The Earth atmosphere‐like bulk nitrogen isotope composition obtained by stepwise combustion analyses of Ryugu return samples
Ko Hashizume; Akizumi Ishida; Ayano Chiba; Ryuji Okazaki; Kasumi Yogata; Toru Yada; Fumio Kitajima; Hisayoshi Yurimoto; Tomoki Nakamura; Takaaki Noguchi; Hikaru Yabuta; Hiroshi Naraoka; Yoshinori Takano; Kanako Sakamoto; Shogo Tachibana; Masahiro Nishimura; Aiko Nakato; Akiko Miyazaki; Masanao Abe; Tatsuaki Okada; Tomohiro Usui; Makoto Yoshikawa; Takanao Saiki; Fuyuto Terui; Satoshi Tanaka; Satoru Nakazawa; Sei‐ichiro Watanabe; Yuichi Tsuda; Michael W. Broadley; Henner Busemann, Abstract

The nitrogen isotope compositions of two samples returned from the asteroid Ryugu were determined using a stepwise combustion method, along with Ivuna (CI) and Y‐980115, a CI‐like Antarctic meteorite, as references. The two Ryugu samples A0105‐07 and C0106‐07 showed bulk δ¹⁵N values of +1.7 ± 0.5‰ and +0.2 ± 0.6‰, respectively, significantly lower than Ivuna with +36.4 ± 0.4‰, but close to Y‐980115 with +4.0 ± 0.3‰. The Ryugu samples are further characterized by C/N and ³⁶Ar/N ratios up to 3.4× and 4.9× the value of Ivuna, respectively. Among all Ryugu samples and CI chondrites, a positive correlation was observed between nitrogen concentrations and δ¹⁵N values, with samples with lower nitrogen concentrations exhibiting lower δ¹⁵N. This trend is explained by a two‐component mixing model. One component is present at a constant abundance among all CI‐related samples, with a δ¹⁵N value around 0‰ or lower. The other varies in abundance between different samples, and exhibits a δ¹⁵N value of +56 ± 4‰. The first ¹⁵N‐poor endmember is seemingly tightly incorporated into a carbonaceous host phase, whereas the ¹⁵N‐rich endmember can be mobilized and decoupled from carbon, potentially because it is in the form of ammonia. Asteroid materials with volatile compositions that are similar to those reported here for the Ryugu samples are attractive candidates for the volatile sources among Earth's building blocks., Wiley
Meteoritics & Planetary Science, 2024年04月30日

Microscale Simultaneous Measurement of Carbon and Nitrogen Isotopes on Natural Diamond
Akizumi Ishida; Kouki Kitajima; Ko Hashizume; Michael J. J. Spicuzza; Alexander Zaitsev; Daniel J. J. Schulze; John W. W. Valley, Simultaneous analysis of carbon and nitrogen isotope ratios by SIMS was applied for the first-time to a natural diamond from the Kelsey Lake kimberlite, State Line Distinct, Colorado (UWD-1). This in situ procedure is faster, reduces sample size for analysis, and measures both isotope ratios from a single similar to 10 mu m diameter pit, a critical advantage for zoned diamonds. The carbon isotope ratio (expressed as delta C-13(VPDB)) of the bulk UWD-1 crystal, determined by the conventional combustion method in the present study, is -5.9 parts per thousand +/- 0.2 parts per thousand (VPDB, 2s). Nitrogen mass fraction ([N]) and isotope ratio (expressed as delta N-15(Air)) were determined by stepwise combustion and gas-source mass-spectrometry, resulting in 553 +/- 64 mu g g(-1) and -6.7 parts per thousand +/- 1.1 parts per thousand (Air, 2s), respectively. Secondary ions of C-12(2)-, (CC-)-C-12-C-13, (CN-)-C-12-N-14, and (CN-)-C-12-N-15 were simultaneously measured by SIMS using three Faraday cups and one electron multiplier. The spot-to-spot reproducibility of delta C-13 and delta N-15 values for the UWD-1 (178 spots on sixteen chips, 10 mu m spots), were 0.3 parts per thousand and 1.6 parts per thousand, respectively (2s). While (CN-)-C-12-N-14/C-12(2)- ratios, which are an indicator for [N], varied up to 12% among these sixteen chips, such variation did not correlate with either delta C-13 or delta N-15 values. We propose that UWD-1 is a suitable reference sample for microscale in situ analysis of delta C-13 and delta N-15 values in diamond samples., WILEY
GEOSTANDARDS AND GEOANALYTICAL RESEARCH, 2023年04月

Noble gases and nitrogen in samples of asteroid Ryugu record its volatile sources and recent surface evolution
Ryuji Okazaki; Bernard Marty; Henner Busemann; Ko Hashizume; Jamie D. Gilmour; Alex Meshik; Toru Yada; Fumio Kitajima; Michael Ward Broadley; David Byrne; Evelyn Füri; My E.I. Riebe; Daniela Krietsch; Colin Maden; Akizumi Ishida; Patricia Clay; Sarah A. Crowther; Lydia Fawcett; Thomas Lawton; Olga Pravdivseva; Yayoi N. Miura; Jisun Park; Ken-ichi Bajo; Yoshinori Takano; Keita Yamada; Shinsuke Kawagucci; Yohei Matsui; Mizuki Yamamoto; Kevin Righter; Saburo Sakai; Naoyoshi Iwata; Naoki Shirai; Shun Sekimoto; Makoto Inagaki; Mitsuru Ebihara; Reika Yokochi; Kunihiko Nishiizumi; Keisuke Nagao; Jong Ik Lee; Akihiro Kano; Marc W. Caffee; Ryu Uemura; Tomoki Nakamura; Hiroshi Naraoka; Takaaki Noguchi; Hikaru Yabuta; Hisayoshi Yurimoto; Shogo Tachibana; Hirotaka Sawada; Kanako Sakamoto; Masanao Abe; Masahiko Arakawa; Atsushi Fujii; Masahiko Hayakawa; Naoyuki Hirata; Naru Hirata; Rie Honda; Chikatoshi Honda; Satoshi Hosoda; Yu-ichi Iijima; Hitoshi Ikeda; Masateru Ishiguro; Yoshiaki Ishihara; Takahiro Iwata; Kosuke Kawahara; Shota Kikuchi; Kohei Kitazato; Koji Matsumoto; Moe Matsuoka; Tatsuhiro Michikami; Yuya Mimasu; Akira Miura; Tomokatsu Morota; Satoru Nakazawa; Noriyuki Namiki; Hirotomo Noda; Rina Noguchi; Naoko Ogawa; Kazunori Ogawa; Tatsuaki Okada; Chisato Okamoto; Go Ono; Masanobu Ozaki; Takanao Saiki; Naoya Sakatani; Hiroki Senshu; Yuri Shimaki; Kei Shirai; Seiji Sugita; Yuto Takei; Hiroshi Takeuchi; Satoshi Tanaka; Eri Tatsumi; Fuyuto Terui; Ryudo Tsukizaki; Koji Wada; Manabu Yamada; Tetsuya Yamada; Yukio Yamamoto; Hajime Yano; Yasuhiro Yokota; Keisuke Yoshihara; Makoto Yoshikawa; Kent Yoshikawa; Shizuho Furuya; Kentaro Hatakeda; Tasuku Hayashi; Yuya Hitomi; Kazuya Kumagai; Akiko Miyazaki; Aiko Nakato; Masahiro Nishimura; Hiromichi Soejima; Ayako Iwamae; Daiki Yamamoto; Kasumi Yogata; Miwa Yoshitake; Ryota Fukai; Tomohiro Usui; Harold C. Connolly Jr.; Dante Lauretta; Sei-ichiro Watanabe; and Yuichi Tsuda., The near-Earth carbonaceous asteroid (162173) Ryugu is expected to contain volatile chemical species that could provide information on the origin of Earth's volatiles. Samples of Ryugu were retrieved by the Hayabusa2 spacecraft. We measured noble gas and nitrogen isotopes in Ryugu samples and found that they are dominated by presolar and primordial components, incorporated during Solar System formation. Noble gas concentrations are higher than those in Ivuna-type carbonaceous (CI) chondrite meteorites. Several host phases of isotopically distinct nitrogen have different abundances among the samples. Our measurements support a close relationship between Ryugu and CI chondrites. Noble gases produced by galactic cosmic rays, indicating a ~5 million year exposure, and from implanted solar wind record the recent irradiation history of Ryugu after it migrated to its current orbit., AAAS
Science, 2023年02月24日, ［査読有り］

