Language：English   Publishing type：Research paper (scientific journal)   Publisher：American Chemical Society (ACS)  

DOI： 10.1021/acs.analchem.3c03463

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Wiley  

Abstract

We report Nd and Sm isotopic compositions of four samples of Ryugu returned by the Hayabusa2 mission, including “A” (first touchdown) and “C” (second touchdown) samples, and several carbonaceous chondrites to evaluate potential genetic relationships between Ryugu and known chondrite groups and track the cosmic ray exposure history of Ryugu. We resolved Nd and Sm isotopic anomalies in small (<20 ng Nd and Sm) sample sizes via thermal ionization mass spectrometer using 10¹³ Ω amplifiers. Ryugu samples exhibit resolvable negative μ¹⁴²Nd values consistent with carbonaceous chondrite values, suggesting that Ryugu is related to the parent bodies of carbonaceous chondrites. Ryugu's negative μ¹⁴⁹Sm values are the result of exposure to galactic cosmic rays, as demonstrated by the correlation between ¹⁵⁰Sm/¹⁵²Sm and ¹⁴⁹Sm/¹⁵²Sm ratios that fall along the expected neutron capture correlation line. The neutron fluence calculated in the “A” samples (2.75 ± 1.94 × 10¹⁵ n cm⁻²) is slightly higher compared to the “C” samples (0.95 ± 2.04 × 10¹⁵ n cm⁻²), though overlapping within measurement uncertainty. The Sm results for Ryugu, at this level of precision, thus are consistent with a well‐mixed surface layer at least to the depths from which the “A” and “C” samples derive.

DOI： 10.1111/maps.14109

Language：English   Publishing type：Research paper (scientific journal)   Publisher：European Association of Geochemistry  

DOI： 10.7185/geochemlet.2341

Language：English   Publishing type：Research paper (scientific journal)   Publisher：American Astronomical Society  

Abstract

The nucleosynthetic isotope composition of planetary materials provides a record of the heterogeneous distribution of stardust within the early solar system. In 2020 December, the Japan Aerospace Exploration Agency Hayabusa2 spacecraft returned to Earth the first samples of a primitive asteroid, namely, the Cb-type asteroid Ryugu. This provides a unique opportunity to explore the kinship between primitive asteroids and carbonaceous chondrites. We report high-precision μ²⁶Mg* and μ²⁵Mg values of Ryugu samples together with those of CI, CM, CV, and ungrouped carbonaceous chondrites. The stable Mg isotope composition of Ryugu aliquots defines μ²⁵Mg values ranging from –160 ± 20 ppm to –272 ± 30 ppm, which extends to lighter compositions relative to Ivuna-type (CI) and other carbonaceous chondrite groups. We interpret the μ²⁵Mg variability as reflecting heterogeneous sampling of a carbonate phase hosting isotopically light Mg (μ²⁵Mg ∼ –1400 ppm) formed by low temperature equilibrium processes. After correcting for this effect, Ryugu samples return homogeneous μ²⁶Mg* values corresponding to a weighted mean of 7.1 ± 0.8 ppm. Thus, Ryugu defines a μ²⁶Mg* excess relative to the CI and CR chondrite reservoirs corresponding to 3.8 ± 1.1 and 11.9 ± 0.8 ppm, respectively. These variations cannot be accounted for by in situ decay of ²⁶Al given their respective ²⁷Al/²⁴Mg ratios. Instead, it requires that Ryugu and the CI and CR parent bodies formed from material with a different initial ²⁶Al/²⁷Al ratio or that they are sourced from material with distinct Mg isotope compositions. Thus, our new Mg isotope data challenge the notion that Ryugu and CI chondrites share a common nucleosynthetic heritage.

DOI： 10.3847/2041-8213/ad09d9

Other Link： https://iopscience.iop.org/article/10.3847/2041-8213/ad09d9/pdf

Language：English   Publishing type：Research paper (scientific journal)   Publisher：American Association for the Advancement of Science (AAAS)  

Studies of material returned from Cb asteroid Ryugu have revealed considerable mineralogical and chemical heterogeneity, stemming primarily from brecciation and aqueous alteration. Isotopic anomalies could have also been affected by delivery of exogenous clasts and aqueous mobilization of soluble elements. Here, we show that isotopic anomalies for mildly soluble Cr are highly variable in Ryugu and CI chondrites, whereas those of Ti are relatively uniform. This variation in Cr isotope ratios is most likely due to physicochemical fractionation between ⁵⁴ Cr-rich presolar nanoparticles and Cr-bearing secondary minerals at the millimeter-scale in the bulk samples, likely due to extensive aqueous alteration in their parent bodies that occurred after Solar System birth. In contrast, Ti isotopes were marginally affected by this process. Our results show that isotopic heterogeneities in asteroids are not all nebular or accretionary in nature but can also reflect element redistribution by water.

DOI： 10.1126/sciadv.adi7048

Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)  

DOI： https://doi.org/10.1093/rpd/ncad048

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.3847/1538-4357/acf37b

Language：English   Publishing type：Research paper (scientific journal)   Publisher：American Astronomical Society  

Abstract

We present oxygen isotopic analyses of fragments of the near-Earth C_b-type asteroid Ryugu returned by the Hayabusa2 spacecraft that reinforce the close correspondence between Ryugu and CI chondrites. Small differences between Ryugu samples and CI chondrites in ${ { \rm{\Delta } } }^{ { \prime} 17}{\rm{O } }$ can be explained at least in part by contamination of the latter by terrestrial water. The discovery that a randomly sampled C-complex asteroid is composed of CI-chondrite-like rock, combined with thermal models for formation prior to significant decay of the short-lived radioisotope ²⁶Al, suggests that if lithified at the time of alteration, the parent body was small (≪50 km radius). If the parent planetesimal was large (>50 km in radius), it was likely composed of high-permeability, poorly lithified sediment rather than consolidated rock.

