcanic activity. Dr. Benson’s research in the Lithium Triangle and in Nevada show that the lithium deposit in the Cauchari-Olaroz salar in Argentina is similar in origin to the Thacker Pass deposit in Nevada.

“The mechanisms that are involved in the formation of these South American brine deposits are very similar to what happens at Thacker Pass,” Benson said. “At the end of the day, you have a type of rhyolite magma, for one reason or another enriched in lithium, that erupts on the surface of the earth and is sitting there.

“Then over hundreds of thousands to millions of years that lithium is transferred into local groundwater, meteoric water, and deposits in the nearby basin.

“In the case of South America, it’s in the salar de Atacama, the giant salt flats. In the case of Thacker Pass, it’s in a caldera lake like you see at Crater Lake in Oregon, modern day, so the fundamental principles are all the same. I’ve been talking to other (lithium) researchers today, and that has shown that we’re starting to understand it more and more, and that’s just helping our models and improving them,” Benson said.

Below is a map of the Atacama Salt Flats and adjacent calderas, the remnants of ancient super volcanoes. Click the stick pins for details.

Whether the lithium metal is in sedimentary clay like at Thacker Pass or in a salt flat brine or soft rock or harder spodemene, the source is volcanic said Benson. Lithium is widely dispersed in the earth’s crust.

“How you start to enrich lithium in the crust, and this is true for all lithium deposits hard rock, brine, sedimentary or clay, is you need a mechanism to enrich it, and where you do that is in a magma chamber.”

Inside a magma chamber the geochemical processes are complex, but suffice it to say, lithium metal is concentrated in volcanoes.

“These magmas, sometimes they erupt as giant tuffs and form calderas like at Thacker Pass and in these giant calderas in South America. That lithium enriched material has been sitting on the surface of the earth.

“Then you have environmental differences that cause it to become a clay deposit versus a brine deposit, but the fundamental source for the lithium is all volcanoes.

“In the case of hard rock or pegmatite deposits, that rhyolite magma that’s under the surface of the earth never erupts. It just sits there and slowly cools and crystallizes. Lithium doesn’t want to crystallize, so it remains in the last bit of magma until that magma crystallizes, and that’s what a pegmatite is.”

Volcanologist Dr. Tom Benson in Argentina. Dr. Benson is a research scientist for the Lithium Americas Corporation – image – Lithium Americas Corporation

Mining for profit

The federal government funds almost all of the research represented at AGU. Fundamental research scientists are rarely on staff at traditional metals mining companies; and mining companies almost never directly fund fundamental research. Tom Benson and Lithium Americas are exceptions.

Federally funded research at universities or agencies like the United States Geological Survey can seek to understand more foundational aspects of where and why lithium deposits form. Doing fundamental research for a for-profit corporation has a distinctly practical objective.

“They (Lithium Americas) are funding this research because we want to know, to understand how these deposits form and where we can look for new ones,” Dr. Benson said.

Fruitless mineral research can waste time and lots of money drilling test holes haphazardly in search of valuable deposits. Scientifically knowing the source of lithium metal and how it ends up in the salars can guide the strategic and tactical deployment of limited resources.

Lithium Americas is expected to begin mining lithium as soon as next year at the Cauchari-Olaroz salar. Lithium Nevada expects to begin Thacker Pass mine construction as soon as 2021. Dr. Benson contends that the knowledge borne of fundamental geophysical research shared at AGU makes Lithium Americas and other companies more robust and competitive in developing natural resources that will positively affect the planet’s carbon balance.

“It’s nice to work for a company that values that research. Because it’s essential, it makes you, it makes your models better. It makes your exploration more effective. And it just improves the company overall,” Benson said.

Trumped up mining claims have long been the bait of con men. To prevent the salting and hyping of mine sites, several governments have established legal standards by which resource exploration information is reported. The most widely adopted system is the Canadian Institute of Mining, Metallurgy and Petroleum or CIM classification system.

Under the CIM system, companies must refer to valuable materials in the ground using particular language. In a broad sense, there are either resources or reserves. There are three primary types of mineral resources that coincide with three levels of confidence the resource can be economically developed namely, Inferred, Indicated and Measured. A reserve is a known resource that can be extracted and sold at a profit. There are two types of reserve, probable and proved.

Coming from academia, Benson said it took some getting used to the commercial lithium milieu. Breezy conclusions based on limited data are often made about mineral deposits that would never stand the scrutiny of an AGU poster session or talk.

“So what we (Lithium Americas) do is we have a whole drilling campaign. We get a resource. We have a model, and then we do a press release, because we want to get it right. We focus on doing it right because you have one chance to make an impression, and if you screw that up in the beginning, no one’s going to believe you in the future. So doing it accurate, doing it right, doing it in a sustainable manner, doing it in a cost effective manner. Not being a promoter is what turned me on to this company. I think it’s within the company culture. I think it’s a model for how other companies should work.”

Benson’s poster attracted several scientists in the time I was nearby to include LeeAnn Munk, a noted lithium researcher from the University of Alaska. Benson said the AGU 2019 fall meeting represents a big leap forward in lithium exploration science.

“It’s exciting that now where all the academics are starting to get together to tackle these problems because we need to understand more about lithium deposits and how they form in order to explore for more because we’re going to need more lithium to power all these electric vehicles.”