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Volume 31 (1997)
- Issue 6 Pages 345-
- Issue 5 Pages 263-
- Issue 4 Pages 189-
- Issue 3 Pages 125-
- Issue 2 Pages 63-
- Issue 1 Pages 1-
Volume 31, Issue 4
Displaying 1-4 of 4 articles from this issue
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Tetsuo Hashimoto, Noriyuki Sugai, Hisanobu Sakaue, Kenya Yasuda, Nobut ...1997 Volume 31 Issue 4 Pages 189-201
Published: August 20, 1997
Released on J-STAGE: April 08, 2008
JOURNAL FREE ACCESSAn on-line spectrometric system installed with a small spectrometer and an image intensifier unit has been developed for weak and changeable TL-spectrum measurements with rising temperature for application to natural minerals. The detection sensitivity over visible wavelength regions was corrected using a known spectrum from a standard light source, and the detection sensitivity was also examined by a chemical luminol reaction. In an applied experiment, two quartz grain samples from two pyroclastic flows of the same origin, were subjected to testing with the present measuring system. The original data, consisting of 512 channels for every second at a constant heating rate of 1°C/s, were used to create a contour map or a 3-dimensional expression of TL-spectra after subtraction of background radiation. The artificially irradiated quartz grains clearly showed both red (RTL) and blue TL (BTL) in contrast to RTL alone from naturally accumulated TL. Both spectral expressions and glow curves from the same original data were found to be available to estimate quartz formation temperatures, together with thermoluminescence colour images (TLCIs).View full abstractDownload PDF (2748K) -
Yuri A. Taran, Boris G. Pokrovsky, Oleg N. Volynets1997 Volume 31 Issue 4 Pages 203-221
Published: August 20, 1997
Released on J-STAGE: April 08, 2008
JOURNAL FREE ACCESSThe hydrogen isotopic composition of hornblendes (Hb) and biotites (Bi) from Quaternary volcanic rocks along the Kamchatka-Kurile volcanic arcs was measured. Volcanoes from three different tectonic environments were sampled: The Kurile chain, East Kamchatkan volcanic belt and Sredinny Ridge. Large local and regional variations were observed. There is no correlation between δD values of minerals and their chemical composition, including Cl and F contents. All observed trends are caused by regional variations in the major element chemistry (Hb) or Cl and F contents (Bi). Minerals from the Kuriles and East Kamchatka are most enriched in D, have a low F content, and a high Cl content, the latter 500-1000 ppm. Hb and Bi from Sredinny Ridge are D-depleted, enriched in F (up to 1.7 wt.% in Bi) and depleted in Cl. Based on the data set for Shiveluch and Avacha volcanoes, δD variations for Hb are caused mainly by degassing of the erupted material; the most degassed rocks contained the most D-depleted Hb. We believe that the maximum δD values correspond to isotopic equilibrium of OH-bearing minerals with a “parent magmatic water”, dissolved in the melt prior to eruption. Magmatic water for the Kurile volcanoes with δD in the range of -40 to -25‰ could be derived mainly from subducted oceanic sediments. Magmatic water for the East Kamchatka volcanoes is slightly depleted in D (-46 to -36%) and corresponds to a mixture of “devolved” water from subducted sediments and water released from altered basalts of oceanic crust. The water source of the Sredinny Ridge magmas with δD values in the range of -70 to -80‰ may not be related to oceanic slab-derived fluids; rather, they may preserve a depleted mantle isotopic signature. The regional variation of maximum D/H ratios for Hb and Bi agrees well with trends of the Sr isotopic composition and the 10Be content in volcanic rocks throughout the modem Kurile-Kamchatka arc.View full abstractDownload PDF (5219K) -
Kwang-Sik Lee, Ho-Wan Chang1997 Volume 31 Issue 4 Pages 223-243
Published: August 20, 1997
Released on J-STAGE: April 08, 2008
JOURNAL FREE ACCESSA detailed geochemical and isotopic study was performed on the Ogcheon amphibolites from the central Ogcheon Belt, Korea, to investigate the source characteristics and petrogenesis. Major and trace element data indicate that the parental rocks of the amphibolites are mostly transitional basalts, except for a few tholeiitic basalts. The tholeiitic basalts are less enriched in incompatible elements than transitional basalts and are geochemically close to primary magmas. Some transitional basalts with low SiO2 (<45 wt%) and high Fe2O3 (>16 wt%) are clearly distinguished from others and are believed to be derived from a ferro-basaltic magma. On the basis of several contamination parameters (e.g., La/Nb ratio, Nb/Th ratio, Nb and Ta anomaly), we suggest that crustal contamination has not significantly influenced the chemistry of the amphibolites. All amphibolite samples are moderately enriched in incompatible elements and plot in within-plate fields on a number of tectonic discriminant diagrams, and are consistent with previous works. The parental magmas of the amphibolites were derived from a heterogenous mantle source. Sm-Nd isotope whole rock data define a poor linear array. Considering variations in incompatible elements and Nd isotopes, the linear array may be not a true isochron but rather a mixing pseudoisochron due to source heterogeneity.View full abstractDownload PDF (5210K) -
Yoshikazu Sampei, Eiji Matsumoto, Takeshi Kamei, Takao Tokuoka1997 Volume 31 Issue 4 Pages 245-262
Published: August 20, 1997
Released on J-STAGE: April 08, 2008
JOURNAL FREE ACCESSThis paper presents the characteristics of sulfur and organic carbon concentrations, and the general factors controlling them in the brackish coastal lake sediments. Three sediment cores taken from the Lakes Nakaumi and Shinji, southwest Japan, were analyzed for total sulfur (TS), total organic carbon (TOC) and total nitrogen (TN) concentrations in dry weight. The cores' lengths were 12-30 m and the ages of the bottom layers in each core were 7000-10000 yr.B.P. The TS, TOC and TN profiles in the cores were similar, i.e., they were low in the lower portion of the cores, increased upward in the middle portion and decreased upward in the upper portion. Although there were variations in the TS, TOC and TN, the relationship between TS and TOC, and that between TN and TOC showed good correlations. The slopes of TS-TOC and TN-TOC regression lines depended on the depositional environments. The slope of the TS-TOC regression line generally correlated with the mean C/N ratio. The high value of the slope corresponded to the low C/N ratio. This suggests that the effective sulfate reduction depends on the organic matter type. Primarily the degree of preservation of freshly deposited planktonic organic matter is important. The TS-TOC regression line was: TS = 1.13TOC + 0.084 (r = 0.777, n = 278), which slope was apparently different from the slope of normal marine sediments (0.36). This is indirectly due to the primary productivity, the sedimentation rate and the water depth. In addition, the “initial minimum” amount of consumed organic carbon in the process of sulfate reduction was estimated on the basis of mass balance between consumed TOC and fixed TS.View full abstractDownload PDF (5027K)
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