DOI： 10.3847/psj/acea62

Other Link： https://iopscience.iop.org/article/10.3847/PSJ/acea62/pdf

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Springer Science and Business Media LLC  

DOI： 10.1038/s41561-023-01226-y

Other Link： https://www.nature.com/articles/s41561-023-01226-y

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1140/epjp/s13360-023-04279-5

Language：English   Publishing type：Research paper (scientific journal)   Publisher：American Association for the Advancement of Science (AAAS)  

Preliminary analyses of asteroid Ryugu samples show kinship to aqueously altered CI (Ivuna-type) chondrites, suggesting similar origins. We report identification of C-rich, particularly primitive clasts in Ryugu samples that contain preserved presolar silicate grains and exceptional abundances of presolar SiC and isotopically anomalous organic matter. The high presolar silicate abundance (104 ppm) indicates that the clast escaped extensive alteration. The 5 to 10 times higher abundances of presolar SiC (~235 ppm), N-rich organic matter, organics with N isotopic anomalies (1.2%), and organics with C isotopic anomalies (0.2%) in the primitive clasts compared to bulk Ryugu suggest that the clasts formed in a unique part of the protoplanetary disk enriched in presolar materials. These clasts likely represent previously unsampled outer solar system material that accreted onto Ryugu after aqueous alteration ceased, consistent with Ryugu’s rubble pile origin.

DOI： 10.1126/sciadv.adh1003

Language：English   Publishing type：Research paper (scientific journal)   Publisher：American Astronomical Society  

Abstract

Rock fragments of the Cb-type asteroid Ryugu returned to Earth by the JAXA Hayabusa2 mission share mineralogical, chemical, and isotopic properties with the Ivuna-type (CI) carbonaceous chondrites. Similar to CI chondrites, these fragments underwent extensive aqueous alteration and consist predominantly of hydrous minerals likely formed in the presence of liquid water on the Ryugu parent asteroid. Here we present an in situ analytical survey performed by secondary ion mass spectrometry from which we have estimated the D/H ratio of Ryugu’s hydrous minerals, D/H_Ryugu, to be [165 ± 19] × 10⁻⁶, which corresponds to δD_Ryugu = +59 ± 121‰ (2σ). The hydrous mineral D/H_Ryugu’s values for the two sampling sites on Ryugu are similar; they are also similar to the estimated D/H ratio of hydrous minerals in the CI chondrites Orgueil and Alais. This result reinforces a link between Ryugu and CI chondrites and an inference that Ryugu’s samples, which avoided terrestrial contamination, are our best proxy to estimate the composition of water at the origin of hydrous minerals in CI-like material. Based on this data and recent literature studies, the contribution of CI chondrites to the hydrogen of Earth’s surficial reservoirs is evaluated to be ∼3%. We conclude that the water responsible for the alteration of Ryugu’s rocks was derived from water ice precursors inherited from the interstellar medium; the ice partially re-equilibrated its hydrogen with the nebular H₂ before being accreted on the Ryugu’s parent asteroid.

DOI： 10.3847/2041-8213/acc393

Other Link： https://iopscience.iop.org/article/10.3847/2041-8213/acc393/pdf

Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1093/rpd/ncad015

Language：English   Publishing type：Research paper (scientific journal)   Publisher：American Association for the Advancement of Science (AAAS)  

The extraterrestrial materials returned from asteroid (162173) Ryugu consist predominantly of low-temperature aqueously formed secondary minerals and are chemically and mineralogically similar to CI (Ivuna-type) carbonaceous chondrites. Here, we show that high-temperature anhydrous primary minerals in Ryugu and CI chondrites exhibit a bimodal distribution of oxygen isotopic compositions: ¹⁶ O-rich (associated with refractory inclusions) and ¹⁶ O-poor (associated with chondrules). Both the ¹⁶ O-rich and ¹⁶ O-poor minerals probably formed in the inner solar protoplanetary disk and were subsequently transported outward. The abundance ratios of the ¹⁶ O-rich to ¹⁶ O-poor minerals in Ryugu and CI chondrites are higher than in other carbonaceous chondrite groups but are similar to that of comet 81P/Wild2, suggesting that Ryugu and CI chondrites accreted in the outer Solar System closer to the accretion region of comets.

DOI： 10.1126/sciadv.ade2067

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Springer Science and Business Media LLC  

DOI： 10.1038/s41550-022-01846-1

Other Link： https://www.nature.com/articles/s41550-022-01846-1

Language：English   Publishing type：Research paper (scientific journal)  

Little is known about the origin of the spectral diversity of asteroids and what it says about conditions in the protoplanetary disk. Here we show that samples returned from Cb-type asteroid Ryugu have Fe isotopic anomalies indistinguishable from Ivuna-type (CI) chondrites, which are distinct from all other carbonaceous chondrites. Iron isotopes, therefore, demonstrate that Ryugu and CI chondrites formed in a reservoir that was different from the source regions of other carbonaceous asteroids. Growth and migration of the giant planets destabilized nearby planetesimals and ejected some inwards to be implanted into the Main Belt. In this framework, most carbonaceous chondrites may have originated from regions around the birthplaces of Jupiter and Saturn, while the distinct isotopic composition of CI chondrites and Ryugu may reflect their formation further away in the disk, owing their presence in the inner Solar System to excitation by Uranus and Neptune.

DOI： 10.1126/sciadv.add8141

Scopus

PubMed

Language：English   Publishing type：Research paper (scientific journal)   Publisher：European Association of Geochemistry  

DOI： 10.7185/geochemlet.2238

Language：English   Publishing type：Research paper (scientific journal)   Publisher：American Astronomical Society  

We have conducted a NanoSIMS-based search for presolar material in samples
recently returned from C-type asteroid Ryugu as part of JAXA's Hayabusa2
mission. We report the detection of all major presolar grain types with O- and
C-anomalous isotopic compositions typically identified in carbonaceous
chondrite meteorites: 1 silicate, 1 oxide, 1 O-anomalous supernova grain of
ambiguous phase, 38 SiC, and 16 carbonaceous grains. At least two of the
carbonaceous grains are presolar graphites, whereas several grains with
moderate C isotopic anomalies are probably organics. The presolar silicate was
located in a clast with a less altered lithology than the typical extensively
aqueously altered Ryugu matrix. The matrix-normalized presolar grain abundances
in Ryugu are 4.8$^{+4.7}_{-2.6}$ ppm for O-anomalous grains, 25$^{+6}_{-5}$ ppm
for SiC grains and 11$^{+5}_{-3}$ ppm for carbonaceous grains. Ryugu is
isotopically and petrologically similar to carbonaceous Ivuna-type (CI)
chondrites. To compare the in situ presolar grain abundances of Ryugu with CI
chondrites, we also mapped Ivuna and Orgueil samples and found a total of SiC
grains and 6 carbonaceous grains. No O-anomalous grains were detected. The
matrix-normalized presolar grain abundances in the CI chondrites are similar to
those in Ryugu: 23 $^{+7}_{-6}$ ppm SiC and 9.0$^{+5.3}_{-4.6}$ ppm
carbonaceous grains. Thus, our results provide further evidence in support of
the Ryugu-CI connection. They also reveal intriguing hints of small-scale
heterogeneities in the Ryugu samples, such as locally distinct degrees of
alteration that allowed the preservation of delicate presolar material.

