Papers by Hidenori Kumagai
東北大学金属材料研究所附属量子 エネルギー材料科学国際研究センター 共同利用研究経過報告書 平成18年度, Dec 1, 2007
Proceedings of International Symposium on Extremophiles and Their Applications International Symposium on Extremophiles and Their Applications 2005, 2007
Butsuri-tansa(geophysical Exploration), 2023
OCEANS 2022 - Chennai, Feb 21, 2022
Since their discovery in the late 1970s, deep-sea hydrothermal systems have been considered as li... more Since their discovery in the late 1970s, deep-sea hydrothermal systems have been considered as likely candidates for the origin and early evolution of life on Earth. However, while subsequent investigations have revealed a great diversity of modern deep-sea hydrothermal ecosystems, they have done little to shed light on the issues of the origin and early evolution of life, metabolism, cells, or communities. Phylogenetic, biochemical and geochemical clues all seem to point to the early evolution of hydrogenotrophic chemolithoautotrophy such as methanogenesis and sulfur-reduction, thus pinpointing the availability of hydrogen as one of the key elements needed for the early evolution of earthly life. Hydrogen-driven, photosynthesis-independent communities are very rare on the contemporary Earth, however, being unambiguously found only in subsurface environments of H 2-dominated hydrothermal systems. Such systems have been termed hyperthermophilic subsurface lithoautotrophic microbial ecosystems (HyperSLiMEs) (Takai et al., 2004; Nealson et al., 2005). The supply of abundant hydrogen and available inorganic carbon sources to power such communities is most likely coupled to hydrothermal serpentinization of ultramafic rocks and input of magmatic volatiles, both of which are related to specific geological settings. We propose here, on the basis of findings in the modern Earth and implications for the deep-sea hydrothermal systems in the Archean Earth, that ''Ultramafics-Hydrothermalism-Hydrogenesis-HyperSLiME'', a linkage we refer to as Ultra H 3 , provided a suitable habitat for the early microbial ecosystem on the Archean Earth.
Japan Geoscience Union, 2017
Environmental impact assessment is essential to reduce loads of seafloor metal-mining operations ... more Environmental impact assessment is essential to reduce loads of seafloor metal-mining operations to marine environments. Accidental leakage of crushed hydrothermal ores from mining vessel is one of the possible concerns. Metals and metalloids could be released from mineral particulates and damage marine phytoplankton communities, the primary producers at the base of the marine food chain. Our previous study found that high amounts of metals can be released from fine particulates of oxidized hydrothermal ores into seawater, and they inhibit the growth of a marine phytoplankton species. In this study, metal leaching potential of deoxidized (fresh) ores was evaluated using whole round core (WRC) samples collected from Izena Hole, Okinawa Trough, by D/V Chikyu (CK16-05). Also, the toxicity of the leachates on marine phytoplankton was estimated onboard using delayed fluorescence (DF) -based bioassay method which is a useful tool to estimate rapidly and easily toxic metals (Yamagishi et a...
Proceedings of the 13th SEGJ International Symposium, Tokyo, Japan, 12–14 November 2018, 2019
Earth, Planets and Space, 2017
Submarine hydrothermal deposits are one of the promising seafloor mineral resources, because they... more Submarine hydrothermal deposits are one of the promising seafloor mineral resources, because they can store a large amount of metallic minerals as sulfides. The present study focuses on the electrical properties of active modern submarine hydrothermal deposits, in order to provide constraints on the interpretation of electrical structures obtained from marine electromagnetic surveys. Measurements of resistivity and spectral induced polarization (IP) were made using drillcore samples taken from the Iheya North Knoll and the Iheya Minor Ridge in Okinawa Trough, Japan. These hydrothermal sediments are dominantly composed of disseminated sulfides, with minor amounts of massive sulfide rocks. The depth profiles of resistivity and spectral IP properties were successfully revealed to correspond well to layer-by-layer lithological features. Comparison with other physical properties and occurrence of constituent minerals showed that resistivity is essentially sensitive to the connectivity of interstitial fluids, rather than by sulfide and clay content. This suggests that, in active modern submarine hydrothermal systems, not only typical massive sulfide rocks but also high-temperature hydrothermal fluids could be imaged as low-resistivity anomalies in seabed surveys. The spectral IP signature was shown to be sensitive to the presence or absence of sulfide minerals, and total chargeability is positively correlated with sulfide mineral abundance. In addition, the massive sulfide rock exhibits the distinctive IP feature that the phase steadily increases with a decrease of frequency. These results show the effective usage of IP for developing and improving marine IP exploration techniques.
JAMSTEC Report of Research and Development, 2009
Japan Geoscience Union, Mar 14, 2019
Annual Meeting of the Geological Society of Japan, 2009
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Papers by Hidenori Kumagai