Antarctic Science

Table of Contents - 2009 - Volume 21, Issue 03  

Cambridge Journals Online - CUP Full-Text Page
Antarctic Science (2009), 21:255-267 Cambridge University Press
Copyright © Antarctic Science Ltd 2009
doi:10.1017/S0954102009001783

Earth Sciences

Noble gas and stable isotope geochemistry of thermal fluids from Deception Island, Antarctica

Minoru Kusakabea1 c1, Keisuke Nagaoa2, Takeshi Ohbaa3, Jung Hun Seoa4, Sung-Hyun Parka1, Jong Ik Leea1 and Byong-Kwon Parka1

a1 Korea Polar Research Institute, KORDI, Songdo Techno Park, Incheon 406-840, Korea
a2 Laboratory for Earthquake Chemistry, University of Tokyo, Tokyo 113-0033, Japan
a3 Volcanic Fluid Research Center, Tokyo Institute of Technology, Tokyo 152-8551, Japan
a4 School of Earth and Environmental Sciences, Seoul National University, Seoul 151-742, Korea
Article author query
kusakabe m [PubMed]  [Google Scholar]
nagao k [PubMed]  [Google Scholar]
ohba t [PubMed]  [Google Scholar]
seo jh [PubMed]  [Google Scholar]
park sh [PubMed]  [Google Scholar]
lee ji [PubMed]  [Google Scholar]
park bk [PubMed]  [Google Scholar]

Abstract

New stable isotope and noble gas data obtained from fumarolic and bubbling gases and hot spring waters sampled from Deception Island, Antarctica, were analysed to constrain the geochemical features of the island's active hydrothermal system and magmatism in the Bransfield back-arc basin. The 3He/4He ratios of the gases (< 9.8 × 10-6), which are slightly lower than typical MORB values, suggest that the Deception Island magma was generated in the mantle wedge of a MORB-type source but the signature was influenced by the addition of radiogenic 4He derived from subducted components in the former Phoenix Plate. The N2/He ratios of fumarolic gas are higher than those of typical mantle-derived gases suggesting that N2 was added during decomposition of sediments in the subducting slab. The δ13C values of -5 to -6‰ for CO2 also indicate degassing from a MORB-type mantle source. The H2/Ar- and SiO2 geothermometers indicate that the temperatures in the hydrothermal system below Deception Island range from ~150°C to ~300°C. The δD and δ18O values measured from fumarolic gas and hot spring waters do not indicate any contribution of magmatic water to the samples. The major ionic components and δD-δ18O-δ34S values indicate that hot spring waters are a mixture of local meteoric water and seawater. Mn and SiO2 in spring waters were enriched relative to seawater reflecting water-rock interaction at depth.

(Received June 13 2008)

(Accepted November 09 2008)

Key wordsBransfield back-arc basin; δD-δ18O-δ13C-δ34S values; fumarolic gas; 3He/4He ratio; hot spring water; hydrothermal geochemistry; source mantle

Correspondence:

c1 currently at Department of Environmental Biology and Chemistry, University of Toyama, 3190 Gofuku, Toyama 930-8555, Japan kusakabe@sci.u-toyama.ac.jp

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