Self-shielding effects on isotope fractionation
Hashizume K., Springer-Verlag, Berlin Heidelberg
Encyclopedia of Astrobiology, 2023年02月18日, ［査読有り］, ［招待有り］

Nitrogen isotopes.
Hashizume K., Springer-Verlag, Berlin Heidelberg
Encyclopedia of Astrobiology, 2023年02月18日, ［査読有り］, ［招待有り］

The noble gas and nitrogen relationship between Ryugu and carbonaceous chondrites
M.W. Broadley; D.J. Byrne; E. Füri; L. Zimmermann; B. Marty; R. Okazaki; T. Yada; F. Kitajima; S. Tachibana; K. Yogata; K. Sakamoto; H. Yurimoto; T. Nakamura; T. Noguchi; H. Naraoka; H. Yabuta; S. Watanabe; Y. Tsuda; M. Nishimura; A. Nakato; A. Miyazaki; M. Abe; T. Okada; T. Usui; M. Yoshikawa; T. Saiki; S. Tanaka; F. Terui; S. Nakazawa; H. Busemann; K. Hashizume; J.D. Gilmour; A. Meshik; M.E.I. Riebe; D. Krietsch; C. Maden; A. Ishida; P. Clay; S.A. Crowther; L. Fawcett; T. Lawton; O. Pravdivtseva; Y.N. Miura; J. Park; K. Bajo; Y. Takano; K. Yamada; S. Kawagucci; Y. Matsui; M. Yamamoto; K. Righter; S. Sakai; N. Iwata; N. Shirai; S. Sekimoto; M. Inagaki; M. Ebihara; R. Yokochi; K. Nishiizumi; K. Nagao; J.I Lee; A. Kano; M.W. Caffee; R. Uemura, Elsevier
Geochimica et Cosmochimica Acta, 2023年01月26日, ［査読有り］

Oxygen isotopes.
Hashizume K., Springer-Verlag, Berlin Heidelberg
Encyclopedia of Astrobiology, 2022年12月06日, ［査読有り］, ［招待有り］

First asteroid gas sample delivered by the Hayabusa2 mission: A treasure box from Ryugu
Ryuji Okazaki; Yayoi N. Miura; Yoshinori Takano; Hirotaka Sawada; Kanako Sakamoto; Toru Yada; Keita Yamada; Shinsuke Kawagucci; Yohei Matsui; Ko Hashizume; Akizumi Ishida; Michael W. Broadley; Bernard Marty; David Byrne; Evelyn Füri; Alex Meshik; Olga Pravdivtseva; Henner Busemann; My E.I. Riebe; Jamie Gilmour; Jisun Park; Ken-ichi Bajo; Kevin Righter; Saburo Sakai; Shun Sekimoto; Fumio Kitajima; Sarah A. Crowther; Naoyoshi Iwata; Naoki Shirai; Mitsuru Ebihara; Reika Yokochi; Kunihiko Nishiizumi; Keisuke Nagao; Jong Ik Lee; Patricia Clay; Akihiro Kano; Marc W. Caffee; Ryu Uemura; Makoto Inagaki; Daniela Krietsch; Colin Maden; Mizuki Yamamoto; Lydia Fawcett; Thomas Lawton; Tomoki Nakamura; Hiroshi Naraoka; Takaaki Noguchi; Hikaru Yabuta; Hisayoshi Yurimoto; Yuichi Tsuda; Sei-ichiro Watanabe; Masanao Abe; Masahiko Arakawa; Atsushi Fujii; Masahiko Hayakawa; Naoyuki Hirata; Naru Hirata; Rie Honda; Chikatoshi Honda; Satoshi Hosoda; Yu-ichi Iijima; Hitoshi Ikeda; Masateru Ishiguro; Yoshiaki Ishihara; Takahiro Iwata; Kosuke Kawahara; Shota Kikuchi; Kohei Kitazato; Koji Matsumoto; Moe Matsuoka; Tatsuhiro Michikami; Yuya Mimasu; Akira Miura; Tomokatsu Morota; Satoru Nakazawa; Noriyuki Namiki; Hirotomo Noda; Rina Noguchi; Naoko Ogawa; Kazunori Ogawa; Tatsuaki Okada; Chisato Okamoto; Go Ono; Masanobu Ozaki; Takanao Saiki; Naoya Sakatani; Hiroki Senshu; Yuri Shimaki; Kei Shirai; Seiji Sugita; Yuto Takei; Hiroshi Takeuchi; Satoshi Tanaka; Eri Tatsumi; Fuyuto Terui; Ryudo Tsukizaki; Koji Wada; Manabu Yamada; Tetsuya Yamada; Yukio Yamamoto; Hajime Yano; Yasuhiro Yokota; Keisuke Yoshihara; Makoto Yoshikawa; Kent Yoshikawa; Shizuho Furuya; Kentaro Hatakeda; Tasuku Hayashi; Yuya Hitomi; Kazuya Kumagai; Akiko Miyazaki; Aiko Nakato; Masahiro Nishimura; Hiromichi Soejima; Ayako Iwamae; Daiki Yamamoto; Kasumi Yogata; Miwa Yoshitake; Ryota Fukai; Tomohiro Usui; Trevor Ireland; Harold C. Connolly Jr.; Dante S. Lauretta; and Shogo Tachibana, The Hayabusa2 spacecraft returned to Earth from the asteroid 162173 Ryugu on 6 December 2020. One day after the recovery, the gas species retained in the sample container were extracted and measured on-site and stored in gas collection bottles. The container gas consists of helium and neon with an extraterrestrial 3He/4He and 20Ne/22Ne ratios, along with some contaminant terrestrial atmospheric gases. A mixture of solar and Earth’s atmospheric gas is the best explanation for the container gas composition. Fragmentation of Ryugu grains within the sample container is discussed on the basis of the estimated amount of indigenous He and the size distribution of the recovered Ryugu grains. This is the first successful return of gas species from a near-Earth asteroid., AAAS
Science Advances, 2022年11月16日, ［査読有り］

Heat-Induced Dolomitization of Amorphous Calcium Magnesium Carbonate in a CO2‑Filled Closed System
Shingo Sugawara; Wataru Fujiya; Hiroyuki Kagi; Akira Yamaguchi; and Ko Hashizume, ラスト(シニア)オーサー, ACS Publications
ACS Omega, 2022年11月09日, ［査読有り］

D-depleted water isotopic measurement with a miniaturized cavity ring-down spectrometer aiming for exploration of lunar water
Murayama; J.; Yamanaka; C.; Hashizume; K. and Takigami; S., Elsevier
Sensors and Actuators A: Physical, 2022年03月05日, ［査読有り］

Hydrothermal Activities on C-Complex Asteroids Induced by Radioactivity
Wataru Fujiya; Hisato Higashi; Yuki Hibiya; Shingo Sugawara; Akira Yamaguchi; Makoto Kimura; Ko Hashizume, ラスト(シニア)オーサー, Abstract

C-complex asteroids, rich in carbonaceous materials, are potential sources of Earth’s volatile inventories. They are spectrally dark resembling primitive carbonaceous meteorites, and thus, C-complex asteroids are thought to be potential parent bodies of carbonaceous meteorites. However, the substantial number of C-complex asteroids exhibits surface spectra with weaker hydroxyl absorption than water-rich carbonaceous meteorites. Rather, they best correspond to meteorites showing evidence for dehydration, commonly attributed to impact heating. Here, we report an old radiometric age of 4564.7 million years ago for Ca carbonates from the Jbilet Winselwan meteorite analogous to dehydrated C-complex asteroids. The carbonates are enclosed by a high-temperature polymorph of Ca sulfates, suggesting thermal metamorphism at >300°C subsequently after aqueous alteration. This old age indicates the early onset of aqueous alteration and subsequent thermal metamorphism driven by the decay of short-lived radionuclides rather than impact heating. The breakup of original asteroids internally heated by radioactivity should result in asteroid families predominantly consisting of thermally metamorphosed materials. This explains the common occurrence of dehydrated C-complex asteroids., American Astronomical Society
The Astrophysical Journal Letters, 2022年01月01日

