研究者詳細 - 中村　栄三

MISC - 中村　栄三

分割表示 135 件中 61 - 80 件目／全件表示 >>

Precise analysis of the Ra-228/Ra-226 isotope ratio for short-lived U-series disequilibria in natural samples by total evaporation thermal ionization mass spectrometry (TE-TIMS)

T Yokoyama, E Nakamura

JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY 19 ( 6 ) 717 - 727 2004年

記述言語：英語出版者・発行元：ROYAL SOC CHEMISTRY

We report a new analytical technique for precise and accurate determination of the Ra-228/Ra-226 ratio by total evaporation thermal ionization mass spectrometry (TE-TIMS). An improved chromatographic separation method employing a new tandem column technique that enables high yield and high purity of Ra is also described. Repeated analysis of Ra standard solution (Ra-228/Ra-226 = 1.1) yielded an analytical reproducibility for Ra-228/Ra-226 ranging from 0.2% to 0.9% (2sigma) for 170 to 2 fg of Ra. Reproducibility was strongly controlled by counting statistics of Ra-226(+) and Ra-228(+) ion beam intensities collected by an ion counting detector, implying that in-run precision for Ra isotope analysis of our method can be evaluated using a counting statistics law. Determination of Ra-226 abundances in silicate rock samples were examined by isotope dilution TE-TIMS, and reproducibility was 0.3% (2sigma) for JR-2 (Ra-226 = 3700 fg g(-1)) and 0.6% (2sigma) for JB-2 (Ra-226 = 81 fg g(-1)); the reproducibility of these measurements are 2 - 3 times better than previously published conventional TIMS procedures. The Ra-226/Ra-228 ratio in natural samples can be also measured with an analytical uncertainty of similar to1% (2sigma). The accuracy of our method was confirmed by measuring (Ra-226/Th-230) and (Ra-228/Th-232) ratios for JR-2, a sample old enough (1 Ma) to be in Th-230 -Ra-226 and Th-232 - Ra-228 radioactive equilibria. Our method is especially effective for samples with a very low abundance of Ra.

DOI： 10.1039/b400829d

Web of Science

researchmap

Determination for lithium contents in silicates by isotope dilution ICP-MS and its evaluation by isotope dilution TIMS

Moriguti, T, Makishima, A, Nakamura, E

Geostandards Newsletter 2004年

Lithium, boron and lead isotope and trace element systematics of Quaternary basaltic volcanic rocks in northeastern Japan: Implications for variation of slab-derived fluid composition due to mineralogical reactions in the subducting slab

Moriguti, T, Shibata, T, Nakamura, E

Chemical Geology 2004年

Ultrahigh-pressure metabasaltic garnets as probes into deep subduction-zone cycling

King, R.L, Bebout, G.E, Kobayashi, K, Nakamura, E, van der Klauw, S.N.G.C

Geochemistry, Geophysics, Geosystems 2004年

Suppression of Zr, Nb, Hf and Ta coprecipitation in fluoride compounds for determination in Ca-rich materials

R Tanaka, A Makishima, H Kitagawa, E Nakamura

JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY 18 ( 12 ) 1458 - 1463 2003年12月

記述言語：英語出版者・発行元：ROYAL SOC CHEMISTRY

We have evaluated recovery yields of Zr, Nb, Hf and Ta, which are called high field strength elements (HFSE), in the synthetic Ca-Al-Mg-HF solution system using two different methods: at <70&DEG;C in an ultrasonic-bath (denoted as the ultrasonic method) and at 205&DEG;C using a TFE Teflon(R) bomb (denoted as the bomb method). Full recovery of HFSE into the supernatant HF solution was not achieved in cases where fluorite (CaF2) forms in the precipitate in both methods and sellaite (MgF2) forms in the ultrasonic method. In order to suppress fluorite precipitation, an 'Al-addition method' was developed in which Al solution is added to the sample before decomposition to change the matrix solution to a composition in which no fluorite forms. Using the Al-addition method, HFSE concentrations of Ca-rich materials were analyzed by inductively coupled plasma mass spectrometry (ICP-MS) by an isotope dilution method for Zr and Hf and by a calibration curve method for Nb and Ta. Furthermore, we found isotopic disequilibria of Zr and Hf between sample and spike without Al-addition for Ca-rich samples, and that the Al-addition method was very effective in achieving isotopic equilibria and full recovery of HFSE, resulting in high accuracy in their determination.

