Gas chemistry and isotope compositions at Sulphur Banks, Kīlauea Volcano, Hawai`i

Sulphur Banks, near the summit of Kīlauea Volcano on the Island of Hawai`i, is a thermal area where volcanic gases and steam are discharged. A research well drilled in the 1920s at Sulphur Banks (Allen, 1922) has developed into a “fumarole” that has been used for gas sampling over the years (e.g., Friedman and Reimer, 1987; Hilton and McMurtry, 1997; Shinohara and others, 1999), but has not been subject to periodic monitoring. 
Following the 2018 Kilauea eruption, draining of the lava lake, and cessation of activity at the summit (Neal and others, 2019), Sulphur Banks represents a continuing window into the outgassing dynamics at Kīlauea’s summit. Gas samples were collected at Sulphur Banks periodically since March 2018 in evacuated bottles for chemical compositional analysis and for stable carbon isotopes (13C-CO2), and in copper tubes for noble gas isotope ratio determinations. The goal of this effort is to track temporal variations that relate to volcanic activity at Kilauea. 
Gas concentrations were analyzed at the U.S. Geological Survey (USGS) Volcano Gas Geochemistry Laboratory in Menlo Park, California using a Varian gas chromatograph with a dual-injection system using argon and helium carrier gases (Bergfeld and others, 2014). Analyzed gases include carbon dioxide (CO2), sulfur dioxide (SO2), nitrogen (N2), oxygen (O2), and argon (Ar), hydrogen (H), helium (He), and carbon monoxide (CO). Stable carbon isotope ratios for the carbon dioxide component were measured at the USGS Stable Isotope Laboratory in Reston, Virginia. Gaseous CO2 samples were analyzed on a dual-inlet isotope-ratio mass spectrometer (Coplen, 1973) and normalized (Coplen, 1988) with CO2 reference gases prepared using the method of Coplen and Kendall (1982). Noble gas isotope ratios were measured at the USGS Noble Gas Lab in Denver, Colorado following methods described in Hunt (2015). Temperatures measured during sampling with a K-type thermocouple and digital thermometer did not exceed 95.5°C, the approximate boiling temperature at the site’s elevation (1230 m). 
Gas concentrations are reported as volume percent, normalized to 100%. Stable carbon isotopes are reported in permil (‰) notation relative to standard V-PDB (Vienna Pee Dee Belemnite). Helium isotope data are reported as R/RA (3He/4He ratios in the sample over the ratio in the atmosphere). 
References 
Allen, E. T., 1922. Preliminary tests of the gases at Sulphur Banks, Hawaii, Monthly Bulletin of the Hawaii Volcano Observatory, Vol. X, No. 8. 
Bergfeld, D., Lowenstern, J.B., Hunt, A.G., Shanks, W.C.P., III, and Evans, W.C., 2014. Gas and isotope chemistry of thermal features in Yellowstone National Park, Wyoming (ver. 1.1, September 2014): U.S. Geological Survey Scientific Investigations Report 2011–5012, 28 p. and data files, https://doi.org/10.3133/sir20115012. 
Coplen, T.B., 1973. A double focusing, double collecting mass spectrometer for light stable isotope ratio analysis: International Journal Mass Spectrometry and Ion Physics, v. 11, pp. 37–40. 
Coplen, T. B., 1988.  Normalization of Oxygen and Hydrogen Isotope Data, Chemical Geology (Isotope Geoscience Section), v. 72, pp. 293-297. 
Coplen, T.B., and Kendall, C., 1982. Preparation and stable isotope determination of NBS 16 and NBS 17 carbon dioxide reference samples: Analytical Chemistry, v. 54, pp. 2611–2612. 
Friedman, I., and Reimer, G.M., 1987. Helium at Kilauea Volcano. Part 1: Spatial and Temporal Variations at Sulphur Bank. USGS Prof Paper 1350 (1987), pp. 809-813. 
Hilton, D.R., McMurtry, G.M., and Kreulen, R., 1997. Evidence for extensive degassing of the Hawaiian mantle plume from helium‐carbon relationships at Kilauea volcano. Geophysical Research letters, 24, pp. 3065-3068. 
Hunt, A.G., 2015. Noble Gas Laboratory’s standard operating procedures for the measurement of dissolved gas in water samples: U.S. Geological Survey Techniques and Methods, book 5, chap. A11, 22 p., http://dx.doi.org/10.3133/tm5A11. 
Neal, C., Brantley, S., Antolik, L., Babb, J., Burgess, M., Calles, K., Cappos, M., Chang, J. C., Conway, S., Desmither, L., Dotray, P., Elias, T., Fukunaga, P., Fuke, S., Johanson, I. A., Kamibayashi, K., Kauahikaua, J., Lee, R. L., Pekalib, S., Miklius, A., Million, W., Moniz, C. J., Nadeau, P. A., Okubo, P., Parcheta, C., Patrick, M. R., Shiro, B., Swanson, D. A., Tollett, W., Trusdell, F., Younger, E. F., Zoeller, M. H., Montgomery‐Brown, E. K., Anderson, K. R., Poland, M. P., Ball, J. L., Bard, J., Coombs, M., Dietterich, H. R., Kern, C., Thelen, W. A., Cervelli, P. F., Orr, T., Houghton, B. F., Gansecki, C., Hazlett, R., Lundgren, P., Diefenbach, A. K., Lerner, A. H., Waite, G., Kelly, P., Clor, L., Werner, C., Mulliken, K., Fisher, G., and Damby, D., 2019. The 2018 rift eruption and summit collapse of Kīlauea Volcano. Science, 363(6425), 367– 374. 
Shinohara, H., Martini, M., and Hirabayashi, J., 1999. Preliminary Evaluation of Analytical Results for Samples Collected During Sixth Field Workshop on Volcanic Gases. IAVCEI Commission on the Chemistry of Volcanic Gases Newsletter, No. 14, pp. 2-11. https://www.iavceivolcano.org/about-iavcei/iavcei-commissions/iavcei-commissions-list.html

Tags: carbon-isotopes, gas-chemistry, hawaii-volcanoes-national-park, noble-gas-isotopes, sulphur-banks, usgs-5fad8bbdd34eb413d5df4722, volcano
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