水を始めとした月の軽元素資源
橋爪 光, 月サイエンスブック編集委員会
月サイエンスブック 第一部, 2021年08月05日, ［査読有り］

残された課題
長岡 央、川村 太一、大竹 真紀子、橋爪 光, 月サイエンスブック編集委員会
月サイエンスブック 第一部, 2021年08月05日, ［査読有り］

Carbon isotopic evolution of aqueous fluids in CM chondrites: Clues from in-situ isotope analyses within calcite grains in Yamato-791198.
Fujiya W; Aoki Y; Ushikubo T; Hashizume K; Yamaguchi T, We report the variability in carbon and oxygen isotopic compositions, chemical compositions, and cathodoluminescence intensities within calcite grains in the Yamato-791198 CM chondrite measured by secondary ion mass spectrometry. To understand the change in carbon isotopic compositions during calcite formation, the carbon isotope-analyses were performed on a series of crystal growth bands of each calcite grain. The crystal growth of calcite grains was inferred from comprehensive analyses of oxygen isotopes, chemical compositions, and cathodoluminescence characteristics. The observed δ18O variations within individual grains are as large as 13‰. The oxygen-isotope data plot on a single straight line with a slope of 0.61 ± 0.06 (2σ) in an oxygen three-isotope diagram. This slope steeper than that of the terrestrial fractionation line indicates that the oxygen isotopic compositions of aqueous fluids evolved from higher δ18O and Δ17O to lower δ18O and Δ17O compositions due to the oxygen-isotope exchange between water and anhydrous silicates in the parent body. Thus, calcite crystals grew from higher Δ17O to lower Δ17O areas. The crystal growth inferred from oxygen isotopic compositions is corroborated by the morphology and cathodoluminescence characteristics of the calcite grains. The minor element concentrations of the calcite grains did not increase/decrease monotonically during calcite formation. The δ13C variations within individual grains are no more than 4‰ except for one grain. The intra-grain δ13C variations observed here are much smaller than inter-grain δ13C variations of ∼80‰ previously reported. These observations indicate that the carbon isotopic compositions of dissolved carbon species did not change during calcite formation and that they were locally heterogeneous which reflects variable proportions of carbon reservoirs with different isotopic compositions., Elsevier
Geochimica et Cosmochimica Acta, 2020年04月, ［査読有り］

月面に供給される揮発性物質とその起源
橋爪 光, 日本惑星科学会
日本惑星科学会誌・遊星人, 2019年04月, ［査読有り］

月内部に存在する揮発性成分
鹿山 雅裕; 橋爪 光, 日本惑星科学会
日本惑星科学会誌・遊星人, 2019年04月, ［査読有り］

Microbial nitrogen cycle enhanced by continental input recorded in the Gunflint Formation
Ishida A.; Hashizume K.; Kakegawa T., Nitrogen isotope compositions (delta N-15 values) of kerogen in the sedimentary rocks from the 1878 Ma Gunflint Formation were analysed to understand the relationships among microbial activities, ocean chemistry, and tectonic evolution in the Animikie Basin. In the present study, the stepwise combustion analysis, performed on 13 kerogen samples, indicates that the delta N-15 values of kerogen can be sub-divided into two fractions with discrete values depending on the combustion temperatures: a lower-temperature fraction (from 500 to 575 degrees C), and a higher- temperature fraction (higher than 575 degrees C). A positive correlation was observed between the delta N-15 values of the lower-temperature fractions and Pr/Sm ratios, which represent contributions from the continental input. In contrast, no correlation was observed between the delta N-15 values of the higher-temperature fractions and the Pr/Sm ratios. This relationship between the delta N-15 values and the continental inputs is explained by the isotopic fractionation effects of the biological nitrogen cycle associated with the enhanced microbial activity, triggered by the active tectonic settings in the Animikie basin., EUROPEAN ASSOC GEOCHEMISTRY
Geochemical Perspectives Letters, 2017年, ［査読有り］

A biological switch at the ocean surface as a cause of laminations in a Precambrian iron formation
K. Hashizume; D. L. Pinti; B. Orberger; C. Cloquet; M. Jayananda; H. Soyama, Banded iron formations (BIFs) exhibit alternating silica- and iron-rich laminae, potentially reflecting the dynamics of the paleo-environments in which they were formed, although the exact mechanism remains unclear. Here the formation of a 2.7-2.9 Ga BIF from Dharwar Craton, India, is deciphered by analyzing the inter-band variations of the redox-sensitive isotope biomarkers, N-15/N-14 and Fe-56/Fe-54. Organic matter with delta N-15 values as high as +12.0 +/- 0.8 parts per thousand appears to be trapped in silica. Iron oxides exhibit systematically positive delta Fe-56 values, ranging between +0.80 +/- 0.05 parts per thousand and +1.67 +/- 0.02 parts per thousand. Compared to the iron-rich bands, silica-rich bands, which show higher delta Fe-56 values, exhibit an order of magnitude higher concentrations of N-15-rich organic nitrogen, normalized by the abundances of its host silica. The presence of N-15-rich organic matter may imply the emergence of a modern-like biological nitrogen cycle that requires the formation of oxidized nitrogen compounds. The higher concentration of N-15-rich organic nitrogen for the silica-rich bands possibly suggests that the photosynthetic activity was higher during the formation periods of these bands. The heavier iron isotope compositions of the silica-rich bands cannot be explained alone by iron oxidation through probable pathways. The relative Fe-56-enrichment in silica rich bands is explained here by the progressive dissolution of iron oxides to the ocean, through iron reduction by N-15-rich organic matter actively produced at the ocean surface. The formation of iron-rich bands possibly corresponds to periods of reduced biological productivity, when precipitated iron was not effectively dissolved to the ocean. The observed shift in the organic concentration between Fe- and Si-rich bands could be the switch that triggered the BIF laminations. This shift could conceivably represent periodic fluctuations in the oxygen generation, which possibly occurred over periods of millennia, at the dawn of the Great Oxidation Event. (C) 2016 Elsevier B.V. All rights reserved., ELSEVIER SCIENCE BV
EARTH AND PLANETARY SCIENCE LETTERS, 2016年07月, ［査読有り］

Stepwise combustion analyses of distinct nitrogen isotopic compositions on Paleoproterozoic organic matter
Akizumi Ishida; Ko Hashizume; Takeshi Kakegawa, Nitrogen isotopic analyses were conducted on two kerogenous samples from the Gunflint Formation (ca. 1.9 Ga) using the stepwise combustion technique to evaluate a potential analytical problem for the carbonaceous samples and to assess if this method is appropriate for the analysis of ancient rocks. Two discriminated (delta N-15 plateaux are identified for each sample with mean values of +5.0 parts per thousand and +7.3 parts per thousand for sample 0708, and +6.1 parts per thousand and +5.2 parts per thousand for sample 0704, respectively. The direction of the delta N-15 shift is opposite in each sample. This characteristic excludes the possibility of analytical artifact as the source of isotope fractionation and metamorphism isotope fractionation. The two delta N-15 plateaux observed for each of the samples are characterized by different activation energies for the co-released carbon. These results suggest that similarly aged sedimentary rocks may contain at least two types of organic matter that record different source information for delta N-15., GEOCHEMICAL SOC JAPAN
GEOCHEMICAL JOURNAL, 2012年, ［査読有り］

Oxygen isotopic compositions of asteroidal materials returned from Itokawa by the Hayabusa mission.
Hisayoshi Yurimoto; Ken-ichi Abe; Masanao Abe; Mitsuru Ebihara; Akio Fujimura; Minako Hashiguchi; Ko Hashizume; Trevor R Ireland; Shoichi Itoh; Juri Katayama; Chizu Kato; Junichiro Kawaguchi; Noriyuki Kawasaki; Fumio Kitajima; Sachio Kobayashi; Tatsuji Meike; Toshifumi Mukai; Keisuke Nagao; Tomoki Nakamura; Hiroshi Naraoka; Takaaki Noguchi; Ryuji Okazaki; Changkun Park; Naoya Sakamoto; Yusuke Seto; Masashi Takei; Akira Tsuchiyama; Masayuki Uesugi; Shigeyuki Wakaki; Toru Yada; Kosuke Yamamoto; Makoto Yoshikawa; Michael E Zolensky, 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 oxygen isotopic compositions of asteroids themselves have not been established. We measured, using secondary ion mass spectrometry, oxygen isotopic compositions of rock particles from asteroid 25143 Itokawa returned by the Hayabusa spacecraft. Compositions of the particles are depleted in (16)O relative to terrestrial materials and indicate that Itokawa, an S-type asteroid, is one of the sources of the LL or L group of equilibrated ordinary chondrites. This is a direct oxygen-isotope link between chondrites and their parent asteroid.
Science (New York, N.Y.), 2011年08月26日, ［査読有り］

