A5033441219- Geology and Paleoclimatology Research
- Isotope Analysis in Ecology
- Geochemistry and Elemental Analysis
- Radioactive contamination and transfer
- Geological and Geochemical Analysis
- Astro and Planetary Science
- Radioactive element chemistry and processing
- Methane Hydrates and Related Phenomena
- Planetary Science and Exploration
- earthquake and tectonic studies
- Nuclear Physics and Applications
- Groundwater and Isotope Geochemistry
- Geochemistry and Geologic Mapping
- Paleontology and Stratigraphy of Fossils
- Analytical chemistry methods development
- High-pressure geophysics and materials
- Clay minerals and soil interactions
- Chemical Synthesis and Characterization
- Advanced ceramic materials synthesis
- Radioactivity and Radon Measurements
- Stellar, planetary, and galactic studies
- Geomagnetism and Paleomagnetism Studies
- Pleistocene-Era Hominins and Archaeology
- Climate change and permafrost
- Aluminum Alloy Microstructure Properties
Japan Agency for Marine-Earth Science and Technology
2015-2024
National Museum of Japanese History
2024
Shikoku (Japan)
2022
The University of Tokyo
2021
Kōchi University
2020
Hokkaido University
2011-2016
Nagoya University
2005-2016
University of Kochi
2015
Meteorite studies suggest that each solar system object has a unique oxygen isotopic composition. Chondrites, the most primitive of meteorites, have been believed to be derived from asteroids, but compositions asteroids themselves not established. We measured, using secondary ion mass spectrometry, rock particles asteroid 25143 Itokawa returned by Hayabusa spacecraft. Compositions are depleted in (16)O relative terrestrial materials and indicate Itokawa, an S-type asteroid, is one sources LL...
Abstract Ferromanganese minerals are widely distributed in subseafloor sediments and on the seafloor oceanic abyssal plains. Assessing their input, formation preservation is important for understanding global marine manganese cycle associated trace elements. However, extent of ferromanganese buried remains unclear. Here we show that abundant (10 8 –10 9 particles cm −3 ) micrometer-scale mineral (Mn-microparticles) found oxic pelagic clays South Pacific Gyre (SPG) from to ~100...
Abstract– High‐precision isotope imaging analyses of reversely zoned melilite crystals in the gehlenitic mantle Type A CAI ON01 Allende carbonaceous chondrite reveal that there are four types oxygen isotopic distributions within single crystals: (1) uniform depletion 16 O (δ 18 ≈ −10‰), (2) enrichment −40‰), (3) variations composition from O‐poor core to O‐rich rim −10‰ −30‰, −20‰ −45‰, and −35‰) with decreasing åkermanite content, (4) ≥ −10‰) along crystal rim. Hibonite, spinel, perovskite...
This paper describes an analytical technique for highly precise and accurate determination of radiogenic stable Sr isotopic composition using double-spike thermal ionization mass spectrometry. Repeated analyses the in-house reference Wako-9999 against NIST SRM-987 gave average δ88Sr +0.32‰, with a long-term 2 SD external reproducibility ±0.02‰ (n = 15). Detailed evaluation isotope fractionation behavior during column chromatographic separation process spec resin showed systematic variation...
The Sr isotopic composition of rivers and groundwaters in the Bengal Plain is a major contributor to global oceanic inventory. stable strontium isotope ratios (δ 88 Sr) provide new tool identify chemical weathering reactions terrestrial water. In this study, we investigated spatiotemporal variations δ samples river water, bedload sediment, groundwater collected from Ganges–Brahmaputra–Meghna drainage basin Bangladesh, which known strongly influence 87 Sr/ 86 ratio seawater. average values...
Although thermal ionization mass spectrometry (TIMS) has been employed for the high-precision analysis of isotope ratios, direct quantification artificial mono-nuclide in environment is difficult by even using dilution (ID) due to coexistence great magnitude natural stable nuclides or isobars. In traditional TIMS and ID-TIMS, a sufficient amount Sr doped on filament required realize adequate ion-beam intensity (i.e., thermally ionized beams). However, background noise (BGN) at m/z 90,...
Abstract Recent studies showed the potential of stable isotopes macronutrient calcium (δ 44/40 Ca) and nonessential strontium 88/86 Sr) as new trophic level indicators in terrestrial vertebrates marine teleost fishes. In this study, we tested whether similar Ca Sr isotopic fractionation trends existed macroinvertebrate‐dominated stream food webs compared to despite their physiological differences. We have determined δ values well 87 Sr/ 86 ratios macroinvertebrates small gobies metal sources...
