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Volume 44, Issue 1
Displaying 1-9 of 9 articles from this issue
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REVIEW
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Hiroshi NISHIMURA, Kumiko KISHI, Hiroaki OZAWA, Mamoru MURATA1996 Volume 44 Issue 1 Pages 1-11
Published: 1996
Released on J-STAGE: July 20, 2007
JOURNAL FREE ACCESSMany experimental results and theoretical considerations have been reported in relation to the isotope abundances of meteoritic lithium. The methods of the experimental investigations are grouped in two categories. One is surface ionization mass spectrometry and the other is secondary ion mass spectrometry. In almost all isotope analyses, and in using both experimental methods, 7Li/6Li ratios in meteorites are reported not to have any anomaly compared with the ratios for terrestrial samples. However, lithium is one of the less abundant elements together with berillium and boron, and the synthetic mechanism of these elements and isotopes are not clarified both experimentally and theoretically. We have possibility that there may be an anomaly of lithium isotope abundances in meteorites according to several theoretical considerations. In this report, mass spectrometric results of lithium isotope analyses for many kinds of meteorites are reviewed and the theoretical and experimental consideration about the nucleosynthesis of lithium are searched.View full abstractDownload PDF (794K)
REGULAR PAPERS
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Noritoshi MORIKAWA, Noboru NAKAMURA, Satoshi NAKANISHI, Koshi YAMAMOTO ...1996 Volume 44 Issue 1 Pages 13-20
Published: 1996
Released on J-STAGE: July 20, 2007
JOURNAL FREE ACCESSPrecise isotope dilution technique of Li, along with other alkalis, alkaline earths and iron, for tiny silicate materials (having as low as 10 pg Li) is described. Samples were decomposed by acids, equilibrated with mixed spikes including 6Li and directly loaded on a mass spectrometer filament without chemical separation. Li and other lithophiles were measured by successive heating procedures. Results of precise Li analyses are presented for 7 Allende chondrules, 5 bulk chondrites and three standard rocks, JB-1, JB-2, and BCR-1.View full abstractDownload PDF (473K) -
Mitsuru ASANO, Toshio HARADA, Yasuo MIZUTANI1996 Volume 44 Issue 1 Pages 21-27
Published: 1996
Released on J-STAGE: July 20, 2007
JOURNAL FREE ACCESSPartial pressures of RbBO2 (g) and Rb2(BO2)2 (g) in the RbBO2-SiO2 system are measured by a mass-spectrometric Knudsen effusion method. On the basis of the partial pressures, chemical activities of the RbBO2 and SiO2 components and molar Gibbs energies of mixing are determined in the whole composition range. The chemical activities of both RbBO2 and SiO2 show negative deviation from Raoult's law at 1000 K. From low molar Gibbs energies of mixing, the melts in the RbBO2-SiO2 system are concluded to be very stable thermodynamically.View full abstractDownload PDF (412K) -
Hiroyuki ITO, Toru SAKURAI, Takekiyo MATSUO, Hisashi MATSUDA, Toshio I ...1996 Volume 44 Issue 1 Pages 29-37
Published: 1996
Released on J-STAGE: July 20, 2007
JOURNAL FREE ACCESSAbundance distributions were studied for cadmium-cesium and zinc-cesium positively charged cluster ions. The cluster ions were produced by Cs+ ion bombardment on initially pure metal sheets of either cadmium or zinc, and mass analysis was performed using a grand-scale sector mass spectrometer. Mass spectra revealed the abundance distributions indicating that specific clusters having 8, 20, 34, 40, and 58 valence electrons were particularly stable. Observed abundances of [CdnCs]+, [ZnnCs]+, and [Znn-2Cs2]+ can be fully explained in terms of the electronic-shell structures of the metals studied. It was found that the origin of the “magic numbers” are different from those of HgnCs+ cluster.View full abstractDownload PDF (603K) -
Keisuke NAGAO, Atsumi OGATA, Yayoi N. MIURA, Kenji YAMAGUCHI1996 Volume 44 Issue 1 Pages 39-61
Published: 1996
Released on J-STAGE: July 20, 2007
JOURNAL FREE ACCESSTwo noble gas mass spectrometry systems (MS-I and MS-II) have been installed in 1989, one of which was designed in our laboratory for Ar isotope analysis to measure K-Ar age by isotope dilution method using 38Ar-spike. The whole system was modified and improved to obtain high quality Ar data. The improved system composed of an Ar extraction and purification line and a Modified-VG5400 mass spectrometer enables us to determine precise Ar isotope composition easily and speedily irrespective to operator's skillfulness.
