Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：American Geophysical Union (AGU)  

DOI： 10.1029/2019JB019143

researchmap

Other Link： https://onlinelibrary.wiley.com/doi/full-xml/10.1029/2019JB019143

Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Oxford University Press (OUP)  

Abstract

New K–Ar ages, major and trace element concentrations, and Sr–Nd–Pb isotope data are presented for Oligocene to recent mafic volcanic rocks from the Ethiopian Plateau, the Main Ethiopian Rift (MER), and the Afar depression. Chronological and geochemical data from this study are combined with previously published datasets to reveal secular variations in magmatism throughout the entire Ethiopian volcanic region. The mafic lavas in these regions show variability in terms of silica-saturation (i.e. alkaline and sub-alkaline series) and extent of differentiation (mafic through intermediate to felsic). The P–T conditions of melting, estimated using the least differentiated basalts, reveal a secular decrease in the mantle potential temperature, from when the flood basalt magmas erupted (up to 1600 °C) to the time of the rift-related magmatism (<1500°C). Variations in the Sr–Nd–Pb isotopic compositions of the mafic lavas can account for the involvement of multiple end-member components. The relative contributions of these end-member components vary in space and time owing to changes in the thermal condition of the asthenosphere and the thickness of the lithosphere. The evolution of the Ethiopian rift is caused by a transition from plume-driven to plate-driven mantle upwelling, although the present-day mantle beneath the MER and the Afar depression is still warmer than normal asthenosphere.

DOI： 10.1093/petrology/egz043

researchmap

Other Link： http://academic.oup.com/petrology/article-pdf/60/8/1681/31282958/egz043.pdf

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

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

Web of Science

Scopus

researchmap

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

DOI： 10.1038/s41467-019-10832-7

Scopus

researchmap

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

Web of Science

Scopus

researchmap

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

We present K-Ar ages, major and trace element concentrations, and Sr-Nd-Pb isotope data for late Cenozoic volcanic rocks from the Chugoku district, southwest Japan arc. Andesite and dacite lavas in this region are enriched in Sr (mostly &gt
800 μg g−1) and show geochemical characteristics of volcanic rocks commonly referred to as “adakite.” K-Ar dating of these lavas revealed that the eruption of high-Sr andesitic to dacitic magmas occurred during the last 2 Myr, following or concurrent with the eruption of basalt in adjacent regions. Trace-element characteristics of high-Sr andesites and dacites are consistent with the formation of their parent magmas by partial melting of the basaltic layer of the subducting Shikoku Basin Plate. Mass balance modeling of trace element concentrations and isotopic compositions suggests that the parental magmas of high-Sr andesites and dacites are best explained by mixing of partial melts from oceanic crust (F = 5–15%) and sediment (F = 30%) at 80:20 to 55:45 ratios. Spatial coincidence of the occurrences of high-Sr andesites and dacites and seismic gaps of the subducting slab demonstrates the causal link between slab melting and mantle upwelling at slab tears. We speculate that these tears could have been formed by subduction of ridges on the plate. A warm mantle upwelled through tears, preventing the solidification of the siliceous slab melts in the mantle and facilitating the transportation of these melts to the surface.

DOI： 10.1029/2017JB015066

Scopus

researchmap

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

DOI： 10.1016/j.lithos.2017.03.011

Scopus

researchmap

Publishing type：Research paper (scientific journal)   Publisher：American Geophysical Union (AGU)  

DOI： 10.1002/2015GC005914

Scopus

researchmap

Other Link： https://onlinelibrary.wiley.com/doi/full-xml/10.1002/2015GC005914

Publishing type：Research paper (scientific journal)   Publisher：American Geophysical Union (AGU)  

DOI： 10.1002/2015GC005786

Scopus

researchmap

Publishing type：Research paper (scientific journal)  

DOI： 10.1016/j.chemgeo.2014.12.025

Scopus

researchmap

Publishing type：Research paper (scientific journal)   Publisher：Oxford University Press (OUP)  

DOI： 10.1093/petrology/egu054

Scopus

researchmap

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

Web of Science

Scopus

researchmap

Other Link： https://onlinelibrary.wiley.com/doi/full-xml/10.1111/j.1751-908X.2013.00205.x

