Gas Emissions From Volcanoes of the Kuril Island Arc (NW Pacific): Geochemistry and Fluxes

The Kuril Island arc extending for about 1,200 km from Kamchatka Peninsula to Hokkaido Island is a typical active subduction zone with similar to 40 historically active subaerial volcanoes, some of which are persistently degassing. Seven Kurilian volcanoes (Ebeko, Sinarka, Kuntomintar, Chirinkotan, Pallas, Berg, and Kudryavy) on six islands (Paramushir, Shiashkotan, Chirinkotan, Ketoy, Urup, and Iturup) emit into the atmosphere >90% of the total fumarolic gas of the arc. During the field campaigns in 2015-2017 direct sampling of fumaroles, MultiGas measurements of the fumarolic plumes and DOAS remote determinations of the SO2 flux were conducted on these volcanoes. Maximal temperatures of the fumaroles in 2015-2016 were 510 degrees C (Ebeko), 440 degrees C (Sinarka), 260 degrees C (Kuntomintar), 720 degrees C (Pallas), and 820 degrees C (Kudryavy). The total SO2 flux (in metric tons per day) from fumarolic fields of the studied volcanoes was measured as similar to 1,800 +/- 300 t/d, and the CO2 flux is estimated as 1,250 +/- 400 t/d. Geochemical characteristics of the sampled gases include delta D and delta O-18 of fumarolic condensates, delta C-13 of CO2, delta S-34 of the total sulfur, ratios He-3/He-4 and Ar-40/Ar-36, concentrations of the major gas species, and trace elements in the volcanic gas condensates. The mole ratios C/S are generally < 1. All volcanoes of the arc, except the southernmost Mendeleev and Golovnin volcanoes on Kunashir Island, emit gases with He-3/He-4 values of > 7R(A) (where R-A is the atmospheric He-3/He-4). The highest He-3/He-4 ratios of 8.3R(A) were measured in fumaroles of the Pallas volcano (Ketoy Island) in the middle of the arc.