Papers by Toshiro Yamanaka
AGU Fall Meeting Abstracts, Dec 1, 2004
Chemical Geology, Sep 1, 2013
Shallow-water hydrothermal activity, represented by venting of hydrothermal fluid around 200°C, o... more Shallow-water hydrothermal activity, represented by venting of hydrothermal fluid around 200°C, occurs in the Wakamiko submarine crater at 200 m water depth in Kagoshima Bay, southwest Japan. The crater is the center of large eruptions that formed a volcanic caldera, which is semi-submerged at present. The crater is covered with thick volcanic sediments of felsic composition. We studied the distribution and chemical composition of hydrothermal clay minerals that are abundant in the sediment collected by piston coring. We also conducted chemical analysis of pore fluids squeezed from the sediment to understand hydrothermal interactions that resulted in formation of these clay minerals. The PC-2 core (340 cm in length) collected in the vicinity of a high-temperature fluid venting site was characterized by abundant Mg-saponite that is limited to a layer between 270 and 300 centimeters below the seafloor (cmbsf) and montmorillonite throughout the core below 55 cmbsf. Vertical profiles of pore fluid chemistry suggest that saponite formation is related to the interface between the seawater and the hydrothermal component in the sediment layer. Formation temperatures of the montmorillonite were estimated to be 118-163°C, based on oxygen isotope thermometry. Formation of the montmorillonite is attributed to hydrothermal interaction between seawater-dominant pore fluid and volcanic glass. The formation temperature of the saponite was estimated to be~164°C, based on oxygen isotope thermometry. Formation of the saponite is attributed to hydrothermal interaction between seawater-dominant pore fluid and the montmorillonite, which had been formed at a prior stage. The PC-1 core (240 cm in length) collected from a relatively low-temperature fluid shimmering site was characterized by the occurrence of kerolite in the lower section (210-240 cmbsf). Vertical profiles of pore fluid chemistry suggest that the kerolite formation occurred at the interface between seawater and the hydrothermal component of the sediment layer. Formation temperature of the kerolite was estimated to be about~211°C, based on oxygen isotope thermometry. Formation of the kerolite is attributed to precipitation from a fluid that was a mixture of a hydrothermal component and seawater. This study revealed the occurrence of Mg-rich clay minerals, saponite and kerolite, beneath a submarine hydrothermal field that developed within sediment of felsic composition. During hydrothermal interactions that formed these clay minerals, seawater penetrated into the sediment and was an important Mg source. Formation of Mg-rich clay minerals, saponite and kerolite, are controlled by pore fluid chemistry, which varies from a seawaterdominant to hydrothermal-dominant component. Exclusive formation of Mg-rich clay minerals at different sites could be explained by different water-rock ratios of the hydrothermal interactionsaponite formation at low water-rock ratio and kerolite precipitation at high water-rock ratio. Occurrence of Mg-rich clay minerals provides clues to the hydrological structure in sediment-covered hydrothermal systems in an arc volcanic caldera setting.
Japan Geoscience Union, Apr 7, 2014
Journal of Analytical Science and Technology, May 9, 2023
Toxic gases can be emitted when sulfides form compounds with heavy metals; thus, a series of pret... more Toxic gases can be emitted when sulfides form compounds with heavy metals; thus, a series of pretreatments are required prior to the analysis of sulfur isotope ratios to remove unnecessary elements. In addition, it is necessary to verify the effect of sulfur isotope fractionation caused by the plurality of sulfides comprising different sulfide species during the pretreatment process. In this study, H 2 S (gas) was extracted from mixed sulfides comprising pyrite and galena and reacted with mixed acids (i.e., HCl + HI + H 3 PO 2) at 200 °C, in sealed conditions filled with N 2. Subsequently, CdS (s) was precipitated from the reaction with H 2 S (gas) in a trap filled with Cd(CH 3 COO) 2(aq). CdS (s) was then ionized to SO 4 2− (aq) after reacting with H 2 O 2(l) , followed by the addition of BaCl 2(l) to precipitate BaSO 4(s). The sulfur isotope values of the products (barite: av. 5.9‰) were lower than those of the reactants (sulfides: av. 6.9‰); this is attributed to the preferential fractionation of galena with a low isotope ratio when converting sulfide to H 2 S (gas). Therefore, in the pretreatment process for the sulfur isotope analysis of a sample composed of a sulfide mixture, the effect of isotope fractionation between sulfur species should be considered.
