Study Detects Mantle-Derived Helium in Zambian Hot Springs, Supporting Suspected Kafue Rift Activity

A new study published Monday in the journal Frontiers in Earth Science reports that gas samples from hot springs and geothermal wells in Zambia contain elevated levels of helium-3, indicating that fluids from Earth's mantle are rising through the suspected Kafue Rift.

The study was led by Rūta Karolytė when she was a postdoctoral research fellow at the University of Oxford. Karolytė is currently a principal product scientist at UK-based Snowfox Discovery.

Researchers collected samples from six sites in a highly concentrated area along the suspected rift. They also sampled two hot springs located about 60 miles (95 kilometers) from the suspected rift. The team measured the ratio between helium-3 and helium-4 in the gas samples.

The samples from the rift area showed more helium-3 than normally found in the crust, indicating mantle fluids. No similar increase in the helium-3 ratio was found in the two hot springs 60 miles (95 kilometers) from the rift. 3 per cent were found in the fluids reaching the surface in the Kafue Rift.

1799564. “We have the first geochemical data from this area. That’s quite a different line of evidence that really strengthens the idea that we have rift activity in the area,” Rūta Karolytė stated.

“There’s hot water bubbling up to the surface, and we sampled the gas that’s coming up from that,” she added. “We found more helium-3 than you’d normally find in the crust, which is generally a signal of mantle fluids coming up into the water,” Karolytė stated. “What our data confirms is that this system is currently ‘awake’ and geologically active,” she said.

The Kafue Rift is part of a roughly 1,500-mile-long (2,500-kilometer) rift line spanning from Tanzania to Namibia and possibly out into the Atlantic Ocean. It forms part of a 2500-kilometre-long rift zone stretching from Tanzania to Namibia. Geologists previously thought the Kafue Rift was long dead.

Previous studies reported earthquakes too faint to be felt by people but detectable by instruments, increased underground temperature, and minute changes in ground elevation spotted by satellites. “How does a new plate boundary begin? Mature plate boundaries are easy to recognize.

The earliest stages are much more subtle,” Estella Atekwana stated. “At the fastest, it could happen in a couple of million years. At the slowest, it could take 10 or 20 million years,” Mike Daly stated.

Folarin Kolawole stated that the findings provide a “strong confirmation” that there is direct upward flow of fluids from the mantle to the surface through newly forming rift zones. Patrice Rey stated that the new geochemical evidence reveals the Kafue Rift is an early-stage continental rift where mantle fluids rich in primordial helium-3 are rising through faults.

The East African Rift is tens of millions of years old, has several volcanoes, and is seismically active.

Tectonic plates move at a speed comparable to the growth rate of fingernails. Pangea began to separate into today’s continents about 200 million years ago. Tectonic plates have a thickness of up to about 120 miles (190 kilometers).

The mantle layer is up to 190 kilometres below the surface in the context of the Kafue Rift fluids.