Major and trace element abundances in volcanic glass shards in visible tephras in SG93 and SG06 drillcore samples from Lake Suigetsu,central Japan,obtained using femtosecond LA–ICP–MS |
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| Authors: | Seiji Maruyama Keiji Takemura Takafumi Hirata Tohru Yamashita Tohru Danhara |
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| Institution: | 1. Kyoto Fission-Track Co., Ltd., 44-4 Oomiyaminamitajiri-cho, Kita-ku, Kyoto, 603-8832 Japan;2. Institute for Geothermal Sciences, Graduate School of Science, Kyoto University, Noguchibaru, Beppu, Oita, 874-0903 Japan;3. Geochemical Research Center, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033 Japan |
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| Abstract: | The major and trace element concentrations of volcanic glass shards from visible tephra layers in the SG93 and SG06 cores from Lake Suigetsu, central Japan, were determined by femtosecond laser ablation–inductively coupled plasma–mass spectrometry. The glass-shard analyses, together with the petrographic properties of the tephra samples, allow the Suigetsu tephra layers to be broadly classified into tephras derived from calderas on Kyushu Island, and from Daisen and Sambe volcanoes in the Chugoku district of southwest Japan. The layers correlated with tephras from Kuju caldera and Daisen volcano, and with the younger Sambe tephras, have adakitic elemental features. A Suigetsu tephra sample correlated with the Sambe?Kisuki tephra based on petrographic properties has an elemental pattern similar to that of the Toya tephra from Hokkaido Island, northeast Japan. This match implies that tephras from northeast Japan, as well as Kyushu–Chugoku tephras, are possible correlatives of the Suigetsu tephra layers. Both petrographic properties and major–trace element data of volcanic glass shards are essential for robust tephra correlations, and hierarchical cluster analysis proved additionally useful in statistically evaluating relationships among the tephras. |
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