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Volume 25 (1991)
- Issue 6 Pages 411-
- Issue 5 Pages 357-
- Issue 4 Pages 199-
- Issue 3 Pages 137-
- Issue 2 Pages 57-
- Issue 1 Pages 1-
Volume 25, Issue 3
Displaying 1-5 of 5 articles from this issue
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Sumino Nishioka, Yoji Arakawa, Yoji Kobayashi1991 Volume 25 Issue 3 Pages 137-146
Published: 1991
Released on J-STAGE: April 08, 2008
JOURNAL FREE ACCESSThe chemical and Sr isotope compositions of the Akiyoshi Limestone (SW Japan) were determined. This limestone is a continuous sequence ranging in age from Early Carboniferous to Late Permian and is considered as an organic reef complex deposited on a basaltic seamount. The Sr isotope compositions (87Sr/86Sr) of the Akiyoshi Limestone range from 0.7068 to 0.7088. The time dependent change of the Sr isotope compositions is approximated to the two decreases in Early Carboniferous and Early to Late Permian, and one smooth increase in Middle Carboniferous to Early Permian. Although it is assumed that post-depositional diagenetic alteration may more or less have modified the original isotope values, the profile of the Sr isotope compositions of the Akiyoshi Limestone is interpreted as preserving the temporal change of sea water Sr isotope compositions during Carboniferous to Permian.View full abstractDownload PDF (2814K) -
Gao Shan, Zhang Benren1991 Volume 25 Issue 3 Pages 147-161
Published: 1991
Released on J-STAGE: April 08, 2008
JOURNAL FREE ACCESSLinear correlations between Al2O3 and ΣREE (14 REEs) are defined for post-Archean fine-grained clastic sedimentary rocks from the Qinling region, Central China and Australia: ΣREE = −16(±71) + 12Al2O3, and for Archean fine-grained clastic sedimentary rocks worldwide: ΣREE = −78(±78) + 12Al2O3. One important property of such correlations is the additivity, i.e., the correlation equation for ΣREE is equal to the sum of the correlation equations for individual REE, and each REE shows a roughly constant slope. These correlations indicate that the REE of fine-grained clastic sedimentary rocks or metamorphosed equivalents are in general dominantly contained in clay minerals or their metamorphosed products. Using these correlations, the REE abundances of the upper continental crust, sedimentary cover and Devonian strata were calculated for different tectonic units of the Qinling region. The results generally agree with the estimate from direct sampling within 18%.View full abstractDownload PDF (3506K) -
Yayoi Miura, Keisuke Nagao1991 Volume 25 Issue 3 Pages 163-171
Published: 1991
Released on J-STAGE: April 08, 2008
JOURNAL FREE ACCESSSix igneous rocks of the GSJ reference samples were analyzed mass spectrometrically to determine the elemental abundances and isotopic compositions of noble gases. The concentrations of noble gases except for radiogenic 4He and 40Ar are low and in the range reported for various types of igneous rocks. In JR-1 obsidian a significant enrichment in Ne was found, which might be caused by diffusion of atmospheric Ne into the sample. K-Ar ages of JR-1, JGb-1 and JA-2 calculated using the 40Ar contents measured in this study and K in literature are 0.94 ± 0.09, 96 ± 10 and 13 ± 1 Ma, respectively. They agree with the ages previously reported. JG-1 has excesses of 21Ne and heavy Xe isotopes, which can be attributed to the nuclear reaction 18O(α, n)21Ne and 238U spontaneous fission, respectively. Since the 3He/4He ratio of JP-1 peridotite is similar to the ratio of MORB, which is higher than the ratio associated with arc volcanism, this sample may provide information about the noble gas state in the wedge mantle beneath the Japanese Islands. The low 40Ar/36Ar ratio of 384 for this sample implies that 99.8% of total 36Ar came from atmosphere. If the contaminative Ar was transported from sea water to the subducting oceanic plate, 0.2 mg of water for each gram of peridotite is sufficient to account for the contamination. The 3He/4He ratio, however, is not changed by this contamination.View full abstractDownload PDF (2626K) -
M. Santosh, Harue Masuda1991 Volume 25 Issue 3 Pages 173-185
Published: 1991
Released on J-STAGE: April 08, 2008
JOURNAL FREE ACCESSThe granulite facies deep crustal segment in the southern Indian Shield evidenced a prominent alkaline silicic magmatic event of within-plate affinity at ca. 550–750 Ma, represented by a suite of alkali granite and syenite plutons, emplaced on or close to regional fault systems. Their mineral associations and geochemical patterns are typical of alkaline plutons, invoking magma derivation from the deepcrust or uppermantle. A reconnaissance oxygen isotope study involving ten representative plutons yielded a dramatic increase in δ18O values from 3.9‰ in the north, near the amphibolite-granulite transition zone, to 10.9‰ at the southern margin of the granulite terrane. From north to south, these intrusives define a low oxygen isotope zone (δ18O = 3.99 to 4.6‰; 3 plutons), an intermediate oxygen isotope zone (6.9 to 8.6‰; 5 plutons) and a high oxygen isotope zone (9.2 to 10.9‰; 2 plutons). Whole rock sulfur isotopes display positive values, with a wide spread in δ34S from 2.5‰ to 14.5‰. Although the isotopic patterns of some of these plutons are consistent with varying degrees of fluid-rock exchange or supracrustal interaction, our data are in broad agreement with source heterogeneities, and suggest the possibility of isotopic gradients in the subcontinental mantle beneath the southern Indian Shield.View full abstractDownload PDF (3539K) -
Seiya Nagao, Satoru Nakashima1991 Volume 25 Issue 3 Pages 187-197
Published: 1991
Released on J-STAGE: April 08, 2008
JOURNAL FREE ACCESSA convenient method has been developed for the determination of colors of wet and powdered marine sediments. The colors of the sediments are determined with a simple colorimeter and described in the second CIE 1976 color space (L*a*b* color space). This method can sensitively detect color differences impossible to detect by the naked eye for wet and powdered sediment samples. It generally gives standard deviations of about 3% for replicate determinations of L*a*b* values for powdered samples of brown, dark brown, and greenish gray sediments, and less than 8% for wet black sediments. The color measurement of wet core samples on board the ship can be rapidly performed by this method, which is much more convenient and quantitative than the conventional visual color description using rock color chart. The effects of water content, grain size and oxidation artifact on color of sediments are also discussed.View full abstractDownload PDF (2888K)
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