DOI： 10.3847/2041-8213/ac83bd

Scopus

arXiv

Other Link： http://arxiv.org/pdf/2208.07976v1

Language：English   Publishing type：Research paper (scientific journal)   Publisher：American Association for the Advancement of Science (AAAS)  

Carbonaceous meteorites are thought to be fragments of C-type (carbonaceous) asteroids. Samples of the C-type asteroid (162173) Ryugu were retrieved by the Hayabusa2 spacecraft. We measure the mineralogy, bulk chemical and isotopic compositions of Ryugu samples. They are mainly composed of materials similar to carbonaceous chondrite meteorites, particularly the CI (Ivuna-type) group. The samples consist predominantly of minerals formed in aqueous fluid on a parent planetesimal. The primary minerals were altered by fluids at a temperature of 37 ± 10°C, (Stat.) (Syst.) million years after formation of the first solids in the Solar System. After aqueous alteration, the Ryugu samples were likely never heated above ~100°C. The samples have a chemical composition that more closely resembles the Sun’s photosphere than other natural samples do.

DOI： 10.1126/science.abn7850

Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1017/S0016756822000164

Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：American Astronomical Society  

Abstract

Cosmic-ray exposure records of 13 lunar meteorites, Dhofar 081, Dhofar 910, Dhofar 911, Northwest Africa (NWA) 482, NWA 2995, NWA 2996, NWA 3136, NWA 3163, NWA 4472, NWA 4734, NWA 4884, NWA 4932, and NWA 4936, were characterized from the abundances of spallogenic (¹⁰Be and ²⁶Al) and neutron-captured (³⁶Cl, ⁴¹Ca,¹⁵⁰Sm, and ¹⁶⁸Er) nuclides produced by cosmic-ray irradiation. Assuming a single-stage irradiation model for individual meteorites, 11 of the 13 meteorites had resided at shallow depths in the range of 55 to 330 g cm⁻² from the lunar surface and experienced cosmic-ray irradiations for 140–870 Ma on the Moon. In contrast, 2 of the 13 meteorites, Dhofar 911 and NWA 4932, cannot be simply explained by a single-stage irradiation, but need at least two-stage irradiation on the Moon. Furthermore, the neutron fluences of thermal and epithermal energy regions for individual meteorites were quantified from a combination of the isotopic shifts of ¹⁴⁹Sm–¹⁵⁰Sm and ¹⁶⁷Er–¹⁶⁸Er, respectively. Our estimates gave 8–11 times higher epithermal neutron fluences (1.7–13.7 × 10¹⁷ neutrons cm⁻²) than the thermal neutron fluences (0.65–13.8 × 10¹⁶ neutrons cm⁻²) for 9 of the 13 meteorites, which are consistent with those from the lunar regolith materials in our previous study. This result also supports the long cosmic-ray irradiation of most lunar meteorites on the surface of the Moon.

File： apj_925_2_209.pdf

DOI： 10.3847/1538-4357/ac423a

Other Link： https://iopscience.iop.org/article/10.3847/1538-4357/ac423a/pdf

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

DOI： 10.1016/j.gca.2021.02.013

Authorship：Lead author,　Last author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：American Astronomical Society  

DOI： 10.3847/1538-4357/abbffe

Web of Science

Other Link： https://iopscience.iop.org/article/10.3847/1538-4357/abbffe

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：MDPI AG  

Isotopic analyses of elements in the natural reactor materials have often been performed to understand the distribution behaviors of the fission products and to evaluate the function of nuclear reactions since the first discovery of a natural reactor in 1972. Several types of unique microminerals, including significant amounts of fission products, have been found in and around the Oklo and the Bangombé natural reactors. In the past two decades, microbeam techniques using ion and laser probe facilities have been effectively applied for the in situ isotopic analyses of individual microminerals to investigate the migration behaviors of fissiogenic radioisotopes produced in the reactors. This paper presents a review of interpretations of the isotopic results of microminerals found in and around the natural reactors.

DOI： 10.3390/min10121060

Web of Science

Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Geochemical Society of Japan  

DOI： 10.2343/geochemj.2.0609

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Geochemical Society of Japan  

DOI： 10.2343/geochemj.2.0610

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1111/iar.12319

Web of Science

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Authorship：Lead author,　Last author,　Corresponding author   Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Springer  

DOI： 10.1007/978-3-319-89698-4_3

Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1016/j.gr.2018.07.003

Web of Science

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1016/j.precamres.2018.07.024

Web of Science

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier B.V.  

U–Pb zircon geochronology of two granite intrusions containing bluish‑tint K-feldspars and two biotite-hornblende gneisses in the Kagasawa area, situated at the center part of the Hida metamorphic complex, southwest Japan, reveals the early Triassic low P/T metamorphism in the Hida metamorphic complex (251–247 Ma). The granite intrusions into the Hida gneiss occurred at two different stages (235.4 ± 1.6 Ma and 183.6 ± 1.8 Ma) and thermally affected the Hida gneiss. In the Unazuki area, situated at the northeast margin of the Hida metamorphic complex, a quartzo-feldspathic schist and a biotite granite containing a quartzo-feldspathic schist as xenolith yielded U–Pb zircon ages of 258.0 ± 2.3 Ma and 253.0 ± 1.9 Ma, respectively, which indicates that the medium P/T metamorphism in the Unazuki area occurred in late Permian. The similarity between the geochemical compositions in whole rocks and zircons of the quartzo-feldspathic schist and the granite suggests that felsic volcanics were deposited on basement rocks at 258 Ma and, after affecting the medium P/T metamorphism, residual felsic magma was exhumed while taking the Unazuki schists as a xenolith at 253 Ma. Although the time interval between protolith formation and post-peak regional metamorphism in the Unazuki area (0.8–9.2 Ma) is similar to that in the Kagasawa area (1–8.6 Ma), the different timing of the regional metamorphism indicates that the protolith of the Unazuki metasediments was deposited not on the proximal Hida metamorphic complex but on ancient rocks containing Eoarchean-Paleoproterozoic components of the North China Craton.

DOI： 10.1016/j.chemgeo.2017.12.016

Web of Science

Scopus

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Academic Press Inc.  

