Leakage of magmatic-hydrothermal volatiles from a crater bottom formed by a submarine eruption in 1989 at Teishi Knoll, Japan

详细信息    查看全文

• 作者：Kenji Notsu ; Rumi Sohrin ; Hideki Wada ; Tatsuya Tsuboi ; Hirochika Sumino ; Toshiya Mori ; Urumu Tsunogai ; Pedro A. Hern谩ndez ; Yusuke Suzuki ; Ryoya Ikuta ; Kohei Oorui ; Masato Koyama ; Toshiaki Masuda ; Naoyuki Fujii
• 关键词：Teishi Knoll ; Submarine eruption ; Volcanic gas ; Carbon isotope ratio ; Radioactive carbon isotope (14C) ; Noble gases
• 刊名：Journal of Volcanology and Geothermal Research
• 出版年：15 January, 2014
• 年：2014
• 卷：270
• 期：Complete
• 页码：90-98
• 全文大小：792 K

文摘

A submarine eruption occurred off the Izu Peninsula of Japan on 13 July 1989, forming Teishi Knoll, which has a diameter of 450 m and a height of ca. 10 m above the surrounding 90-100 m deep seafloor. Immediately after the eruption, intense gas release was observed from two vents in the crater. The gas bubbling gradually decreased and apparently ceased in 1990. Given that no survey has been undertaken to examine volatile release from the crater of Teishi Knoll, we collected seawater samples at three different sites from just above the crater bottom on 17 July 2012, in order to detect signs of magmatic volatile release. Seawater samples from the crater bottom have dissolved CH₄ contents and 未¹³C values higher than those of shallower (50-100 m deep) seawater samples. Total inorganic carbon contents from the bottom seawater samples are also higher, and 未¹³C and 螖¹⁴C values lower than those of shallower seawater samples. These data indicate the addition of minor CH₄ and CO₂ of hydrothermal or magmatic origin to the bottom seawater from the crater. ³He/⁴He ratios and total organic carbon data are also consistent with the leakage of magmatic fluids. The most prominent CH₄ and CO₂ anomalies were observed at the site located closest to one of the bubbling gas sites of the 1989 eruption. As such, volcanic gas emissions still continue today at extremely low levels, 23 years after eruption of this monogenetic volcano. The monitoring of ultra-trace amounts of chemical components in seawater is a prospective method to monitor temporal changes in magmatic activity at such submarine volcanoes.