Elsevier BV Acta Medica Okayama 0016-7037 400 2025 Lithium- and oxygen-isotope compositions of a Si-rich nebular reservoir determined from chondrule constituents in the Sahara 97103 EH3 chondrite 51 71 EN Torii Douglas-Song The Pheasant Memorial Laboratory Institute for Planetary Materials, Okayama University Tsutomu Ota The Pheasant Memorial Laboratory Institute for Planetary Materials, Okayama University Masahiro Yamanaka The Pheasant Memorial Laboratory Institute for Planetary Materials, Okayama University Hiroshi Kitagawa The Pheasant Memorial Laboratory Institute for Planetary Materials, Okayama University Ryoji Tanaka The Pheasant Memorial Laboratory Institute for Planetary Materials, Okayama University Christian Potiszil The Pheasant Memorial Laboratory Institute for Planetary Materials, Okayama University Tak Kunihiro The Pheasant Memorial Laboratory Institute for Planetary Materials, Okayama University Here we report the in situ ion-microprobe analyses of the Li- and O-isotope compositions of enstatite, FeO-rich pyroxene, olivine, glass, and cristobalite grains from six chondrule-related objects from the Sahara 97103 EH3 chondrite. The O-isotope composition of the enstatite grains scattered around the intersection between the terrestrial fractionation and primitive chondrule minerals lines. Whereas, that of olivine varied along the primitive chondrule minerals line. Based on the mineralogy, we found cristobalite formed as a result of Si saturation, instead of the reduction of FeO-rich silicates, consistent with Si-enrichment of whole rock enstatite chondrites. Based on the mineralogy and O-isotope compositions, we infer that olivines in some chondrules are relict grains. In chondrules that contained olivine, no abundant niningerite [(Mg,Fe,Mn)S] was observed. Thus, enstatite formation can be explained by the interaction of an olivine precursor with additional SiO2 (Mg2SiO4 + SiO2 → Mg2Si2O6), instead of sulfidation (Mg2SiO4 + S → 1/2 Mg2Si2O6 + MgS + 1/2 O2). Using the equation Mg2SiO4 + SiO2 → Mg2Si2O6 and the O-isotope compositions of enstatite and olivine, the O-isotope composition of the additional SiO2 was estimated. Based on the O-isotope composition, we infer that there could be a Si-rich gas with an elevated Δ17O value similar to, or greater than the second trend line (Δ17O = 0.9 ‰) suggested by Weisberg et al. (2021), during chondrule formation. The variation in the Li-isotope compositions of enstatite and olivine grains from EH3 chondrules is smaller than that for the same phases from CV3 chondrules. The variation in the Li-isotope compositions of the enstatite and olivine grains from EH3 chondrules is also smaller than that of their O-isotope compositions. During the recycling of enstatite-chondrite chondrules, both Li- and O-isotope compositions were homogenized. Although enstatite is the major carrier of Li in EH3 chondrules, the Li-isotope composition (δ7Li) of enstatite is lower than that of whole rock EH3 chondrites, suggesting the existence of a phase with higher δ7Li. Meanwhile, the Li-isotope composition and concentration (δ7Li, [Li]) of enstatite is higher than that of olivine. The Li-isotope composition of the Si-rich gas was estimated to be δ7Li = 1 ‰, using a similar mass-balance calculation as applied for the O-isotope composition. The Li-isotope composition of the Si-rich gas from the enstatite-chondrite-chondrule forming-region, is consistent with that of whole rock EH3 chondrites, and differs significantly from that of the Si-rich gas from the carbonaceous-chondrite-chondrule forming-region (δ7Li = −11 ‰) determined by a previous study. We speculate that the Si-rich gas in the carbonaceous-chondrite-chondrule forming-region maintained the Li-isotope heterogeneity inherited from light lithium synthesized by galactic cosmic-ray spallation in the interstellar medium. No potential conflict of interest relevant to this article was reported.

Elsevier BV Acta Medica Okayama 0012-821X 653 2025 Meteoritic and asteroidal amino acid heterogeneity: Implications for planetesimal alteration conditions and sample return missions 119205 EN Christian Potiszil Pheasant Memorial Laboratory, Institute for Planetary Materials, Okayama University Tsutomu Ota Pheasant Memorial Laboratory, Institute for Planetary Materials, Okayama University Masahiro Yamanaka Pheasant Memorial Laboratory, Institute for Planetary Materials, Okayama University Katsura Kobayashi Pheasant Memorial Laboratory, Institute for Planetary Materials, Okayama University Ryoji Tanaka Pheasant Memorial Laboratory, Institute for Planetary Materials, Okayama University Eizo Nakamura Pheasant Memorial Laboratory, Institute for Planetary Materials, Okayama University Carbonaceous chondrites (CC) and asteroid return samples contain amino acids (AA), which are essential for an origin of life on the early Earth and can provide important information concerning planetesimal alteration processes. While many studies have investigated AA from CC, separate studies have often found differing abundances for the same meteorite. Accordingly, analytical bias, differing terrestrial contamination levels and intrinsic sample heterogeneity have been proposed as potential reasons. However, current analytical techniques allow for the analysis of several mg-sized samples and can thus enable an investigation of AA heterogeneity within single meteorite specimens. Here, such an analytical technique is applied to characterise the AA in triplicate aliquots of three CCs. The results indicate that CCs are heterogenous in terms of their AA at the mm-scale. Furthermore, the results help to further constrain the effects of planetesimal alteration on organic matter and the requirements of future sample return missions that aim to obtain organic-bearing extraterrestrial materials. No potential conflict of interest relevant to this article was reported.