Space weathering is an important process on the Moon and other airless celestial bodies. The most common space weathering effects are amorphization of the top surface of soil grains and formation of nanophase iron particles (npFe) within the partially amorphous rims. Hence, space weathering significantly affects optical properties of the surface of the Moon and other airless celestial bodies. Transmission electron microscope (TEM) analysis of Apollo 15 soil grains displays npFe (≤5 nm in size) embedded in the space-weathered rim (∼60 nm in thickness) of a pyroxene grain, consistent with previous studies. In contrast, submicron-sized fragments that adhere to the pyroxene grain show distinct space weathering features. Silicon oxide nanoparticles (npSiOx) were observed with npFe in a submicron-sized Mg–Fe silicate fragment. This is the first discovery of npSiOx as a product of space weathering. The npSiOx and the coexisting npFe are ∼10–25 nm in size, significantly larger than the typical npFe in the space weathered rim of the pyroxene grain. The coexisting npSiOx and npFe were probably formed directly in micrometeorite shock-induced melt, instead of in a solar-wind generated vapor deposit or irradiated rim. This new observation will shed light on space weathering processes on the Moon and airless celestial bodies.

DOI： 10.1016/j.icarus.2017.12.028

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Scopus

Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

Porphyry Copper Deposits (PCDs) dominantly form in convergent plate margins genetically related to volcanic arcs. However, their temporal relationships with active volcanism are less clear. Active volcanic activity is often considered to impede the formation of PCDs and some workers have concluded that PCD formation must take place at times of volcanic quiescence or at a waning stage of volcanism. However, several studies have documented evidence suggesting syn-eruption PCD formation. A combination of radiometric dating, geochemistry studies and observations of rock cores from the Cerro Colorado PCD, a BHP Billiton property located in N. Chile, provides evidence compatible with syn-volcanic PCD formation within a volcanic edifice.Textural observations at both hand specimen and microscopic scales combined with new LA-ICPMS and SHRIMP dating of zircons suggest the intrusive history of the Cerro Colorado area can be separated into two main units: a porphyritic tonalite ca. 53.5 Ma and a porphyritic quartz monzonite ca. 50 Ma. There is also evidence for crystallisation at ca. 60 Ma, but a corresponding distinct lithology was not identified. A quartz porphyry unit previously identified as the youngest intrusive body is reinterpreted as an altered equivalent of the monzonite. The youngest intrusive units are represented by porphyritic granodiorite with an age 51-50 Ma. These units only show minor metal mineralisation suggesting that the main phase of mineralisation in the Cerro Colorado mine occurred over a few million years, bracketed by the two main pulses of igneous intrusion, which are consistent with documented Ar-Ar ages. Re-Os ages reported by previous studies suggest an earlier phase of mineralisation at ca. 56-54 Ma. U-Pb dating of zircon from a volcanic-related breccia that cuts the host rocks of the Cerro Colorado Mine reveals a phase of volcanic activity at ca. 57 Ma, after formation of the regional Cretaceous Cerro Empexa Formation. This age range overlaps the ages derived for the intrusive porphyry units suggesting a close temporal relationship between volcanism and the ore-forming subvolcanic intrusions in Cerro Colorado. A link between active volcanism and mineralisation is reinforced by the ultrafine-grained matrix and the presence of strong brecciation associated with the monzonite-quartz porphyry stock suggesting decompression and volatile release have taken place during emplacement.

DOI： 10.1016/j.oregeorev.2017.12.019

Web of Science

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Institute of Physics Publishing  

Aqueous alteration is one of the primitive activities that occurred on meteorite parent bodies in the early solar system. The Tagish Lake meteorite is known to show an intense parent body aqueous alteration signature. In this study, quantitative analyses of the alkaline elements and isotopic analyses of Sr and Ba from acid leachates of TL (C2-ungrouped) were performed to investigate effects of aqueous alteration. The main purpose of this study is to search for isotopic evidence of extinct 135Cs from the Ba isotopic analyses in the chemical separates from the Tagish Lake meteorite. Barium isotopic data from the leachates show variable 135Ba isotopic anomalies (ϵ = -2.6 ∼ +3.6) which correlatewith 137Ba and 138Ba suggesting a heterogeneous distribution of s- and r-rich nucleosynthetic components in the early solar system. The 87Rb-87Sr and 135Cs-135Ba decay systems on TL in this study do not provide any chronological information. The disturbance of the TL chronometers is likely a reflection of the selective dissolution of Cs and Rb given the relatively higher mobility of Cs and Rb compared to Ba and Sr, respectively, during fluid mineral interactions.

DOI： 10.3847/1538-4357/aaa1e3

Web of Science

Scopus

Language：English   Publishing type：Research paper (scientific journal)   Publisher：PERGAMON-ELSEVIER SCIENCE LTD  

Mesosiderites are a group of stony-iron meteorites, which are thought to be the result of mixing of silicates with Fe-Ni metal. In this study, we combined textural observations with geochemical and chronological studies of two zircon grains found in the Estherville mesosiderite. One of the zircons (Zrc1) occurs with pyroxene, plagioclase, troilite, and silica, and the other (Zrc2) is located at a boundary between Fe-Ni metal and a silicate part mainly composed of pyroxene and plagioclase. The textural observations demonstrate that Zrc1 is relatively homogenous, whereas Zrc2 is composed of at least two chemically distinct domains. Trace element analyses of Zrc2 resolve large concentration gradients within this single grain with variations that are an order of magnitude for rare earth elements (REE) and two orders of magnitude for U and Th. The lowest trace element concentration in Zrc2 is more than an order of magnitude lower than those of lunar and eucritic zircons. However, it is similar to those of Zrc1 and a zircon from the Vaca Muerta mesosiderite. The calculated REE composition of the melt in equilibrium with Zrc2 shows that Zrc2 and perhaps also Zrc1 did not crystallize from a melt that was produced by fractional crystallization of the primary magmatic mineral assemblages. The zircons with low REE, U, and Th concentrations can be interpreted to have formed in a residual melt after incorporation of large amounts of REE, U, and Th into secondary phosphate minerals, which formed during the metal-silicate mixing event. The large concentration gradients observed in Zrc2 suggest significant heterogeneities in the melt from which the zircon crystallized. Alternatively, either mixing or diffusion between a relict zircon and a newly formed zircon could explain the observed concentration gradients. However, the REE patterns of Zrc2 cannot be explained by mixing or diffusion between the two distinct generations of zircons. These considerations suggest that Zrc1 and Zrc2 formed during a high-temperature reheating event, which is probably related to the metalsilicate mixing event. The weighted average Pb-207-Pb-206 age obtained by SIMS from both zircons is 4521 +/- 26 Ma (2 sigma). This age is younger than that of a primary magmatic zircon from Vaca Muerta (4563 +/- 15 Ma) and probably corresponds to the timing of the metal-silicate mixing event or a later impact event. (C) 2017 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.gca.2017.07.028

