GEOCHEMICAL JOURNAL
Online ISSN : 1880-5973
Print ISSN : 0016-7002
ISSN-L : 0016-7002
Volume 20, Issue 4
Displaying 1-6 of 6 articles from this issue
  • Gil Michard, Bernard Sanjuan, Annie Criaud, Christian Fouillac, Elka N ...
    1986 Volume 20 Issue 4 Pages 159-171
    Published: August 20, 1986
    Released on J-STAGE: April 08, 2008
    JOURNAL FREE ACCESS
    Sixteen hot alkaline waters from geothermal drillholes in S. W. Bulgaria have been studied. Nine of them are in approximate equilibrium with chalcedony, albite, adularia, calcite, kaolinite, and low-temperature calcium zeolite at a temperature close to the outflow temperature. The others are in equilibrium with calcite and kaolinite and oversaturated with albite, chalcedony and adularia at the outflow temperature. Calculations of the evolution of chemical species due to the cooling indicate that equilibrium with these minerals is established at a temperature close to the temperature derived from the chemical geothermometers. Na/K, Na-K-Ca (β=4/3) and chalcedony (or quartz) geothermometers give satisfactory results in the low temperature range 40–140°C. Results obtained corroborate the model previously presented by Michard and Fouillac (1980) for alkaline hot waters.
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  • S. S. Hughes, R. A. Schmitt, Y. L. Wang, G. J. Wasserburg
    1986 Volume 20 Issue 4 Pages 173-189
    Published: August 20, 1986
    Released on J-STAGE: April 08, 2008
    JOURNAL FREE ACCESS
    Multi-element abundances in twenty-four samples from the Serra Geral continental flood basalt system (Parana Basin) were determined by INAA to assess the trace element signature of primary magmatric sources. Isotopic Sr and Nd data were obtained on a 24-sample composite and three individual samples of the suite to constrain the influences of older enriched material. Twenty basaltic samples have enriched LILE commensurate with most continental tholeiites and, display fractionated REE patterns similar to those in the Columbia River Group and other flood basalt provinces. The mafic units exhibit low-moderate Ti, variable V, Cr and Ni and relatively uniform Co and Sc abundances. Four intermediate to silicic units exhibit higher overall incompatible element abundances, strongly fractionated patterns and depletions of compatible elements consistent with derivation by fractionation of basaltic parents. Isotopic data for two basalts and the composite analysis indicate 87Sr/86Sr = 0.7090 to 0.7105 and εNd = -6.6 to -6.9 requiring magma genesis in an evolved LILE-enriched upper mantle or lower crust. A silicic sample has 87Sr/86Sr = 0.7219 and εNd = -9.2 reflecting a stronger crustal influence. Chemical comparisons within the basaltic members allow the delineation of ten least-evolved compositions having a regionally characteristic trace element pattern and two additional samples (of one flow) representing a second, less fractionated pattern. Trace element models for both types predict magma segregation from lower lithospheric sources having relatively uniform enrichments of incompatible elements via regional metasomatism. The most viable scenarios for basalt magma production require either enriched mantle partial-melt liquids, some of which comingle with crustal components, or partial melting of ultramafic, LILE-enriched lower crust. Either process requires a zone of primary magma extraction in a region where initially uniform source enrichments act independently of subsequent contamination, probably in the crust/mantle transition zone.
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  • Yoshiyuki Tatsumi, Noboru Nakamura
    1986 Volume 20 Issue 4 Pages 191-196
    Published: August 20, 1986
    Released on J-STAGE: April 08, 2008
    JOURNAL FREE ACCESS
    High pressure experiments up to 4.0GPa on natural serpentinite, one of constituent members of the hydrated subducted oceanic lithosphere, show that it decomposes totally at temperatures below 700°C. The results suggest that the serpentinite-derived aqueous fluid can be supplied to the mantle wedge only beneath the fore-arc region. The concentration of Rb, Sr and Yb in the aqueous fluid released through the dehydration process of serpentinite are estimated on the basis of open-system dehydration experiments under 1.5 and 3.0GPa, in which the fluid is lost through perforations on a gold sample container; the aqueous fluid transports a larger amount of an element with a larger ionic radius under higher pressures.
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  • Hidehiko Shimazaki, Minoru Kusakabe
    1986 Volume 20 Issue 4 Pages 197-200
    Published: August 20, 1986
    Released on J-STAGE: April 08, 2008
    JOURNAL FREE ACCESS
    Oxygen isotopic compositions are determined for eleven clinopyroxenes from the Kamioka (-2.4 ∼ -0.4‰, SMOW), Tsumo (+5.0 ∼ +7.0), Yaguki (-1.5 ∼ +2.5) and Fujigatani (+10.5 ∼ +10.8) skarn deposits in Japan. Oxygen isotope values of ore-forming fluids estimated from the obtained data on clinopyroxenes are generally in good agreement with those estimated from the published data on skarn calcites. Among the studied deposits, the skarns in the Kamioka and Yaguki mines were formed under the influence of fluids with considerably low oxygen isotopic ratios.
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  • Yuuko Itihara, Kanenori Suwa, Mitsuo Hoshino
    1986 Volume 20 Issue 4 Pages 201-207
    Published: August 20, 1986
    Released on J-STAGE: April 08, 2008
    JOURNAL FREE ACCESS
    Concentrations and chemical forms of carbon and nitrogen are examined on the Kavirondian sedimentary rocks of Archaean period in Kenya (2, 500–2, 800Ma). Elemental composition and graphitization degree of kerogen fraction (carbonaceous matter) in the Kavirondian shales are also examined. Among various types of the sedimentary rocks, i.e., shales, sandstones, matrices of conglomerates and pyroclastics, only shales contain significant amounts of organic carbon and insoluble nitrogen in KCl solution. But their concentrations are low in comparison with those in Phanerozoic muddy sediments. The insoluble nitrogen is composed mainly of ammonium-nitrogen and contains a small amount of organic nitrogen. The ammonium-nitrogen must have been inherited from organic matters of sedimentary rocks as it is presumed from geochemical studies of nitrogen in Phanerozoic muddy sediments of Japan. The kerogen fractions in two Kavirondian shales are graphite, but their graphitization degree has not yet reached the fully ordered state. The graphitization degree is conformable with metamorphic grade of the shales. The elemental composition of the kerogen fractions shows that these kerogens have high H/C ratio and low N/C ratio in comparison with those of other Archaean shales in other areas.
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  • Akira Ueda, H. Roy Krouse
    1986 Volume 20 Issue 4 Pages 209-212
    Published: August 20, 1986
    Released on J-STAGE: April 08, 2008
    JOURNAL FREE ACCESS
    Sulphide and sulphate minerals mixed with V2O5 and SiO2, were heated in a vacuum at 950°C for 15 minutes. The evolved SO3 was converted to SO2 by reaction with metallic Cu for sulphur isotope determinations. This technique yields SO2 of consistent oxygen isotope composition regardless of whether sulphide or sulphate is converted. The reproducibilities of sulphur conversion and δ34S values were 98 ±5% and ±0.2‰, respectively. The technique is particularly suitable for small samples. Successful isotope determinations have been obtained with natural samples containing less than 1 mg S. In some cases, variations in δ34S of 2‰ have been found for single grains analysed from a small specimen.
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