American Astronomical Society Acta Medica Okayama 0004-637X 965 1 2024 Unraveling the Cr Isotopes of Ryugu: An Accurate Aqueous Alteration Age and the Least Thermally Processed Solar System Material 52 EN Ryoji Tanaka The Pheasant Memorial Laboratory for Geochemistry and Cosmochemistry, Institute for Planetary Materials, Okayama University Dilan M. Ratnayake The Pheasant Memorial Laboratory for Geochemistry and Cosmochemistry, Institute for Planetary Materials, Okayama University Tsutomu Ota The Pheasant Memorial Laboratory for Geochemistry and Cosmochemistry, Institute for Planetary Materials, Okayama University Noah Miklusicak The Pheasant Memorial Laboratory for Geochemistry and Cosmochemistry, Institute for Planetary Materials, Okayama University Tak Kunihiro The Pheasant Memorial Laboratory for Geochemistry and Cosmochemistry, Institute for Planetary Materials, Okayama University Christian Potiszil The Pheasant Memorial Laboratory for Geochemistry and Cosmochemistry, Institute for Planetary Materials, Okayama University Chie Sakaguchi The Pheasant Memorial Laboratory for Geochemistry and Cosmochemistry, Institute for Planetary Materials, Okayama University Katsura Kobayashi The Pheasant Memorial Laboratory for Geochemistry and Cosmochemistry, Institute for Planetary Materials, Okayama University Hiroshi Kitagawa The Pheasant Memorial Laboratory for Geochemistry and Cosmochemistry, Institute for Planetary Materials, Okayama University Masahiro Yamanaka The Pheasant Memorial Laboratory for Geochemistry and Cosmochemistry, Institute for Planetary Materials, Okayama University Masanao Abe Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency Akiko Miyazaki Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency Aiko Nakato Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency Satoru Nakazawa Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency Masahiro Nishimura Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency Tatsuaki Okada Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency Takanao Saiki Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency Satoshi Tanaka Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency Fuyuto Terui Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency Yuichi Tsuda Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency Tomohiro Usui Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency Sei-ichiro Watanabe Department of Earth and Planetary Sciences, Nagoya University Toru Yada Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency Kasumi Yogata Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency Makoto Yoshikawa Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency Eizo Nakamura The Pheasant Memorial Laboratory for Geochemistry and Cosmochemistry, Institute for Planetary Materials, Okayama University The analysis of samples returned from the C-type asteroid Ryugu has drastically advanced our knowledge of the evolution of early solar system materials. However, no consensus has been obtained on the chronological data, which is important for understanding the evolution of the asteroid Ryugu. Here, the aqueous alteration age of Ryugu particles was determined by the Mn–Cr method using bulk samples, yielding an age of 4.13 + 0.62/−0.55 Myr after the formation of Ca–Al-rich inclusions (CAI). The age corresponds to 4563.17 + 0.60/−0.67 Myr ago. The higher 55Mn/52Cr, ε54Cr, and initial ε53Cr values of the Ryugu samples relative to any carbonaceous chondrite samples implies that its progenitor body formed from the least thermally processed precursors in the outermost region of the protoplanetary disk. Despite accreting at different distances from the Sun, the hydrous asteroids (Ryugu and the parent bodies of CI, CM, CR, and ungrouped C2 meteorites) underwent aqueous alteration during a period of limited duration (3.8 ± 1.8 Myr after CAI). These ages are identical to the crystallization age of the carbonaceous achondirtes NWA 6704/6693 within the error. The ε54Cr and initial ε53Cr values of Ryugu and NWA 6704/6693 are also identical, while they show distinct Δ'17O values. This suggests that the precursors that formed the progenitor bodies of Ryugu and NWA 6703/6693 were formed in close proximity and experienced a similar degree of thermal processing in the protosolar nebula. However, the progenitor body of Ryugu was formed by a higher ice/dust ratio, than NWA6703/6693, in the outer region of the protoplanetary disk. No potential conflict of interest relevant to this article was reported.

