掲載種別：研究論文（学術雑誌）   出版者・発行元：Mary Ann Liebert Inc  

DOI： 10.1089/ast.2021.0158

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その他リンク： https://www.liebertpub.com/doi/pdf/10.1089/ast.2021.0158

掲載種別：研究論文（学術雑誌）   出版者・発行元：Japan Academy  

DOI： 10.2183/pjab.98.015

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掲載種別：研究論文（学術雑誌）   出版者・発行元：Geological Society of America  

Abstract

Lithium is of great interest as a tracer of metamorphic reactions and related fluid-mineral interactions because of its potential to isotopically fractionate during inter- and intracrystalline diffusional processes. Study of its transfer through subduction zones, based on study of arc volcanic and metamorphic rocks, can yield insight regarding ocean-to-mantle chemical cycling.

We investigated major- and trace-element concentrations and δ7Li in garnet in ultrahigh-pressure (UHP) Lago di Cignana metasedimentary rocks, relating these observations to reconstructed prograde devolatilization history. In all garnet crystals we studied, heavy rare earth elements (HREEs), Y, and Li showed strong zoning, with elevated concentrations in cores (15–50 ppm Li) and marked high-concentration anomalies (up to 117 ppm Li, 5500 ppm Y; little or no major-element shift) as growth annuli, in which some crystals showed subtle elevation in δ7Li greater than analytical error of ~3% (2σ). Rutile inclusions appeared abruptly at annuli and outward toward rims, accompanied by inclusions of a highly zoned, Ca- and rare earth element–rich phase and decreased Nb concentrations in garnet. These relationships are interpreted to reflect prograde garnet-forming reaction(s), in part involving titanite breakdown to stabilize rutile, which resulted in delivery of more abundant Y and HREEs at surfaces of growing garnet crystals to produce annuli. Co-enrichments in Li and Y + REEs are attributed to mutual incorporation via charge-coupled substitutions; thus, increased Li uptake was a passive consequence of elevated concentrations of Y + REEs. The small-scale fluctuations in δ7Li (overall range of ~9%) observed in some crystals may correlate with abrupt shifts in major- and trace-element concentrations, suggesting that changes in reactant phases exerted some control on the evolution of δ7Li. For one garnet crystal, late-stage growth following partial resorption produced deviation in major- and trace-element compositions, including Li concentration, accompanied by a 10%–15% negative shift in δ7Li, perhaps reflecting a change in the mechanism of incorporation or source of Li.

These results highlight the value of measuring the major- and trace-element and isotope compositions of garnets in high-pressure and UHP metamorphic rocks in which matrix mineral assemblages are extensively overprinted by recrystallization during exhumation histories. Lithium concentrations and isotope compositions of the garnets can add valuable information regarding prograde (and retrograde) reaction history, kinetics of porphyroblast growth, intracrystalline diffusion, and fluid-rock interactions. This work, integrated with previous study of devolatilization in the Schistes Lustrés/Cignana metasedimentary suite, indicates retention of a large fraction of the initially subducted sedimentary Li budget to depths approaching those beneath volcanic fronts, despite the redistribution of this Li among mineral phases during complex mineral reaction histories.

DOI： 10.1130/ges02473.1

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掲載種別：研究論文（学術雑誌）   出版者・発行元：Elsevier BV  

DOI： 10.1016/j.lithos.2022.106609

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掲載種別：研究論文（学術雑誌）   出版者・発行元：American Astronomical Society  

Abstract

The Japanese Hayabusa2 mission has revealed in detail the physical characteristics of the C-type asteroid 162173 Ryugu, in particular, its spinning top-shaped rubble-pile structure and potentially high organic content. A widely accepted formation scenario for Ryugu is catastrophic collision between larger asteroids and the subsequent slow gravitational accumulation of collisional debris. An alternative scenario is that Ryugu is an extinct comet that lost its icy components. Here, we numerically simulated the sublimation of water ice from a porous cometary nucleus until the refractory components, such as silicate rocks and organic matter, were left behind as evaporative residues. Such a process represents the transformation from a comet to an asteroid. The spin-up related to the shrinking nucleus, associated with water ice sublimation, was also calculated. The result of the calculation indicates that the cometary origin scenario can account for all the features of Ryugu discussed above. We conclude that organic-rich spinning top-shaped rubble-pile asteroids, such as Ryugu, are comet–asteroid transition objects or extinct comets.

