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  • 1980-1984  (8)
  • 1
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    Stillwater anorthosites - A lunar analog? (1983)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Samples of anorthosite from Stillwater complex units AN-I and AN-II have been studied by instrumental neutron activation analysis for FeO, CaO, Na2O, REE, and other trace elements, and the results are discussed. No systematic variations of chemical composition with stratigraphic position were observed. The major and trace compositions of both units appear to be identical, with plagioclase compositions virtually constant throughout both. Thus, there is almost no evidence for evolution of parent magma composition during the genesis of these units. The bulk of the anorthosites appear to consist of cumulus-adcumulus plagioclase and pyroxene. Very little trapped liquid component was found. The chemical elements are not normally or lognormally distributed among samples taken from either anorthosite unit. The irregular distribution of pyroxene oikocrysts indicates that interstitial melt migrated substantially prior to final consolidation of the rock.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research, Supplement (ISSN 0148-0227); 88; B27-B39
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    NASA TECHNICAL REPORTS
  • 2
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    Compositional inhomogeneities in a single Icelandic tholeiite flow (1981)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: New trace element analyses of 25 basalt samples from a vertical traverse in an 11 m thick flow of Icelandic tholeiite show compositional differences which exceed analytical uncertainties and are random with respect to height. These variations suggest a short-range segregation model in which the amounts of phenocrysts, groundmass materials, and residual liquid vary randomly in different samples of the flow; a least-squares method is applied to determine if these variations reflect different proportions of crystallizing phases and residual liquid. Monte Carlo computations indicate that short-range segregation results in inhomogeneity of a magnitude of interflow compositional differences; this causes incoherence in elements with different geochemical behaviors while preserving coherence in elements of similar behavior.
    Keywords: GEOPHYSICS
    Type: Geochimica et Cosmochimica Acta; 45; Jan. 198
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  • 3
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    An electrochemical study of Ni/2+/, Co/2+/, and Zn/2+/ ions in melts of composition CaMgSi2O6 (1982)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Results are reported for a study of the behavior of Ni(2+), Co(2+), and Zn(2+) in molten diopside, determined by cyclic voltametry, as a first step in adapting electrochemical methods for use in experimental geochemistry. The techniques used are described, the theory is briefly discussed, and it is demonstrated that Ni(2+), Co(2+), and Zn(2+) can be reduced, then reoxidized in an uncomplicated case of reversible charge transfer at the Pt electrode. This implies that the neutral metal atoms remain undissolved in the melt. The kinetics of the reduction process, the effects of concentration, the standard reduction potentials, and the diffusion coefficients are discussed in detail. The observations are consistent with the mechanism of Ni(2+) diffusion by transport from site to site. As the proportion of SiO2 in the melt increases, a higher activation energy is required for Ni(2+) to move, and the rate of diffusion is lowered.
    Keywords: INORGANIC AND PHYSICAL CHEMISTRY
    Type: Geochimica et Cosmochimica Acta; 46; Oct. 198
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  • 4
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    Antarctic meteorite ALHA81005 - Not just another lunar anorthositic norite (1983)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: It is contended that 81005 requires the existence of a component that is poor in large-ion lithophile elements, at least as mafic as anorthositic norite, and magnesian rather than ferroan. While no such component has yet been observed in nearside samples, as an end-member in mixing models it would conveniently account for the composition of some polymict samples that heretofore have been difficult to explain as mixtures of endogenous rock types. The results presented here therefore suggest that the early lunar crust contained a significant proportion of both ferroan and magnesian anorthositic norites as primary igneous rocks. It is acknowledged that this conclusion is at variance with models that treat materials of anorthositic norite composition as mixtures of anorthosite plus norite, troctolite, and dunite.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Geophysical Research Letters (ISSN 0094-8276); 10; Sept
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  • 5
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    The 'North American shale composite' - Its compilation, major and trace element characteristics (1984)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: North American shale composite (NASC) major element composition and compilation are presented, together with rare earth element (REE) redeterminations obtained by high precision analytical methods. The major element composition of the NASC compares closely with other average shale compositions, and significant portions of the REE and some other trace elements are contained in minor phases. The uneven REE distribution in NASC powder appears to yield the heterogeneity in analyzed aliquants. REE distributions of detrital sediments may to some extent be dependent on their minor mineral assemblages and the sedimentological factors controlling these assemblages.
    Keywords: GEOPHYSICS
    Type: Geochimica et Cosmochimica Acta (ISSN 0016-7037); 48; 2469-248
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  • 6
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    On compositional modeling of lunar highlands soils, including application to the orbiting gamma-ray experimental data (1982)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: The compositions of remotely sensed highlands soils are compared with those of acquired highlands soils through the use of a compositional model. This model previously demonstrated its ability to describe compositions of acquired highlands soils with an accuracy approximating the present knowledge of the compositions. The principal question addressed here is whether the compositional end-members used to describe the acquired highlands soils are adequate to describe the remotely sensed ones or whether in some remotely sensed regions volumetrically significant components of different composition are required. Owing to the large analytical uncertainties in the gamma-ray data, only the presence of substantial proportions of significantly different components would be detectable by this (or any other) analysis of those data.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar and Planetary Science Conference; Mar 16, 1981 - Mar 20, 1981; Houston, TX
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    NASA TECHNICAL REPORTS
  • 7
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    On compositional variations among lunar anorthosites (1982)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: Ferroan anorthosite (FAN) is the most abundant 'pristine' highlands igneous rock in the Apollo sample collection. The presence of substantial FAN in the lunar crust is one argument used in favor of a global magma ocean on which crystallizing plagioclase could float. Information about the composition of the proposed magma ocean or whatever liquids might have been parental to FAN is sparse. As a first step toward learning about the nature of the FAN parent and the processes by which FAN attained its compositional characteristics, attention is given to the concentrations for a number of major and trace elements whose behavior during magmatic processes is somewhat understood. Serious difficulties are found with both FAN and the Marcy anorthosite in interpreting incompatible trace element concentrations in the plagioclases or the whole rocks in terms of residues from parent liquids. A description is presented of the nature of these difficulties.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar and Planetary Science Conference; Mar 16, 1981 - Mar 20, 1981; Houston, TX
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  • 8
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    A synthesis of lunar highlands compositional data (1980)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: Based on compositions of lunar soils and endogeneous highland rocks and mineral phase relationships, a composition for the non-KREEP, mafic portion of the lunar highlands is determined through the use of a mixing model. It is found that the most common materials making up the surface highlands appear to be ferroan anorthosite (FAN) and a material of olivine norite composition (HON, highlands olivine norite) in roughly equal proportions. It is also found that the composition of HON is similar to that of the residual liquid from crystallization of FAN and that the proportion of FAN to HON at the lunar surface appears to be much higher than the phase relations allow for the extent of evolution of HON from a primitive plagioclase-saturated liquid. This is seen as implying an excess of FAN in the upper highlands.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar and Planetary Science Conference; Mar 17, 1980 - Mar 21, 1980; Houston, TX
    Format: text
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