Applied and Environmental Microbiology, Oct 1, 2016
It has been suggested that iron is one of the most important energy sources for photosynthesis-in... more It has been suggested that iron is one of the most important energy sources for photosynthesis-independent microbial ecosystems in the ocean crust. Iron-metabolizing chemolithoautotrophs play a key role as primary producers, but little is known about their distribution and diversity and their ecological role as submarine iron-metabolizing chemolithotrophs, particularly the iron oxidizers. In this study, we investigated the microbial communities in several iron-dominated flocculent mats found in deep-sea hydrothermal fields in the Mariana Volcanic Arc and Trough and the Okinawa Trough by culture-independent molecular techniques and X-ray mineralogical analyses. The abundance and composition of the 16S rRNA gene phylotypes demonstrated the ubiquity of zetaproteobacterial phylotypes in iron-dominated mat communities affected by hydrothermal fluid input. Electron microscopy with energy-dispersive X-ray microanalysis and X-ray absorption fine structure (XAFS) analysis revealed the chemical and mineralogical signatures of biogenic Fe-(oxy)hydroxide species and the potential contribution of Zetaproteobacteria to the in situ generation. These results suggest that putative iron-oxidizing chemolithoautotrophs play a significant ecological role in producing iron-dominated flocculent mats and that they are important for iron and carbon cycles in deep-sea low-temperature hydrothermal environments. IMPORTANCE We report novel aspects of microbiology from iron-dominated flocculent mats in various deep-sea environments. In this study, we examined the relationship between Zetaproteobacteria and iron oxides across several hydrothermally influenced sites in the deep sea. We analyzed iron-dominated mats using culture-independent molecular techniques and X-ray mineralogical analyses. The scanning electron microscopy-energy-dispersive X-ray spectroscopy SEM-EDS analysis and X-ray absorption fine structure (XAFS) analysis revealed chemical and mineralogical signatures of biogenic Fe-(oxy)hydroxide species as well as the potential contribution of the zetaproteobacterial population to the in situ production. These key findings provide important information for understanding the mechanisms of both geomicrobiological iron cycling and the formation of iron-dominated mats in deepsea hydrothermal fields.
Japan Geoscience Union, Mar 10, 2017
Proceedings of the International Ocean Discovery Program, Sep 27, 2021
We cored two holes at Site U1550. Hole U1550A is located at 27°15.1602ʹN, 111°30.4163ʹW in a wate... more We cored two holes at Site U1550. Hole U1550A is located at 27°15.1602ʹN, 111°30.4163ʹW in a water depth of 2000.8 m. In Hole U1550A, we used the advanced piston corer (APC), half-length APC (HLAPC), and extended core barrel (XCB) systems to advance from the seafloor to a final depth of 207.0 meters below seafloor (mbsf) with a recovery of 190.9 m (92%). We made formation temperature measurements at several depths with the advanced piston corer temperature (APCT-3) and Sediment Temperature 2 (SET2) tools. In Hole U1550B, located at 27°15.1704ʹN, 111°30.4451ʹW in a water depth of 2001.2 m, we deployed the APC, HLAPC, and XCB systems. Cores penetrated from the seafloor to a final depth of 174.2 mbsf and recovered 160.8 m (92%). Hole U1550B was dedicated to extensive microbial and biogeochemical sampling that required the deployment of perfluorocarbon tracers (PFTs) downhole on all cores to monitor drilling fluid (seawater) contamination. The pace of coring in Hole U1550B was adjusted to accommodate the complex microbial sampling program conducted on the core receiving platform. A total of 72.0 h, or 3.0 days, were spent at Site U1550. Table T1 provides an overview of cores, penetration depths, core recovery, and operations schedule for Site U1550. Contents Summary 6 Background and objectives 7 Operations 9 Lithostratigraphy 16 Igneous petrology and alteration 24 Structural geology 28 Biostratigraphy 29 Paleomagnetism 33 Inorganic geochemistry 37 Organic geochemistry 43 Microbiology 45 Petrophysics 48 References
Journal of Forestry Research, Oct 22, 2019
isotope ratio in beech but not in the other tree species. The results of this study showed that i... more isotope ratio in beech but not in the other tree species. The results of this study showed that it is possible to infer the type and timing of processes relevant to N resorption by analyzing leaf δ 15 N variation during senescence.
PLOS ONE, Jun 15, 2018
The Shinkai Seep Field (SSF) in the southern Mariana forearc discovered in 2010 is the deepest (~... more The Shinkai Seep Field (SSF) in the southern Mariana forearc discovered in 2010 is the deepest (~5,700 m in depth) known serpentinite-hosted ecosystem dominated by a vesicomyid clam, Calyptogena (Abyssogena) mariana. The pioneering study presumed that the animal communities are primary sustained by reducing fluid originated from the serpentinization of mantle peridotite. For understanding the nutrient and energy sources for the SSF community, this study conducted four expeditions to the SSF and collected additional animal samples such as polychaetes and crustaceans as well as sediments, fragments of chimneys developing on fissures of serpentinized peridotite, seeping fluid on the chimneys, and pore water within the chimneys. Geochemical analyses of seeping fluids on the chimneys and pore water of the chimneys revealed significantly high pH (~10) that suggest subseafloor serpentinization controlling fluid chemistry. Stable isotope systematics (carbon, nitrogen, and sulfur) among animals, inorganic molecules, and environmental organic matter suggest that the SSF animal community mostly relies on the chemosynthetic production while some organisms appear to partly benefit from photosynthetic production despite the great depth of SSF.