DOI： 10.3847/2041-8213/ac4bd5

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その他リンク： https://iopscience.iop.org/article/10.3847/2041-8213/ac4bd5/pdf

掲載種別：研究論文（学術雑誌）   出版者・発行元：American Geophysical Union (AGU)  

DOI： 10.1029/2021je007052

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その他リンク： https://onlinelibrary.wiley.com/doi/full-xml/10.1029/2021JE007052

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：WILEY  

Sample return missions represent great opportunities to study terrestrially uncontaminated solar system materials. However, the size of returned samples will be limited, and thus, it is necessary to understand the most appropriate techniques to apply. Accordingly, the sensitivity of laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS) and secondary ion mass spectrometry (SIMS) was compared through the analyses of trace elements in reference materials and the Allende CV3 chondrite. While the SIMS method was found to be more sensitive than the laser method toward all elements of interest, the LA-ICPMS appears to be more suitable in terms of precision for certain elements. Using both analytical techniques, we measured chemical composition of an Allende chondrule and its igneous rim. These data were used to understand the nature of the reservoir that interacted with the host chondrule during formation of its igneous rim. We find that the igneous rim is enriched in silica, alkalis, and rare earth elements compared to the host chondrule. We suggest that the igneous rim could be explained by melting of a mixture of the chondrule-like and REE-enriched CAI-like precursors that accreted on the surface of the host chondrule followed by gas-melt interaction with a silica- and alkali-rich gas. Alternatively, these observations could be interpreted as a result of interaction between the chondrule and the melt resulting from partial melting of a pre-existing planetesimal in the early stages of its differentiation.

DOI： 10.1111/maps.13665

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：MARY ANN LIEBERT, INC  

The Hayabusa2 mission successfully collected samples from the asteroid Ryugu last year and will return these to Earth in December 2020. It is anticipated that the samples will enable the analysis of terrestrially uncontaminated organic matter and minerals. Such analyses are in turn expected to elucidate the evolution of organic matter through Solar System history, including the origination and processing of biogenically important molecules, which could have been utilized by the first organisms on Earth. In anticipation, studies have made predictions concerning the properties of Ryugu, including its composition. The spectral characteristics of Ryugu, such as albedo, have been employed to relate the asteroid to members of the carbonaceous chondrite group that have been identified on Earth. However, the recent Hayabusa2 touchdown highlights a disparity between the color of surfaces of displaced platy fragments, indicating a brightening trend for the surface exposed to space compared to that facing into the body. Here we present a mass balance calculation with reference to data from the literature, which indicates that Ryugu may contain a significantly higher abundance of organic matter (likely >50%) than the currently most accepted meteorite analogues. A high organic content may result in high levels of extractable organic matter for the second touchdown site, where the spacecraft sampled freshly exposed material. However, high abundances of insoluble aromatic/graphitic rich organic matter may be present in the first touchdown site, which sampled the surface of Ryugu that had been exposed to space. Moreover, we suggest that the potentially high organic abundance and the rubble-pile nature of Ryugu may originate from the capture of rocky debris by a comet nucleus and subsequent water-organic-mineral interactions and sublimation of water ice.

DOI： 10.1089/ast.2019.2198

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掲載種別：研究論文（学術雑誌）  

Carbonaceous chondrites contain many abiotic organic compounds, some of which are found in life on Earth. Both the mineral and organic matter phases, of these meteorites, have been affected by aqueous alteration processes. Whilst organic matter is known to be associated with phyllosilicate phases, no such relationship has yet been identified for specific organic compound classes. Furthermore, ongoing sample return missions, Hyabusa 2 and OSIRIS-Rex, are set to return potentially organic rich C-type asteroid samples to the Earth. Consequently, strategies to investigate organic-mineral relationships are required. Here we report spatial data for free/soluble organic matter (FOM/SOM) components (akylimidazole and alkylpyridine homologues) and mineral phases. Low and intermediate molecular weight alkylimidazole homologues are more widely distributed than higher molecular weight members, likely due to their affinity for the aqueous phase. On aqueous alteration of anhydrous mineral phases, transported FOM is adsorbed onto the surface or into the interlayers of the resulting phyllosilicates and thus concentrated and protected from oxidising fluids. Therefore, aiding the delivery of biologically relevant molecules to earth, shortly preceding the origin of life.