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

DOI： 10.1016/j.jvolgeores.2013.07.002

Scopus

researchmap

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

Web of Science

Scopus

researchmap

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

A method for the simultaneous determination of Cd with In, Tl and Bi by isotope dilution-internal standardisation (ID-IS) ICP-QMS using the same aliquot for rare earth element and other trace element determinations was developed. Samples mixed with an enriched 149Sm spike were decomposed using a HF-HClO4 mixture, which was evaporated and then diluted with HNO3. After determination of Sm by ID-ICP-QMS and Cd, In, Tl and Bi concentrations were determined using the 149Sm intensity as an internal standard. The interference of MoO+ on Cd+ was corrected using the MoO+/Mo+ ratio separately measured using a Mo standard solution, and the validity of the externally determined oxide-forming ratio correction was evaluated. The MoO+/Mo+ ratios measured using the standard solution and samples were ∼ 0.0002 and <0.002, respectively. Detection limits for Cd, In, Tl and Bi in silicate samples were at levels of <1ngg-1 with a total uncertainty of <7%. Cadmium in the carbonaceous chondrites, Orgueil (CI1), Murchison (CM2) and Allende (CV3) as well as Cd, In, Tl and Bi in the reference materials, JB-2, JB-3, JA-1, JA-2, JA-3, JP-1 (GSJ), BHVO-1, AGV-1, PCC-1 and DTS-1 (USGS) and NIST SRM 610, 612, 614 and 616 were determined to show the applicability of this method. © 2010 International Association of Geoanalysts.

DOI： 10.1111/j.1751-908x.2010.00054.x

Scopus

researchmap

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

DOI： 10.1016/j.gca.2010.10.009

Scopus

researchmap

Authorship：Lead author   Publishing type：Research paper (scientific journal)   Publisher：Oxford University Press (OUP)  

DOI： 10.1093/petrology/egn029

Scopus

researchmap

Publishing type：Research paper (scientific journal)   Publisher：Oxford University Press (OUP)  

DOI： 10.1093/petrology/egi021

Scopus

researchmap

Language：English   Publisher：Japan Association of Mineralogical Sciences  

Simultaneous determination of Li, Be, Rb, Sr, Y, Cs, Ba, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Pb, Th and U by isotope dilution and internal standardization (ID-IS) method by ICP-MS was developed.

DOI： 10.14824/jampeg.2004.0.64.0

CiNii Article

CiNii Books

researchmap

DOI： 10.1039/b309948b

Web of Science

researchmap

Publishing type：Research paper (scientific journal)   Publisher：Royal Society of Chemistry (RSC)  

DOI： 10.1039/b309948b

Scopus

researchmap

Authorship：Lead author,　Corresponding author   Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Japan Association of Mineralogical Sciences  

Whole-rock K-Ar dating for a basaltic andesite lava from the Uegusukudake Formation in Kume-jima, Central Ryukyu Arc, yields age of 2.13±0.19 Ma. The sample dated is from the middle horizon of the Formation. This age is compatible with recently published K-Ar ages of 2.76±0.48 and 2.24±0.10 Ma for a picrite basalt from the lowest part and an andesite from the upper part of the Formation, respectively. The age, however, is inconsistent with the previously reported K-Ar ages of 5.5 and 4.6 Ma. The result is also concordant with ages estimated from Sr isotopic ratios for molluscan fossils (∼3.2-3.1 Ma) for the Aka Formation underlying the Uegusukudake Formation. This result suggests that tholeiitic basalts and basaltic andesites erupted after the eruption of picrite basalts with a short time interval at the late Pliocene.

DOI： 10.2465/gkk.30.237

Scopus

CiNii Article

CiNii Books

researchmap

Other Link： https://jlc.jst.go.jp/DN/JALC/00151298462?from=CiNii

Publishing type：Research paper (scientific journal)  

DOI： 10.3847/1538-4357/ad276a

researchmap

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

DOI： 10.3390/universe9060293

researchmap

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

DOI： 10.3390/life13071448

researchmap

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

Abstract

All life on Earth contains amino acids and carbonaceous chondrite meteorites have been suggested as their source at the origin of life on Earth. While many meteoritic amino acids are considered indigenous, deciphering the extent of terrestrial contamination remains an issue. The Ryugu asteroid fragments (JAXA Hayabusa2 mission), represent the most uncontaminated primitive extraterrestrial material available. Here, the concentrations of amino acids from two particles from different touchdown sites (TD1 and TD2) are reported. The concentrations show that N,N-dimethylglycine (DMG) is the most abundant amino acid in the TD1 particle, but below detection limit in the other. The TD1 particle mineral components indicate it experienced more aqueous alteration. Furthermore, the relationships between the amino acids and the geochemistry suggest that DMG formed on the Ryugu progenitor body during aqueous alteration. The findings highlight the importance of aqueous chemistry for defining the ultimate concentrations of amino acids in primitive extraterrestrial samples.

DOI： 10.1038/s41467-023-37107-6

researchmap

Other Link： https://www.nature.com/articles/s41467-023-37107-6

Authorship：Lead author,　Corresponding author   Language：English  

CiNii Article

CiNii Books

researchmap

Other Link： http://hdl.handle.net/20.500.12000/5383