Chemical Geology
still <0). Orpiment is stable in a wide range of log 10 a of H 2 AsO 4-, in reduced conditions an... more still <0). Orpiment is stable in a wide range of log 10 a of H 2 AsO 4-, in reduced conditions and at high S activity. Barite is stable in wide range of log 10 a of Ba 2+ and precipitates in slightly reduced to slightly oxic conditions.
We studied Holocene paleolimnological changes inferred from multi-proxy data set of CNS elements,... more We studied Holocene paleolimnological changes inferred from multi-proxy data set of CNS elements, biomarkers and microscopic observation of microalgae and cyanobacteria in sediment cores from Rundvågshetta lakes (Maruwanminami-ike and Maruwan o-ike) in the Soya Coast region of East Antarctica, along with sedimentary facies and AMS 14C dating. They are discussed with paleoenvironmental changes, transition ages and glacio-isostatic uplift rates in the Soya Coast region and East Antarctica. Ages of the Maruwanminami-ike core (MwS4C-01, length 147 cm) and Maruwan-oike (Mw4C-01, length 226 cm) ranged from 1,230-5,010 cal BP) and 2,240-5,700 cal BP, respectively. Reservoir effects of the Rundvågshetta lakes were very high which may be due to the influence of dead carbon in glacially eroded marine sediments and base rocks. Average sedimentation rates of Lakes Maruwanminami-ike and Maruwan-oike were 0.389 and 0.649 mm/yr, respectively. Crustal uplift rates of Lakes Maruwanminami-ike and Mar...
Economic and Environmental Geology, 2021
2:1 clay minerals such as smectite incorporating ammonium were extracted to investigate the ammon... more 2:1 clay minerals such as smectite incorporating ammonium were extracted to investigate the ammonium behavior and nitrogen isotope characteristics for two different sediment cores which were collected from shimmering sites on seafloor of the Wakamiko crater, southwestern Japan. Inorganic nitrogen contents in clay fraction were estimated by calibration curve based on consistently decreasing carbon and nitrogen ratio during the treatment to decompose organic materials, after removing inorganic carbon. The results show that the proportions of inorganic nitrogen for total nitrogen in clay fraction of SWS site(Core#1094MR: av. 18.2%) are higher than those in SES site(Core#1093MG: av. 11.5%). Relatively good crystallinity of the former suggests that exchangeable ammonium was transformed to non-exchangeable ammonium during more evolving diagenetic process. Nitrogen isotope variance of clay fraction(SES site: Core#1093MG:-4.4 ~ +0.2 ‰, av.-2.4 ‰; SWS site: Core#1094MR:-0.7 ~ +3.0 ‰, av. +1.5 ‰) during sequential decomposition of exchangeable ammonium suggests that heat flow derived from deep magma led to nitrogen isotope fractionation between dissolved ammonium and ammonia in the fluids involved in the formation of 2:1 clay mineral incorporating ammonium with local temperature variation.
Japan Geoscience Union, 2017
The seafloor hydrothermal fluids occurred in the arc and back-arc systems where are often covered... more The seafloor hydrothermal fluids occurred in the arc and back-arc systems where are often covered with thick sediments contained organic matter are characterized by a high concentration of ammonium which is considered to originate from decomposition of the sedimentary organic matter. Under these conditions, ammonium cation can be fixed in interlayer space of 2:1 clay mineral during their formation associated with hydrothermal mineralization. However, the role of this process with respect to the nitrogen cycle around the Earth’s surface has not been well understood until today. In this study, we measured ammonium concentrations and their isotopic ratios in the venting hydrothermal fluids and clay fraction in the hydrothermal altered sediments obtained from Kagoshima Bay, southern Kyushu, Japan. The submarine volcano, Wakamiko, located in the submerged Aira Caldera, which formed during the late Pleistocene (ca. 29 ka) resulting from the huge eruption of the Ito pyroclastic flow, and a...
