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  • LUNAR AND PLANETARY EXPLORATION  (6)
  • EARTH RESOURCES AND REMOTE SENSING  (4)
  • 1
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    The Igwisi Hills extrusive 'kimberlites' (1975)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: The petrography and mineral chemistry of volcanic rocks from the Igwisi Hills in Tanzania are discussed. There is considerable evidence to suggest that the Igwisi rocks are extrusive kimberlites: a two-component nature with high P-T minerals in a low P-T matrix; the presence of chrome pyrope, Al enstatite, chrome diopside, chromite and olivine; a highly oxidized, volatile-rich matrix with serpentine, calcite, magnetite, perovskite; high Sr, Zr, and Nb contents; occurrence in a narrow isolated vent within a stable shield area. The Igwisi rocks differ from kimberlite in the lack of magnesian ilmenite, the scarcity of matrix phlogopite, and the overall low alkali content. They apparently contain material from phlogopite-bearing garnet peridotites with a primary mineral assemblage indicative of equilibrium at upper mantle temperatures and pressures. This primary assemblage was brought rapidly to the surface in a gas-charged, carbonate-rich fluid. Rapid upward transport, extrusion, and rapid cooling have tended to prevent reaction between inclusions and the carbonate-rich matrix that might otherwise have yielded a more typical kimberlite.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
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    NASA TECHNICAL REPORTS
  • 2
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    Olivine crystal types in harrisitic rocks of the Rhum pluton and in Archean spinifex rocks (1974)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: Geological Society of America Bulletin; 85; Nov. 197
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    NASA TECHNICAL REPORTS
  • 3
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    Experimentally reproduced textures and mineral chemistries of high-titanium mare basalts (1975)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: Many of the textures, morphologies, and mineral chemistries of the high-titanium mare basalts have been experimentally duplicated using single-stage cooling histories. Lunar high-titanium mare basalts are modeled in a 1 m thick gravitationally differentiating flow based on cooling rates, thermal models, and modal olivine contents. The low-pressure equilibrium phase relations of a synthetic high-titanium basalt composition were investigated as a function of oxygen fugacity, and petrographic criteria are developed for the recognition of phenocrysts which were present in the liquid at the time of eruption.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar Science Conference; Mar 17, 1975 - Mar 21, 1975; Houston, TX
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    NASA TECHNICAL REPORTS
  • 4
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    Experimental modeling of the cooling history of Apollo 12 olivine basalts (1975)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: An analog of the Apollo 12 olivine vitrophyres has been crystallized in a 1-atm gas-mixing furnace at cooling rates ranging between 1250 and 0.7 C/hr and isothermally at degrees of supercooling ranging from 10 C to 325 C. Mineral chemistry, crystal shapes, grain sizes and textures are systematically related to cooling rate and degree of supercooling. At linear cooling rates not exceeding 40 C/hr the texture is porphyritic - large olivine crystals are set in a groundmass of finer-grained pyroxene, plagioclase, and ilmenite; a later generation of olivine never crystallizes. There are three shapes of olivine crystals in the Apollo 12 olivine vitrophyres: glomerocrysts of subhedral crystals, large subequant skeletons, and highly elongate skeletons. These result from three generations of nucleation and a two-stage cooling history - a slow preeruption stage and a rapid continuously increasing posteruption stage. It seems likely that the Apollo 12 olivine basalt magmas were erupted with olivine crystals in suspension. The nucleation temperature of olivine in cooling-rate experiments is dependent on the experimental technique, and hence results of cooling experiments should be applied with caution.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar Science Conference; Mar 17, 1975 - Mar 21, 1975; Houston, TX
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    NASA TECHNICAL REPORTS
  • 5
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    Geology, petrology, and crystallization of Apollo 15 quartz-normative basalts (1975)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar Science Conference; Mar 17, 1975 - Mar 21, 1975; Houston, TX
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  • 6
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    Experimentally reproduced textures and mineral chemistry of Apollo 15 quartz normative basalts (1974)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar Science Conference; Mar 18, 1974 - Mar 22, 1974; Houston, TX
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    NASA TECHNICAL REPORTS
  • 7
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    A geochemical and petrographic study of 1-2-mm fines from Apollo 17 (1975)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: Samples of fines less than 1-mm and 155 1-2 mm particles from several Apollo 17 sites were analyzed for Na, Sc, Cr, Mn, Fe, Co, Ni, Hf, Ta, Th, and REE. Products of comminution and construction are present in the 1-2 mm particles, and the compositions of the rock fragments clearly indicate the general chemical characteristics of their parent rock types. The likely sources of materials for the glassy particles are considered. Glasses are enriched over their parent soils in Fe, Sc, Mn, and Cr, and are relatively enriched in light REE, so that some chemical fractionation accompanies glass-forming processes. Elements were determined by instrumental neutron activation analysis.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar Science Conference; Mar 17, 1975 - Mar 21, 1975; Houston, TX
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    NASA TECHNICAL REPORTS
  • 8
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    Supercooling on the lunar surface - A review of analogue information (1977)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: Terrestrial analog studies of the phase petrology of supercooled melts and rapid crystal growth are reviewed for possible light shed on lunar crystallization, supercooling, and petrogenic processes, in particular rapid consolidation of lavas extruded on the lunar surface, and impact liquids. Crystallization of major constituent minerals (olivine, pyroxene, plagioclase) in dendritic or skeletal forms is found much more characteristic of lunar igneous rocks than of terrestrial counterparts. Olivine and pyroxene occur often as skeletal phenocrysts, and their stage of crystallization is crucial to the genesis and cooling history of porphyritic lavas. Widespread occurrence of glass and of immature radiate crystallization, particularly of highly zoned pyroxenes and zoned plagioclase, is noted.
    Keywords: LUNAR AND PLANETARY EXPLORATION
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  • 9
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    An experimental investigation of olivine morphology (1976)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: Results are reported for a morphological study of olivine and an experimental investigation performed to determine the degrees of supercooling and the cooling rates necessary to crystallize particular morphologies. Ten arbitrary categories of three-dimensional olivine crystal shape are identified: polyhedral, granular, hopper, chain, lattice, plate, branching, radiate, feather, and swallow-tail. The morphological study establishes that equant and tabular crystals are the common shapes of olivine, nonequant crystals are elongate parallel to the a or c axis, and skeletal crystals result when a particular form is missing or only partially developed. In the experiment, olivine crystals were grown by melting rock samples above their liquidus temperatures before initiating crystallization. The results show that olivine morphology changes systematically as a function of the degree of melt supercooling, the melt cooling rate, and the normative olivine and water contents of the melt. It is also found that each shape has a specific range of temperature stability which is essentially independent of melt composition.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: Contributions to Mineralogy and Petrology; 57; 1976
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    NASA TECHNICAL REPORTS
  • 10
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    Laboratory duplication of comb layering in the Rhum pluton (1977)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: A description is provided of the texture of harrisite comb layers, taking into account the results of crystallization experiments at controlled cooling rates, which have reproduced the textural change from 'cumulate' to comb-layered harrisite. Melted samples of harrisite were used in the dynamic crystallization experiments considered. The differentiation of a cooling rate run with respect to olivine grain size and shape is shown and three possible origins of hopper olivine in differentiated crystallization runs are considered. It is found that olivine nucleation occurred throughout cooling, except for the incubation period during early cooling. The elongate combed olivines in harrisite apparently grew as the magma locally supercooled to at least 30 C. It is suggested that the branching crystals in most comb layers, including comb-layered harrisite, probably grew along thermal gradients.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: Mineralogical Magazine; 41; Sept
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