Extreme oxygen isotope anomaly with a solar origin detected in meteoritic organics
Ko Hashizume; Naoto Takahata; Hiroshi Naraoka; Yuji Sano, Materials formed in the early Solar System generally exhibit a characteristic oxygen isotopic signature known as the non-mass-dependent oxygen isotope anomaly(1,2), the origins of which are unclear. The anomalies are thought to reflect isotopic fractionation in the chemical reaction that first formed solid material from the gaseous medium, but the proposed mechanism and environment of formation are the subject of debate(3-6). Here we analyse micrometre-sized grains of acid-insoluble organic matter from a carbonaceous chondritic meteorite recovered in Antarctica. We find that the organic matter has the highest (18)O/(16)O and (17)O/(16)O ratios known in planetary material, except for pre-solar grains(7). The oxygen ratios are enhanced by up to 53 +/- 11% and the (13)C/(12)C values by 29 +/- 5% relative to terrestrial values. We suggest that the coherent enrichments of (17)O, (18)O and (13)C in the organic matter can best be explained by its formation being due to the photodissociation of carbon monoxides in a gas medium at temperatures of about 60 K or higher. These conditions are equivalent to those expected at the envelope of the proto-solar nebula, and we suggest the organic matter formed there., NATURE PUBLISHING GROUP
NATURE GEOSCIENCE, 2011年03月, ［査読有り］

Early life record from nitrogen isotopes
Daniele L. Pinti; Ko Hashizume, Biological activity fractionates the nitrogen isotopes in a peculiar way, making them a reliable biosignature and an accurate paleoenvironmental proxy. Nitrogen has been ignored for long time, being extremely fragile compared to the more stable graphitic forms of C
however, N has an advantage over other isotopic systems such as those of C and S. The dominant source of N at the surface of the Earth, that is, the atmospheric triple-bonded N2, is so stable that only a very limited number of metabolic processes can bridge the abiotic and biotic world. Therefore we can draw relatively simple flux models for N. In this contribution, we review the N isotopic record in the last 4 billions years. Large isotopic shifts recorded by nitrogen are related to specific metabolic changes as a direct response to major environmental stress such as the rise of oxygen in the atmosphere and the evolution of nitrifiers and denitrifiers in the ocean. These isotopic changes are not unique but well correlated with those of C and Fe, indicating that nitrogen can be successfully used for modeling the interplay of changing microbial metabolisms over Earth's history and relate them to precise environmental changes. © 2011 Springer Science+Business Media B.V., Springer Netherlands
Earliest Life on Earth: Habitats, Environments and Methods of Detection, 2011年, ［査読有り］, ［招待有り］

Biological activity and Earth’s surface evolutions: Insights from carbon, sulfur, nitrogen and iron stable isotopes in the rock record.
Thomazo C; Pinti D. L; Busigny V; Ader M; Hashizume K; Philippot P, The search for early Earth biological activity is hindered by the scarcity of the rock record. The very few exposed sedimentary rocks have all been affected by secondary processes such as metamorphism and weathering, which might have distorted morphological microfossils and biogenic minerals beyond recognition and have altered organic matter to kerogen. The search for biological activity in such rocks therefore relies entirely on chemical, molecular or isotopic indicators. A powerful toot used for this purpose is the stable isotope signature of elements related to life (C, N, S, Fe). It provides key informations not only on the metabolic pathways operating at the time of the sediment deposition, but more globally on the biogeochemical cycling of these elements and thus on the Earth's surface evolution. Here, we review the basis of stable isotope biogeochemistry for these isotopic systems. Rather than an exhaustive approach, we address some examples to illustrate how they can be used as biosignatures of early life and as proxies for its environment, while keeping in mind what their limitations are. We then focus on the covariations among these isotopic systems during the Archean time period to show that they convey important information both on the evolution of the redox state of the terrestrial surface reservoirs and on co-occurring ecosystems in the Archean. To cite this article: C. Thomazo et al., C R. Palevol 8 (2009). (C) 2009 Academie des sciences. Published by Elsevier Masson SAS. All rights reserved., ELSEVIER FRANCE-EDITIONS SCIENTIFIQUES MEDICALES ELSEVIER
Comptes Rendus Palevol, 2009年11月, ［査読有り］

Timescales for the evolution of oxygen isotope compositions in the solar nebula
J. R. Lyons; E. A. Bergin; F. J. Ciesla; A. M. Davis; S. J. Desch; K. Hashizume; J. -E. Lee, We review two models for the origin of the calcium-, aluminum-rich inclusion (CAI) oxygen isotope mixing line in the solar nebula: (1) CO self-shielding, and (2) chemical mass-independent fractionation (MIF). We consider the timescales associated with formation of an isotopically anomalous water reservoir derived from CO self-shielding, and also the vertical and radial transport timescales of gas and solids in the nebula. The timescales for chemical M IF are very rapid. CO self-shielding models predict that the Sun has Delta(17)O(SMOW) similar to -20 parts per thousand, (Clayton, 2002). and chemical mass-independent fractionation models predict Delta(17)O(SMOW) similar to 0 parts per thousand. Preliminary Genesis results have been reported by McKeegan et al. (McKeegan K. D., Coath C. D., Heber, V., Jarzebinski G., Kallio A. P., Kunihiro T., Mao P. H. and Burnett D. S. (2008b) The oxygen isotopic composition of captured solar wind: first results from the Genesis. EOS Trans. AGU 89(53), Fall Meet. Suppl., P42A-07 (abstr)) and yield a Delta(17)O(SMOW) Of similar to -25 parts per thousand consistent with a CO self-shielding scenario. Assuming that subsequent Genesis analyses support the preliminary results, it then remains to determine the relative contributions of CO self-shielding from the X-point, the surface of the solar nebula and the parent molecular cloud.
The relative formation ages of chondritic components can be related to several timescales in the self-shielding theories. Most importantly the age difference of similar to 1-3 My between CAIs and chondrules is consistent with radial transport from the outer solar nebula (>10 AU) to the meteorite-forming region, which supports both the nebular surface and parent cloud self-shielding scenarios. An elevated radiation field intensity is predicted by the surface shielding model, and yields substantial CO photolysis (similar to 50%) on timescales of 0.1-1 My. An elevated radiation field is also consistent with the parent cloud model. The elevated radiation intensities may indicate solar nebula birth in a medium to large cluster, and may be consistent with the injection of (60)Fe from a nearby supernova and with the photoevaporative truncation of the solar nebula at KBO orbital distances (similar to 47 AU). CO self-shielding is operative at the X-point even when H(2) absorption is included, but it is not yet clear whether the self-shielding signature can be imparted to silicates. A simple analysis of diffusion times shows that oxygen isotope exchange between (16)O-depleted nebular H(2)O and chondrules during chondrule formation events is rapid (similar to minutes), but is also expected to be rapid for most components of CAIs, with the exception of spinel. This is consistent with the observation that spinel grains are often the most (16)O-rich component of CAIs, but is only broadly consistent with the greater degree of exchange in other CAI components. Preliminary disk model calculations of self-shielding by N(2) demonstrate that large delta(15)N enrichments (similar to +800 parts per thousand) are possible in HCN formed by reaction of N atoms with organic radicals (e.g., CH(2)) which may account for (15)N-rich hotspots observed in lithic clasts in some carbonaceous chondrites and which lends support to the CO self-shielding model for oxygen isotopes. (C) 2009 Elsevier Ltd. All rights reserved., PERGAMON-ELSEVIER SCIENCE LTD
GEOCHIMICA ET COSMOCHIMICA ACTA, 2009年09月, ［査読有り］

