1.2 billion-year-old groundwater is some of the oldest on Earth
(Image credit: Dr. Oliver Warr/University of Toronto)
Groundwater that was recently discovered deep underground in a mine in South Africa is estimated to be 1.2 billion years old. Researchers suspect that the groundwater is some of the oldest on the planet, and its chemical interactions with the surrounding rock could offer new insights about energy production and storage in Earth’s crust.
In fact, Oliver Warr, a research associate in the department of Earth sciences at the University of Toronto in Canada and lead author of a new study about the groundwater discovery, described the location in a statement as a “Pandora’s box of helium-and-hydrogen-producing power.”
The South African groundwater was also enriched in the highest concentration of radiogenic products — elements produced by radioactivity — yet discovered in fluids, according to the study, demonstrating that ancient groundwater sites may one day potentially serve as energy sources.
“One of the most exciting parts about this new discovery is that at first we thought the groundwater at Kidd Creek was an outlier,” Warr told Live Science. “But now we have this brand-new site located somewhere different with a completely different geologic history that also preserves fluid on a billion-year timescale. It looks like this is a feature of these environments, which represent about 72% of the total continental crust by surface area.”
Until now, “We only had one data point, and it’s pretty hard to say that, yes, this is applicable to the entire world,” Warr said. “But this new site reaffirmed what we considered to be true: that these systems trap water over extremely long time spans.”
Warr described the way that rocks release this billion-year-old groundwater as similar to the way that liquid escapes from a water balloon.
“These deep mines are the perfect location for what we do, since, as researchers, we don’t have the time or the money to put a hole in the ground, but that’s what a mine does. When they drill bore holes, the water that has been trapped inside the rock starts gushing out — it’s like piercing a water balloon — and we’re able to capture it.”
After collecting the samples at Moab Khotsong, Warr and his team of international researchers examined their contents and found that the water contained properties that resembled those of water at Kidd Creek.
“In these deep settings, water is held in cracks in the rock and, over time, they interact, resulting in uranium, which then decays over millions, and even billions, of years, creating noble gases,” Warr said. As these noble gases accumulate in the water, researchers can measure their concentrations and how long they were present within the rock.
Warr explained that the samples collected contained high salt content — about eight times more than that of seawater — as well as concentrations of uranium, radiogenic helium, neon, argon, xenon and krypton. They also found the presence of hydrogen and helium, both of which are important energy sources. This finding offers a previously unseen glimpse of helium diffusion from deep within the planet, an important process to consider as we face an ongoing helium shortage, and could hint at energy production under the surface of other planets, too, according to the study.
“As long as there is water and rock, you’ll see the production of helium and hydrogen — and that doesn’t necessarily mean this has to be taking place only on Earth,” Warr said. “If there is water on the subsurface of Mars or any other rocky planet, helium and hydrogen could be generated there too, leading to yet another energy source.”