DOI： 10.7185/geochemlet.2010

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：PERGAMON-ELSEVIER SCIENCE LTD  

We report in situ ion-microprobe analyses of Li- and O-isotope compositions for olivine, low-Ca pyroxene, high-Ca pyroxene, and chondrule mesostasis/plagioclase in nine chondrules from the Allende CV3 chondrite. Based on their mineralogy and O-isotope compositions, we infer that the chondrule mesostasis/plagioclase and ferroan olivine rims were extensively modified or formed during metasomatic alteration and metamorphism on the Allende parent asteroid. We excluded these minerals in order to determine the correlations between Li and both O and the chemical compositions of olivines and low-Ca pyroxenes in the chondrules and their igneous rims. Based on the O-isotope composition of the olivines, nine chondrules were divided into three groups. Average Delta O-17 of olivines (Fo(>65)) in group 1 and 2 chondrules are -5.3 +/- 0.4 and -6.2 +/- 0.4 parts per thousand, respectively. Group 3 chondrules are characterized by the presence of O-16-rich relict grains and the Delta O-17 of their olivines range from -23.7 to -6.2 parts per thousand. In group 1 olivines, as Fa content increases, variation of delta Li-7 becomes smaller and delta Li-7 approaches the whole-rock value (2.4 parts per thousand; Seitz et al., 2012), suggesting nearly complete Li-isotope equilibration. In group 2 and 3 olivines, variation of delta Li-7 is limited even with a significant range of Fa content. We conclude that Li-isotope compositions of olivine in group 1 chondrules were modified not by an asteroidal process but by an igneous-rim formation process, thus chondrule olivines retained Li-isotope compositions acquired in the protosolar nebula. In olivines of the group 3 chondrule PO-8, we observed a correlation between O and Li isotopes: In relict O-16-rich olivine grains with Delta O-17 of similar to-25 to -20 parts per thousand, delta Li-7 ranges from -23 to -3 parts per thousand; in olivine grains with Delta O-17 > -20 parts per thousand, delta Li-7 is nearly constant (-8 +/- 4 parts per thousand). Based on the Li-isotope composition of low-Ca pyroxenes, which formed from melt during the crystallization of host chondrules and igneous rims, the existence of a gaseous reservoir with a delta Li-7 similar to -11 parts per thousand is inferred. (C) 2019 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.gca.2019.02.038

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：JAPAN ACAD  

A comprehensive geochemical study of the Chelyabinsk meteorite reveals further details regarding its history of impact-related fragmentation and melting, and later aqueous alteration, during its transit toward Earth. We support an similar to 30 Ma age obtained by Ar-Ar method (Beard et al., 2014) for the impact-related melting, based on Rb-Sr isotope analyses of a melt domain. An irregularly shaped olivine with a distinct 0 isotope composition in a melt domain appears to be a fragment of a silicate-rich impactor. Hydrogen and Li concentrations and isotopic compositions, textures of Fe oxyhydroxides, and the presence of organic materials located in fractures, are together consistent with aqueous alteration, and this alteration could have pre-dated interaction with the Earth's atmosphere. As one model, we suggest that hypervelocity capture of the impact-related debris by a comet nucleus could have led to shock-wave-induced supercritical aqueous fluids dissolving the silicate, metallic, and organic matter, with later ice sublimation yielding a rocky rubble pile sampled by the meteorite.

DOI： 10.2183/pjab.95.013

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：WILEY  

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.

DOI： 10.1111/ggr.12245

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We review the oxygen isotopic compositions of chondrite components (refractory inclusions, chondrules, and matrix) and their inter- and intra- crystalline oxygen isotopic distributions. Primary oxygen isotopic compositions, acquired before planetesimal accretion, are easily disturbed by parent-body processes such as aqueous alternation and thermal metamorphism. Primary or original oxygen isotopic compositions of refractory inclusions (Ca-, Al-rich inclusions and amoeboid olivine aggregates) distribute along a slope-1 line on the three-oxygen isotope diagram over the range of -60% < SnO δ17O ≈ δ18 < +10%. The variations suggest that oxygen isotopic compositions of the solar nebular gas temporally and spatially varied between l6O-rich and 17O-, 18O-rich during refractory inclusion formation. On the other hand, primary minerals of most chondrules have small isotopic variations and are enriched in 17170 and l8O relative to refractory inclusions, suggesting that chondrule formation occurred in 17O-, 18O-rich nebular gas. However, rare 16O-rich chondrules have been found, suggesting some overlap in the timing of formation of chondrules and refractory inclusions in the solar nebula. Oxygen isotopic compositions of matrix grains distribute along the slope-1 line over the same range as refractory inclusions and chondrules. The similarity in oxygen isotopic distributions suggests that matrix was originally a mechanical mixture of nebular dusts co-generated with chondrules and refractory inclusions. Presolar grains with oxygen isotopic compositions that are clearly distinct from those of solar nebular materials are a trace component of chondrite matrices. Based on these oxygen isotopic characteristics, more than 99.5% of the solid materials in the nebula formed locally in the solar nebula, and the remainder formed in interstellar space. The astrophysical setting of chondrite component formation in the early Solar System is also discussed. Refractory inclusions and 16O-rich matrix dusts formed around the inner edge of the solar nebula. On the other hand, most chondrules and 17O-, 18O-rich matrix dusts seem to have formed elsewhere in the solar nebula. Efficient, large-scale radial mixing of the solar nebular materials may have been an essential process in the formation of chondritic planetesimals.

