Active degassing of mantle-derived fluid: A geochemical study along the Vulture line, southern Apennines (Italy

Abstract

We report the results of a geochemical study of gas emissions along a NE–SW transect in southern Italy in order to test the hypothesis that the region around Monte Vulture is affected by degassing of mantle-derived fluids through a lithospheric discontinuity. We also investigated lavas from the Monte Vulture volcano displaying 3He/4He (up to ~6.0 Ra) and Sr isotopes that are consistent with an origin inmantle that has hadminimal pollution from subducted Adriatic slab. Similar 3He/4He in fluids from around Mt. Vulture indicate that the deep volcanic systemis still degassing. Mantle-derived He occurs in fluids along the length of the Vulture line, reinforcing the hypothesis that it is a deep tectonic discontinuity along which mantle fluids and/or melts advect to the surface. The CO2/3He ratios are highly variable (2.7×108–2.15×1011) in response to processes such as gas dissolution into aquifers, addition of crustal gases and degassing fractionation.