The Pheasant Memorial Laboratory for Geochemistry and Cosmochemistry, Institute for Planetary Materials, Okayama University Acta Medica Okayama 2021 Element concentrations of chondrule constituents, supplement to: Tak Kunihiro et al. (2021): The trace element composition of chondrule constituents: Implications for sample return methodologies and the chondrule silicate reservoir. Meteorit Planet Sci EN Tak Kunihiro The Pheasant Memorial Laboratory, Institute for Planetary Materials, Okayama University Tsutomu Ota The Pheasant Memorial Laboratory, Institute for Planetary Materials, Okayama University Masahiro Yamanaka The Pheasant Memorial Laboratory for Geochemistry and Cosmochemistry, Institute for Planetary Materials, Okayama University Eizo Nakamura The Pheasant Memorial Laboratory, Institute for Planetary Materials, Okayama University 10.18926/61900 No potential conflict of interest relevant to this article was reported.

Wiley Acta Medica Okayama 1639-4488 43 1 2018 Determination of Abundances of Fifty-Two Elements in Natural Waters by ICP-MS with Freeze-Drying Pre-concentration 147 161 EN Que D. Hoang The Pheasant Memorial Laboratory for Geochemistry and Cosmochemistry, Institute for Planetary Materials, Okayama University Tak Kunihiro The Pheasant Memorial Laboratory, Institute for Planetary Materials, Okayama University Chie Sakaguchi The Pheasant Memorial Laboratory for Geochemistry and Cosmochemistry, Institute for Planetary Materials, Okayama University Masahiro Yamanaka The Pheasant Memorial Laboratory for Geochemistry and Cosmochemistry, Institute for Planetary Materials, Okayama University Hiroshi Kitagawa The Pheasant Memorial Laboratory for Geochemistry and Cosmochemistry, Institute for Planetary Materials, Okayama University Eizo Nakamura The Pheasant Memorial Laboratory, Institute for Planetary Materials, Okayama University To precisely determine the abundances of fifty-two elements found within natural water samples, with mass fractions down to fg g(-1) level, we have developed a method which combines freeze-drying pre-concentration (FDC) and isotope dilution internal standardisation (ID-IS). By sublimation of H2O, the sample solution was reduced to < 1/50 of the original volume. To determine element abundance with accuracy better than 10%, we found that for solutions being analysed by mass spectrometry the HNO3 concentration should be > 0.3 mol l(-1) to avoid hydrolysis. Matrix-affected signal suppression was not significant for the solutions with NaCl concentrations lower than 0.2 and 0.1 cg g(-1) for quadrupole ICP-MS and sector field ICP-MS, respectively. The recovery yields of elements after FDC were 97-105%. The detection limits for the sample solutions prepared by FDC were <= 10 pg g(-1), except for Na, K and Ca. Blanks prepared using FDC were at pg-levels, except for eleven elements (Na, Mg, Al, P, Ca, Mn, Fe, Co, Ni, Cu and Zn). The abundances of fifty-two elements in bottled drinking water were determined from five different geological sources with mass fractions ranging from the fg g(-1) to mu g g(-1) level with high accuracy. No potential conflict of interest relevant to this article was reported.

John Wiley Acta Medica Okayama 16394488 43 4 2019 Method to Suppress Isobaric and Polyatomic Interferences for Measurements of Highly Siderophile Elements in Desilicified Geological Samples 611 633 EN Xiaoyu Zhou The Pheasant Memorial Laboratory for Geochemistry and Cosmochemistry, Institute for Planetary Materials, Okayama University Ryoji Tanaka The Pheasant Memorial Laboratory for Geochemistry and Cosmochemistry, Institute for Planetary Materials, Okayama University Masahiro Yamanaka The Pheasant Memorial Laboratory for Geochemistry and Cosmochemistry, Institute for Planetary Materials, Okayama University Chie Sakaguchi The Pheasant Memorial Laboratory for Geochemistry and Cosmochemistry, Institute for Planetary Materials, Okayama University Eizo Nakamura The Pheasant Memorial Laboratory for Geochemistry and Cosmochemistry, Institute for Planetary Materials, Okayama University Sample decomposition using inverse aqua regia at elevated temperatures and pressures (e.g., Carius tube or high‐pressure asher) is the most common method used to extract highly siderophile elements (HSEs: Ru, Rh, Pd, Re, Os, Ir, Pt and Au) from geological samples. Recently, it has been recognised that additional HF desilicification is necessary to better recover HSEs, potentially contained within silicate or oxide minerals in mafic samples, which cannot be dissolved solely by inverse aqua regia. However, the abundance of interfering elements tends to increase in the eluent when conventional ion‐exchange purification procedures are applied to desilicified samples. In this study, we developed an improved purification method to determine HSEs in desilicified samples. This method enables the reduction of the ratios of isobaric and polyatomic interferences, relative to the measured intensities of HSE isotope masses, to less than a few hundred parts per million. Furthermore, the total procedural blanks are either comparable to or lower than conventional methods. Thus, this method allows accurate and precise HSE measurements in mafic and ultramafic geological samples, without the need for interference corrections. Moreover, the problem of increased interfering elements, such as Zr for Pd and Cr for Ru, is circumvented for the desilicified samples. No potential conflict of interest relevant to this article was reported.