DOI： 10.2138/rmg.2008.68.8

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：WILEY  

Software designed for analytical laboratories to guarantee traceability and accessibility of rocks with their geochemical properties has been developed. The software documents the sample origin, current sample location and the location of any sample subsets (e.g., thin sections, solutions, etc.), and archives all associated geochemical data sets. The software can be installed on a personal computer so is available for use in any laboratory and allows curation before and after publication. The software will be of use in integrating and sharing geological reference materials within and among institutes. In this article, the system design and implementation are detailed. All source codes for the software are available at .

DOI： 10.1111/j.1751-908X.2013.00205.x

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：NATL ACAD SCIENCES  

Records of micrometeorite collisions at down to submicron scales were discovered on dust grains recovered from near-Earth asteroid 25143 (Itokawa). Because the grains were sampled from very near the surface of the asteroid, by the Hayabusa spacecraft, their surfaces reflect the low-gravity space environment influencing the physical nature of the asteroid exterior. The space environment was examined by description of grain surfaces and asteroidal scenes were reconstructed. Chemical and O isotope compositions of five lithic grains, with diameters near 50 mu m, indicate that the uppermost layer of the rubble-pile-textured Itokawa is largely composed of equilibrated LL-ordinary-chondrite-like material with superimposed effects of collisions. The surfaces of the grains are dominated by fractures, and the fracture planes contain not only sub-mu m-sized craters but also a large number of sub-mu m-to several-mu m-sized adhered particles, some of the latter composed of glass. The size distribution and chemical compositions of the adhered particles, together with the occurrences of the sub-mu m-sized craters, suggest formation by hypervelocity collisions of micrometeorites at down to nm scales, a process expected in the physically hostile environment at an asteroid's surface. We describe impact-related phenomena, ranging in scale from 10(-9) to 10(4) meters, demonstrating the central role played by impact processes in the long-term evolution of planetary bodies. Impact appears to be an important process shaping the exteriors of not only large planetary bodies, such as the moon, but also low-gravity bodies such as asteroids.

DOI： 10.1073/pnas.1116236109

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記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：日本表面科学会  

DOI： 10.1380/jsssj.33.681

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.2138/am.2011.3857

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掲載種別：研究論文（学術雑誌）  

It is widely acknowledged that olivine-hosted melt inclusions retain compositional information unavailable from the study of bulk-rock samples alone. Whether or not the compositions of melt inclusions are truly representative of geologically significant melt bodies has, however, been called into question; isotopic data are critical to resolving this debate but the rare existing data are contradictory. Previous studies of Pb isotope ratios suggest that large compositional variations are preserved by melt inclusions whereas Sr isotope data apparently do not. A new and extensive laser ablation Pb-isotope database is presented here and displays a degree of isotopic heterogeneity in key samples from Mangaia and the Pitcairn seamounts significantly less than previously reported. More than 95% of the inclusions analysed, including results for the low abundance Pb-isotope, 204Pb, which has previously proven difficult to measure, are within error of bulk-rock analyses from these locations. Trace element measurements on two inclusions of different isotopic character from the Pitcairn Seamounts are closely similar to each other, and do not easily support models in which melt inclusions from this locality represent mixing between the Pitcairn mantle plume and the local MORB magmas or lithosphere. Instead, a second component, likely derived from within the plume, is required to explain the isotope and trace element variations observed. In terms of isotopic compositions then, melt inclusions may in most cases be representative of geochemical conditions prevailing within the magmatic plumbing system. The range of isotopic compositions found in a single sample likely includes the composition of the transporting melt (groundmass of the rock) and compositions previously trapped in crystals in the magmatic plumbing system. © 2011 Elsevier B.V.