Abstract Strontium-90 is a major radioactive nuclide released by nuclear accidents and discharge waste. Input of such into earth surface environment causes potential threat long-term internal exposure when taken up organism. Rapid precise measurement 90 Sr in variety environmental sample important to understand the distribution dynamics local after accident assess effect inputs on bodies. However, previous techniques have drawbacks as long times for radiometry high detection limits mass...
Widespread diagenesis of clay minerals occurs in deeply buried marine sediments under high-temperature and high-pressure conditions. For example, the smectite-to-illite (S-I) transformation has been often observed at situ temperatures above ~60°C. However, it remains largely unknown whether such diagenetic processes naturally occur relatively shallow low-temperature and, if so, what consequences are any related chemical reactions to geochemical characteristics deep biosphere. We evaluated...
Abstract Nucleosynthetic isotope anomalies in meteorites are useful for investigating the origin of materials protoplanetary disk and dynamical processes planetary formation. In particular, calcium aluminum-rich inclusions (CAIs) found chondrites key minerals decoding initial conditions solar system before accretion small bodies. this study, we report isotopic analyses three Allende CAIs, fluffy type A (FTA), B, fine-grained spinel rich (FS) inclusions, with a specific emphasis on...
ABSTRACT This study characterized cremated bone to better understand isotope exchanges during burial, using archeological samples. The bones of Jokei, a Buddhist monk (AD 1155–1213), found in an urn from the Jisho-in Temple, Nara Prefecture, Japan, were used for analysis. 14 C dates determined eight Jokei fragments different colors (black, gray, and white). white had highest x-ray diffractometry (XRD) crystallinity index (CI) values (0.89–1.05), Fourier-transform infrared spectroscopy (FTIR)...
Slab-dehydrated fluid is considered to be involved in island arc magmatism. In this study, Li isotope ratios were determined for deep groundwater samples from the non-volcanic forearc region of SW Japan. The contribution slab-dehydrated Philippine Sea Plate (PHS) was investigated Arima area and eastern Kii Peninsula area, corresponding slab depths ~60 km 20-30 km, respectively. high-temperature thermal waters with high salinity called Arima-type clarified have low δ7Li values +1-+3‰....
Thermal ionization mass spectrometry (TIMS) was used to directly quantify an ultratrace of radioactive 90Sr in microliter droplet samples. No chemical separation required removing isobaric interferences on M = 90 such as 90Zr and organic molecules the spectrum because difference evaporation (emission) temperature among molecules, Zr Sr, allows us control emission manner significantly suppress interferences. Direct quantification achieved by improving intercalibration Faraday cups ion...
Abstract We investigated the water-mass structure on Okinawa Trough and Pacific sides of southern Ryukyu Island Arc (Yonaguni, Iriomote, Ishigaki subareas) using Nd isotope composition ( 143 Nd/ 144 ratios; expressed as εNd values) benthic foraminiferal tests in surface sediments, which reflect bottom-water composition, along with hydrogen oxygen compositions (δD δ 18 O values, respectively) physical properties (temperature salinity) seawater. The side has lower values than due to...
Variations in the stable isotopic composition of seawater Sr ( δ 88 Sr) is a new tool for estimating rates global carbonate sedimentation over geologic time, yet isotope compositions major sources and sinks to world oceans are still need further constraint. We report values vent fluids from arc/back-arc seafloor hydrothermal systems western Pacific. In sediment-starved fields Manus Basin, Izu-Bonin Arc, Mariana Trough, end-member each site showed little variation (0.29–0.30‰) were close...
本研究では,同位体分析を行うために単一の試料溶液からSr・Nd・Pbの3元素を分離する湿式化学分離法を開発した.新手法では,元素選択制の高い3種類の抽出樹脂(Sr樹脂・TRU樹脂・Ln樹脂)と陽イオン交換樹脂を用いた4段の小型カラムクロマトグラフィーを採用し,低ブランク・高時間効率のもとにこれら3元素を逐次分離することが可能になった.新手法においてTRU樹脂は,試料溶液から選択的にNdを含む希土類元素を分離するために用いられるが,TRU樹脂のNd保持率はカラムに導入された試料溶液中のFe量に依存して大きく変化することが明らかになった.本研究では,分析試料のタイプに応じて樹脂容量の異なる3種類のカラムを用意し,それぞれの樹脂容量ごとにNd保持率の低下を起こすFe量の上限値を明らかにした.適切なNd分離を行うためには,試料中のFe濃度をあらかじめ測定し,カラムに導入する試料量をコントロールすることが必要となる.新手法によって,単一試料溶液からの3元素逐次分離を低ブランク下で行うことが可能になったため,今後,掘削試料より分離した少量の有孔虫や,岩石薄片よりマイクロドリリングで分離した極...