Geochemical variations of air-free crater fumaroles at Mt Etna: New inferences for forecasting shallow volcanic activity

We investigated the gas geochemistry of fumaroles
close to the Voragine crater of Mt Etna that have a
temperature of 90–95 C, are CO2-dominated, and have an
air content as low as <1%. This is the first report of the
monitoring of such air-free fumaroles at the Etnean crater
area—previous studies indicated an air contribution of 70%
or more. The helium and carbon isotopes (Rc/Ra = 6.5 ±
0.4, d13CCO2 = 1.7 ± 0.5%) suggest that the released gas
is directly related to the magmatic degassing. The fumaroles
were sampled 12 times between June 2007 and June 2008,
which revealed an increase in Rc/Ra from 6.1 to 6.9 that can
be related to the increasing volcanic activity at the summit
area of Mt Etna. These fumaroles offer a new tool for
detecting magmatic processes (magma ascent, refilling,
degassing, etc.), and will be useful for volcano surveillance.

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