Isotopic fractionation of nitrogen and carbon in Paleoarchean cherts from Pilbara craton, Western Australia: Origin of N-15-depleted nitrogen
Daniele L. Pinti; Ko Hashizume; Akiyo Sugihara; Marc Massault; Pascal Philippot, Nitrogen and carbon isotopic compositions, together with mineralogy and trace element geochemistry, were studied in a few kerogen-rich Paleoarchean cherts, a barite and a dolomitic stromatolite belonging to the eastern (Dixon Island Formation) and western (Dresser and Strelley Pool Chert Formations; North Pole Dome and Marble Bar) terranes of Pilbara Craton, Western Australia. The aim of the study was to search for N-15-depleted isotopic signatures, often found in kerogens of this period, and explain the origin of these anomalies. Trace elements suggest silica precipitation by hydrothermal fluids as the main process of chert formation with a contamination from volcanoclastic detritus. This is supported by the occurrence of hydrothermal-derived minerals in the studied samples indicating precipitation temperatures up to 350 degrees C. Only a dolomitic stromatolite from Strelley Pool shows a superchondritic Y/Ho ratio of 72 and a positive Eu/Eu* anomaly of 1.8, characteristic of chemical precipitates from the Archean seawater. The bulk delta C-13 vs. delta N-15 values measured in the cherts show a roughly positive co-variation, except for one sample from the North Pole (PI-85-00). The progressive enrichment in N-15 and C-13 from a pristine source having delta C-13 <= -36 parts per thousand and delta N-15 <= -4 parts per thousand is correlated with a progressive depletion in N-15 content and to variations in Ba/La and Co/As ratios. These trends have been interpreted as a progressive hydrothermal alteration of the cherts by metamorphic fluids. Isotopic exchange at 350 degrees C between NH4(rock)+ and N-2(fluid) may explain the isotopic and elemental composition of N in the studied cherts. However, we need to assume isotopic exchange at 350 degrees C between carbonate C and graphite to explain the large C-13 enrichment recorded. Only sample PI-85-00 shows a large N loss (90%) with a positive delta N-15 value (+11 parts per thousand), while C (up to 120 ppm and delta C-13 -38 parts per thousand) seems to be unaffected. This pattern has been interpreted as the result of devolatilization and alteration (oxidation) of graphite by low-temperature fluids. The N-15-C-13-depleted pristine source has delta N-15 values from -7 parts per thousand to -4 parts per thousand and Ar-40/Ar-36 ratios from 30,000 to 60,000, compatible with an inorganic mantle N source, although the elemental abundance ratios N/C and Ar-40/C are not exactly the same with the mantle source. The component alternatively could be explained by elemental fractionation from metabolic activity of chemolithoautotrophs and methanogens at the proximity to the hydrothermal vents. However, ambiguities between mantle vs organic sources of N subsist and need further experimental work to be fully elucidated. (C) 2009 Elsevier Ltd. All rights reserved., PERGAMON-ELSEVIER SCIENCE LTD
GEOCHIMICA ET COSMOCHIMICA ACTA, 2009年07月, ［査読有り］

Two oxygen isotopic components with extra-selenial origins observed among lunar metallic grains – In search for the solar wind component.
Hashizume K; Chaussidon M, Oxygen isotopic analyses were performed in the surface layers of lunar metallic grains from lunar regolith samples 71501 and 79035, presumably exposed Lit the Moon surface at different times. We were able to reproduce the two extreme O components previously found [Hashizume K. and Chaussidon M. (2005) A non-terrestrial (16)O-rich isotopic composition for the protosolar nebula. Nature 434, 619-622; Ireland T. R., Holden P., Norman M. D. and Clarke J. (2006) Isotopic enhancements of (17)O and (18)O from solar wind particles in the lunar regolith. Nature 440, 776-778], with a range observed of -12 +/- 5 < Delta(17)O < +33 +/- 3 parts per thousand (1 sigma). The relatively minor (16)O-rich component corresponding to all end-member Delta(17)O Value lower than -20 parts per thousand is likely the solar component. This comes from the fact that its concentration roughly agrees with the maximum solar wind abundance expected among the grains from the two samples. At variance the (16)O-poor component is 5-10 times more abundant and thus likely non-solar. The delta(18)O range found for the (16)O-poor component may reflect various Processes such Lis isotope exchange reaction during oxidation of metallic iron and/or isotope fractionation by evaporation/condensation at the surface of the Moon or during implantation at depth in the lunar metallic grains. The present study suggests that planetary solid materials in bulk are systematically depleted in (16)O relative to the solar isotopic composition, suggesting the existence of non-mass-dependent isotopic fractionations associated to the formation of solids in the accretion disk. (C) 2009 Elsevier Ltd. All rights reserved., PERGAMON-ELSEVIER SCIENCE LTD
Geochimica et Cosmochimica Acta, 2009年05月, ［査読有り］

同位体イメージング法により探るマーチソン隕石有機物中の酸素同位体組成
橋爪 光; 高畑 直人; 佐野 有司; 奈良岡 浩, Nanosims を用いた近年の始原コンドライト隕石中の水素・窒素同位体イメージングの研究によると、隕石有機物全体の組成とは極端に異なる、1mm あるいはそれ以下のサイズの有機微粒子が見つかっている.我々は、これらの微粒子の少なくとも一部には隕石有機物全体の組成とは大きく異なる酸素同位体比異常が見られるのではないかと考え、分析技術の開発を進めている。講演では分析手法の概要、および、窒素同位体ホットスャbト中の酸素同位体比組成などの preliminary resultsを報告する。, 日本地球化学会
日本地球化学会年会要旨集, 2008年

Oxygen in the Sun
Davis A. M.; Hashizume K.; Chaussidon M.; Ireland T. R.; Allende-Prieto C.; Lambert D., We review elemental and isotopic abundances of oxygen in the Sun and their implications for solar physics and Solar System formation. The oxygen content of the Sun, expressed as the O/H atom ratio, is 468 ppm. This value, obtained relatively recently, is significantly lower than earlier estimates, but is supported by observations of several photospheric lines. The new, lower solar oxygen abundance (and a new, lower solar carbon abundance) are compatible with many astrophysical constraints but are in conflict with helioseismology-based constraints on the standard model of the Sun. The oxygen isotopic composition of the Sun is surprisingly poorly known, despite the fact that the Sun contains nearly all (similar to 98%) of the Solar System's oxygen. Spectroscopy of the solar photosphere suggests a slight enhancement in O-18/O-16 Compared to terrestrial composition, but with a precision of 6%. One measurement of solar oxygen trapped in lunar metal grains indicates that the Sun is depleted in O-16 by a few percent, whereas another indicates an enrichment of similar magnitude; some models predict that the Sun is enriched in O-16 by a few percent and others predict that solar and terrestrial oxygen are of similar isotopic composition. It is hoped that forthcoming isotopic measurements on solar wind sampled by the Genesis sample return mission will bring some closure to this issue., MINERALOGICAL SOC AMER
Reviews in Mineralogy and Geochemistry, 2008年, ［査読有り］

Biogenic nitrogen and carbon in Fe-Mn-oxyhydroxides from an Archean chert, Marble Bar, Western Australia
Daniele L. Pinti; Ko Hashizume; Beate Orberger; Jean-Paul Gallien; Christophe Cloquet; Marc Massault, [ 1] To quantify and localize nitrogen (N) and carbon (C) in Archean rocks from the Marble Bar formation, Western Australia, and to gain insights on their origin and potential biogenicity, we conducted nuclear reaction analyses (NRA) and carbon and nitrogen isotope ratio measurements on various samples from the 3460-Myr-old Fe-rich Marble Bar chert. The Marble Bar chert formed during the alteration of basaltic volcanoclastic rocks with Fe- and Si-rich hydrothermal fluids, and the subsequent precipitation of magnetite, carbonates, massive silica, and, locally, sulfides. At a later stage, the magnetite, sulfides, and carbonates were replaced by Fe- Mn-oxyhydroxides. Nuclear reaction analyses indicate that most of the N and C resides within these Fe-Mn-oxyhydroxides, but a minor fraction is found in K-feldspars and Ba-mica dispersed in the silica matrix. The N and C isotopic composition of Fe- oxides suggests the presence of a unique biogenic source with delta(15)N(AIR) values from + 6.0 +/- 0.5 parts per thousand to 7.3 +/- 1.1 parts per thousand and a delta(13)C(PDB) value of - 19.9 +/- 0.1 parts per thousand. The C and N isotope ratios are similar to those observed in Proterozoic and Phanerozoic organic matter. Diffusion-controlled fractionation of N and C released during high combustion temperatures indicates that these two elements are firmly embedded within the iron oxides, with activation energies of 18.7 +/- 3.7 kJ/mol for N and 13.0 +/- 3.8 kJ/mol for C. We propose that N and C were chemisorbed on iron and were subsequently embedded in the crystals during iron oxidation and crystal growth. The Fe- isotopic composition of the Marble Bar chert (delta(56)Fe = -0.38 +/- 0.02 parts per thousand) is similar to that measured in iron oxides formed by direct precipitation of iron from hydrothermal plumes in contact with oxygenated waters. To explain the N and C isotopic composition of Marble Bar chert, we propose either ( 1) a later addition of N and C at the end of Archean when oxygen started to rise or ( 2) an earlier development of localized oxygenated environments, where biogeochemical cycles similar to modern ones could have developed., AMER GEOPHYSICAL UNION
GEOCHEMISTRY GEOPHYSICS GEOSYSTEMS, 2007年02月, ［査読有り］

