日本結晶学会誌
Online ISSN : 1884-5576
Print ISSN : 0369-4585
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選択された号の論文の13件中1~13を表示しています
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特集 鉱物結晶学で解き明かす地球惑星ダイナミズム
1.鉱物の微細組織と結晶学
  • 富岡 尚敬
    60 巻 (2018) 1 号 p. 2-8
    公開日: 2018/03/06
    ジャーナル フリー

    Microstructures and symmetries of synthetic and natural(Mg, Fe)SiO3 garnet(majorite)have been investigated by transmission electron microscopy. Modulated and twin structures commonly observed in the synthetic majorite suggest a cubic-tetragonal phase transition due to cation ordering in its octahedral sites during quenching. Natural tetragonal majorite, which was newly discovered in a shock meteorite, has less-ordered octahedral cations than those in the synthetic samples. The order-disorder state of majorite provides important constraints not only on shock metamorphism of meteorites, but also on the deep Earth's mineralogy.

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  • 大藤 弘明
    60 巻 (2018) 1 号 p. 9-16
    公開日: 2018/03/06
    ジャーナル フリー

    The crystallization process of diamond in the graphite-diamond transformation was studied through detailed microtextural observation of synthetic and natural nano-polycrystalline diamonds (NPDs) by transmission electron microscopy. The transformation occurs by two types of processes, diffusion-controlled (nucleation and growth) process and diffusion-less (martensite) process, which produce different types of microtextures, typically, granular and lamellar (layered) textures. We found that the transformation process and the microtexture of diamonds are largely influenced by the crystallinity of the graphite starting material. This allows us to produce a variety of NPDs with novel microtextures by using graphitic starting materials with various degrees of crystalinity. We also studied impact diamonds from a large meteorite crater as a natural counterpart of NPD and revealed that they formed mainly by the martensitic transformation from single crystalline graphite which were originally contained in the host metamorphic rock at the impact site. Shock-induced fragmentation of the source graphite and subsequent rapid transformation to diamond in the limited time scale result in multiple diamond nucleation and suppression of the overall grain growth, producing the unique nanocrystalline texture of natural NPD.

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  • 長瀬 敏郎
    60 巻 (2018) 1 号 p. 17-23
    公開日: 2018/03/06
    ジャーナル フリー

    Various mineral species are produced by geological process. Dynamical processes in the Earth expand varieties of mineral species, and their textures and crystal structures. Mineral textures include historical information about the growth, transition and deformation of the minerals in the Erath. Hence, analyses of mineral textures are conducted macro- to nano-scale using optical and electron microscopies. I present our study about lutecite, which is a kind of aggregate of fine quartz and mogánite crystals, and discuss metastable precipitation processes of minerals in geological conditions.

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2.地球惑星内部における鉱物の構造と物性
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