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Volume 30 (1996)
- Issue 6 Pages 323-
- Issue 5 Pages 261-
- Issue 4 Pages 201-
- Issue 3 Pages 139-
- Issue 2 Pages 71-
- Issue 1 Pages 1-
Volume 30, Issue 2
Displaying 1-6 of 6 articles from this issue
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Yuichi Morishita, Bruno J. Giletti, John R. Farver1996 Volume 30 Issue 2 Pages 71-79
Published: April 20, 1996
Released on J-STAGE: April 08, 2008
JOURNAL FREE ACCESSOxygen self-diffusion coefficients in natural titanite (sphene) single crystals were experimentally determined under hydrothermal conditions at 700° to 900°C and 100 MPa water pressure using an ion microprobe (SIMS). Oxygen self-diffusion parallel to the c-axis is described by an Arrhenius relation with pre-exponential factor D0 = 1–1+5 × 10–8 m2/sec and activation energy Q = 254 ± 28 kJ/mol. Oxygen diffusion is isotropic within the measurement reproducibility of approximately a factor of 2. The relatively low diffusion coefficients for oxygen yield closure temperatures of 450° to 750°C for small crystals of titanite at typical cooling rates, which suggests that useful data on cooling rates of igneous rocks, or of metamorphic episodes, can be obtained because the size of titanite crystals in rocks is normally small.View full abstractDownload PDF (2258K) -
Hidenori Kumagai, Ichiro Kaneoka, Teruaki Ishii1996 Volume 30 Issue 2 Pages 81-87
Published: April 20, 1996
Released on J-STAGE: April 08, 2008
JOURNAL FREE ACCESSIn order to estimate the active period of the Ayu Trough, which lies at the boundary between the Philippine Sea Plate and the Caroline Plate, we measured K-Ar ages of submarine rocks dredged from the region. Samples recovered from the trough axis are similar to typical MORB and/or BABB in chemical and petrological features and show K-Ar ages of around 1 Ma. This suggests that the Ayu Trough might have been a spreading center at least during the last 1 million years. While, samples recovered at a site 62 km east of the axial rift valley show K-Ar ages of 20–25 Ma, and they are high-alkali andesites. If these samples indicate that an island arc existed there at 25 Ma, the activity of the Ayu Trough might have started at 25 Ma or later.View full abstractDownload PDF (2072K) -
Hajime Mita, Akira Shimoyama, Yoshimichi Kajiwara1996 Volume 30 Issue 2 Pages 89-98
Published: April 20, 1996
Released on J-STAGE: April 08, 2008
JOURNAL FREE ACCESSAmino acids in the Cretaceous/Tertiary (K/T) boundary sediments at Kawaruppu were analyzed. A maximum of eight kinds of amino acids including diagenetically unstable serine and threonine was detected in the water extracts at most at one n mol g–1 sample level. The number of kinds and quantities of amino acids from the HCl extracts were smaller than those from the water extracts. The D/L ratios of these amino acids indicate that they are not so old as 65 million years. α-Aminoisobutyric acid (2-amino-2-methylpopanoic acid) and isovaline (2-amino-2-methylbutanoic acid) were not detected in any samples, in contrast to the previous study of amino acids in the K/T boundary at Stevns Klint, Denmark (Zhao and Bada, 1989). Our results show that amino acids of possible extraterrestrial and/or 65 million year old terrestrial in origin were not present in the K/T boundary at Kawaruppu. Three plausible explanations for the different results between the present and previous studies are discussed in the text. In addition, our results do not support the cometary dust origin proposed for the presence of the two extraterrestrial amino acids at Stevns Klint (Zahnle and Grinspoon, 1990).View full abstractDownload PDF (2429K) -
Etsuo Uchida, Yuichi Goryozono, Masahiro Naito1996 Volume 30 Issue 2 Pages 99-109
Published: April 20, 1996
Released on J-STAGE: April 08, 2008
