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  • 1975-1979  (4)
Document type
Publisher
Years
Year
  • 1
    Electronic Resource
    Electronic Resource
    Uranium in spinel peridotite inclusions in basalts from Sardinia (1976)
    Springer
    Contributions to mineralogy and petrology 54 (1976), S. 245-254 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract The uranium distribution in spinel peridotite inclusions and their host basalt from Sardinia, Italy, was determined by fission-track mapping. Whole-rock U concentrations range from 14 to 55 ppb. Although the partitioning of U among major silicate phases of the inclusions — olivine, orthopyroxene and clinopyroxene — remains roughly constant, the U content in the minerals is highly variable, e.g. ranging from 27 ppb to 177 ppb in clinopyroxene. The U variation in the minerals shows no apparent correlation with their major element chemistry. Liquid which equilibrated with the assemblages of inclusions with high U content, had U concentrations higher than those found in basaltic rocks. It is suggested that the inclusions were contaminated with a phase strongly enriched in U and subsequently recrystallized. The available data show that spinel peridotite inclusions of basaltic rocks frequently have complex multistage evolution and thus cannot provide a representative picture of the upper mantle radioactivity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00389406
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    The origin of garnet-cordierite-sillimanite bearing rocks from Chandos Township, Ontario (1975)
    Springer
    Contributions to mineralogy and petrology 49 (1975), S. 163-175 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Garnet-cordierite-sillimanite bearing rocks from the contact aureole of the Precambrian Loon Lake pluton in Chandos Township, southeastern Ontario were analyzed for the major and rare-earth elements. In comparison with the associated Apsley biotite gneisses, they are rich in Al, Mg, and Fe, low in Si, Na, and K and their REE distribution patterns show a depletion of light REE with a negative Eu anomaly. These rocks are probably residuum left after partial melting of biotite gneiss. Leucogranite associated with the GCS rocks may represent the extracted anatectic material. It is suggested that some of the garnet cordierite-sillimanite gneisses which frequently occur in high-grade regionally metamorphosed areas of the Grenville Province of the Canadian Shield may also be of a similar residual origin as proposed by Lal and Moorhouse (1969).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00373859
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Geochemistry and origin of volcanic rocks of the Andes (26°–28°S) (1977)
    Springer
    Contributions to mineralogy and petrology 63 (1977), S. 113-128 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Mesozoic to Recent volcanic rocks from a transect of the Central Andes between latitudes 26 ° and 28 ° South in northern Chile and Argentina show chemical and temporal zonation with respect to the Peru-Chile trench. Jurassic to Eocene lavas occur closer to the trench and are comparable to calc-alkaline rocks of island arcs. Eastwards they are followed by Miocene to Quaternary sequences of typical continental margin calc-alkaline rocks which have higher contents of K, Rb, Sr, Ba, Zr, and REE and also higher K/Na and La/Yb ratios. The rocks occurring farthest from the trench have shoshonitic affinities. The distribution of major and trace elements is consistent with a model in which magmas were derived by anatexis of an upper mantle source already enriched in LILE and located above the descending oceanic slab. It is suggested that the chemical variations across the volcanic belt reflect systematic changes in the composition of the magmas due to a decreasing degree of partial melting with increasing depth, and probably also due to the heterogeneity of the source materials.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00398774
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Uranium in metamorphic rocks (1978)
    Springer
    Contributions to mineralogy and petrology 66 (1978), S. 409-414 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract The distribution of U has been studied in two metamorphic rock-series with a gradient of regional metamorphism. One series ranges from the lowest greenschist to amphibolite facies and the other one shows increasing metamorphic grade from amphibolite to granulite facies. Several medium and high pressure granulitic inclusions from alkali basalts were also analyzed. The abundances of U in the rocks do not appear to be affected by metamorphism below the granulite facies grade. Granulites are depleted in U in comparison with equivalent rocks of amphibolite facies grade. There are also differences in their U distribution, as the bulk of U in amphibolite facies rocks is located along the fractures and cleavage planes of ferro-magnesian minerals and in U-rich accessories, while in granulites, most of the U resides in accessory minerals. It seems that the depletion of U in granulites is due to a loss of U which is not located in accessory minerals or in the crystal structure of rock-forming minerals and may also be related to a migration of hydrous fluids, perhaps during dehydration.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00403426
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    Paper (German National Licenses)
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