Web of Science

Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

The Eastern Ghats Belt (EGB) is an orogenic belt which is known to evolve through Proterozoic time before cratonisation with Proto-India and holds an important key to the reconstruction of erstwhile supercontinents. To track the comprehensive evolution of the EGB with respect to Proto-India prior to and during its cratonisation, we carried out a detailed petrological and high-resolution geochronological investigation (zircon U-Pb SHRIMP and monazite U-Th-total Pb EPMA) on systematically sampled rocks from a transect across the western boundary of the EGB. Our results reveal that along a narrow zone near the thrust-bound margin between the EGB and Proto-India, the entire crustal segment, i.e. from deep-crustal granulites to mid-crustal cratonic amphibolites to shallow-crustal quartz breccia, was involved actively in the thrust-related tectonics during cratonisation of the EGB at similar to 550-500 Ma. This youngest imprint of the similar to 550-500 Ma event erased all the earlier age histories from the zircon and monazite grains of the marginal granulites. On the other hand, the older age-imprints are better preserved in the interior of the orogeny (similar to 30 km east of thrust-boundary between the EGB and the BC and further eastward) with little or no age-imprints of the final tectonic pulse. Combining all the new and earlier geochronological data with P-T calculations and textural characterisation, we propose a comprehensive and geochronologically well-constrained tectonic evolution of the EGB, which encompasses its earliest deep-crustal metamorphic to latest shallow-crustal sedimentation histories. The outcome of this study also reveals, for the first time, that the entire crustal section participated actively during the cratonisation. The new geochronological data coupled with field evidence and textural evidence from the shallow-crustal rock finally suggest that the thrusting vis-a-vis cratonisation was continued, at least, up to Late Cambrian, thus post-dating the Pan-African orogeny. (C) 2017 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.lithos.2017.07.020

Web of Science

Language：English   Publishing type：Research paper (scientific journal)   Publisher：IOP PUBLISHING LTD  

It is known that most lunar meteorites have complicated cosmic-ray exposure experiences on the Moon and in space. In this study, cosmic-ray irradiation histories of six lunar meteorites, Dhofar 489, Northwest Africa 032 (NWA 032), NWA 479, NWA 482, NWA 2995, and NWA 5000, were characterized from neutron-captured isotopic shifts of Sm and Gd, and from the abundances of long-lived cosmogenic radionuclides like Be-10, Al-26, Cl-36, and Ca-41. Sm and Gd isotopic data of all of six meteorites show significant isotopic shifts of Sm-149-Sm-150 and Gd-157-Gd-158 caused by accumulation of neutron capture reactions due to cosmic-ray irradiation, corresponding to the neutron fluences of (1.3-9.6). x. 10(16) n cm(-2). In particular, very large Sm and Gd isotopic shifts of NWA 482 are over those of a lunar regolith 70002, having the largest isotopic shifts among the Apollo regolith samples, corresponding to cosmic-ray exposure duration over 800 million years in the lunar surface (2 pi irradiation). Meanwhile, the concentrations of cosmogenic radionuclides for individual six meteorites show the short irradiation time less than one million years as their bodies in space (4 pi irradiation). Our data also support the results of previous studies, revealing that most of lunar meteorites have long exposure ages at shallow depths on the Moon and short transit times from the Moon to the Earth.

DOI： 10.3847/1538-3881/aa7139

Web of Science

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Geological Society of London  

We present detailed and high-precision geochronological data on granulites occurring along the western boundary of the Eastern Ghats Belt, India. Age data on systematically sampled rocks coupled with geochemical observation have a potential to unravel the overprinted tectonothermal events operated during Precambrian time. Zircon U-Pb SHRIMP and monazite electron probe microanalysis (EPMA) U-Th-total Pb analyses, chemical zoning, microtextural investigation, and pressure-temperature calculations were carried out on samples of four different rock types. Inherited zircons from migmatitic quartzofeldspathic gneiss and mafic granulite yielded ages of approximately 2900-2350 Ma, representing an older crustal component. The age of granulite metamorphism recorded from charnockite and pelitic granulite ranges between approximately 950 and 930 Ma (from zircon and monazite). A possible decompression event from this area that occurred during Rodinia break-up is recorded from the Y-rich zones of monazite closely associated with porphyroblastic garnet in pelitic granulite and dates from approximately 800 to 750 Ma. Zircon grains of charnockite also yield a similar age. The youngest age of approximately 525-510 Ma documented from the monazite grains of migmatitic quartzofeldspathic gneiss and pelitic granulite, along with a spot age from zircon of migmatitic quartzofeldspathic gneiss, testifies to the final assembly of East Antarctica with cratonic India as a part of East Gondwana.

DOI： 10.1144/SP457.1

Web of Science

Scopus

Authorship：Lead author,　Corresponding author   Language：Japanese   Publishing type：Research paper (conference, symposium, etc.)   Publisher：GEOCHEMICAL SOCIETY OF JAPAN  

<p>The model for early solar irradiation from young Sun has long been suggested, but is somehow model-depending and still disputable. Isotopic evidence of excess 10B decayed from 10Be in Calcium-Aluminum-rich inclusions (CAIs) and astronomical observations of intensive X-ray emissions from stellar analogues of the young Sun suggest that a fraction of the early solar materials were intensively irradiated by the young Sun. For further quantitative discussion about the early solar irradiation models, the possible occurrence of chemical fractionation of volatile elements including spallogenic B and Li during or after irradiation has been pointed out. In order to dissolve this issue, 138La has been chosen to be an adequate isotopic tracer as one of refractory and spallogenic products caused by solar irradiation. Finding of spallogenic 138La may provide isotopic constraints on the early solar irradiation models.</p>

DOI： 10.14862/geochemproc.64.0_199

Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-BLACKWELL  

A detailed zircon U-Pb (SHRIMP) geochronological study of the amphibolite to granulite-grade rocks of the Rengali Province of eastern India records the growth history of the southern margin of the Singhbhum Craton. Pelitic and mafic granulites from the gneissic belt exhibit contrasting styles of metamorphism. Zircon of the pelitic granulites from the eastern segment yields c. 3528-3064 Ma detrital ages. Charnockitic gneiss from the eastern segment has protolith age of 3058 +/- 15 Ma while that from the central segment has protolith age of 2861 +/- 30 Ma. The latter rock records high-grade metamorphism at 2818 +/- 15 Ma. Hornblende gneiss from the central sector has a protolith age of 2828 +/- 9 Ma. Deformed leucogranite in the central and undeformed granitoid in the eastern segment were emplaced at 2807 +/- 13 and 2809 +/- 13 Ma respectively. The protolith of felsic gneiss from the central sector was emplaced at 2776 +/- 24 Ma. Most of the zircon samples contain overgrowths of c. 2500 Ma, inferred to be the age of reworking of the gneissic belt. Our data suggest that the Rengali Province evolved as an orogenic belt in the Neoarchean time (c. 2800-2500 Ma) during southward growth of the Singhbhum Craton. These tectonothermal imprints at the margin of the Singhbhum Craton are possibly related to its inclusion within the supercontinent Ur.

