40 Ar‐ 39 Ar Spectra of Alunite from Phreatic Craters in the Muine Volcano, Hokkaido, Japan
2003; Wiley; Volume: 53; Issue: 3 Linguagem: Inglês
10.1111/j.1751-3928.2003.tb00171.x
ISSN1751-3928
Autores Tópico(s)Geomagnetism and Paleomagnetism Studies
ResumoAbstract. 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.
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