Micro-facies and origin of some Archaean Cherts (Pilbara, Australia)
Orberger B.; Rouchon V.; Westall F.; deVries S.T.; Pinti D.L.; Wagner C.; Wirth R. and Hashizume K, The Geological Society of America
The Geological Society of America Special Paper, 2006年01月01日, ［査読有り］

Biogeochemical cycles of sulfur and nitrogen in the Archean ocean and atmosphere.
Shen Y; Pinti D.L.; Hashizume K., Early geodynamic processes modeled the surface of the Earth, providing suitable environments and energy sources for the development of life. Studying the ancient biogeochemical cycles is thus a valuable way to understand the physico-chemical conditions of the early environments, such as the redox state of the primitive oceans and the atmosphere. To investigate early biogeochemistries, the measurement of stable isotopes of S, N, and C from ancient sedimentary rocks is crucial. Here we review the sulfur and nitrogen isotopic signatures measured in Archean rocks that suggest the antiquity of sulfate-reducing bacteria and chemolithotrophs living in a low-oxygen environment., AMER GEOPHYSICAL UNION
AGU Geophysical Monographs, 2006年, ［査読有り］

A non-terrestrial (16)O-rich isotopic composition for the protosolar nebula
K Hashizume; M Chaussidon, The discovery in primitive components of meteorites(1,2) of large oxygen isotopic variations that could not be attributed to mass-dependent fractionation effects has raised a fundamental question: what is the composition of the protosolar gas from which the host grains formed? This composition is probably preserved in the outer layers of the Sun, but the resolution of astronomical spectroscopic measurements is still too poor to be useful for comparison with planetary material(3,4). Here we report a precise determination of the oxygen isotopic composition of the solar wind from particles implanted in the outer hundreds of nanometres of metallic grains in the lunar regolith. These layers of the grains are enriched in (16)O by >20 +/- 4 parts per thousand relative to the Earth, Mars and bulk meteorites, which implies the existence in the solar accretion disk of reactions-as yet unknown-that were able to change the (17)O/(16)O and (18)O/(16)O ratios in a way that was not dependent strictly on the mass of the isotope. Photochemical self-shielding of the CO gas irradiated by ultraviolet light(5-7) may be one of these key processes, because it depends on the abundance of the isotopes, rather than their masses., NATURE PUBLISHING GROUP
NATURE, 2005年03月, ［査読有り］

Nitrogen Isotopic Analyses at the Sub-Picomole Level Using an Ultralow Blank Laser Extraction Technique
Ko Hashizume; Bernard Marty, This chapter presents a new analytical procedure aimed to measure the isotopic composition of sub-picomole quantities of nitrogen. Two major points have been improved with respect to standard analytical procedures, the level of the hot blank and that of interfering species, especially that of N2H. The hot blank is lowered by minimizing the hot area during the extraction procedure using a defocused laser beam as a heating device. The amount of the interfering species N2H arising from the mass-spectrometer ion source was lowered by optimizing the ion source condition. The aim of this development is to enable isotopic analysis of single mineral grains using the smallest quantity of nitrogen with a precision sufficient to resolve isotopic variations of nitrogen in extraterrestrial samples. There are certain limiting factors also. Hydrocarbon is mass-resolved with mass-spectrometer. Isotopic analyses of sub-picomole quantities of N2 with a precision typically of + 10% is done. The required amount of samples for nitrogen isotopic analyses, in the case of the lunar regolith, is reduced by a factor of ~10-5. Hence, mass-spectrometry system performs nitrogen isotopic analyses within limits imposed only by the counting statistics., Elsevier Inc.
Handbook of Stable Isotope Analytical Techniques, 2004年12月18日, ［査読有り］

Protosolar carbon isotopic composition: Implications for the origin of meteoritic organics
K Hashizume; M Chaussidon; B Marty; K Terada, New ion probe isotopic measurements of carbon trapped within the 50 nm thick surface layer of lunar regolith grains strongly suggest that solar wind C is depleted in C-13 by at least 10% relative to terrestrial C. In order to account for the general C-13 enrichment of planetary C relative to solar C, we propose that the main carriers of C in these objects, i.e., organics, were formed in an environment that allowed a strong isotopic enrichment of C-13 in the solid phase. Such an environment is most likely a dense and warm circumstellar or interstellar gas medium, which could well correspond to the nebula surrounding the proto-Sun, where isotopic fractionation could be triggered by photochemical reactions., UNIV CHICAGO PRESS
ASTROPHYSICAL JOURNAL, 2004年01月, ［査読有り］

Nitrogen isotopes on the Moon: Archives of the solar and planetary contributions to the inner solar system
B Marty; K Hashizume; M Chaussidon; R Wieler, The two isotopes of nitrogen, N-14 and N-15, have relative abundances extremely variable among solar system reservoirs such as planets and their atmospheres, primitive and differentiated meteorites, and comets. Expressed in the delta notation (delta(15)N = {[N-15/N-14](sample)/[N-15/N-14](standard)- 1} x 1000, in parts per mil, or parts per thousand, where the standard is atmospheric N having N-15/N-14 = 0.003676), delta(15)N ranges from -250parts per thousand (the lower limit of lunar soil values) up to 1600parts per thousand (measured in the meteorites benccubinites). The lunar surface constitutes a unique archive of the past corpuscular (solar and meteoritic) contributions to planetary surfaces. Nitrogen trapped in the lunar regolith presents a highly variable isotopic composition, which represents either secular variation of the solar wind composition although this possibility conflicts with the apparent isotope stability over time of other solar wind volatile elements, or more likely different contributions from solar corpuscular radiation and non-solar sources. In this case, the solar nitrogen component is depleted by more than 24% in N-15, whereas non-solar, planetary sources (meteorites, micrometeorites, possibly comets) are enriched in the heavy isotope of nitrogen by greater than or equal to 10% on average. Variations in the nitrogen isotopic composition of lunar soils are explained by a secular change in the strength of the planetary flux, and a correlation between N isotopic compositions and surface exposure age for different soils suggest that the planetary contribution to the inner solar system might have increased in the last 0.4 Gy. The variability of the N isotope composition among solar system objects might be due to incomplete equilibration of nitrogen isotopes from different host phases of pre-solar origin. Alternatively, it could result from mixing between N-15-depleted protosolar nitrogen originally present in the gas and presolar solid (organic?) compounds enriched in N-15., SPRINGER
SPACE SCIENCE REVIEWS, 2003年, ［査読有り］

Analyses of nitrogen and argon in single lunar grains: towards a quantification of the asteroidal contribution to planetary surfaces
K Hashizume; B Marty; R Wieler, We performed nitrogen and argon isotopic analyses in single 200-mum-sized ilmenite grains of lunar regolith samples 71501, 79035 and 79135. Cosmogenic and trapped components were discriminated using stepwise heating with a power-controlled CO2 laser. Cosmogenic N-15 and Ar-38 correlate among different ilmenite grains, yielding a mean N-15(c)/Ar-38(c) production ratio of 14.4 +/- 1.0 atoms/atom. This yields a N-15 production rate in bulk lunar samples of 3.8 - 5.6 pg (g rock)(-1) Ma(-1), which agrees well with previous estimates. The trapped delta(15)N values show large variations (up to 300parts per thousand) among different grains of a given soil, reflecting complex histories of mixing between different end-members. The Ar-36/N-14 ratio, which is expected to increase with increasing contribution of solar ions, varies from 0.007 to 0.44 times the solar abundance ratio. The trapped delta(15)N values correlate roughly with the Ar-36/N-14 ratios from a non-solar end-member characterized by a Ar-36/N-14 ratio close to 0 and variable but generally positive delta(15)N values, to lower delta(15)N values accompanied by increasing Ar-36/N-14 ratios, supporting the claim of Hashizume et al. (2000) that solar nitrogen is largely depleted in N-15 relative to meteoritic or terrestrial nitrogen. Nevertheless, the Ar-36/N-14 ratio of the N-15-depleted (solar) end-member is lower than the solar abundance ratio by a factor of 2.5-5. We explain this by a reprocessing of implanted solar wind atoms, during which part of the chemically inert rare gases were lost. We estimate that the flux of non-solar N necessary to account for the observed delta(15)N values is comparable to the flux of micrometeorites and interplanetary dust particles estimated for the Earth. Hence we propose that the variations in delta(15)N values observed in lunar regolith can be simply explained by mixing between solar wind contributions and micrometeoritic ones infalling on the Moon. Temporal variations of delta(15)N values among samples of different antiquities could be due to changes in the micrometeoritic flux through time, in which case such flux has increased by up to an order of magnitude during the last 0.5 Ga. (C) 2002 Elsevier Science B.V. All rights reserved., ELSEVIER SCIENCE BV
EARTH AND PLANETARY SCIENCE LETTERS, 2002年09月, ［査読有り］

