GEOCHEMICAL JOURNAL
Online ISSN : 1880-5973
Print ISSN : 0016-7002
ISSN-L : 0016-7002
9 巻 , 1 号
選択された号の論文の5件中1~5を表示しています
  • Brian Mason
    1975 年 9 巻 1 号 p. 1-5
    発行日: 1975/03/20
    公開日: 2008/04/08
    ジャーナル フリー
    The high content of titanium and many refractory trace elements is a remarkable feature of many lunar basalts, and its origin is imperfectly understood. A unique titanium-rich pyroxene in the Allende meteorite shows an abundance pattern for Ti, Ba, Sr, rare earth elements, Y, Zr, Hf, and Nb paralleling that for the high-titanium lunar basalts. Its probable origin as a high-temperature condensate from the primitive solar nebula indicates that it may have been an important phase in the original accretion of the Moon. A small degree of partial melting of material containing this phase would give a magma with abundance patterns for these elements comparable to those measured in basalts collected on the Apollo 11 and 17 missions; the younger and less Ti-rich basalts of other missions can plausibly be explained by a greater degree of partial melting and dilution with other phases.
  • Nobuyuki Nakai, Hideki Wada, Yasuhiro Kiyosu, Mikio Takimoto
    1975 年 9 巻 1 号 p. 7-24
    発行日: 1975/03/20
    公開日: 2008/04/08
    ジャーナル フリー
    Possible origins of lake water, salts dissolved in water of a saline lake, Lake Vanda, those contained in cored sediments of the lake and those distributed on the ground surface in the adjacent area were investigated on the basis of the stable isotope compositions, 13C/12C, 18O/16O and 34S/32S. The lake water is concluded to be neither marine nor volcanic in origin but surface fresh water such as glacial melt water, because of the low δ18O values ranging from -30.3 to -31.9‰. On the other hand, sulfate in lake water and in cored sediments from Lake Vanda shows δ34S values similar to that of sea water sulfate. Therefore, it is supposed to be marine in origin. Salts distributed on the ground surface near the lake consist mainly of calcite, gypsum, thenardite, sodium niter and halite. The isotopic compositions of carbonate and sulfate minerals range from -14.4 to +17.6‰ for δ13C and from -0.4 to +22.3‰ for δ18O of calcite and from +14.1 to +20.3 ‰ for δ34S of gypsum. From the isotopic compositions of calcite and gypsum, three different origins, hydrothermal, marine and marine aerosol are considered according to their occurrences and localities. Salts distributed in this area, however, do not constitute the source for those contained in Lake Vanda. The genesis and historical events of the saline lake also were examined. The lake was once a fjord containing sea water and was isolated from the ocean by glaciation after the Tertiary. After the isolation of the lake from the ocean, evaporation of lake water in cold climate and supply of glacial melt water in warm climate have alternately taken place several times.
  • Hiroshi Wakita, J. C. Laul, R. A. Schmitt
    1975 年 9 巻 1 号 p. 25-41
    発行日: 1975/03/20
    公開日: 2008/04/08
    ジャーナル フリー
    A regular correlation between the Sm abundances and the Eu anomalies in all kinds of lunar samples strongly suggests that a series of ANT-KREEP type rocks and the source material for the Apollo 11, 12, 15 and 17 mare basalts may have been derived from a systematic and common magmatic differentiation. In such a differentiation, significant quantities of trapped liquid were occluded with the cumulates and upon partial melting of these source materials, the trapped liquids played a dominant role in the derivation of mare basalts. After increasing the concentration of LIL trace elements to ≈10× chondrites by crystallization of Mg-rich mafic minerals such as olivine, both plagioclase and olivine began to crystallize simultaneously. Varying amounts of melt were trapped with pure anorthosites and yielded overall positive Eu anomalies. These anorthosites remained near the lunar surface. Simultaneously, mafic cumulates and any melt inclusions plus significant amounts of trapped liquid in the cumulate layers settled to yield source matter for the Apollo 15 basaltic rocks with minimum Eu anomalies. With increasing plagioclase and mafic mineral crystallization, the magma changed its chemical composition and the Sm/Eu ratio. Toward the end of the crystallization sequence, the plagioclase differentiation series became KREEP material. The settling mafic cumulates and their trapped liquids account for the sequence of the Apollo 15, 12, 17 and 11 mare basalt source materials. Appreciable amounts of apatite may have settled out with the Apollo 11 and 17 mafic cumulates. Subsequent partial melting of the solidified melt inclusions and trapped liquid, accessory minerals and a fraction of the major mafic minerals from the source materials yielded the respective mare basalts. The melt at the last stage probably had a chemical composition similar to the ilmenite microgabbros.
  • Brian W. Robinson
    1975 年 9 巻 1 号 p. 43-46
    発行日: 1975/03/20
    公開日: 2008/04/08
    ジャーナル フリー
    Calcite-carbon solute species-water theoretical and experimental isotope fractionation factors, plus salinity correction data, allow theoretical calcite equilibrium isotope values to be calculated as a function of the temperature of deposition when other variables are constant. In several ore deposits carbonate isotope values lie close to theoretical equilibrium curves as depositional temperatures decrease and a large reservoir of carbon in solution is implied. Models attributing isotopic variations in hydrothermal calcites as due to pH and fO2 changes assume such a reservoir, and hence can be valid. In addition, the carbon isotopic value of the carbon in solution can be calculated to determine the origin of the carbon.
  • R. D. Russell
    1975 年 9 巻 1 号 p. 47-50
    発行日: 1975/03/20
    公開日: 2008/04/08
    ジャーナル フリー
    This paper presents a study of the adjustment of published values for lead isotope reference materials by the double spike technique. The objective was to learn, through hindsight, about the characteristics of common analytical errors in lead isotope analyses. The conclusion is that the great majority of such errors are substantially reduced by the double spike technique. The results emphasize the precision with which the isotope ratios of the Broken Hill and California Institute of Technology reference materials are known.
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