Integrated Ocean Drilling Program (IODP) Expedition 302 Arctic Coring Expedition (ACEX) obtained ... more Integrated Ocean Drilling Program (IODP) Expedition 302 Arctic Coring Expedition (ACEX) obtained the first relatively continuous long sediment cores from the Lomonosov Ridge in the central Arctic Ocean in 2004. Preceding microfossil studies indicated the dominance of low salinity surface waters in the early to middle Eocene Arctic basin. The main purpose of this study is to reconstruct paleoceanographic conditions including the extent of saline (seawater) mass presence. To attain this goal we performed geochemical analyses of total sulfur (%TS), total organic carbon (%TOC) and stable sulfur isotopic composition (d34S) on the early to middle Eocene section of the ACEX cores. The %TS were high in all the examined intervals and the sedimentary sulfur occurred mainly as framboidal pyrite, indicating that sufficient sulfate, indicative of seawater, was present in the deep layer of the paleo-Arctic basin and that the pyrite was formed in the sediments under sufficient iron input. The high %TS values with low d34S values also indicate the continuous existence and supply of seawater. The high accumulation of sulfide in Unit 1/6 was due to a significant increase of TOC supply which increased sulfate reduction rates by bacteria. The %TOC-%TS diagram shows excess sulfur content relative to the TOC, suggesting euxinic condition of the bottom water during the studied period. Such an oxygen depleted environment was brought about by salinity stratification and restricted water circulation. The patterns observed in the ACEX data can be comparable with the Mediterranean sapropels. The global d34S of seawater sulfate abruptly increased from + 17 to + 22 per mil in the early to middle Eocene. Previous studies suggested that enhanced pyrite burial caused the isotopic shift during this period. The large pyrite burial in the anoxic Arctic basin could have contributed to the remarkable isotopic event accounting for about 3 per mil of the global increase during this period.
Japan Geoscience Union, 2015
The Center for Academic Resources and Archives, Tohoku University, Department of Earth Science, G... more The Center for Academic Resources and Archives, Tohoku University, Department of Earth Science, Graduate School of Science, Tohoku University, Earthquake Research Institute, The University of Tokyo, Graduate School of Environmental Studies, Nagoya University.,Graduate School of Science and Engineering for Education, University of Toyama, Japan Agency for Marine-Earth Science and Technology, Graduate School of Natural Science and Technology, Okayama University
Guaymas Basin Tectonics and Biosphere, 2021
Introduction 4 Background 7 Site summaries 40 Preliminary scientific assessment 45 References
Guaymas Basin Tectonics and Biosphere, 2021
Two holes were cored at Site U1551. Hole U1551A is located at 27°12.3887′N, 111°13.1943′W in a wa... more Two holes were cored at Site U1551. Hole U1551A is located at 27°12.3887′N, 111°13.1943′W in a water depth of 1844.1 m. In Hole U1551A, we used the advanced piston corer (APC) and halflength APC (HLAPC) systems to advance from the seafloor to a final depth of 120.3 meters below seafloor (mbsf) with a recovery of 122.1 m (102%). We made formation temperature measurements at several depths using the advanced piston corer temperature (APCT-3) tool. Coring was terminated because unconsolidated sand layers prevented us from reaching the deeper drilling objectives. In Hole U1551B, located at 27°12.3832′N, 111°13.1841′W in a water depth of 1843.9 m, we deployed the APC system. Cores penetrated from the seafloor to a final depth of 48.5 mbsf and recovered 50.0 m (103%). Hole U1551B was dedicated to extensive microbial and biogeochemical sampling that required the deployment of perfluorocarbon tracers (PFTs) downhole on all cores to monitor drilling fluid (seawater) contamination. The pace of coring in Hole U1551B was at times adjusted to accommodate the complex microbial sampling program conducted on the core receiv-Contents 1 Summary 6 Background and objectives 7 Operations 8 Lithostratigraphy 14 Structural geology 17 Biostratigraphy 19 Paleomagnetism 22 Inorganic geochemistry 24 Organic geochemistry 28 Microbiology 29 Petrophysics 33 References
Guaymas Basin Tectonics and Biosphere, 2021
Background and objectives 8 Operations 14 Lithostratigraphy 26 Igneous petrology and alteration 3... more Background and objectives 8 Operations 14 Lithostratigraphy 26 Igneous petrology and alteration 37 Structural geology 39 Biostratigraphy 42 Paleomagnetism 50 Inorganic geochemistry 54 Organic geochemistry 62 Microbiology 65 Petrophysics 77 References
Goldschmidt Abstracts, 2020
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Papers by Toshiro Yamanaka
described in Gulf of Mexico.Despite these evidences, biological communities associated with cold seeps or oil seepages were never been described in Brazil. For this reason chemosynthetic ecosystem studies shall be considered as the main goal of this cruise and the
first priority for the dives using Shinkai 6500 in 2nd Leg was the discovery of methane/sulfide seep communities. For comparison etween chemosynthetic vs non-seep ecosystems, it will be investigated both background and chemosynthetic communities across different sites.