DOI： 10.1016/j.chemgeo.2011.08.005

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：PERGAMON-ELSEVIER SCIENCE LTD  

Elemental and isotopic abundances of lithium in chondrule constituents in the Allende CV3 meteorite were determined using secondary ion mass spectrometry. Olivines and mesostasis dominated by a feldspathic phase are depleted in Li (< 1 mu g g(-1) and 0.1-0.6 mu g g(-1), respectively). In contrast, low-Ca pyroxenes and mesostasis dominated by a Na-rich phase are enriched in Li (similar to 1-8 mu g g(-1) and 0.4-3.5 mu g g(-1), respectively) and the interchondrule matrix is generally enriched in Li (similar to 2.0 mu g g(-1) on average). The Li isotopic abundance of olivine ranges from delta(7)Li similar to -32 to 21. The spatial distributions of elemental and isotopic abundances of Li in olivines within individual chondrules exhibit no systematic pattern. This suggests that the distribution of Li in olivine was not disturbed during aqueous alteration or thermal metamorphism on the Allende meteorite parent body. Although mesostasis is the last crystallizing phase from a chondrule melt and is expected to be enriched in Li, in the Allende meteorite it is generally depleted in Li. We suggest that during aqueous alteration on the CV asteroid, Li in mesostasis was leached out by aqueous fluids. The Li-enriched Na-rich mesostasis was probably produced later by infiltration of Na-rich fluids. It seems likely that aqueous fluids sequestered alkali elements from the Allende-chondrite region in the CV parent asteroid, although significant amounts of Li are preserved in ferrous olivine in the interchondrule matrix. (C) 2008 Elsevier Ltd. All rights reserved,

DOI： 10.1016/j.gca.2008.10.039

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掲載種別：研究論文（学術雑誌）  

One of the primary objectives of the Genesis sample return mission is to measure the oxygen isotopic composition of the Sun to permil-level precision. The returned samples pose a unique analytical challenge, and around the world, there has been parallel development of several competing techniques to make the oxygen measurement on the Genesis concentrator samples. At UCLA, we have developed a hybrid instrument: a secondary ion mass spectrometer (SIMS) front-end combined with an accelerator mass spectrometer (AMS), whose purpose is to eliminate molecular interferences via dissociation. We describe here the current status of the development of the instrument and the remaining issues to address before we request the Genesis samples for analysis. © 2008 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.apsusc.2008.05.175

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掲載種別：研究論文（学術雑誌）  

Subduction of lithosphere, involving surficial materials, into the deep mantle is fundamental to the chemical evolution of the Earth. However, the chemical evolution of the lithosphere during subduction to depth remains equivocal. In order to identify materials subjected to geological processes near the surface and at depths in subduction zones, we examined B and Li isotopes behavior in a unique diamondiferous, K-rich tourmaline (K-tourmaline) from the Kokchetav ultrahigh-pressure metamorphic belt. The K-tourmaline, which includes microdiamonds in its core, is enriched in 11B relative to 10B (δ11B = -1.2 to +7.7) and 7Li relative to 6Li (δ7Li = -1.1 to +3.1). It is suggested that the K-tourmaline crystallized at high-pressure in the diamond stability field from a silicate melt generated at high-pressure and temperature conditions of the Kokchetav peak metamorphism. The heavy isotope signature of this K-tourmaline differs from that of ordinary Na-tourmalines in crustal rocks, enriched in the light B isotope (δ11B = -16.6 to -2.3), which experienced isotope fractionation through metamorphic dehydration reactions. A possible source of the heavy B-isotope signature is serpentine in the subducted lithospheric mantle. Serpentinization of the lithospheric mantle, with enrichment of heavy B-isotope, can be produced by normal faulting at trench-outer rise or trench slope regions, followed by penetration of seawater into the lithospheric mantle. Serpentine breakdown in the lithospheric mantle subducted in subarc regions likely provided fluids with the heavy B-isotope signature, which was acquired during the serpentinization prior to subduction. The fluids could ascend and cause partial melting of the overlying crustal layer, and the resultant silicate melt could inherit the heavy B-isotope signature. The subducting lithospheric mantle is a key repository for modeling the flux of fluids and associated elements acquired at a near the surface into the deep mantle. © 2008 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.gca.2008.05.002

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掲載種別：研究論文（学術雑誌）  

With one exception, the low-FeO relict olivine grains within high-FeO porphyritic chondrules in the type 3.0 Acfer 094 carbonaceous chondrite have Δ17O (= δ17O - 0.52 × δ18O) values that are substantially more negative than those of the high-FeO olivine host materials. These results are similar to observations made earlier on chondrules in CO3.0 chondrites and are consistent with two independent models: (1) Nebular solids evolved from low-FeO, low-Δ17O compositions towards high-FeO, more positive Δ17O compositions; and (2) the range of compositions resulted from the mixing of two independently formed components. The two models predict different trajectories on a Δ17O vs. log Fe/Mg (olivine) diagram, but our sample set has too few values at intermediate Fe/Mg ratios to yield a definitive answer. Published data showing that Acfer 094 has higher volatile contents than CO chondrites suggest a closer link to CM chondrites. This is consistent with the high modal matrix abundance in Acfer 094 (49 vol.%). Acfer 094 may be an unaltered CM chondrite or an exceptionally matrix-rich CO chondrite. Chondrules in Acfer 094 and in CO and CM carbonaceous chondrites appear to sample the same population. Textural differences between Acfer 094 and CM chondrites are largely attributable to the high degree of hydrothermal alteration that the CM chondrites experienced in an asteroidal setting. Copyright © 2005 Elsevier Ltd.

