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Volume 38 (1990)
- Issue 6 Pages 269-
- Issue 5 Pages 241-
- Issue 4 Pages 151-
- Issue 3 Pages 95-
- Issue 2 Pages 65-
- Issue 1 Pages 1-
Volume 38, Issue 6
Displaying 1-7 of 7 articles from this issue
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REGULAR PAPERS
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Ko Hashizume, Naoji Sugiura1990 Volume 38 Issue 6 Pages 269-286
Published: 1990
Released on J-STAGE: May 01, 2007
JOURNAL FREE ACCESSA system to precisely analyze the isotope of nanogram-order nitrogen was constructed using a quadrupole mass-spectrometer. Neon and argon isotopes can also be measured by the system. The reproducibility of the nitrogen isotopic ratio is better than 3‰. The minimum amount of standard air nitrogen required for precise isotopic determination is 3 ng. The system is oriented to measure extra-terrestrial samples with low nitrogen concentration. The detail of the stepwise combustion method to separate a trace amount of indigenous nitrogen from the terrestrial nitrogen is also reported.View full abstractDownload PDF (1354K) -
Hideki Wada, Ryozo Ito1990 Volume 38 Issue 6 Pages 287-294
Published: 1990
Released on J-STAGE: May 01, 2007
JOURNAL FREE ACCESSA conventional dynamic mass spectrometer with an inlet system specially modified for microscale samples was used to measure carbon isotopic ratio of subsamples within individual graphite crystals collected from Hida metamorphic belt, central Japan. The graphite crystals with three different occurrences i.e., in pelitic gneiss, skarn deposit, and crystalline limestone were examined for their isotopic zonation. Single graphite crystals collected from pelitic gneiss and hedenbergite skarn deposit has homogeneous isotopic distribution, whereas composite graphites of marble show complicated zonation which may imply the evolution of the metamorphic fluid during metamorphism.View full abstractDownload PDF (606K) -
Itsuro Kita, Keisuke Nagao, Isao Takashima, Sakuro Honda, Benjavun Rat ...1990 Volume 38 Issue 6 Pages 295-305
Published: 1990
Released on J-STAGE: May 01, 2007
JOURNAL FREE ACCESSHydrogen and oxygen isotopic compositions of hot spring waters and meteoric waters from San Kamphaeng, Fang, and their vicinity in northern Thailand were measured. Although most of the data fall on the global meteoric water line δD=8δ18O+10, some meteoric waters exhibit high δD and δ18O values which plot on a different line defined by δD=8δ18O-5. The isotopic compositions of hot spring waters vary in the range defined by the above meteoric water lines with the δD variation between -50 and -62‰. No large oxygen isotopic shift was observed for all geothermal waters collected in this survey, indicating that the geothermal waters originate from the local meteoric waters.
A distinct difference was observed in hydrogen concentrations of soil gases between San Kamphaeng and Fang geothermal areas. In Fang the high H2 concentration areas are distributed around the hot spring zone and a closed fluorite mine which is a product of past hydrothermal activity. No such areas were found in the San Kamphaeng area, suggesting that geothermal activity may be higher in Fang than in San Kamphaeng.
The 3He/4He ratios of helium in hot spring gas samples from the Fang area are higher than those from the San Kamphaeng area, although these values are lower than 3×10-7. The δ13C values of CO2 in these hot spring gas samples (-7 to -11‰) are close to those for volcanic CO2. This suggests that the volcanic CO2 is supplied from the deep seated geothermal system and a possibility that mantle He is diluted by a large amount of crustal He originated from abundant radioactive elements in granitic rocks widely distributed in northern Thailand.View full abstractDownload PDF (720K) -
Eitaro Wada, Yuko Kabaya, Kyoko Tsuru, Ryoshi Ishiwatari1990 Volume 38 Issue 6 Pages 307-318
Published: 1990
Released on J-STAGE: May 01, 2007
JOURNAL FREE ACCESSThe distribution of δ13C and δ15N in sedimentary organics from the Tama River, Sumida River and Arakawa River estuaries and Tokyo Bay was determined to establish an isotope biogeochemical structure to assess the fate of organic matter in the estuary-bay system. Variation in isotope ratios in intertidal river sediment was primary governed by the mixing of terrestrial and riverine organic matter. Fluctuation in isotopic composition in the intertidal zone may possibly result from different flushing times at each site.