DOI： 10.1111/jmg.12201

Web of Science

Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

The present study aims at tracking sediment provenance for a Mesoproterozoic craton-margin basin in eastern India, i.e. the Ampani Basin. Occurring on the eastern flank of the Archean Bastar Craton, the basin occupies a very strategic geographic position coinciding with the boundary between Archean craton and a Proterozoic orogenic belt with spatially varied tectonothermal history. The studied basin succession includes unmetamorphosed siliciclastic sediments deposited under three different environmental set-up viz. fluvial, shoreface and shelf. The basin sediment package defines a fining-upward succession with fluvial products at its base, shoreface deposits in the middle and shelf sandstone-siltstone-shale sediments at the top. In this study sandstone-siltstone and shale units encompassing the entire basin succession are analyzed geochemically and with U-Pb detrital zircon geochronology in order to characterize the sediment source/s. The basin was fed mainly by the Paleoarchean to late Paleoproterozoic granitoid source with minor contribution from mafic source particularly at the closing part of its depositional history. Except for relative enrichment, REE and trace element patterns of the three arenaceous units, viz. fluvial, shoreface, shelf sandstone are quite similar. U-Pb analysis of detrital zircon grains from the three units indicate that in the initial phase of basin deposition, sediments were sourced from Paleo- to Neoarchean and Palaeoproterozoic (with an age spread from ca. 3700 to 2400 Ma) provenance. From the middle shoreface part upwards, the Paleo- to Neoarchean sources fade away and a new Mesoproterozoic source (Co. 2000 -1700 Ma) was added with the continued Paleoproterozoic source/s. The youngest zircon populations of the three analyzed units yield an upper age limit of sedimentation at 2079 +/- 44 Ma (lower being close to 1446 +/- 21 Ma, as evident from the age of tuffaceous rocks on the middle shoreface part of the basin). The change in detrital zircon age spectra from the middle part of the stratigraphy might be due to some basin-adjacent tectonic activities. (C) 2016 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.precamres.2016.06.011

Web of Science

Language：English   Publishing type：Research paper (scientific journal)   Publisher：IOP PUBLISHING LTD  

It is known that the Sayama meteorite (CM2) shows an extensive signature for aqueous alteration on the meteorite parent body, and that most of the primary minerals in the chondrules are replaced with phyllosilicates as the result of the aqueous alteration. In this paper, it is confirmed from the observation of two-dimensional Raman spectra that a part of olivine in a chondrule collected from the Sayama chondrite is serperntinized. Ion microprobe analysis of the chondrule showed that alkaline elements such as Rb and Cs are heterogeneously redistributed in the chondrule. The result of higher Rb and Cs contents in serpentinized phases in the chondrule rather than in other parts suggested the selective adsorption of alkaline elements into the serpentine in association with early aqueous activity on the meteorite parent body. Furthermore Ba isotopic analysis provided variations of Ba-135/Ba-138 and Ba-137/Ba-138 in the chondrule. This result was consistent with our previous isotopic data suggesting isotopic evidence for the existence of the presently extinct nuclide Cs-135 in the Sayama meteorite, but the abundance of Cs-135 in the solar system remains unclear because of large analytical uncertainties.

DOI： 10.1088/0004-637X/815/1/76

Web of Science

Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

A diverse assemblage of accretionary complex, island-arc, ophiolitic and high-pressure, low-temperature metamorphic rocks occurs within the serpentinite melange at Port Macquarie on the eastern extremity of the New England Orogen of eastern Australia. New field observations, U-Pb zircon dating, petrography and geochemistry presented here establish a more robust chronology and interpretation of these rocks. Previously, all basalt, chert and volcaniclastic sandstones at Port Macquarie were grouped into the Watonga Formation. Ordovician to middle Devonian radiolarians and conodonts from 'Watonga' chert-basalt associations shows that they are older than, and unrelated to, 'Watonga' volcaniclastic rocks like those at Green Mound which contain volcanic/detrital zircons as young as 335 Ma that were derived from a Carboniferous arc. Volcanic detritus with pillow lava forming a block within the serpentinite melange yielded 452 +/- 10 Ma igneous zircons, indicating an Ordovician age. The Tacking Point Gabbro has an age of 390 +/- 7 Ma (Devonian) and geochemical affinities with intra-oceanic arc igneous suites. It was intruded into deformed cherts of the Watonga Formation giving a spatial link between an Ordovician-Devonian? Accretionary complex and adjacent Devonian island-arc. The MORE-like basalt-chert association of the Watonga Formation and the Devonian Tacking Point gabbro represents a mid-Paleozoic assemblage allochthonous to Gondwana, which possibly correlates with the Djungati and Gamilaroi terranes respectively located further west in the New England Orogen. Zircon dating shows that post-serpentinite mafic-felsic dykes were emplaced into the Port Macquarie serpentinite at 247 +/- 20 Ma and further disrupted. Therefore, tectonism affecting the serpentinite continued into the Early Triassic, with final movement during the Hunter-Bowen Orogeny. Our results from Port Macquarie are compatible with a tectonic model for the New England Orogen that involves episodic island-arc collisional events (Gamilaroi and Gympie terranes) interspersed with periods of continental margin "Andean-type" magmatism and accretion along eastern Gondwana. Crown Copyright (C) 2014 Published by Elsevier B.V. on behalf of International Association for Gondwana Research. All rights reserved.

