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  • 1
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    In situ trace element microanalysis (1983)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: The use of particle-track-radiography and X-ray- fluorescence techniques in the in situ measurement of trace (less than 1000 ppm) elements in single mineral phases of polished sections is surveyed, and examples of their application to ordinary, carbonaceous and enstatite chondrites are provided. Radiographic methods surveyed include fission-track radiography (for U, Th, and Pu-244), alpha radiography using nuclear reactions (for Li and B), alpha autoradiography (for Bi and Pb), and beta autoradiography (for several elements in synthetic or biological samples). Two X-ray-fluorescence methods are compared: (1) photon-induced X-ray emission (PIXE), and (2) the potential use of synchrotron radiation. The latter is shown to allow much greater sensitivity than current PIXE technology and a much broader range of elements than particle-track radiography: the ppm analysis of 10-micron grains for all elements heavier than Na. These advantages are seen as balancing the high cost of accelerator use.
    Keywords: INORGANIC AND PHYSICAL CHEMISTRY
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    NASA TECHNICAL REPORTS
  • 2
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    Partitioning of K, U, and Th between sulfide and silicate liquids - Implications for radioactive heating of planetary cores (1986)
    In:  Other Sources
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    Publication Date: 2019-07-12
    Description: Experimental partitioning studies are reported of K, U, and Th between silicate and FeFeS liquids designed to test the proposal that actinide partitioning into sulfide liquids is more important then K partitioning in the radioactive heating of planetary cores. For a basaltic liquid at 1450 C and 1.5 GPa, U partitioning into FeFeS liquids is five times greater than K partitioning. A typical value for the liquid partition coefficient for U from a granitic silicate liquid at one atmosphere at 1150 C and low fO2 is about 0.02; the coefficient for Th is similar. At low fO2 and higher temperature, experiments with basaltic liquids produce strong Ca and U partitioning into the sulfide liquid with U coefficient greater than one. The Th coefficient is less strongly affected.
    Keywords: INORGANIC AND PHYSICAL CHEMISTRY
    Type: Journal of Geophysical Research (ISSN 0148-0227); 91; 8126-813
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    NASA TECHNICAL REPORTS
  • 3
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    Laboratory studies of actinide partitioning relevant to 244Pu chronometry (1978)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: Actinide partitioning and light lanthanide fractionation have been studied to gain an understanding of Pu chemistry under meteoritic and lunar conditions. The goal of the study was to identify conditions and samples from which chronological information can be retrieved. The laboratory investigations involved particle track radiography of the crystal/liquid partitioning of Th, U and Pu among diopsidic clinopyroxene, whitlockite and liquid. It is found that trivalent Pu plays an important role in partitioning for lunar and most meteoritic conditions. The use of Pu/Nd for relative age assessments is supported to some extent by the investigations; samples with unfractionated U, Th and Nd abundances (relative to average solar system values) may be suitable for Pu chronometry.
    Keywords: INORGANIC AND PHYSICAL CHEMISTRY
    Type: Lunar and Planetary Science Conference; Mar 13, 1978 - Mar 17, 1978; Houston, TX
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    NASA TECHNICAL REPORTS
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