Aerial view of the Kafue Rift southern boundary fault zone. The hot springs where researchers sampled gases lie in the green thickets
Michael Daly
Signs suggest the African continent may be splitting at a new location. In Zambia, gases from hot springs appear to originate from deep below Earth’s crust, indicating the potential formation of a new tectonic plate boundary.
Many rift valleys worldwide have seen continents drift apart over millions of years, such as the East African Rift Valley stretching from the Red Sea to Mozambique. While rifting can eventually divide a tectonic plate, finding a site where this process is just starting is rare, according to RÅ«ta KarolytÄ— from the University of Oxford.
The Kafue Rift in Zambia is part of a 2500-kilometre-long rift zone extending from Tanzania to Namibia and potentially into the Atlantic Ocean. Geologists suspect the region might be in the early stages of forming a new continental plate boundary due to its geography, low-gravity anomalies, high sub-surface temperatures, and low-level seismic activity. However, until now, there was no geochemical proof.
KarolytÄ— and her team have analyzed gas samples from five hot springs and three geothermal wells in central Zambia. They discovered that the helium and carbon isotope ratios match those found deep beneath Earth’s crust, suggesting that fluids from the mantle, as deep as 190 kilometres below the surface, are rising. This points to a potential tear in the region’s tectonic plates.
“Our data confirms that this system is currently ‘awake’ and geologically active,” KarolytÄ— states. “While an active rift doesn’t guarantee an ocean in 100 million years, it remains a possibility.”
In the initial phases of continental rifting, gases that have accumulated in rocks over millions of years, such as helium, are released. In the Kafue Rift, helium concentrations in surface fluids have reached up to 2.3 per cent, drawing industrial interest.
“Finding the right tectonic conditions to concentrate and release helium for capture is challenging,” KarolytÄ— explains.
Patrice Rey from the University of Sydney, Australia, concurs that despite the lack of active volcanoes and significant seismic activity, the area exhibits various signs of tectonic activity.
The recent geochemical evidence from the hot springs indicates that the Kafue Rift is an early-stage continental rift where mantle fluids rich in primordial helium-3 are ascending through faults. Rey suggests, “It is reasonable to think that the Kafue Rift may evolve into a plate boundary sometime in the future.”
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