Neon and argon isotope systematics of arc-related volcanism

Neon and argon isotope systematics of arc-related volcanism 

Neon isotope data sources 1 = Patterson et al. 1994, 2 = Kennedy et al. 

1996) and 2.1-3.4 Ra (Vesuvius, Campian Magmatic Provence Tedesco et al. 1998). In both cases, neon seems to originate overwhelmingly from a crustal source yet a significant fraction of the helium (almost 100% in the case of Vulcano) is of mantle derivation. A satisfactory explanation for this apparent He-Ne decoupling has still to emerge. 

The origin of the radiogenic argon is more problematic as both mantle and crustal reservoirs are characterized by high Ar/ Ar ratios. Kennedy et al. (1991) attributed radiogenic °Ar in Honduran geothermal fluids to a crustal source based upon measured 

To date, there is no convincing evidence in the arc-related database that Ar/ Ar ratios deviate significantly from the air value except in cases of mass fractionation (Nagao et al. 1981). 

---