GEOCHEMICAL JOURNAL
Online ISSN : 1880-5973
Print ISSN : 0016-7002
ISSN-L : 0016-7002
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Volume 30, Issue 6
Displaying 1-4 of 4 articles from this issue
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  • Advances in U-Pb zircon geochronology of Mesozoic plutonism in the southwestern part of Ryeongnam massif, Korea
    Cheong-Bin Kim, Andrew Turek
    1996 Volume 30 Issue 6 Pages 323-338
    Published: December 20, 1996
    Released on J-STAGE: April 08, 2008
    DOIhttps://doi.org/10.2343/geochemj.30.323
    JOURNAL FREE ACCESS
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    The Ryeongnam massif of Korea is composed predominantly of crystalline Precambrian rocks, which have been intruded by mafic to felsic plutons of Mesozoic age. This study reports six new U-Pb zircon ages for plutons in the southwestern part of the massif. These ages are: Machon gabbro 223 ± 3 Ma, diorite 210 ± 2 Ma, Tongbok metaporphyry 219 ± 3 Ma, Chahwangsan syenite 197 ± 1 Ma, Yulhyunri foliated granite 195 ± 2 Ma, Sinwon foliated granodiorite 189 ± 3 Ma. The above ages together with existing published zircon ages for other plutons in the region indicate three periods of igneous activity. Foliated mafic and felsic plutons were emplaced between 205–230 Ma and 180–200 Ma and nonfoliated, also mafic and felsic, plutons were intruded at 170–180 Ma. The Honam shear zone, which separates the Ryeongnam massif from the Ogcheon fold belt to the north, developed at ca. 180 Ma. K-Ar and Ar-Ar ages in the area are younger than zircon ages and probably apply to metamorphic activity related to the deformation along the Honam shear zone. Ages for Mesozoic plutons in the Ryeongnam massif are similar to ages reported in the Qinling-Dabie belt of China and indicate coeval igneous activity and possibly similar tectonic evolution.
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  • Empirical expressions of quartz solubility in H2O, H2O + CO2, and H2O + NaCl fluids
    Yasuhiro Shibue
    1996 Volume 30 Issue 6 Pages 339-354
    Published: December 20, 1996
    Released on J-STAGE: April 08, 2008
    DOIhttps://doi.org/10.2343/geochemj.30.339
    JOURNAL FREE ACCESS
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    An empirical equation of quartz solubility in H2O at elevated pressures and temperatures (up to 10 kb and 900°C) is obtained based on the published experimental results. The resultant solubility equation is as follows: lnSwater = –1.51914 + 1.99970lnρwater – 2636.78T–1 + 0.00387766T + 0.0198582PT–1, where Swater, Pwater, T, and P stand for quartz solubility (mol/kg H2O), density (g/cm3) of pure water, temperature (Kelvin), and pressure (bar), respectively. Densities of pure water are calculated by the equation of Haar et al. (1984). The solubility equation is then modified for describing the solubility behavior of quartz in H2O + CO2 or H2O + NaCl fluid. For the modification, this study uses the weight fraction of water in the solvent (F), density of the aqueous fluid (ρaq), and an empirical constant (Θ) as the additional terms. The ratio of quartz solubility in aqueous fluid (Saq) to that in pure water (Swater) at the same pressure-temperature condition is then expressed as ln(Saq/Swater) = Θln(ρaqF/ρwater). Densities of H2O + CO2 and H2O + NaCl fluids are computed with the equations of Kerrick and Jacobs (1981) and Anderko and Pitzer (1993a), respectively. The empirical constant for quartz solubility in H2O + CO2 fluid is 1.49063. For obtaining the constant, this study considers the published experimental results done at 1.5 kb to 5 kb, 600° to 700°C, and up to 71 wt% CO2 concentration (mole fraction of CO2 = 0.505). The O value for quartz solubility in H2O + NaCl fluid is 3.24740, which gives the calculated solubilities consistent with the experimental results done at 0.2 kb to 2 kb, 200° to 700°C, and up to 33.6 wt% NaCl concentration.
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  • Multivariate analysis of Japanese volcanic rocks: Volatile and major elements
    Katsuro Anazawa, Minoru Yoshida
    1996 Volume 30 Issue 6 Pages 355-372
    Published: December 20, 1996
    Released on J-STAGE: April 08, 2008
    DOIhttps://doi.org/10.2343/geochemj.30.355
    JOURNAL FREE ACCESS
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    Four types of multivariate procedures (principal components analysis (PCA), factor analysis (FA), cluster analysis and multiple regression analysis (MR)) were applied to find the relationship between volatile contents and genesis of Japanese volcanic rocks. Twelve major elements and seven volatile minor elements were considered on 44 rock samples obtained from various areas of Japan. The variation in the data was demonstrated by 5 components and 5 common factors in PCA and FA, respectively. The first factor implies similar behavior among the major elements; the second factor represents the contribution of seawater to magma genesis; the third factor corresponds to the contribution of the mantle component; the fourth factor suggests separation of sulfide phase from silicate phase; and the fifth factor shows the contribution of sedimentary materials to magma genesis.
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  • Handling of Pt catalyst in H2-H2O equilibration method for D/H measurement of water
    Takeshi Ohba, Jun-ichi Hirabayashi
    1996 Volume 30 Issue 6 Pages 373-377
    Published: December 20, 1996
    Released on J-STAGE: April 08, 2008
    DOIhttps://doi.org/10.2343/geochemj.30.373
    JOURNAL FREE ACCESS
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    In the H2-H2O equilibration method for D/H measurement of water samples, an improved handling of Pt catalyst was proposed. The catalyst was wrapped in a Teflon® filter to prevent dispersion of fine fragments of the catalyst. Despite a reduced rate of isotope exchange reaction, equilibrium was attained within 24 h at 25°C. A conventional unit for automatic CO2-H2O isotope exchange reaction can be used for this purpose.
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