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  • 1
    Publication Date: 2013-08-31
    Description: One of the characteristic features of CK chondrites is the wide compositional range displayed by feldspar grains in matrix relative to the narrow range of compositions exhibited by the highly equilibrated olivines and pyroxenes. Recently, it was suggested that these heterogeneous feldspar compositions may have been strongly influenced by shock metamorphisms. It is shown that the apparent range of feldspar compositions in Maralinga probably results from annealing during parent body thermal metamorphism rather than shock. The majority of matrix feldspars in Maralinga are typically 50 microns in size and are compositionally zoned, with oligoclase cores (approximately An40) and bytownite rims (approximately An80). The contact between core and rim is sharp and abrupt and is readily observed in backscattered scanning electron microscopy (SEM) images.
    Keywords: ASTROPHYSICS
    Type: Lunar and Planetary Inst., Twenty-Fourth Lunar and Planetary Science Conference. Part 2: G-M; p 783-784
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  • 2
    Publication Date: 2013-08-31
    Description: The majority of hydrated interplanetary dust particles (IDPs) have compositions that resemble CI and CM chondrites, however, their mineralogies are most similar to the fine grained material in certain altered type-3 carbonaceous and ordinary chondrites. During the transmission electron microscope studies of hydrated IDPs, a unique particle was discovered whose mineralogy is very similar to that reported from CI chondrites. W7013F5 is the first IDP whose mineralogy and chemistry approximates that of CI chondrites. The similarity in mineralogy and mineral chemistry suggests that W7013F5 was altered under conditions similar to those that existed on the CI parent bodies.
    Keywords: ASTROPHYSICS
    Type: Lunar and Planetary Inst., Abstracts for the 54th Annual Meeting of the Meteoritical Society; p 115
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  • 3
    Publication Date: 2013-08-31
    Description: A distinctive feature of micron sized plagioclase grains from mature lunar soils is a thin (20 to 100 nm) amorphous rim surrounding the grains. These rims were originally described from high voltage electron microscope observations of lunar plagioclase grains by Dran et al., who observed rims up to 100 nm thick on plagioclase grains from Apollo 11 and 12 soils. These rims are believed to be the product of solar wind damage. The amorphous rims were studied on micron sized plagioclase grains from a mature Apollo 16 soil using a JEOL 200FX transmission electron microscope equipped with an energy dispersive x ray spectrometer. It was found that the amorphous rims are compositionally distinct from the interior plagioclase and it is proposed that a major component of vapor condensates is present in the rims.
    Keywords: ASTROPHYSICS
    Type: Lunar and Planetary Inst., Abstracts for the 54th Annual Meeting of the Meteoritical Society; p 114
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  • 4
    Publication Date: 2019-06-28
    Description: The nature of the carbon-bearing phases in IDP's provides information regarding the chemical and physical processes involved in the formation and evolution of the early solar system. Several carbon-bearing materials have been observed in IDP's, but details of their nature, abundance, and distribution are still poorly known. A knowledge of the abundance and nature of carbon in IDP's is useful in constraining the sources of IDP's and for comparisons with other chondritic materials. Estimates of carbon abundance in anhydrous and hydrated IDP's indicate that most of these particles have significantly higher carbon than the carbonaceous chondrites. Mineralogical analyses show that carbonates are only a minor component of most hydrated IDP's, and so the high carbon abundances in this group of IDP's indicates that other carbon-bearing phases are present in significant concentrations. Using the technique of electron energy-loss spectroscopy (EELS), we have identified two forms of carbon in a hydrated IDP, oxidized carbon (carbonates), and amorphous elemental carbon.
    Keywords: ASTROPHYSICS
    Type: Lunar and Planetary Inst., The Twenty-Fifth Lunar and Planetary Science Conference. Part 2: H-O; p 687-688
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  • 5
    Publication Date: 2019-06-28
    Description: Carbon is an important and significant component of most anhydrous and hydrated IDP's. We have analyzed approx. 40 anhydrous and hydrated chondritic IDP's for major and minor elements, including C and O. Quantitative analyses of light elements in small particles are difficult and require careful procedures in order to obtain reliable results. In our work, we have completed extensive analytical checks to verify the accuracy and precision of C abundances in IDP's. In our present work, additional methods are used to verify C abundances in IDP's including analysis of IDP thin sections embedded in S, and direct observation of carbonaceous material in thin sections. Our work shows conclusively that C is strongly enriched in IDP's relative to CI abundances.
    Keywords: ASTROPHYSICS
    Type: Lunar and Planetary Inst., Workshop on the Analysis of Interplanetary Dust Particles; p 49-50
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  • 6
    Publication Date: 2019-06-28
    Description: Currently, one of the best sources of information regarding the nature and formation of carbonaceous materials in the early solar system comes from studies of primitive interplanetary dust particles (IDP's). Carbon is a significant component of most IDP's, and the nature of the C-rich phases bears on the chemical and physical processes that have affected C from its nucleosynthesis to its incorporation into primitive solar system bodies. We review the data regarding C in IDP's since approximately 1987. Brownlee summarized the state of C in IDP's in a workshop help at ARC in 1987; other recent reviews have summarized the formation mechanisms that have been proposed for carbonaceous materials in primitive solar system materials. We discuss the abundance of C in IDP's, the nature and distribution of C, and topics and strategies for future work.
    Keywords: ASTROPHYSICS
    Type: Lunar and Planetary Inst., Workshop on the Analysis of Interplanetary Dust Particles; p 30-31
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