Proposing Archaean highly alkaline hydrothermal fluid modelh (2010)

Based on the petrology of 3.5 Ga hydrothermally altered Archean basaltic greenstones, we proposed that highly alkaline, SiO2-rich, Fe-poor hydrothermal fluid (white-smoker) was generated in the Archean CO2-rich subseafloor hydrothermal system. This model can well explain the abiotic formation of voluminous chert and the pH-controlled generation of banded iron formation. Such high-temperature alkaline fluids could have had a significant role not only in the early ocean geochemical processes but also in the early evolution of life.

Shibuya, T., Komiya, T., Nakamura, K., Takai, K. & Maruyama, S.
Highly alkaline, high-temperature hydrothermal fluids in the early Archean ocean. Precambrian Res., (2010) 182:230-238


Fig. (Upper Left)@A relation between CO2 concentration and pH of hydrothermal fluid.
Fig. (Right)@Comparative illustrations for modern and Archean seafloor hydrothermal vent systems. (a) The hot hydrothermal fluid paths in the subseafloor and at the seafloor (chimneys and mounds) are highly enriched with Fe and metal sulfides. The hydrothermal plumes also contain Fe- and metal-sulfide particles but the particles are oxidized by the oxic seawater during the deposition. Biogenic silica precipitation dominates in the seafloor distal from the hydrothermal vents. (b) The hot, vigorous vent fluids spread out from white siliceous chimneys and mounds and the subseafloor fluid paths are cemented by silica veins and dikes. The emissions are not black smokers but clear fluids at the vent orifices attributed to the scarcity of soluble iron and other metal sulfides. Several meters away from the vents, the emissions become white and turbid by precipitation of the oversaturated silica. With increasing distance from the vents, a cloud of reddish brown particles of iron oxyhydroxides dominates hydrothermal plumes. In the vicinity of the hydrothermal vent systems, the silica particles are predominant in the hydrothermal sediments, but the iron oxyhydroxides are abundant with increasing distance from the vent systems.
Fig. (Lower Left)@3.2 Ga banded iron formation, showing alternation of silica (white) and iron oxide (red-black) layers.

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Succeeding in experimental verification of UltraH3 Linkage: "Laboratory experiment of rocks and water at high pressure and temperature reactor" (2009)

At Precambrian Ecosystem Laboratory, we developed a system to simulate deep-sea hydrothermal reaction site at 500‹C, 600atm. Easy to imagine, it was never easy to carry out experiments at high temperature and pressure, however, we kept pushing ourselves until we finally got successful results. After our four yearsf endeavor, we could finally prove that kmatiite, the ancient rock in deep-sea, can produce sufficient amount of hydrogen that is necessary for HyperSLiMEfs metabolism. Yes, we were right to keep trying!

Yoshizaki, M., Shibuya, T., Suzuki, K., Shimizu, K., Nakamura, K., Takai, K., Omori, S., & Maruyama, S.
H2 generation by experimental hydrothermal alteration of komatiitic glass at 300‹C and 500 bars: A preliminary result from on-going experiment. Geochem. J. (Express Letter), (2009) 43:e17-e22.


Fig. (Upper Left) A batch type, high temperature and pressure reaction experiment device. Can be set up to 600‹C, 600atm.
Fig. (Upper Right) Water and rocks are boiled at more than 300‹C, 500atm, in gold containers.
Fig. (Lower Left) Graph showing hydrogen concentration created by komatiite-pure water reaction. 2.4mmol/kg hydrogen was observed at maximum.
Fig. (Lower Right) Comparison of hydrogen from the natural hydrothermal fluid sampled from the various fields and the artificially composed hydrogen composed in our lab.


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Establishing a new record for organism's maximum proliferation temperature and discovering unusually heavy isotopic methane compositions (2009)

We succeeded in breaking the record of upper temperature limits of life and biosphere by isolating a hyperthermophilic methanogen from Kairei Field, in Indian Ocean. This achievement enabled us to know more about the possibilities and conditions of life in the universe. SUGAR (Subsurface Geobiology and Advanced Research Program) and Precambrian Ecosystem Laboratory at JAMSTEC have developed a high temperature & pressure cultivation method (Takai method), and verified cell proliferation at 122‹C. Another evolutionary achievement was to find out methane composition made in the deep-sea condition by microorganisms are actually isotopically heavy, rather than the commonly known fact in Earth Science that often said the opposite. These achievements will surely lead us to further search for origin of methane on Earth and Mars.

Takai, K., Nakamura, K., Toki, T., Tsunogai, U., Miyazaki, M., Miyazaki, J., Hirayama, H., Nakagawa, S., Nunoura, T., & Horikoshi, K. (2008) Cell proliferation at 122‹C and isotopically heavy CH4 production by a hyperthermophilic methanogen under high-pressure cultivation. Proc. Natl. Acad. Sci. USA, 105:10949-10954.

Fig. Electron microscopic photograph of strain 116@of Methanopyrus kandleri (Left), and history of fifty years record on upper temperature limit of life (Middle). Classification scheme of carbon isotope ratio for methane in natural environment, on organic geochemistryfs textbook (Right). We used to believe that all organisms on Earth can be gkilledh at 121‹C, however, this organism proved that our belief was wrong (Middle). The conventional statement, gMethane made by microorganisms is isotopically lighth also begged us to think once more and prove it again (Right).


