Helium isotopes at Satsuma-Iwojima volcano, Japan.

Abstract

We present isotopic analyses of helium in fluids collected during two field trips at Satsuma-Iwojima and Shin-Iwojima islands in November 1998 and October 2000. These are the first reported helium measurements at Shin-Iwojima. Copper tubes tightly closed by clamps at both ends were used to sample 1) gases from high and low temperature fumaroles in the summit area of Iwodake cone, 2) gases from a fumarole on Shin-Iwojima, 3) gas bubbling from the sea-floor along Shin-Iwojima where an increasing bubbling intensity was observed between 1998 and 2000, 4) waters from Sakamoto and Higashi hot springs. For gas samples, two types of correction for atmospheric contamination are discussed, using either the neon concentration or just the partial pressure of condensable gases at liquid nitrogen temperature; this latter method turned out to be very efficient for many samples. For all gas samples, we found 3 He/ 4 He isotopic ratios between 7.1 and 8.2 times the atmospheric ratio, pointing to a magmatic origin for fumaroles both at Iwodake crater and at Shin-Iwojima island. Our measurements show a decrease of the isotopic ratios at Iwodake with decreasing temperature of the fumarole. Comparing the results of both field trips and those published in previous studies, we suggest this volcanic system is undergoing a recent increase of activity.served both on and off-shore, including high (>800°C) and low temperature fumaroles, hot springs and gas bubbling, which provide a good opportunity to sample and study this volcanic system. In this aim, helium has interesting properties: a gaseous state, inertness, and above all, its isotopes show contrasting ratios in the continental crust (<0

He, Ar, N and C isotope compositions in Tatun Volcanic Group (TVG), Taiwan: Evidence for an important contribution of pelagic carbonates in the magmatic source

“…Helium isotope compositions in subduction zones ranged from 5Ra to 8Ra (Fourre et al, 2002;Marty et al, 1989;Poreda and Craig, 1989;Sano and Marty, 1995;Sano and Williams, 1996). Based on the correlation between 3 He/ 4 He versus 4 He/ 20 Ne (Fig.…”

Effect of the volcanic front migration on helium, nitrogen, argon, and carbon geochemistry of hydrothermal/magmatic fluids from Hokkaido volcanoes, Japan

“…Hot springs from Tokachi and Meakan are not reported because they are affected by crustal contamination and do not represent the magmatic source. For comparison, MORB (black star) and volcanic arc (gray domain) fields are reported (Marty et al, 1989;Sano and Marty, 1995;Sano and Williams, 1996;Fourre et al, 2002;Hilton et al, 2002). The high CO 2 / 3 He and low Rc/Ra for Tarumae fumaroles, in comparison with other fumaroles, is the result of CO 2 and radiogenic 4 He addition.…”

“…CO 2 / 3 He, Rc/Ra, δ 13 C-CO 2 , and δ 15 N data from Tarumae, Tokachi and Meakan volcanoes versus the distance from the crater are shown in Fig. 3a-d. For comparison, the volcanic arc average values for CO 2 / 3 He, Rc/Ra, δ 13 C-CO 2, and δ 15 N are 1.5 ± 1.1 × 10 10 (Sano and Williams, 1996), 4.96Ra to 8.1Ra (Poreda and Craig, 1989;Sano and Marty, 1995;Fourre et al, 2002), −5.5 ± 2.2‰ (Sano and Marty, 1995) and −3‰-+6‰ , respectively.…”

“…Isotope signature of the magma source 5.6.1. Helium magmatic source Helium isotope compositions in subduction zones range between 5Ra to 8Ra (Marty et al, 1989;Poreda and Craig, 1989;Sano and Marty, 1995;Sano and Williams, 1996;Fourre et al, 2002). Based on the correlation between 3 He/ 4 He versus 4 He/ 20 Ne (Fig.…”

Relationship between geological structure and helium isotopes in deep ground-water from the Osaka Basin: Application to deep groundwater hydrology

“…4). One of the procedures for eliminating atmospheric He component is to subtracting the amount of He atm and He ea from the total amount of He (Fourrè et al, 2002;Morikawa et al, 2007). The He atm can be estimate from solubility data.…”