DOI： 10.1039/b309948b

Web of Science

researchmap

Highly precise and accurate isotopic analysis of small amounts of Pb using Pb-205-Pb-204 and Pb-207-Pb-204, two double spikes

T Kuritani, E Nakamura

JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY 18 ( 12 ) 1464 - 1470 2003年12月

記述言語：英語出版者・発行元：ROYAL SOC CHEMISTRY

A new, simple, and practical method has been developed for the accurate and precise isotopic analysis of extremely small amounts of Pb (<&SIM;3 ng) by thermal ionization mass spectrometry. Two different types of double spikes, one consisting of Pb-205 and Pb-204 and another enriched in Pb-207 and Pb-204, are used to reduce "Pb-204 error" and to correct mass fractionation during mass spectrometry. Using this technique, replicate analyses of 1.5 ng of Pb from NBS981 were performed, and an external, precision of 0.02% (2σ) was attained for the Pb-208/Pb-204 ratio. Compared with results for 1.5 ng of Pb by the normal double spike method using a single Pb-207-Pb-204 double spike, the external precision for the isotopic ratios involving Pb-204 is reduced by about 60-70%, simply by addition of the Pb-205-Pb-204 double spike. The two double spikes method was also applied to isotopic analyses of natural rock samples, and we obtained an external precision of 0.06% (2σ) for Pb-208/Ph-204 in &SIM;1.5 ng of Pb separated from fresh peridotite; in which the Pb concentration is as low as. 3.2 ppb. This new technique is superior to any previous method for precise and accurate isotopic analyses of extremely small amounts of Pb, and will be a highly powerful tool in the future of earth science and environmental science.

DOI： 10.1039/b310294g

Web of Science

researchmap

Shift and Rotation of Composition Trends by Magma Mixing: 1983 Eruption at Miyake-jima Volcano, Japan

Takeshi Kuritani, Tetsuya Yokoyama, Katsura Kobayashi, Eizo Nakamura

Journal of Petrology 2003年

Record in metamorphic tourmalines of subduction-zone devolatilization and boron cycling

Bebout, G.E, Nakamura, E

Geology 2003年

Fate of the subduted Farallon plate inferred from eclogite xenoliths in the Colorado Plateau

Usui, T, Nakamura, E, Kobayashi, K, Maruyama,S, Helmstaedt, H

Geology 2003年

Comprehensive geochemical analyses of small amounts(<100mg) of extraterrestrial samples for the analytical competition related to the sample return missiion MUSES-C

Eizo Nakamura, Akio Makishima, Takuya Moriguti, Katsura Kobayashi, Chie Sakaguchi, Tetsuya Yokoyama, Ryoji Tanaka, Takeshi Kuritani, Hiroyuki Takei

The Institute of Space and Astronautical Science Report 2003年

Mantle metasomatism and rapid ascent of slab components beneath island arcs: Evidence from 238U-230Th-226Ra disequilibria of Miyakejima volcano, Izu arc, Japan

Tetsuya Yokoyama, Katsura Kobayashi, Takeshi Kuritani, Eizo Nakamura

Journal of Geophysical Research 2003年

Isotope dating of Neoproterozoic crustal growth in the Usambara Mountains of Northeastern Tanzania: evidence for coeval crust formation in the Mozanbique Belt and the Arabian-Nubian Shield

Maboko, M.A.H, Nakamura, E

Precambrian Research 2002年

U-Pb isotope systematics of micro-zircon inclusions: Implications for the age and origin of eclogite xenolith from the Corolado Plateau

Usui, T, Kobayashi, K, Nakamura, E

Proceedings of Japan Academy 2002年

U-Pb isotope systematics of micro-zircon inclusions: Implications for the age and origin of eclogite xenolith from the Colorado Plateau

Usui, T, Kobayashi, K, Nakamura, E

Proceedings of Japan Academy 78, Ser.B, 51-56 2002年

Precise determination of ferrous iron in silicate rocks

Yokoyama, T, Nakamura, E

Geoshim. Cosmosim. Acta 2002年

Determination of Cr, Ni, Cu and Zn in milligram samples of geological materials using isotope dilution high resolution ICP-MS

Makishima, A. Kobayashi, K, Nakamura, E

Geostandards Newsletter 2002年

Precise isotope analysis of nanogram-level Pb for natural rock ssamples without use of double spikes

Kuritani, T, Nakamura, E

Chemical Geology 2002年

Sm-Nd mineral ages of pegmatite veins and their host rocks from Swat area, Chilas complex, northern Pakistan

A.Ali, E.Nakamura, H.Yamamoto

Journal of Asian Earth Sciences 2002年

Timing and trigger of arc volcanism by flushing from subducting slab

Yokoyama, T, Nakamura, E, Kobayashi, K, Kuritani, T

Proceedings of Japan Academy 2002年

Timing and trigger of arc volcanism controlled by fluid flushing from subducting slab

Yokoyama, T, Nakamura, E, Kobayashi, K, Kuritani, T

Proceedings of Japan Academy 78, Ser.B, 190-195 2002年

　前のページ - 次のページ　

<中村 栄三>

MISC - 中村 栄三

<中村　栄三>

MISC - 中村　栄三