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Volume 27 (1993)
- Issue 6 Pages 367-
- Issue 4-5 Pages 181-
- Issue 3 Pages 131-
- Issue 2 Pages 59-
- Issue 1 Pages 1-
Volume 27, Issue 3
Displaying 1-6 of 6 articles from this issue
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Claude Dupuy, Jaroslan Dostal, Mohammed Chikhaoui1993 Volume 27 Issue 3 Pages 131-145
Published: 1993
Released on J-STAGE: April 08, 2008
JOURNAL FREE ACCESSThe Late Miocene to Recent Atakor volcanic complex of the Hoggar (southern Algeria, central Sahara) is composed of alkali basalts and related rocks (mainly phonolites and trachytes). Most lavas have a restricted spread of their Sr and Nd isotopic ratios. 87Sr/86Sr ratios range from 0.70318 to 0.70422 and 143Nd/144Nd ratios range from 0.512776 to 0.512937. An exception is peralkaline trachyte which has the highest Sr (0.71271) and the lowest Nd (0.512593) isotope values and was formed by an assimilation-fractional crystallization process from basaltic magma. The basaltic rocks have trace element and isotopic compositions similar to ocean island basalts. It is suggested that the parent basaltic magmas were derived from a mantle plume which was modified during its ascent by interaction involving infiltration of a subcontinental lithospheric peridotite by plume-derived melts.View full abstractDownload PDF (4073K) -
Takao Oi, Junko Ogawa, Tomoko Ossaka1993 Volume 27 Issue 3 Pages 147-154
Published: 1993
Released on J-STAGE: April 08, 2008
JOURNAL FREE ACCESSHot spring waters in Shimogamo, Izu Peninsula, Japan, were analyzed for the stable isotopes of boron as well as for chemical compositions. The boron isotopic ratios, 11B/10B, of the waters range from 4.190 to 4.216, corresponding to the variation in δ11B from +36.2 to +42.6 permil. These values are very high compared to those of hot spring waters in other areas on the Japanese islands and close to that of sea water. The results of the isotopic and chemical analyses indicate that the Shimogamo hot spring waters are mixtures of surface water and a deep geothermal brine directly derived from sea water through the interaction with heated silicate rocks.View full abstractDownload PDF (2387K) -
Koichiro Fujimoto, Katsuyuki Fukutani, Makoto Tsunoda, Hiroshi Yamashi ...1993 Volume 27 Issue 3 Pages 155-162
Published: 1993
Released on J-STAGE: April 08, 2008
JOURNAL FREE ACCESSNatural olivine crystals (Fo91) were subjected to water treatment under different temperatures covering 25 to 800°C and different pH covering 2 to 12. Hydrogen analysis using 1H(15N, αγ)12C resonant nuclear reaction was carried out and semi-quantitative hydrogen concentration depth profiles were obtained. The hydrogen depth profiles reveal the presence of high hydrogen concentration at the surface region. The depth of the hydrogen-rich region is less than 20 nm under medium to high pH conditions at 25°C. In contrast, hydrogen penetrates into olivine as deep as 200 nm under low pH conditions at 25°C. The penetration depth is independent of temperature up to 800°C under near neutral conditions. Combining this technique and XPS analysis, the speciation of hydrogen at the near surface region has been examined. The thickness of the leached surface layer is less than 20 nm and seems to be independent of the treatment conditions such as temperature and pH, however, the surface species vary with the treatment conditions. Mg and Fe are selectively leached out under low to medium pH conditions at 25°C. H+ or H3O+ occupies the vacant octahedral sites in this case. The high hydrogen concentration within 200 nm depth in the low pH region arises from infiltration of molecular water. Hydrogen is highly localized at etch pits, etch hole, and dislocations in this case. On the contrary, Si is selectively leached out and hydroxyl species are formed under a high pH condition.View full abstractDownload PDF (2661K) -
Maki Hoashi, Robert R. Brooks, Douglas E. Ryan, Jiri Holzbecher, Roger ...1993 Volume 27 Issue 3 Pages 163-169
Published: 1993
Released on J-STAGE: April 08, 2008
JOURNAL FREE ACCESSOn the basis of compositional evidence from abundances of Ni and noble metals in iron meteorites, pairings of a number of meteorites were examined. It was concluded that: in group IIICD, Carlton is paired with Lamesa; in group IIB, “Onnum Valley” (DP88020) and “CM66” (DP88023) are paired with the Derrick Peak shower; in group IVA, Railway and “G2011” are paired with Gibeon; and in group IIIE, Paneth's Iron is paired with Coopertown rather than with Burlington or Staunton.View full abstractDownload PDF (2184K) -
Yoshinobu Kawano, Hiroo Kagami1993 Volume 27 Issue 3 Pages 171-178
Published: 1993
Released on J-STAGE: April 08, 2008
JOURNAL FREE ACCESSThe Ryukyu Arc is a chain of islands stretching from the southern tip of Kyushu to an area northeast of Taiwan. Cretaceous to Tertiary plutonic rocks occur in the Arc. Four Rb-Sr whole rock ages and one mineral isochron age for plutonic rocks have been obtained. Whole rock isochron ages are 69.8 ± 8.0 Ma (Yonama body), 61.0 ± 6.7 Ma (Kanemi body), 39.3 ± 2.0 Ma (Omoto body), 40.7 ± 14.5 Ma (Chayama body) and the mineral age is 69.3 ± 2.6 Ma (Todoroki body). These ages are about 10 Ma older than the K-Ar biotite or fission track zircon ages for the corresponding rocks. Judging from the Rb-Sr isochron ages and published K-Ar and fission track ages, it is clear that plutonic activity in south Ryukyu migrated toward the Pacific Ocean side with time. Furthermore, plutonic activity terminated in the central Ryukyu Arc before opening of the Okinawa Trough.View full abstractDownload PDF (2289K) -
Keinosuke Nagasawa1993 Volume 27 Issue 3 Pages 179-180
Published: 1993
Released on J-STAGE: April 08, 2008
JOURNAL FREE ACCESSDownload PDF (385K)
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