Evolution of Helium Signatures from Kermadec Arc Under Water Volcanoes

Abstract

Method The isotopic signature R = He/He of primordial helium in hydrothermal fluids and plumes is significantly different from the atmospheric ratio (Ra) and can be identified with high precision in fluid/water samples. During the RV Sonne expedition SO253, we sampled noble gas isotopes from four hydrothermal active volcanoes along the Kermadec arc (SW Pacific) with summit depths between 290 to 1200m below the surface. We extend an existing time series of helium isotopes from the 1990s/2000s in this area [1-4] to observe changes in the underlying plumbing of the hydrothermal systems. The samples were analysed in the lab post-cruise using a combined QMS/SMS [5]. Primordial excess He is reported as δHe, the deviation of R from Ra (in %).