The observation that many lavas associated with mantle plumes have higher 3He/4He ratios than the upper convecting mantle underpins geophysical, geodynamic and geochemical models of Earth’s deep interior. High 3He/4He ratios are thought to derive from the solar nebula or from solar-wind-irradiated material that became incorporated into Earth during early planetary accretion. Traditionally, this high-3He/4He component has been considered intrinsic to the mantle, having avoided outgassing caused by giant impacts and billions of years of mantle convection1,2,3,4. Here we report the highest magmatic 3He/4He ratio(67.2 ± 1.8 times the atmospheric ratio) yet measured in terrestrial igneous rocks, in olivines from Baffin Island lavas. We argue that the extremely high-3He/4He helium in these lavas might derive from Earth’s core5,6,7,8,9. The viability of the core hypothesis relaxes the long-standing constraint—based on noble gases in lavas associated with mantle plumes globally—that volatile elements from the solar nebula have survived in the mantle since the early stages of accretion.

Documented in a recent article in the journal Nature, researchers have found an abundance of both helium-4 and helium-3 trapped in the volcanic rocks on Canada’s Baffin Island.

As the Earth formed, it is thought that helium-4 and helium-3 flowing on the solar wind became trapped in the minerals of the cooling planet. With heavier elements and minerals sinking to the bottom, this trapped helium was transported to the core, where it would have remained locked in its original forms.

Earth isn’t massive enough to hold on to helium in any significant quantities, though. Any that did not get trapped, or that was subsequently released when the minerals melted in the mantle or due to massive impacts, would have eventually seeped up to the surface and floated off into space. So, helium is relatively rare on Earth, and helium-3 is even more so.
[05 Nov 2023] Highest terrestrial 3He/4He credibly from the core
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