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Proving the UltraH3 Linkage in Indian Ocean and finding out it is four billion years old, Hadean eon type (2009)

Kairei Field, which exists in the Central Indian Ridge, is an active hydrothermal field where the first HyperSLiME was found and became the clue of proposing the UltraH3 Linkage Hypothesis. However, there have been much heated debates between our Precambrian Ecosystem Laboratory and the rival American scientists. The question was; is it true that the ultramafic is affecting hydrothermalism (hydrothermal activities)? Here, we finally succeeded in showing clear evidence to prove of this hypothesis to be true, and won the debate.

Nakamura, K., Morishita, T., Bach, W., Klein, F., Hara, K., Okino, K., Takai K., & Kumagai, H. (2009) Serpentinized troctolites exposed near the Kairei Hydrothermal Field, Central Indian Ridge: Insights into the origin of the Kairei hydrothermal fluid supporting a unique microbial ecosystem. Earth and Planetary Science Letters 280:128-136.
Kumagai, H., Nakamura, K., Toki, T., Morishita, T., Okino, K., Ishibashi, J., Tsunogai, U., Kawagucci, S., Gamo, T., Shibuya, T., Sawaguchi, T., Neo, N., Joshima, M., Sato, T., & Takai K. (2008) Geological background of the Kairei and Edmond hydrothermal fields along the Central Indian Ridge: Implications of their vent fluidsf distinct chemistry. Geofluids 8:239-251.

Fig. Geological structures of active hydrothermal fields, including the Kairei Field, 2,450m deep, Indian Ocean. Kairei Field exists on the east side of an abysmal hill on ridge axis, with basalts covering all surrounding areas. Thus, the American research groups assumed the hydrothermal activities in Kairei Field to be the ordinary, basalt-related phenomenon. On the contrary, Precambrian Ecosystem Laboratory has been arguing the possible existence of ultramafics which play the major role in hydrogenesis; supported by a fact that the hydrothermal fluid from Kairei Field containing unusually high concentration of hydrogen. In our research in 2006, we discovered numerous ultramafics in Uraniwa Hills, on the east side of Kairei Field. Those ultramafics were NOT the mantle peridotites, but more magma-like ultramafics, which means they are more like komatiites. This function of ultramafics to alter hydrothermal fluid enabled us to explain almost perfectly of the composition of hydrothermal fluid in Kairei Field. Yes, we finally solved this debate. Now, we have proved the existence of UltraH3 Linkagefs analogue that existed in the Hadean eon!


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Proposing the Earth-Life interactive system gUltraH3 Linkage Hypothesish that supported the oldest ecosystem on Earth (2006)

We proposed the existence of "Ultramafics-Hydrothermalism-Hydrogenesis-HyperSLiME (UltraH3) linkage", assuming that the life was born in deep-sea hydrothermal fields and this linkage has spread to play the role of the very first and the sustainable ecosystem in deep-sea. We estimated that the HyperSliME has been existing only at the seabed hydrothermal fields until today where peridotite is exposed and Earth in its primitive condition is still represented. Furthermore, we brought forward a new hypothesis for the first time that in Hadean eon (approximately four billion years ago from today), HyperSLiME seems to have generally existed in komatiite.

Takai, K., Nakamura, K., Suzuki, K., Inagaki, F., Nealson, K. H., & Kumagai, H. (2006) Ultramafics-Hydrothermalism-Hydrogenesis-HyperSLiME (UltraH3) linkage: a key insight into early microbial ecosystem in the Archean deep-sea hydrothermal systems. Paleontological Res. 10:269-282.

Fig.(Left): Models of ocean, Earth's crust, and mantle structure with deep-sea hydrothermalism interactions of four billion years ago and today. On early-stage Earth, mantle was in higher temperature. It was melted to deeper layer than it is today, thus making subsurface thicker. Because of this thicker subsurface, the mantle rocks are not exposed on seabed. In today's condition, subsurface is thinner compared to four billion years ago, and especially in ridges that expands at very low speed, it becomes possible for mantle rocks to be exposed.
Fig.(Right): Images of deep-sea hydrothermalism supported by komatiite, four billion years ago.


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Discovery of the oldest survivor of ecosystem on Earth in the deepest part of the active hydrothermal field in Indian Ocean (2004)

HyperSLiME is the abbreviation for the Hyperthermophilic Subsurface Lithoautotrophic Microbial Ecosystem. We assumed this sunlight-independent ecosystem to be the oldest ecosystem on the Earth. Thus, we investigated several active deep-sea hydrothermal fields in different parts of the world, and finally discovered the HyperSLiME, a direct descendant of the Earth's oldest ecosystem in the active deep-sea hydrothermal field in Central Indian Ridge.

Takai, K., Gamo, T., Tsunogai, U., Nakayama, N., Hirayama, H., Nealson, K. H., & Horikoshi, K. (2004) Geochemical and microbiological evidence for a hydrogen-based, hyperthermophilic subsurface lithoautotrophic microbial ecosystem (HyperSLiME) beneath an active deep-sea hydrothermal field. Extremophiles, 8:269-282.

Photo (Left): An active deep-sea hydrothermal field in Kairei Field; 2,450 m deep in Indian Ocean where HyperSLiME was found. The hot water contained a large amount of hydrogen that supports HyperSLiME.
Photo (Right): An electron microscope image of Methanotorris formicicum, a kind of hyperthermophilic methanogen, which is the primary producer of HyperSLiME.


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