DOI： 10.1016/j.gr.2014.02.013

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DOI： 10.1038/srep01130

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Language：English   Publishing type：Research paper, summary (international conference)   Publisher：WILEY-BLACKWELL  

Web of Science

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Web of Science

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Event date： 2023.8

Language：English   Presentation type：Oral presentation (general)  

Venue：Los Angeles   Country：United States  

Event date： 2023.7

Language：English   Presentation type：Oral presentation (general)  

Venue：Ryon   Country：France  

Event date： 2023.6

Language：English   Presentation type：Oral presentation (invited, special)  

Venue：Ochang   Country：Korea, Republic of  

Event date： 2022.12

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：熱海   Country：Japan  

Event date： 2022.9

Language：Japanese   Presentation type：Oral presentation (invited, special)  

Venue：東京   Country：Japan  

Event date： 2022.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：高知   Country：Japan  

Event date： 2022.6

Language：English   Presentation type：Oral presentation (invited, special)  

Venue：Strasbourg   Country：France  

Event date： 2021.11

Venue：Nagoya University   Country：Japan  

Event date： 2021.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：Hirosaki University   Country：Japan  

Event date： 2021.9

Language：Japanese   Presentation type：Poster presentation  

Venue：Hirosaki University   Country：Japan  

Event date： 2021.9

Language：Japanese   Presentation type：Poster presentation  

Venue：Hirosaki University   Country：Japan  

Event date： 2020.11

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：オンライン   Country：Japan  

Event date： 2020.6

Language：English   Presentation type：Oral presentation (general)  

Venue：on line  

Event date： 2019.10

Language：English   Presentation type：Oral presentation (invited, special)  

Venue：Algiers   Country：Algeria  

Event date： 2019.9

Language：Japanese   Presentation type：Oral presentation (invited, special)  

Venue：山口   Country：Japan  

Event date： 2019.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：東京   Country：Japan  

Event date： 2019.8

Language：English   Presentation type：Oral presentation (general)  

Venue：Barcelona   Country：Spain  

Event date： 2019.7

Language：English   Presentation type：Oral presentation (general)  

Venue：Sapporo   Country：Japan  

Event date： 2019.3

Language：English   Presentation type：Oral presentation (invited, special)  

Venue：Nagoya   Country：Japan  

Event date： 2019.3

Language：English   Presentation type：Oral presentation (invited, special)  

Venue：Niigata   Country：Japan  

Event date： 2018.11

Language：English   Presentation type：Oral presentation (general)  

Venue：Daejeon   Country：Korea, Republic of  

Event date： 2018.9

Language：Japanese   Presentation type：Oral presentation (invited, special)  

Venue：沖縄   Country：Japan  

Event date： 2018.8

Language：English   Presentation type：Oral presentation (general)  

Venue：Boston   Country：United States  

Event date： 2018.7

Language：English   Presentation type：Oral presentation (general)  

Venue：Moscow   Country：Russian Federation  

Event date： 2018.5

Language：Japanese   Presentation type：Oral presentation (invited, special)  

Venue：千葉   Country：Japan  

Event date： 2018.3

Language：English   Presentation type：Oral presentation (general)  

Venue：Houston   Country：United States  

Event date： 2017.12

Language：English   Presentation type：Oral presentation (general)  

Venue：Tachikawa, Tokyo   Country：Japan  

Previous studies of cosmic-ray exposure (CRE) ages for HED meteorites show the existence of two major clusters of the CRE ages around 20-25 Ma and 35-42 Ma and of other three minor clusters around 6-7 Ma, 10-12 Ma, and 14 Ma (Eugster and Michel, 1995; Welten et al., 1997). Our concern is whether the Sm and Gd isotopic shifts of eucrites also show the consistent trend with the CRE age clusters. 149Sm and 157Gd have very large thermal neutron capture cross sections, and change thier isotopic abundances by 149Sm(n,γ)150Sm and 157Gd(n,γ)158Gd reactions, respectively, induced from cosmic-ray irradiation. Providing that the CRE information from the Sm and Gd isotopic shifts are different from the 81Kr-Kr data, there is a possibility that the inconsistency of the CRE information occurred by the pre-irradiation on the eucritic parent body. In this study, eight basaltic eucrites were used.

Event date： 2017.11

Language：English   Presentation type：Oral presentation (invited, special)  

Venue：Houari Boumediene University of Science and Technology   Country：Algeria  

The Oklo uranium ore in the Francevillian basin at the east part of the Republic of Gabon is known as a fossil of natural fission reactors, because large-scaled fission chain reactions spontaneously occurred in the ore two billion years ago. It is of major concern to characterize the properties of nuclear reactors and to investigate the behavior of fission products in and around the Oklo natural reactors. In this review, geological and physico-chemical characteristics of the Oklo natural fission reactor and its implication for radioactive waste disposal are shown.

Event date： 2017.10

Language：English   Presentation type：Oral presentation (invited, special)  

Venue：KBSI Ochang Center   Country：Korea, Republic of  

As a simple model, most eucrites are interpreted as primary partial melt products from primitive, metal-free, chondritic material (Stolper, 1977). However, assuming a simple differentiation of two components, eucrite and diogenite, originated from chondritic materials, it is difficult to explain the mass balance of REE among eucrites, diogenites and chondrites, because the chondritic REE pattern cannot be reconstructed only from the mixing of REE components from eucrites and diogenites. As a result of REE measurements of whole rock analysis, most of basaltic eucrites show flatter REE patterns with negative or positive Eu anomaly, and their REE contents are 8-10 times higher than those in chondrites. On the other hand, diogenites generally have significant depletion of lighter REE in the patterns. In this study, REE abundances were measured in single minerals of eucrites in order to study REE distribution behavior in eucritic materials in association with gechemical differentiation from chondritic materials.

Event date： 2017.10

Language：English   Presentation type：Oral presentation (invited, special)  

Venue：KBSI Ochang Center   Country：Korea, Republic of  

The data of a series of the elemental abundances of rare earth elements (REE) in planetary materials (REE abundance pattern) have been widely used to understand the geochemical evolution processes of the materials since the pioneering work, because REE have several similarities of physicochemical properties due to their electron configurations of the atomic structures. Furthermore, isotopic compositions of some REE are variable, because they include radiogenic components derived from 138La-138Ce, 146Sm-142Nd, and 147Sm-143Nd decay systems and nucleogenic components like neutron captured products by 149Sm(n,γ)150Sm and 157Gd(n,γ)158Gd due to cosmic-ray irradiation. Here in this talk, I would like to introduce my recent work on La and Sm isotopic study and its application as one of examples for the REE isotopic studies in cosmochemical fields.

