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Volume 18, Issue 1
Displaying 1-5 of 5 articles from this issue
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Susumu Nohda1984 Volume 18 Issue 1 Pages 1-9
Published: February 20, 1984
Released on J-STAGE: April 08, 2008
JOURNAL FREE ACCESSOn the basis of Nd isotopic data on volcanic rocks, island arcs are classified into two types; type A, having high average εNd (8.1) and type B, having variable εNd. A-type island arc volcanics are probably derived from subducted oceanic crust with possibly a small amount of oceanic sediment and seawater. They correspond to ‘immature’ island arcs with active back-arc spreading. B-type island arcs are subdivided into two groups, B-1 and B-2, from the data plot on εNd–87Sr/86Sr correlation diagram. Volcanics of B-1 type, having Nd and Sr isotopic compositions plotted close to the mantle array, suggest involvement of a small amount of crustal component to the magma that had isotopic composition originally similar to that of A-type arc magma. This type of volcanics may be characteristics for the well-developed island arc under tensional stress field conditions of a back-arc basin. Lavas of B-2 type island arcs involve a considerable amount of continental crustal component and are found in the well-developed continental arcs where the compressional stress conditions are observed in the back-arc basins.View full abstractDownload PDF (2578K) -
Motoji Ikeya, Kazuo Ohmura1984 Volume 18 Issue 1 Pages 11-17
Published: February 20, 1984
Released on J-STAGE: April 08, 2008
JOURNAL FREE ACCESSAbsolute electron spin resonance (ESR) ages of Pleistocene shells from Hiradoko and Uji shell beds in Noto Peninsula, Central Japan were deduced from the total absorbed dose of natural radiation (TD) and the internal and external radiation dose. The internal dose from inside the shell was assessed using the 238U, 232Th and K contents and newly developed theoretical equation of TD based on uranium-series disequilibrium in a finite medium. The external environmental radiation was measured by thermoluminescent dosimeter (TLD) of CaSO4(Tm). The ESR ages of around 120, 000 years for shells from both shell beds agreed fairly well with coral ages in the same shell beds determined with 230Th/234U dating (OMURA, 1980).View full abstractDownload PDF (1968K) -
Noriaki Kishima, Hitoshi Sakai1984 Volume 18 Issue 1 Pages 19-29
Published: February 20, 1984
Released on J-STAGE: April 08, 2008
JOURNAL FREE ACCESSA simple gas chromatographic technique was developed for the determination of dissolved gases in the aqueous samples taken out from Dickson-type hydrothermal apparatus, and H2 concentration was measured at temperatures below 500°C and pressures below 1, 000 bars in aqueous systems containing magnetite-hematite, Ni-NiO and fayalite-magnetite-quartz oxygen buffers. Oxygen-fugacity ratios between buffers A and B can be obtained by using a relation: fO2 (A)/fO2 (B) = [CH2 (B)/CH2 (A)]2, where CH2 (A) and CH2 (B) are equilibrium H2 concentrations in the systems A-water and B-water under the same P-T condition. Using a few fO2 ratios thus obtained, corrections were evaluated for the fO2–T relationships of the buffers given by a thermochemical compilation of ROBIE et al. (1979).View full abstractDownload PDF (3357K) -
Gilberto Calderoni, Vincenzo Ferrini1984 Volume 18 Issue 1 Pages 31-41
Published: February 20, 1984
Released on J-STAGE: April 08, 2008
JOURNAL FREE ACCESSPartitioning of Al, Fe, Mn, Zn, Pb, Cu and Tl in pelagic carbonate rocks (29 samples) has been determined by sequential chemical leaching, performed with 1 M NH4OAc (easily extractable fraction), 0.8 M HOAc (carbonate component), 1 M NH2OH HCl and dilute HOAc (hydrous oxides) and HF-HClO4 (residual phases). The analytical results show great homogeneity among the samples, even though they cover a 20m.y. time-span. Mn, Zn, Pb and Cu are associated with the carbonate fraction in high percentages. Hydrous oxides, very likely because they are almost Mn-free, do not carry any significant amount of metals. Fe exhibits high percentage in residual fraction, probably because well-crystallized Fe oxides are not dissolved by NH2OH·HCl/HOAc treatment. Tl is totally contained in residual phases, and as it shows a good, positive correlation with K, it is inferred to be carried by K-bearing silicates. The distribution pattern of elements is interpreted as the result of the redox conditions to which the sediments were submitted during the sedimentation as well as early diagenesis.View full abstractDownload PDF (3143K) -
L. H. Ahrens1984 Volume 18 Issue 1 Pages 43-44
Published: February 20, 1984
Released on J-STAGE: April 08, 2008
JOURNAL FREE ACCESSAttention is drawn to the fact that the first ionization potential (IP) of mercury is conspicuously high, higher than the IPs of any metal. As a consequence, it is suggested that the occurrence of native mercury is due, in part at least, to its very high first ionization potential.View full abstractDownload PDF (500K)
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