The isotopic composition of solar nitrogen and the heterogeneity of the solar system
K Hashizume; B Marty; M Chaussidon; F Robert, The isotopic composition of solar nitrogen is a long standing issue that received recently new impetus. The analysis of nitrogen isotopes in lunar samples and in Jupiter show that solar nitrogen is depleted in N-15 by 30% relative to terrestrial. The systematic enrichment of 15N in terrestrial planets and bulk meteorites requires the contribution of N-15-rich compounds to the total nitrogen in planetary materials. Most of these compounds are possibly of an interstellar origin that never equilibrated with the N-15-depleted protosolar nebula N-2., AMER INST PHYSICS
SOLAR AND GALACTIC COMPOSITION, 2001年, ［査読有り］

Hashizume K., Chaussidon M., Marty B., Robert F.
Isotopic variability of nitrogen in lunar regolith.
Science, 2001年, ［査読有り］, ［招待有り］

The nitrogen and argon elemental and isotopic signature in >3.5 Ga metasediments: clues on the chemical state of the Archean ocean and the deep biosphere.
Pinti D. L.; Hashizume K.; Matsuda J., N and Ar elemental and isotopic analyses were conducted on Archean metasediments of Isukasia, West Greenland and Pilbara Craton, Western Australia, in order to investigate the N isotopic evolution during the first half of Earth's history. The selected samples are deep-sea sediments and hydrothermal deposits having ages from 3.8 to 2.8 Ga and affected by different degrees of metamorphism. The release patterns of N and Ar obtained by high-resolution stepped combustion show the occurrence of at least two trapped components. The first is released at 600 degreesC and it is likely contained in fluid inclusions. N is released together with primordial Ar-36 and shows a delta N-15 value of -1.3 +/- 1.0 parts per thousand, close to that of modern atmospheric N-2 (delta N-15 = 0 parts per thousand). This component is well preserved in hydrothermal-vent silica deposits of North Pole, Pilbara Craton, and nitrogen may represent ammonium salt dissolved in deep-sea hydrothermal fluids. The second N component, released at temperatures higher than 1000 degreesC, is accompanied by radiogenic Ar-40*, and shows a delta N-15 value of -7.4 +/- 1.0 parts per thousand in a kerogen-rich chert from North Pole, Pilbara Craton. This N is likely biogenic and negative N-15 values may reflect a metabolic isotopic fractionation induced by chemosynthetic bacteria using inorganic NH4+ contained in hydrothermal fluids. This N-15-depleted biogenic component may occur in Isukasia Banded Iron Formation (delta N-15 similar to -1.7 parts per thousand), but further data are needed to confirm such a hypothesis. In all other samples, metamorphic-induced Rayleigh distillation has altered the pristine N isotopic signature. Copyright (C) 2001 Elsevier Science Ltd., PERGAMON-ELSEVIER SCIENCE LTD
Geochimica et Cosmochimica Acta, 2001年, ［査読有り］

Pinti D. L., Hashizume K.
15N-depleted nitrogen in Early Archean kerogens: clues on ancient marine chemosynthetic-based ecosystems?
Precambrian Research, 2001年, ［査読有り］

Hashizume K., Chaussidon M., Marty B., Robert F.
Solar Wind Record on the Moon: Deciphering Presolar from Planetary Nitrogen.
Science, 2000年, ［査読有り］

Nitrogen components in primitive ordinary chondrites
N Sugiura; K Kiyota; K Hashizume, Nitrogen and Ar in more than 20 primitive ordinary chondrites were studied by a stepped combustion method. Several N carriers that are characterized by N isotopic composition, N release pattern and trapped Ar release pattern are recognized in the primitive ordinary chondrites. Large fractions of anomalous N and associated Ar are removed by acid treatment in most cases. The N isotopic anomalies cannot be explained by known presolar grains (with a possible exception of graphite), and some of the N isotopic anomalies may be due to unknown presolar grains. There is no specific relationship between the type of N carriers contained in an ordinary chondrite and the chemical type (H, L, or LL) of the chondrite. It is likely that as a result of impacts, the carriers of isotopically anomalous N were mixed in various parent bodies as rock fragments rather than as individual fine particles. The presence of distinctive N isotopic anomalies in primitive meteorites indicates that the primitive solar nebula may have been heterogeneous either spatially or temporally., METEORITICAL SOC
METEORITICS & PLANETARY SCIENCE, 1998年05月, ［査読有り］

地球外物質のガス型元素（希ガス, H, C, N）分析
橋爪 光, 日本惑星科学会
日本惑星科学会誌・遊星人, 1998年04月01日, ［査読有り］

Transportation of gaseous elements and isotopes in a thermally evolving chondritic planetesimal
Ko Hashizume; Naoji Sugiura, The behavior of H, C, N and their isotopes in a thermally evolving planetesimal was evaluated by numerical simulation. Transportation of heat and gas molecules, and the chemical equilibrium involving these elements, were simulated. Our modeled planetesimals initially contain homogeneous amounts of radioactive heat source (26Al)
and H, C, and N in forms of organic materials, graphite, and in some models, water ice. Vaporized gas molecules were transported from the interior of the planetesimal to its surface, although their transportation efficiencies were quite different among the three elements, primarily due to differences in their affinities to metallic Fe. Significant portions of these elements were redistributed into metallic Fe when the planetesimal was heated at 600 °C and above. Nitrogen showed the most prominent siderophile characteristics, resulting in fairly large concentrations of N trapped in metallic Fe, which is consistent with observations by Hashizume and Sugiura (1997). Efficiency of C transportation crucially depended on O fugacity. To realize effective C transportation, it was necessary to assume an oxidizing condition (logfO2>
logfO(2,(FIF)) + 1) in the initially accreted material. Water vapor, generated at the interior of the planetesimal and transported to its near surface, formed a water-rich layer under certain conditions, providing an environment sufficient for aqueous alteration of chondritic materials to occur. Variations in isotopic ratios of N in taenite observed among equilibrated ordinary chondrites can be explained by our gas transportation model. It is required, however, that carriers of isotopically anomalous N, perhaps presolar grains, were initially localized on a large spatial scale within a single planetesimal, which possibly suggests incorporation of preaccretionary objects as large as 0.1x of the final mass of the ordinary chondrite parent body., University of Arkansas
Meteoritics and Planetary Science, 1998年

Hashizume K., Sugiura N.
Transportation of gaseous elements and their isotopes in a thermally evolving chondritic planetesimal.
Meteoritics & Planetary Science, 1998年, ［査読有り］

Kamijo K., Hashizume K., Matsuda J.
Noble gas constraints on the evolution of atmosphere-mantle system.
Geochimica et Cosmochimica Acta, 1998年, ［査読有り］

Distinct indigenous nitrogen isotopic components co-existing in ureilites.
Yamamoto T.; Hashizume K.; Matsuda J.; Kase T., Nitrogen and noble gas isotopic compositions and C abundance of ureilites were analyzed using a stepwise combustion technique. Four Antarctic ureilites, ALHA77257, Asuka 881931, Yamato 791538 and Yamato 790981 were analyzed. Multiple N isotopic components were observed in these ureilites. The delta(15)N values of these N components ranged from +160 to -120 parts per thousand. The minimum delta(15)N values of typically -120 parts per thousand were observed at combustion temperatures at 700-900 degrees C where large amounts of C were released. A heavy N component was observed in only two ureilites, ALHA77257 and Asuka 881931. Silicate-enriched fractions and C-concentrated fractions were prepared for these two ureilites. We conclude that both the light N and the heavy N are trapped in the carbonaceous vein minerals. The lack of correlation between the NIC ratio and the Ar-36/C ratio suggests that the primary carrier phase of the light N does not correspond to that of the planetary noble gases. We consider that the isotopically heavy N, which was observed in this study, is related to the heavy N observed among polymict ureilites. Small amounts (<0.5 ppm) of light N with the minimum delta(15)N value of-120 parts per thousand were observed among the silicate fractions at the highest combustion temperature of 1200 degrees C, although the exact carrier phase of this light N is not known. We consider that the currently observed ureilites were produced by injection of several volatile-rich objects into volatile-poor ureilitic silicates., METEORITICAL SOC
Meteoritics & Planetary Science, 1998年, ［査読有り］

