An estimate of gas emissions and magmatic gas content from Kilauea volcano

Emission rates of CO₂ have been measured at Kilauea volcano, Hawaii, in the east-rift eruptive plume and CO₂ and SO₂ have been measured in the plume from the noneruptive fumaroles in the summit caldera. These data yield an estimate of the loading of Kilauean eruptive gases to the atmosphere and suggest that such estimates may be inferred directly from measured lava volumes. These data, combined with other chemical and geologic data, suggest that magma arrives at the shallow summit reservoir containing (wt.%) 0.32% H₂O, 0.32% CO₂ and 0.09% S. Magma is rapidly degassed of most of its CO₂ in the shallow reservoir before transport to the eruption site. Because this summit degassing yields a magma saturated and in equilibrium with volatile species and because transport of the magma to the eruption site occurs in a zone no shallower than the summit reservoir, we suggest that eruptive gases from Kilauea characteristically should be one of two types: a ‘primary’ gas from fresh magma derived directly from the mantle and a carbon-depleted gas from magma stored in the summit reservoir.