2P-51 PDF
Monitoring Volcanic Activity by Helium Isotope Analyses of Geothermal Fluids
Helium isotope ratio (3He/4He) is a powerful tracer for evaluating magmatic contribution in geothermal fluids around volcanoes. Increases in 3He/4He of fumaroles, hot springs and groundwater preceding or accompanying volcanic eruptions have been reported at several volcanoes. However, on-site, real-time 3He/4He monitoring around a volcano to detect a warning sign of imminent eruption is not practical at present. This is because a highly sensitive, magnetic sector mass spectrometer with adequate mass resolution and a high-vacuum line to purify and separate helium from other gaseous species are required to detect 3He, which accounts for only 0.1-10 ppm of total helium. To break through this situation, we are developing a method for helium isotope analysis using “infiTOF”, a small, portable, high-mass resolution time-of-flight mass spectrometer.