DOI： 10.1016/j.gca.2005.01.031

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掲載種別：研究論文（学術雑誌）  

Chondritic clast PV1 from the Plainview H-chondrite regolith breccia is a subrounded, 5-mm-diameter unequilibrated chondritic fragment that contains 13 wt% C occurring mainly within irregularly shaped 30-400-μm-size opaque patches. The clast formed from H3 chondrite material as indicated by the mean apparent chondrule diameter (310 μm vs. ∼300 μm in H3 chondrites), the mean Mg-normalized refractory lithophile abundance ratio (1.00 ± 0.09×H), the previously determined O-isotopic composition (Δ17O = 0.66‰ vs. 0.68 ± 0.04‰ in H3 chondrites and 0.73 ± 0.09‰ in H4-6 chondrites), the heterogeneous olivine compositions in grain cores (with a minimum range of Fa1-19), and the presence of glass in some chondrules. Although the clast lacks the fine-grained, ferroan silicate matrix material present in type 3 ordinary chondrites, PV1 contains objects that appear to be recrystallized clumps of matrix material. Similarly, the apparent dearth of radial pyroxene and cryptocrystalline chondrules in PV1 is accounted for by the presence of some recrystallized fragments of these chondrule textural types. All of the chondrules in PV1 are interfused indicating that temperatures must have briefly reached ∼1100°C (the approximate solidus temperature of H-chondrite silicate). The most likely source of this heating was by an impact. Some metal was lost during impact heating as indicated by the moderately low abundance of metallic Fe-Ni in PV1 (∼14 wt%) compared to that in mean H chondrites (∼18 wt%). The carbon enrichment of the clast may have resulted from a second impact event, one involving a cometary projectile, possibly a Jupiter-family comet. As the clast cooled, it experienced hydrothermal alteration at low water/rock ratios as evidenced by the thick rims of ferroan olivine around low-FeO olivine cores. The C-rich chondritic clast was later incorporated into the H-chondrite parent-body regolith and extensively fractured and faulted. Copyright © 2005 Elsevier Ltd.

DOI： 10.1016/j.gca.2004.11.001

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掲載種別：研究論文（学術雑誌）  

Two-dimensional 18O/16O isotopic analysis of the Vigarano matrix was conducted by secondary ion-imaging using a novel two-dimensional ion-imager. Quantitative oxygen-isotope images (isotopographs) of the Vigarano matrix show that 16O-rich micrograins are scattered within 16O-poor matrix. This heterogeneous O-isotopic distribution indicates that matrix is composed of different O-isotopic components that formed in different locations and/or at different times. However, the O-isotopic composition of groundmass in the matrix is the same as the bulk isotopic composition of the matrix within ±5‰ uncertainty. The spatial resolution and isotopic precision of our technique should allow submicron-size objects (>0.2 μm) with extreme O-isotopic anomalous characteristics (δ18OSMOW ∼250‰) to be detectable in isotopographs. Because the mean grain size of the matrix is ∼0.2 μm, the inability to detect such O-isotopic anomalous objects indicates that isotopically anomalous micrograins (e.g., presolar grains) are extremely rare in the Vigarano matrix and that most objects in the matrix were formed in the solar nebula or in the parent body. Copyright © 2005 Elsevier Ltd.

DOI： 10.1016/j.gca.2004.07.024

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掲載種別：研究論文（学術雑誌）  

We report the oxygen-isotope compositions of relict and host olivine grains in six high-FeO porphyritic olivine chondrules in one of the most primitive carbonaceous chondrites, CO3.0 Yamato 81020. Because the relict grains predate the host phenocrysts, microscale in situ analyses of O-isotope compositions can help assess the degree of heterogeneity among chondrule precursors and constrain the nebular processes that caused these isotopic differences. In five of six chondrules studied, the Δ17O (=δ17O - 0.52 · δ18O) compositions of host phenocrysts are higher than those in low-FeO relict grains; the one exception is for a chondrule with a moderately high-FeO relict. Both the fayalite compositions as well as the O-isotope data support the view that the low-FeO relict grains formed in a previous generation of low-FeO porphyritic chondrules that were subsequently fragmented. It appears that most low-FeO porphyritic chondrules formed earlier than most high-FeO porphyritic chondrules, although there were probably some low-FeO chondrules that formed during the period when most high-FeO chondrules were forming. Copyright © 2004 Elsevier Ltd.