Formulas calculating radiogenic 40Ar abundance, which takes account of correction for Ar isotopes of both spike and blank, are presented. For samples with young K-Ar age, formulas to estimate the radiogenic 40Ar abundance based on 40Ar/36Ar ratio are also proposed. Replicate analyses on many K-Ar standard samples show that the system can be applicable to samples with ages ranging 0.01 to 1500 Ma without any systematic analytical errors.View full abstractDownload PDF (1359K) -
Nobuo TAKAOKA, Yoshinobu MOTOMURA, Keisuke NAGAO1996 Volume 44 Issue 1 Pages 63-77
Published: 1996
Released on J-STAGE: July 20, 2007
JOURNAL FREE ACCESSTellurobismuthite, quartz and arsenopyrite minerals separated from a specimen of tellurium-bearing ores collected at the Oya mine have been analyzed for noble gas isotopes. The Te minerals released abundant 4He and 40Ar. Quartz released large amounts of noble gases, which are supposed to have been occluded in fluid inclusions. It contains excess 40Ar inherited from precursor materials. Arsenopyrite released abundant He and Ar. Argon is mostly of atmospheric origin. Definite excesses at 129Xe, 130Xe, and 131Xe isotopes but no excesses at 134Xe and 136Xe are found for the Te minerals. Xe isotopic ratios for the quartz are atmospheric and give no evidence for inherited excess 130Xe. Because the quartz, arsenopyrite and Te minerals were deposited from the same hydrothermal fluids, these indicate that the Te minerals contain inherited excess 40Ar and the isotopic ratios of trapped Xe in the Te minerals is atmospheric. Hence the 130Xe excess found in the Te mineral is attributable to the in-situ double-beta decay of 130Te, and the excesses at 129Xe and 131Xe are to the neutron-captures on 128Te and 130Te, respectively. Besides, a quartz-calcite separate from a Te ore specimen collected at the Suwa mine is enriched in 4He but the isotopic ratios of Xe is atmospheric, indicating that Xe contained in hydrothermal fluids at Suwa is atmospheric.
In order to decipher the chronological sequence of mineralization of Te ores and solidification of magma, we summarize the occurrences of sample minerals, the geology of sampling sites and their field relationships. Based on noble gas data measured for the Te and associated minerals as well as geological considerations, we prefer (7.9±1.0)×1020 years to 3 ×1021 years for the absolute half-life of 130Te double-beta decay. From the excess ratio of 129Xe to 131Xe, we have 710 n/cm2y for neutron flux at the Oya mine.View full abstractDownload PDF (1186K)
TECHNICAL REPORTS
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Tsuyoshi TANAKA, Masaharu TANIMIZU, Yoshihiro ASAHARA, Chinatsu YONEZA ...1996 Volume 44 Issue 1 Pages 79-83
Published: 1996
Released on J-STAGE: July 20, 2007
JOURNAL FREE ACCESS143Nd/144Nd isotopic ratio and rare-earth impurities are examined for high purity neodymium oxide prepared by six chemical companies. The isotopic ratios of the reagents are grouped into four and vary from 0.511463 to 0.512238. Some of the reagents contain impurities more than 1 ppm for lanthanum, cerium and samarium. A neodymium isotopic reference will be prepared according to the result.View full abstractDownload PDF (279K) -
Toshio ICHIHARA, Itsuo KATAKUSE1996 Volume 44 Issue 1 Pages 85-89
Published: 1996
Released on J-STAGE: July 20, 2007
JOURNAL FREE ACCESSA sector type single focusing mass spectrometer is constructed. This spectrometer is used for students to training. Students can get elementary knowledge and technique for mass spectrometry. The ion source is an electron bombard type ion source and deflection angle is 22.5. By chopping ions, it can be used as a TOF mass spectrometer.View full abstractDownload PDF (311K) -
Toshio ICHIHARA, Itsuo KATAKUSE, Hiroyuki ITO, Tohru SAKURAI, Takekiyo ...1996 Volume 44 Issue 1 Pages 91-95
Published: 1996
Released on J-STAGE: July 20, 2007
JOURNAL FREE ACCESSWe have made a cooled sputter ion source for producing clusters of volatile samples. A sample holder was cooled by coolant sent by a tube pump from outside of vacuum chamber. The temperature at sample holder reached to -10°C. Stable ion current of mercury-secium clusters, (Hg)nCs+ type, were observed for long time.View full abstractDownload PDF (247K)
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