Global emissions of helium‐3 by subaerial volcanism

The emission rate of helium‐3 by subaerial volcanism is re‐evaluated by coupling 3He/CO2 ratios in volcanic gases with new estimate of the flux of carbon dioxide from both arc and non‐arc volcanoes. Steady volcanic plume emissions are computed to supply 240–310 mole 3He/yr, most of which is due to non‐arc volcanoes. Major eruptions represent minor additions on average, whereas diffuse 3He emanations through volcanic piles may be important sources. Although not including this contribution, the above figure is equivalent to 20–40% of the 3He flux from mid‐ocean ridges and, thus, suggests that primordial 3He degassing from subaerial volcanic regions may be larger than expected.