JOURNAL FREE ACCESSThe effect of NaCl on ion exchange equilibria in the system CaWO4-MeWO4-CaCl2-MeCl2-H2O (Me: Mg, Sr, Ni and Co) was experimentally monitored at 600°C and 1 kbar. The Ca/(Ca + Me) ratio of the aqueous chloride solution in equilibrium with both CaWO4 and McWO4 was constant for Mg and Sr in spite of the addition of NaCl, whereas the ratio decreased significantly for Ni and Co with the increase of NaCl. The experimental results indicate that both Ni2+ and Co2+ do form higher-order chloro-complexes such as NiCl3–aq and COCl3–aq, whereas both Mg2+ and Sr2+ may not. The thermodynamic analysis of the experimental results gives 1.5 and 2.1 in logarithm units for the formation constants for NiCl3–aq and CoCl3–aq, respectively. By combining the results of Uchida et al. (1995), MeCl2aq tends to forms MeCl3–aq in the order of SrCl2aq = CaCl2aq = MgCl2aq << NiCl2aq < FeCl2aq < CoCl2aq < MnCl2aq at 600°C and 1 kbar. Based on ligand field theory, the above order may suggest that the transition metal cations exist as tetrahedral chloro-complexes with low-spin state in the supercritical hydrothermal solutions.View full abstractDownload PDF (2660K) -
Kazuo Fukushima, Makoto Mochizuki, Hidetake Hayashi, Rie Ishikawa, Hit ...1996 Volume 30 Issue 2 Pages 111-130
Published: April 20, 1996
Released on J-STAGE: April 08, 2008
JOURNAL FREE ACCESSLipid compounds in sediments from an inorganically acid freshwater Lake Tazawa-ko in Japan were analyzed. Of first remarked was the occurrence of series of long-chain (C21–C32) branched alkanes, alkenes, alcohols and alkanoic acids, which showed quite small odd-even carbon number preferences with the maximum abundance in the range of C28–C30. These long-chain branched compound series have been observed almost ubiquitously in moderately acidic (pH = 3–6) but neither in circumneutral nor strongly acidic (pH < 2) lake sediments in Japan. Mass spectra of the branched alkanes and alkenes with strong fragment ions of (M-29)+ and (M-30)+, respectively, showed that both series possess an anteiso (3-methyl or (ω-2)-methyl) structure. A relatively large intensity of 57+ ion in the mass spectra of the branched alcohols (as TMS ethers) and alkanoic acids (as methyl esters) indicated that they also have the same anteiso, i.e., (ω-2)-methyl structure. Occurrence of these anteiso compounds was accompanied by a significant decrease of the odd or even carbon-number preference of concomitant straight-chain compounds, which suggested the source of these anteiso compounds might be bacteria. Intimate relationship between these characteristic lipid compositions and the acidic nature of the lake water was substantiated by the observation of core sediments, since the acidification of the Lake Tazawa-ko was onset in 1940 due to artificial introduction of the River Tamagawa water charged with a strongly acidic hot spring water.View full abstractDownload PDF (4153K) -
Dario Tedesco, Raimondo Pece, Rosario Avino1996 Volume 30 Issue 2 Pages 131-138
Published: April 20, 1996
Released on J-STAGE: April 08, 2008
JOURNAL FREE ACCESSMonitoring of the Campi Flegrei caldera has been undertaken since 1983 by measuring radon content (by track etch method), pH and temperature in three thermal water wells. Collection of data started after the area was affected by a dramatic phase of volcano unrest, with a high rate of uplift and increased seismicity. Results show that the radon content is different from well to well; low in the cold well and at least one order of magnitude greater in the two hot wells. Variations in radon content in the three wells sometimes occurred simultaneously and indicate an influence from the same phenomena and feeding source. Three main events, (i) rain fall, (ii) seismic activity and (iii) volcano unrest have been identified to correlate with variations in the radon content, with pH and temperature changes at the same time.View full abstractDownload PDF (1881K)
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