JaLCDOI 10.18926/21177
Title Alternative Microprobe analysis of Japanese standard rocks JB-1 and JG-1
FullText URL pitsr_048_007_011.pdf
Author Sakiyama, Toru| Kagami, Hiroo| Tazaki, Koichi| Asada, Hitoshi|
Abstract The Japanese standard rocks JB-1 and JG-1 are analyzed with the electron microprobe. The glass chips are prepared by direct fusion method by Nicholls (1974). Slight modifications of Nicholls' method for fusion temperature and preparation of rock powder give good results. Production of homogeneous glass chips needs fusion for 20 seconds at temperature 1500 to 1600℃ for basalt (JB-1) and 1800 to 1900℃ for granodiorite (JG-1). Very fine rock powder less than 10μm is preferable.
Publication Title 岡山大学温泉研究所報告
Published Date 1979-03-25
Volume volume48
Start Page 7
End Page 11
ISSN 0369-7142
language 日本語
File Version publisher
NAID 120002310938
JaLCDOI 10.18926/21139
Title Alternative Isotopic Analysis of Rb and Sr Using a Full Automatic Thermal Ionization Mass Spectrometer
FullText URL pitsr_052_051_070.pdf
Author Kagami, Hiroo| Okano, Osamu| Sudo, Hiroshi| Honma, Hiroji|
Abstract Analytical method for strontium isotope ratios and rubidium and strontium concentrations has been established using a full automatic thermal ionization mass spectrometer. The machine is a modified model "MAT 260" of Varian MAT LTD. Each of simultaneously loaded thirteen samples is successively analysed full automatically following to a specific controling program which has been selected as being most suitable for each sample. However, the most characteristic feature of this machine compared to other types is computer controled peak jumping and peak centering before measurment of the signal of each peak. By this the accuracy of isotopic measurement has been surprisingly improved. Analytical procedures are described in detail which include decomposition of samples, separation of Rb and Sr, loading samples on filament and mass spectrometry. Accuracy and reproducibility of isotope analyses are excellent : 43 separate analyses of standard sample NBS 987 over one year gave a mean (87)Sr/(86)Sr ratio of 0.710238 (normalized to the (88)Sr/(86)Sr ratio of 8.375209) with a value of 20δ of 0.000008. The ratio obtained is slightly higher than the value of 0.71014 given by NBS, but it is almost identical to the mean of recently reported twenty analyses. Our determinations for Rb and Sr concentrations of standard samples are as follows : JG-1, Rb 184.4 ppm, Sr 185.5 ppm; JB-l, Rb 41.5Ppm, Sr 448.4 ppm , each of which is near the mean of reported values for corresponding element of the sample (ANDO et al., 1974). Concentrations of Rb and Sr in pure water and regents used in chemical treatement of samples were also measured; a possible error due to the contamination is negligible for most geochemical samples.
Publication Title 岡山大学温泉研究所報告
Published Date 1982-03-25
Volume volume52
Start Page 51
End Page 70
ISSN 0369-7142
language 日本語
File Version publisher
NAID 120002310968
JaLCDOI 10.18926/ESR/13957
FullText URL ESR_1_27.pdf
Author Okano, Osamu| Nishiya, Nanayo| Kagami, Hiroo|
Abstract Rb-Sr isotopic study as well as petrologic investigations have been done on sixteen individul chondrule samples separated from the Allegan (H5) chondrite. The Rb-Sr chondrule isochron does not define a very precise age (4.42±0.17 Ga) and 87Sr/86Sr initial ratio (0.6997±0.0014) due to the very small variation in Rb/Sr ratio for the chondrules, whereas the model ages give a much more speciffic value (4.42±0.02 Ga). These ages may probably be indicative of the time of primary process (es) (e.g. chondrule formation) rather than secondary (metamorphic reheating) or tertiary (shock heating) processes in and/or on the H-chodrite parent body (or bodies). Chemical compositions of oliveines (Fa=17.5mol%, mean deviation (MD)=1.3%) and orthopyoxenes (Fs=15.4mol%, MD=3.2%) are moderately homogenized among the chondrules, while certains chemically uneguilibrated features are also distinctly preserved in this chondrite. Homogeneity of the mineral compositions, therefore, could not have been caused by thermal metamorphism but were probably inherited from processes prior to aggregation of the components. The overall implications of the chondrule isochron and model ages in relation to the petrological features and in comparison with Rb-Sr data of other chondrites of different chemical groups and petrologic types are discussed.
Keywords chondrule age Rb-Sr isochron Allegan H- chondrite meteorite metamorphism olivine pyroxene
Publication Title Okayama University Earth Science Report
Published Date 1994-09-20
Volume volume1
Issue issue1
Start Page 27
End Page 36
ISSN 1340-7414
language 英語
Copyright Holders 岡山大学地球科学研究報告編集委員会
File Version publisher
NAID 120002310261
JaLCDOI 10.18926/ESR/13949
Title Alternative Rb-Sr age of K-rich LL-chondrite Yamato-74442
FullText URL ESR_2_91.pdf
Author Nishiya, Nanayo| Okano, Osamu| Kagami, Hiroo| Nakamura, Noboru|
Abstract Yamato-74442, a brecciated LL-group chondrite, consists of fragments with igeous texture, chondrules, mineral fragments, and host. The fragments involve K-rich fragments as well as normal ones. Typically, both fragments consist mainly of euhedral porphyritic olivines and a few orthopyroxenes in a glassy grundmass. EPMA analyses for these fragments indicate that olivines and orthoptroxenes have a range of Fe/(Fe+Mg) ratio of 27.19~31.33 and 20.10~26.91 mol%, respectively. There is no significant difference in these rations between K-rich (Na2O/K2O<1) and normal framents. The K2O contents of groundmass for K-rich fragments range from 0.51 to 4.89 wt% and that of the normal fragments is 0.38~090 wt%. K2O contents of groundmass vary from fragment to fragment but are rather homegeneous in a single fragment. Rb-Sr isotopic determination on eighteen K-rich fragments (1.5 to 9.5mg in weight) gave an internal isochron age of 4.514±0.022 (2σ) Ga (λ87Rb=1.42×10-11y-1) and initial 87Sr/86Sr ratio of 0.7016±0.0024. This age is somewhat old compared with a whole rock isochron age of LL chondrites (4.493±0.18 Ga; Minster and Allegre, 1981). From a comoarison of the present result with others so far reported, it is inferred that the alkali differentiation as observed in Yamato-74442 probably occurred prior to or during a process of accumulation from LL chondrite parent material in the early solar nebula. 
Keywords LL-chondrite Rb-Sr age Sr isotope K-rich fragment
Publication Title Okayama University Earth Science Report
Published Date 1995-09-20
Volume volume2
Issue issue1
Start Page 91
End Page 102
ISSN 1340-7414
language 日本語
Copyright Holders 岡山大学地球科学研究報告編集委員会
File Version publisher
NAID 120002310270