Yes, this source arises from radioactive decay of uranium and thorium within the Earth. (Alpha particles are helium nuclei.). I was interested and surprised to read that up to 7% of the gas in some US natural gas fields is helium.
Thanks exchemist very interesting. I recall hearing many years ago that helium is from a well in Texas. I remember thinking at the time how weird that was and thinking why there would be a helium well. With your information this makes sense now. Probably all wells have traces of helium and other gases. If there is a deposit of gas that in close proximity to an alpha emitting source then the concentration of helium would be high in that natural gas pocket. Another forgotten mystery from my youth is cleared up. Thanks.
There’s helium in them hills Please Register or Log in to view the hidden image! © Pete Barry https://www.chemistryworld.com/news...s-largest-helium-gas-deposits/1010122.article Helium was discovered to be bubbling up in geothermal pools in Tanzania Unsatisfied by how helium is currently simply stumbled upon, Ballentine and his colleagues have been hunting for it and applied the same principles used by the oil and gas industry. The team has had to identify a source rock in the Earth’s crust, a mechanism for how helium is transported to the surface and how it is trapped before it is lost into space. ‘Step-by-step the source rock for helium – you need uranium and thorium in the rock and you need to store it for a long, long time,’ explains Ballentine. These two radioisotopes decay to helium and are typically found in cratons – ancient, continental rock that has remained stable over the past 541 million years. He goes on to explain that you then need an event, such as rifting, to liberate the helium. ‘The crust splits apart and you have volcanic intrusions coming through and cooking parts of this old rock,’ comments Ballentine. ‘That cooking process releases the helium and, if you’re in the right part of the world, that helium is trapped by the sediments in the same rifting process.’ Working with Helium One, an exploration company, the team realised this process is occurring now in the east African Rift Valley, which crosses nine African countries including Tanzania. ‘We found multiple places in the Tanzanian Rift where you have geothermal pools,’ says Ballentine. ‘In that water it’s bubbling gas and that gas isn’t carbon dioxide, it’s not hydrocarbons, it’s nitrogen with helium contents up to 10%, which is phenomenal.’ Commercial gas deposits, which contain a large amount of carbon dioxide and methane, only contain approximately 0.3% helium. Using seismic profiles of the underlying geology, the team can estimate the total amount of helium stored underground. Estimates suggest over 1.5 billion m3 of helium is in one part of the valley – enough to fill over 1.2 million MRI scanners, according to Ballentine. Only 36,000 MRI scanners are thought to be in use around the world. But he’s reticent to say the helium supply problem is now solved. ‘I don’t think we should be in any way complacent,’ warns Ballentine. ‘On the one hand we’re confident that we understand where and how it’s produced … but we’ve still got to prove that process and find those big deposits.’ ‘This [work] offers a view for future helium recovery that is far different than the past,’ says Lee Sobotka from Washington University, US. Sobotka believes the methodology for finding these deposits is what’s crucial, not necessarily the find itself: ‘This, if confirmed in future “finds”, is a game changer.’ Richard Clarke, a helium resource consultant, echoes Sobotka’s praise. ‘The beauty of this find is that it could be developed to modulate the peaks and troughs of supply and demand, in the way the US Federal Helium Reserve once did,’ Clarke tells Chemistry World. ‘It is not dependent on the co-production of natural gas or carbon dioxide – the carrier gas, nitrogen, has no value and can be rejected to the atmosphere’
