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40 Ar‐ 39 Ar Spectra of Alunite from Phreatic Craters in the Muine Volcano, Hokkaido, Japan
Author(s) -
Watanabe Yasushi
Publication year - 2003
Publication title -
resource geology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.597
H-Index - 43
eISSN - 1751-3928
pISSN - 1344-1698
DOI - 10.1111/j.1751-3928.2003.tb00171.x
Subject(s) - alunite , impact crater , geology , breccia , hydrothermal circulation , volcano , phreatic , phreatic eruption , geochemistry , andesite , k–ar dating , mineralogy , magma , volcanic rock , seismology , astrobiology , groundwater , physics , geotechnical engineering , aquifer
. 40 Ar‐ 39 Ar analyses of two alunite samples from phreatic craters in the Pliocene Muine volcano in southwest Hokkaido, Japan, were carried out. The alunite with 17.4 permil δ 34 S V_CDT value in hydrothermal breccia from the Nagaoyama crater and that with 14.3 permil δ 34 S V_CDT value in silicified andesite from the Konuma crater give total fusion ages of 1.40 ± 0.04 Ma (la uncertainty) and 1.24 ± 0.08 Ma, respectively. However, the spectra of these samples indicate they have been effected by thermal overprinting and/or the existence of excess argon. These preliminary 40 Ar‐ 39 A analyses suggest that the alunite underwent multiple hydrothermal activity by magmatic gas and vapor subsequent to the main hydrothermal activity.