著者

Keitaro OKAMOTO Takahiro KURIBAYASHI Toshiro NAGASE

出版者

Japan Association of Mineralogical Sciences

雑誌

Journal of Mineralogical and Petrological Sciences (ISSN:13456296)

巻号頁・発行日

vol.116, no.5, pp.251-262, 2021 (Released:2022-02-03)

参考文献数

23

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In situ high–pressure single–crystal X–ray diffraction experiments on natural hemimorphite, ideally Zn4[Si2O7](OH)2·H2O, up to 4.7 GPa were conducted to investigate its pressure response property associated with pressure–induced phase transition. After the phase transition confirmed between 2.46 and 3.01 GPa, pairs of satellite reflections were newly found at certain Bragg reflections. The modulation vector q of the satellites was approximately [0, 1/8.4, 0]. The results of the refinements on the averaged structure indicated that the modulation arose from displacements of atomic sites associated with the mechanism of the phase transition, i.e., the rotation of the secondary building unit (SBU). The lower rotation angle of the SBU (Φ) than the value estimated from the non–modulated structure meant that the high–pressure phase contained anti–phase boundaries (APBs) resulting from the opposite direction of the SBU rotation and that the coherency was held across the APBs. Within the coherent domain, the APB’s intervals were distributed along the b–axis with a mean value of 8.4b ≈ 90 Å, where the displacement of each site η (y ) was approximated as the first–harmonic. The distribution of the direction of SBU rotation was initially considered to be inhomogeneous, but the elimination of the APBs had proceeded anisotropically and had been aborted below 3.01 GPa.

著者

Toshiro NAGASE Koichi MOMMA Takahiro KURIBAYASHI Masahiko TANAKA

出版者

Japan Association of Mineralogical Sciences

雑誌

Journal of Mineralogical and Petrological Sciences (ISSN:13456296)

巻号頁・発行日

vol.108, no.2, pp.87-93, 2013 (Released:2013-05-03)

参考文献数

21

被引用文献数

2

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Lutecite is an aggregate of microcrystalline silica; its variety with a hexagon form is known as hexalite. Textures of lutecite and hexalite from the Arz-Bord Range, in northwestern Gobi, Mongolia, and from Banyan-obo, China, were observed by optical microscopy, synchrotron X-ray diffraction, and transmission electron microscopy (TEM). Cross sections of lutecite and hexalite observed through optical microscopy show fibrous textures. TEM observations revealed that the quartz crystals constituting each fiber exhibit irregular shapes elongated parallel to [212], which is nearly perpendicular to (101); a width of 0.5 μm; and length of a few micrometers. The results of selected area electron diffraction analyses show that the fiber bundles have V-shaped cross textures, and the crystals are twinned according to the Reichenstein-Grieserntal law. X-ray diffraction analysis indicates a total moganite content of approximately 10 wt% in this lutecite aggregate, and moganite appears as irregular-shaped domains within quartz under high-resolution TEM.