Event date： 2017.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：東京工業大学、東京   Country：Japan  

核破砕反応によって生成される138La を太陽宇宙線初期照射履歴のためのプロキシとする試みがなされているが、その精密同位体測定例は少ない。本研究では 、Allende 隕石から採取した2つのCAI粒子を酸分解し、所定のイオン交換法によりLaを化学分離し、表面電離型質量分析計により、その精密同位体測定を行った。

Event date： 2017.8

Language：English   Presentation type：Oral presentation (general)  

Country：France  

Isotopic measurements of excess 10B decayed from 10Be in CAIs and astronomical observations of intensive X-ray emissions from stellar analogues of the young Sun suggest a possibility of intensive irradiation by the young Sun. However, the model for early solar irradiation from young Sun is somehow model-depending and still plausible. For further quantitative discussion about the early solar irradiation models, 138La is one of adequate isotopic tracers as one of refractory and spallogenic products caused by solar irradiation. The presence of excess 138La as a spallogenic product may provide isotopic constraints on the early solar irradiation models. In this study, isotopic analyses mainly of La and other REE like Ce, Nd, and Sm in CAIs collected from the Allende CV3 meteorite were performed to understand the spallogenic reactions in the early solar system.

Event date： 2017.7

Language：English   Presentation type：Oral presentation (general)  

Venue：Santa Fe, New Mexico   Country：United States  

Most eucrites have basaltic composition and several of them represent lavas or shallow intrusions from a differen-tiated parent body, possibly asteroid 4 Vesta. Many isotopic studies have been conducted using long- and short lived geochronometers to understand accretion, core formation, mantle differentiation, and the formation of prima-ry basalts on the eucritic parent body (EPB). In our previous study, Sr and Ba isotopic analyses were applied mainly for chronometric purposes of eight basaltic eucrites, but Rb-Sr and Cs-Ba decay systems did not provide any chronological information because of the significant contamination of terrestrial Sr and Ba found in five DaG de-sert eucrites. In this study, Ce, Nd, Sm and Gd isotopic compositions of the eight eucrites were further deter-mined for better understanding of differentiation on the parent body.

Event date： 2017.6

Language：English   Presentation type：Oral presentation (invited, special)  

Venue：Daejeon, Korea   Country：Korea, Republic of  

The data of a series of REE elemental abundances in planetary materials (REE abundance pattern) have been widely used to understand the geochemical evolution processes of the materials since the proposal of pioneering work by Masuda and Matsui (1966), because REE have several similarities of physicochemical properties due to their electron configurations of the atomic structures. Furthermore, isotopic compositions of some REE are variable, because they include radiogenic components derived from 138La-138Ce, 146Sm-142Nd, and 147Sm-143Nd decay systems and nucleogenic components like neutron captured products by 149Sm(n,γ)150Sm and 157Gd(n,γ)158Gd due to cosmic-ray irradiation. In particular, the isotopic variations of REE provide chronological and astrophysical information for cosmochemistry. Here in this talk, I would like to introduce my recent work on La isotopic study and its application as one of examples for the REE isotopic studies in cosmochemical fields.

Event date： 2016.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：大阪   Country：Japan  

Event date： 2016.8

Language：English   Presentation type：Oral presentation (general)  

Venue：Berlin   Country：Germany  

Event date： 2016.6 - 2016.7

Language：English   Presentation type：Oral presentation (general)  

Venue：Yokohama   Country：Japan  

Event date： - 2021.9

Language：Japanese   Presentation type：Poster presentation  

Venue：Hirosaki University   Country：Japan  

Students learn toward completion of master's thesis by acquiring research skills through presentation of scientific papers

In this seminar, we aim to acquire presentation skills through research presentations, and to obtain scientific skills through discussion. Finally, students cultivate the ability to complete the master's thesis.

To study the minimum requirement to understand the advanced issues of geochemical and cosmochemical research fields.

From the fluctuation of isotopic composition in the global environment, we will study the relationship between the Earth's core, mantle, crust, hydrosphere and atmosphere and the history of its formation and development. In particular, this seminar focuses on the qualitative elucidation of the material circulation mechanism using stable isotopes such as oxygen, carbon, sulfur, chromium, iron, neodymium, europium and samarium as tracers.

Study the fundamental knowledge of geochemistry and predict geochemical significance from the chemical data of natural samples using the knowledge.

Study the fundamental knowledge of cosmochemistry to consider and discuss issues on the formation and evolution of the solar system and the solar planets from the comparison of the chemical, isotopic and mineralogical properties between terrestrial and extra-terrestrial materials.

Based upon the knowledge acquired in Department of Earth and Planetary Sciences, students are requested to carry out graduation work in each specialized research field. This course aims that students obtain fundamental and applicative knowledge and cultivate capabilities to consider and discuss issues from a wide perspective.

Study the minimum knowledge to understand general contents of cosmochemistry and geochemistry in the view point of inorganic chemistry and analytical chemistry

Students learn about discussions towards publication of theses through research presentations and discussions and self-evaluate their progress in doctoral dissertations.

From the fluctuations of various natural and artificial isotopic compositions, we will explore the relationship between the Earth's core, mantle, crust, hydrosphere and atmosphere and the history of its formation/development. In this seminar, emphasis will be given to the special field outside the department, in other words, the influence on the circulation of goods by the mining and industrial activities, cultural activities etc. of mankind and the understanding of the interaction system.

Obtaining English reading ability of basic knowledge in Earth Planetary Science and cultivating capability to summarize and make presentations in these contents.

Understanding the basic principles of the solar system and the earth and develop their view of the earth.

To study the minimum requirement to understand the advanced issues of geochemical and cosmochemical research fields.

To study the minimum requirement to understand the advanced issues of geochemical and cosmochemical research fields.

To study the minimum requirement to understand the advanced issues of geochemical and cosmochemical research fields.

To study the minimum requirement for presentation manners related to individual research field.

To study the minimum requirement to understand the advanced issues of geochemical and cosmochemical research fields.

to study the minimum requirements to understand cosmochemistry and geochemistry throughout the reading of advanced research papers and introduction of individual researches.

Study the minimum knowledge to understand general contents of cosmochemistry and geochemistry in the view point of inorganic chemistry

地球惑星科学は太陽系の起源・進化および地球・惑星の内部と表層の諸現象を研究対象としており、その対象領域は
極めて広いため、広範な知識に基づく理解や考察が求められる。初年次教育として地球惑星科学分野の基礎を学ぶた
めに、本講義では地球惑星科学の概観を学びつつ、最新の研究成果や課題の学習を通して地球の特徴や歴史に関する
新たな見方を理解・考察することを目的とする。また、地球環境問題や自然災害などに対して、広い視野から考察し
、論述できるようになるとともに、深い考察力を涵養することを目指す。

Type：Scientific advice/Review 

Type：Academic society, research group, etc.