DOI： 10.1016/j.gca.2004.02.011

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掲載種別：研究論文（学術雑誌）  

We report 26Mg excesses correlated with Al/Mg ratios in five chondrules from the primitive CO3.0 chondrite Yamato 81020 that yield a mean initial 26Al/27Al ratio of only (3.8 ± 0.7) × 10-6, about half that of ordinary chondrite (OC) chondrules. Even if asteroids formed immediately after chondrule formation, this ratio and the mean Al content of CO chondrites is only capable of raising the temperature of a well-insulated CO asteroid to 940 K, which is more than 560 K too low to produce differentiation. The same ratio combined with the higher Al content of CV chondrites results in a CV asteroid temperature of 1100 K. We calculate that the mean initial 26Al/27Al ratio of about 7.4 × 10-6 found in LL chondrules is only able to produce small amounts of melting, too little to produce differentiation. These results cast serious doubt on the viability of 26Al as the heat source responsible for asteroid differentiation. Inclusion of 60Fe raises temperatures about 160 K, but this increment is not enough to cause differentiation, even of an LL-chondrite asteroid. © 2004 Elsevier Ltd.

DOI： 10.1016/j.gca.2004.02.006

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：ELSEVIER SCIENCE BV  

Secondary ion mass spectrometry (SIMS) is widely used to identify the isotope ratio of the micro-area of materials. We demonstrate that the precision and spatial resolution of an ion microscope using SIMS coupled with a newly developed solid-state ion imager can be extended to two-dimensional isotope ratio imaging with permil-precision. An isotopic map for oxygen clearly reveals the distribution of 4% enrichment of 16 O in spinel particles embedded in melilite from a Ca-Al-rich inclusion of a carbonaceous chondrite. This characterization technique called isotopography thus provides the eyes to see small heterogeneity of isotope abundance in micro-scale. It is likely to find broad application in earth, material, and life science research. © 2002 Elsevier Science B.V. All rights reserved.

DOI： 10.1016/S0169-4332(02)00825-5

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：ELSEVIER SCIENCE BV  

The noise characteristics of a stacked CMOS active pixel sensor (SCAPS) for incident charged particles have been analyzed under 4.5 keV Si+ ion irradiation. The source of SCAPS dark current was found to change from thermal to electron leakage with decreasing device temperature. Leakage current at charge integration part in a pixel has been reduced to 0.1electronss-1 at 77K. The incident ion signals are computed by subtracting reset frame values from each frame using a non-destructive readout operation. With increase of irradiated ions, the dominant noise source changed from read noise, and shot noise from the incident ions, to signal frame fixed-pattern noise from variations in sensitivity between pixels. Pixel read noise is equivalent to ten incident ions. The charge of an incident ion is converted to 1.5electrons in the pixel capacitor. Shot noise corresponds to the statistical fluctuation of incident ions. Signal frame fixed-pattern noise is 0.7% of the signal. By comparing full well conditions to noise floor, a dynamic range of 80dB is achieved. SCPAS is useful as a two-dimensional detector for microanalyses such as stigmatic secondary ion mass spectrometry. © 2001 Elsevier Science B.V. All rights reserved.

DOI： 10.1016/S0168-9002(01)00795-1

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：JOHN WILEY & SONS LTD  

A stacked CMOS-type active pixel sensor (SCAPS) for charged particles has been developed. The SCAPS is an integral-type detector that has several advantages over conventional systems, including two-dimensional detection, wide dynamic range, no insensitive time, direct detection of charged particles and a high degree of robustness. The output characteristics of the SCAPS for incident charged particles has been analysed both theoretically and experimentally. The relationships between the output voltage of the SCAPS and the number of incident charged particles were formulated by including corrections for the non-ideal characteristics of transistors in a pixel. The fluctuation of output characteristics of the SCAPS was evaluated experimentally by irradiation of secondary 4.5 keV Si+ ions generated by SIMS. The function was used to determine the number of incident ions into each SCAPS pixel within twice the statistical error. The SCAPS is useful as a two-dimensional detector for microanalysis, such as stigmatic SIMS. Copyright © 2001 John Wiley & Sons, Ltd.

DOI： 10.1002/sia.968

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

A stacked CMOS-active pixel sensor (APS) with a newly devised pixel structure for charged particle detection has been developed. A twin well pixel with a p-MOS readout transistor achieves low leakage current caused by a hot carrier effect at low temperature as low as 5×10-8 V/s at the pixel electrode. The total read noise floor of 0.1mVrms was obtained by non-destructive readout CDS with the CDS interval of 21 seconds.