Variation in δ13C and δ15N was remarkable in the vicinity of the river mouth and inner bay. Enhanced δ15N at the river mouth of the Tama River may possibly have been due to oxidation reduction-reactions through which 15N depleted N2O and N2 were emitted from the aquatic system. The very low values for δ15N and high δ13C in the inner bay may reflect isotope fractionation during assimilation of inorganic nitrogenous compounds with eutrophication and rapid growth of marine phytoplankton, respectively. The variation in isotopic composition was schematically illustrated based on available data.View full abstractDownload PDF (775K) -
Masami Noto, Minoru Kusakabe, Tetsuo Uchida1990 Volume 38 Issue 6 Pages 319-330
Published: 1990
Released on J-STAGE: May 01, 2007
JOURNAL FREE ACCESSDehydration techniques were developed for the analysis of isotopic ratios of framework oxygen of wairakite, one of calcium zeolites often encountered in geothermal systems. Channel water in wairakite were separated from aluminosilicate framework by dehydration in vacuum at 300°, 400°, 450°, 500°, 550°, 650°, 750°, 850°, and 950°C, and by stepwise heating at temperatures from 300° to 700°C. The oxygen isotopic analyses of the separated channel water and the residual aluminosilicate framework of wairakite indicated that dehydration at temperatues higher than 400°C is accompanied by isotopic exchang between the framework oxygen and dehydrating water vapor. The isotopic exchange during the high temperature dehydration makes the δ18O of framework oxygen lower and that of channel water higher than those obtained by dehydration at 300°C. These results are consitent with dehydration behavior of wairakite under vacuum that the maximum rate of dehydration of channel water is attained at about 400°C. Consequently it is recommended to dehydrate wairakite at a temperature as low as possible in order to avoid the effect of the isotopic exchange. Time required to attain complete dehydration becomes longer with lowering the temperature of dehydration. To compromise these conflicting effects, the optimum conditions of dehydration have been found that most of the channel water is dehydrated at 300°C for 24 hours, followed by stepwise heating for additional 17 hours up to 700°C. We obtained a better than ±0.1 reproducibility for the framework oxygen isotopic determinations with this technique.View full abstractDownload PDF (990K) -
Osamu Matsubaya, Minako Yoshida, Kiriko Tanaka-Miyamoto1990 Volume 38 Issue 6 Pages 331-339
Published: 1990
Released on J-STAGE: May 01, 2007
JOURNAL FREE ACCESSBy means of three isotope tracer techniques, proportion of direct runoff and characters of groundwater runoff were studied in the Iwami River drainage during a high runoff period for about 3 days, caused by a heavy rainfall of 85 mm for 17 hours. The proportion of direct runoff is 15% or less of the total runoff caused by the rainfall, while 65% of river water at the peak of runoff. Differences observed in the runoff manners among 18O, 2H, and 3H are interpreted as a result of preferential runoff of previous precipitations stored in some unsaturated zone above the saturated groundwater zone. Cl- content is not conservative as a tracer to study runoff mechanisms.View full abstractDownload PDF (591K)
TECHNICAL REPORT
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Hiroshi Satake, Kouichi Ikegami1990 Volume 38 Issue 6 Pages 341-350
Published: 1990
Released on J-STAGE: May 01, 2007
JOURNAL FREE ACCESSThe automatic measurement system for the light element isotope analysis was developed by installing the specially designed inlet system which was controlled by a computer. The microcomputer system contains specific interface boards for the inlet system and the mass spectrometer, Micromass 602 E. All the components of the inlet and the computer system installed are easily available in Japan. Ten samples can be automatically measured as a maximum of. About 160 minutes are required for 10 measurements of δ18O values of CO2. Thus four samples can be measured per an hour using this system, while usually three samples for an hour using the manual operation. The automatized analysis system clearly has an advantage over the conventional method. This paper describes the detatils of this automated system, such as apparatuses used, the control procedure and the correction for reliable measurement.View full abstractDownload PDF (790K)
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