Assessing the link between mantle source and sub-volcanic plumbing in the petrology of basalts from the 2001 and 2002/2003 eruptions of Mount Etna, Sicily: Evidence from geochemical and helium isotope data

The 2001 and 2002–2003 flank eruptions of Mt. Etna consisted of near continuous explosive activity and sporadic lava flows. Previous studies have suggested that distinct magmas were simultaneously tapped by fissures in different parts of the volcano, indicating a complex plumbing system. From textural and chemical data it has been suggested that “eccentric” eruptions on the south flank were fed by a deep-seated reservoir that is not related to the central conduit. In contrast, materials erupted above 2600 m and from the northeast flank represent partially degassed, more fractionated magma, typical of that residing within the central vents. A concern is that Etna has entered a new phase of activity, with magma supply from a deep reservoir that is capable of generating recurrent flank eruptions posing significant hazard to populated areas and air travel. We have investigated materials that erupted from different vents during both the 2001 and 2002/3 eruptive episodes by means of petrology, whole-rock chemistry and helium isotopic methods. Here we show from trace element chemistry and the 3He/4He isotope record of melt inclusions in olivine that the mantle source for both magma batches is identical. Furthermore, this magmatic source has not changed over the past 0.5 Ma. As such, our data support the premise that the petrological variability exhibited by products that erupted from different parts of the volcano reflects storage, fractionation and degassing at different levels within the crust.

Research Highlights
► The 2001-03 flank eruptions of Mt. Etna tapped distinct magmas from a complex plumbing system.
► Basalt erupted at different vents during this activity is shown to have an identical mantle source.
► He trapped in olivine melt inclusions establishes that the magma source has not changed over 0.5 Ma.
► Variability in erupted products reflects storage, fractionation and degassing under the volcano.