DOI： 10.1109/IEDM.2001.979566

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記述言語：英語   掲載種別：研究発表ペーパー・要旨（国際会議）   出版者・発行元：METEORITICAL SOC  

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記述言語：英語   掲載種別：研究発表ペーパー・要旨（国際会議）   出版者・発行元：PERGAMON-ELSEVIER SCIENCE LTD  

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記述言語：日本語   出版者・発行元：一般社団法人 映像情報メディア学会  

荷電粒子検出用イメージセンサの読み出しノイズを低減するため、新しい画素構造を導入した積層型CMOSイメージセンサを試作、評価した。画素内の読み出しトランジスタのホットキャリア効果を抑圧することで、低温動作時の暗電流ドリフトをほぼ検知限界以下の5×10^<-8>V/sまで低減することができた。また暗電流ノイズ低減と併せて、開口率の改善とチャネル雑音の低減を行い、さらにリセット雑音を非破壊読み出し(Non-Destructive Read Out-CDS: NDRO-CDS)で抑圧することで、感度を大幅に改善した。今回の素子を二次イオン質量分析装置に組み込んで評価した結果、10keVのAlイオン撮像実験において、トータルノイズフロア3ion/pixelかつダイナミックレンジ84dBを達成した。

DOI： 10.11485/itetr.26.26.0_7

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出版者・発行元：一般社団法人日本地球化学会  

南極産炭素質隕石Y81020 (CO3.0)中に見つかった粗粒CAIは内部がメリライトとファッサイトからなりWork-Loveringリムに囲まれている。このCAIを同位体顕微鏡を用いて空間分解能2ミクロンの酸素同位体分布マップを得ることに成功した。本発表ではその分析装置と分析法を示し、その結果の信頼性を吟味する。

DOI： 10.14862/geochemproc.49.0.110.0

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出版者・発行元：一般社団法人日本地球化学会  

同位体顕微鏡による酸素同位体分布マップとEPMAによる元素分布マップを比較することにより南極産炭素質隕石Y81020 (CO3.0)中に見つかった粗粒CAIの鉱物内の同位体不均一が鉱物の結晶成長に伴いどのようにして導入されたのかが議論された。酸素同位体以上は単一プロセスでCAI中に記録されたのではなく、非平衡状態における鉱物の溶融と結晶成長によるものであった。

DOI： 10.14862/geochemproc.49.0.111.0

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記述言語：日本語   出版者・発行元：一般社団法人 映像情報メディア学会  

Output characteristics of two-dimensional solid-state detector for charged particles has been analyzed by ion irradiation with keV level energy. The detector was designed by CMOS rule and constructed as stacked CMOS-device[1]. The detector was operated under nondestructive readout mode due to correction of fixed pattern noises among pixels and reset noise of a pixel. The output signals of a pixel correlated linearly with incoming ions over the range of four orders of magnitude. Non-linear effects of the output is about 10% over the whole dynamic range of a pixel. The dominant effects of the non-linear components are reset voltage drop down by overlap capacitance. After correction of the drop down effect the nonlinearity reduced to percent level, the percent level nonlinearity was due to voltage dependence of pixel capacitance with ion irradiation.

DOI： 10.11485/itetr.24.3.0_13

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記述言語：日本語   出版者・発行元：一般社団法人電子情報通信学会  

積層型荷電粒子検出用CMOSイメージセンサを開発した。本センサを2次イオン質量分析装置に導入し、80dBの広いダイナミックレンジと、良好な線形性を有する荷電粒子像検出システムを実現した。画素のノイズを評価した結果、CMOSセンサの特長である非破壊読み出しを利用してリセットノイズを抑圧できれば、将来的に100dBを超えるダイナミックレンジの実現も可能であると考えられる。

DOI： 10.11485/itetr.23.60.0_7

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記述言語：日本語   出版者・発行元：一般社団法人 映像情報メディア学会  

Charged particles such as ion and electrons with keV order kinetic energy are important for probes and signals for surface analyses. Many detection systems have been developed for measurement of two-dimensional distribution for the particles. However, capabilities of solid-state area detector are not sufficient for quantitative analysis for the charged particles, although solid-state imager such as charge coupled device has been great succeeded to photon detection for optical spectroscopy. This paper discussed performance and characteristics of a novel solid-state imager for charged particles. This device is useful to charged particle detection such as mass spectrometry and electron microscopy.

DOI： 10.11485/itetr.23.5.0_19

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