Geological and microbial anomalies in the extinct submarine volcano, Shiribeshi Seamount, in the eastern margin of the Japan Sea |
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Authors: | MARI OGAWA AKIRA TAKEUCHI MUTSUO HATTORI MASAHARU OKANO MISUMI AOKI MAKIKO IMAMURA TOYOKI KSUBOI TOMONORI TSUBOI DAISUKE TANIMOTO and TAKESHI NAGANUMA |
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Institution: | School of Biosphere Sciences, Hiroshima University, 1-4-4 Kagamiyama, Higashi-Hiroshima 739-8528, Japan (email:;), Department of Biology, Faculty of Letters, Keio University, 4-1-1 Hiyoshi, Kohoku-ku, Yokohama 223-8521, Japan,; Faculty of Science, Toyama University, 3190 Gofuku, Toyama 930-8555, Japan,; Deep Sea Research Department, Japan Marine Science and Technology Center, 2-15 Natsushima-cho, Yoskouka 237-0061, Japan,; Marine Science Department, Nippon Marine Enterprise Ltd, 14-1 Ogawa-cho, Yokosuka 238-0004, Japan and; Technical Research Center, The Chugoku Electric Power Co. Inc., 3-9-1 Kagamiyama, Higashi-Hiroshima 739-0046, Japan |
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Abstract: | Abstract The manned submersible Shinkai 2000 investigated yellow patches on the near-summit slope of Shiribeshi Seamount in the Japan Sea. Yellowish patches are often associated with seepage, and the possibility of seepage at Shiribeshi Seamount was tested by the following four lines of observation: (i) high subsurface temperature was measured at a ring-like patch, although no increase in subsurface temperature was observed at other patches; (ii) high gamma ray (γ-ray) intensity from the thorium series was recorded in the patch zone; (iii) the yellowish deposit was composed of calcite, quartz and amorphous iron compound, as seen at the yellowish patches in other seeps and volcanoes; (iv) lipid phosphate, a measure of microbial abundance, in sediments of the ring-like patch was determined, and the recorded microbial abundance was higher inside the patch than outside it. The four lines of observation are explained consistently by postulating that the seepage of warm fluid contained Fe and γ-ray sources. A hydrothermal origin of the yellow patches is not ruled out for the extinct but young (0.9 Ma) arc volcano. |
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Keywords: | amorphous iron gamma ray phospholipid fatty acid seepage Shiribeshi Seamount |
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