東北日本弧の部分溶融域と地震活動の3次元分布
室 健一、佐藤 博樹、長谷川 昭、橋爪 光
火山, 1997年10月01日, ［査読有り］

窒素・炭素の親鉄性に関する実験的研究 – 地球コア中の軽元素の定量をめざして
橋爪 光; 加瀬友彦; 松田准一; 佐藤博樹, 筆頭著者, 日本火山学会
火山, 1997年10月01日, ［査読有り］

Isotopically anomalous nitrogen in H-chondrite metal
K Hashizume; N Sugiura, The cause of the nitrogen isotopic anomalies observed by Hashizume and Sugiura (1995) among bulk equilibrated ordinary chondrites has been investigated. The bulk nitrogen isotopic anomalies can be explained by the isotopically anomalous nitrogen dissolved in taenite and/or tetra-taenite (gamma/gamma' phase Fe-Ni metal). Nitrogen concentrations in taenite range between 5 and 45 ppm, and in most of the samples within 10 +/- 5 ppm. Nitrogen isotopic ratios trapped in taenite vary with samples in a range of -40 < delta(15)N < +120 parts per thousand. No systematic correlation was observed between the amounts and the isotopic ratios. Another rather minor nitrogen reservoir seems to exist in nonmagnetic fractions, although the exact host phase has not yet been identified. The isotopic ratios of nitrogen trapped in nonmagnetic minerals generally do not coincide with those in taenite. We consider that the nitrogen dissolved in taenite was trapped there at the end of the thermal metamorphic event when the interior of the H-chondrite parent body was cooled down to 500 degrees C, the closure temperature of nitrogen in gamma-Fe,Ni. The concentration and isotopic ratios of nitrogen trapped in taenite reflect the nitrogen equilibrium system within the parent body at greater than or equal to 500 degrees C. The nitrogen isotopic anomalies in taenite cannot be explained by an initially isotopically homogeneous nitrogen reservoir or by processes such as mass-dependent isotopic fractionation. Copyright (C) 1997 Elsevier Science Ltd., PERGAMON-ELSEVIER SCIENCE LTD
GEOCHIMICA ET COSMOCHIMICA ACTA, 1997年02月, ［査読有り］

Magma distribution in island arc mantle in three dimensions
H Sato; K Muro; A Hasegawa; K Hashizume, Distribution of partial melt (magma) in the upper mantle is investigated in detail from the seismic tomography of the mantle wedge beneath northeastern Japan. The comparison of the fine velocity structure with the laboratory velocity data on a partially-molten mantle rock yields estimates of three-dimensional distribution of melt. The results indicate that the cause of island are volcanism in northeastern Japan is the upwelling of hot mantle materials (volcanic plumes) from beneath. The source of volcanic magma is diapir-like melting regions localized within the volcanic plumes. Extensive volcanic activity at the volcanic front is due to the presence of the vast melting zones right beneath the Moho discontinuity. Those melting zones may cause melting of lower crustal materials and produce felsic magma. Melt stays underneath the Moho, where crystallization fractionation may proceed. Melt exists at greater depths in the back-are region, which may cause across-are variations of chemical compositions of the volcanic rocks in northeastern Japan. We suggest that magma migration in the ductile lower crust may cause low-frequency microearthquakes, and magma penetration into the brittle upper crust may produce mid-crustal S-wave reflectors., JAPAN ACAD
PROCEEDINGS OF THE JAPAN ACADEMY SERIES B-PHYSICAL AND BIOLOGICAL SCIENCES, 1996年06月, ［査読有り］

COSMOGENIC NITROGEN ISOTOPIC DISEQUILIBRIUM OBSERVED IN METEORITES
N SUGIURA; K HASHIZUME; Y MIURA; K KIYOTA; S ZASHU, The isotopic disequilibrium of N molecules in meteorites was examined. For a large data-set, consisting of mass compositions of N molecules extracted at 1200 degrees C by stepped combustion of chondrites and eucrites, we find that a cosmogenic-N-enriched component and a normal air-like N component are isotopically disequilibrated with each other. The isotopic composition of the cosmogenic-N-enriched component seems to be variable, although the cause for the variation is not clear. The abundance of indigenous atomic N in silicate minerals seems to be small. Indigenous N in meteoritic silicates, if present, may be present in the form of N molecules., METEORITICAL SOC
METEORITICS, 1995年11月, ［査読有り］

窒素同位体惑星科学
橋爪 光
日本惑星科学会誌・遊星人, 1995年10月01日, ［査読有り］

NITROGEN ISOTOPES IN BULK ORDINARY CHONDRITES
K HASHIZUME; N SUGIURA, Nitrogen isotopic compositions of twenty-one ordinary chondrites were measured using a stepwise combustion technique. We observed a good correlation between the abundances of cosmogenic N-15 and cosmogenic Ar-38. We obtained a relationship between the abundances of these two cosmogenic nuclides as follows:
N-15(c)(atoms/g) = (16.0 +/- 3.7).Ar-38(c)(atoms/g)
Using this relationship, the cosmogenic nitrogen production rate in L-chondrites is calculated to be (5.0 +/- 1.2) x 10(-12) g(-15)N/g . myr, assuming the cosmogenic Ar-38 production rate given by Eugster (1988). This value is consistent with the production rate on the lunar surface estimated by Becker et al. (1976). Isotopic ratios of trapped nitrogen in ordinary chondrites seem to be heterogeneous, among both unequilibrated and equilibrated meteorites. Heterogeneity among the latter are well observed in this study. The isotopic ratios of the trapped components seem to differ by more than 110 parts per thousand, ranging from - 18 parts per thousand, observed in Guarena (H6), to +95 parts per thousand, observed in Jilin (H5). A lack of correlation between nitrogen abundances and isotopic ratios indicates that differences in nitrogen isotopic ratios are not produced by mass-dependent isotopic fractionation. An inverse correlation between nitrogen abundances and the degree of thermal metamorphism is observed among most of the unequilibrated chondrites. Nitrogen abundances decrease from 8-25 p.p.m. to < 1 p.p.m. with increasing petrographic subtype from 3.4-3.9. The nitrogen abundance in equilibrated chondrites is generally higher than the amount expected by extending the trend observed among unequilibrated ones. This is probably because contaminating nitrogen masked the trend at small amounts of trapped nitrogen., PERGAMON-ELSEVIER SCIENCE LTD
GEOCHIMICA ET COSMOCHIMICA ACTA, 1995年10月, ［査読有り］

Reply to Comment on “Measurement of cosmogenic nitrogen using a static mass-spectrometry system and its implication”
Hashizume K.; Sugiura N., PERGAMON-ELSEVIER SCIENCE LTD
Geochimica et Cosmochimica Acta, 1993年, ［査読有り］, ［招待有り］

Sugiura N., Hashizume K.
Nitrogen isotope anomalies in primitive ordinary chondrites.
Earth and Planetary Science Letters, 1992年, ［査読有り］

Hashizume K., Sugiura N.
Measurement of cosmogenic nitrogen using a static mass-spectrometry system and its implication.
Geochimica et Cosmochimica Acta, 1992年, ［査読有り］

Sugiura N., Hashizume K.
Heavy nitrogen in the Yamato-74191 and the heterogeneity of the primitive solar nebula.
Proceedings of the NIPR Symposium on Antarctic Meteorites, 1991年, ［査読有り］

Hashizume K., Sugiura N.
Precise measurement of nitrogen isotopic composition using a quadrupole mass spectrometer.
Journal of the Mass Spectrometry Society of Japan, 1990年, ［査読有り］

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日本地球化学会年会講演要旨集, 2011年

107 微惑星の熱変成とその中での窒素の挙動について : 地球における窒素Inventory解明への示唆(セッションI)
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日本惑星科学会秋期講演会予稿集, 1993年10月15日

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