Journal of Mineralogical and Petrological Sciences
Online ISSN : 1349-3825
Print ISSN : 1345-6296
ISSN-L : 1345-6296
Volume 101 , Issue 1
February
Showing 1-4 articles out of 4 articles from the selected issue
ORIGINAL ARTICLES
  • Mariko NAGASHIMA
    2006 Volume 101 Issue 1 Pages 1-9
    Published: 2006
    Released: March 01, 2006
    JOURNALS FREE ACCESS
    Syntheses of epidote minerals on the join Ca2Al2Fe3+Si3O12(OH)-Ca2Al2Mn3+Si3O12(OH) were conducted using standard cold-seal pressure vessels and solid oxygen buffering techniques at 200-400 MPa and 500 °C. Two types of starting materials were used: (1) oxide mixtures (type 1) + excess H2O, and (2) mixtures of synthetic CaFe3+AlSiO6-pyroxene and oxides (type 2) + excess H2O. The compositions of Ca2Al2Fe3+qMn3+1-qSi3O12.5 starting materials were q = 1.0, 0.9, 0.5 and 0.25 for the type 1, and q = 1.0, 0.75, 0.5 and 0.25 for the type 2. Mn3+-free epidote was not crystallized from the type 1 starting materials, even at 400 MPa, whereas Mn3+-Fe3+-Al piemontites were produced at 300 MPa, but they were along with some associated minerals. Recrystallization of hematite during runs is a major problem when using oxide mixture starting materials. However, recrystallization of hematite was suppressed by using the type 2 starting materials, and Mn-free epidote and Mn3+-Fe3+-Al piemontite were synthesized as almost single phases at 380 MPa and at 200-370 MPa, respectively. The chemical compositions of the synthetic Mn3+-free epidote and Mn3+-Fe3+-Al piemontites formed were generally close to those of the starting materials, except that Fe3+ contents tended to be slightly lower.
         Pressure, temperature and oxygen fugacity have been considered to be the main factors controlling the occurrence of epidote minerals. However, this study demonstrates the importance of Fe3+-source material. Although the results of previous synthesis experiments of epidote minerals have not necessarily been compatible with those of stability experiments and the natural occurrences of epidote minerals, the syntheses here succeeded in producing nearly single phase epidotes with Ca2Al2(Fe3+,Mn3+)Si3O12(OH) at relatively low pressures less than 400 MPa. This aids the understanding of the varied occurrence of natural epidote minerals.
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  • Toshiro SAKAE, Yasushi HAYAKAWA, Akira MORI, Takao KUWADA, Takeshi SAK ...
    2006 Volume 101 Issue 1 Pages 10-13
    Published: 2006
    Released: March 01, 2006
    JOURNALS FREE ACCESS
    Parametric X-rays (PXR) are a new type of X-ray that are generated by crystal-electron interactions. The Laboratory for Electron Beam Research and Application (LEBRA) at Nihon University generates PXR using a double-crystal system generating electrons from a 100-MeV class LINAC. LEBRA-PXR has potential for use as a wavelength tunable, ultra-high bright X-ray source with a macro-/micro-pulse structure. LEBRA-PXR has an energy-dispersion in the horizontal axis, assumed to be 0.2% in the experimental window, but can be used as monochromatic X-ray source for diffraction using a simple slit-system. A diffraction experiment was successfully carried out by applying an 11 keV, or 1.1273 Å, LEBRA-PXR. Near-perfect crystals, such as graphite used for a monochromator showed sharp diffraction peaks. Clear, transparent mineral quartz and fluorapatite crystals also showed sharp diffraction peaks, while the diffraction peaks from clear calcite and silicon powder were not detected. Possible reasons for the lack of diffraction peaks from these materials are discussed. LEBRA-PXR has potential for use in studies on the diffraction of other materials, and is therefore, expected to be a useful tool for crystallographic analysis.
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  • Takeshi NAKAGAWA, Kuniaki KIHARA
    2006 Volume 101 Issue 1 Pages 14-22
    Published: 2006
    Released: March 01, 2006
    JOURNALS FREE ACCESS
    The structure of the high temperature form of melanophlogite (MEP) at 84 °C was refined by using a least squares refinement that was based on the Gram-Charlier expansion of the atomic probability density functions (PDF) up to the fourth-order terms. The refinements of 95 variable parameters on the space group Pm3n converged to R = 0.0275 (Rw = 0.0313) for the 607 observed reflections in single crystal X-ray diffraction. The PDFs for three types of O atom (in total, there were four types, O1 to O4) were both broad and strongly distorted from an ellipsoidal shape: unimodal for O1, bimodal for O2, and concave-spheroidal for O4. Their zero-contours covered areas with radii of 0.75-1.0 Å in sections perpendicular to the shortest axes of thermal ellipsoids. The characteristic appearance of the PDF is interpreted as arising from disordered atoms in the 12 domains of low MEP. The tetragonal cell of low MEP, which is a (2 × 2 × 1)-superstructure of high MEP, is three-fold rotationally twinned around [111] (of the cubic cell) and, then antiphase translation in [100], [010] and [110] generates antiphase domains to result into a cubic average structure.
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  • Teruki OIKAWA, Koji UMEDA, Sunao KANAZAWA, Tatsuji MATSUZAKI
    2006 Volume 101 Issue 1 Pages 23-28
    Published: 2006
    Released: March 01, 2006
    JOURNALS FREE ACCESS
    K-Ar and FT analyses were carried out on biotite, zircon and apatite from the Middle Miocene Ichifusayama Granodiorite pluton in Kyushu, Japan in order to reveal the cooling history. The core and rim of the pluton revealed K-Ar biotite ages of 13.39-13.36 and 13.31-13.54 Ma, FT zircon ages of 13.3-13.1 and 12.7-12.3 Ma, and FT apatite ages of 13.1-13.7 and 10.6-10.8 Ma respectively, suggesting that the core cooled, to 100 °C from 300 °C, faster than the rim, of which the cooling rate is ∼ 100 °C/Ma. The track-length analyses also suggest extremely rapid cooling without a late stage annealing process. The faster cooling of the core in comparison with the rim is unusual. The difference in cooling velocity between the core and rim was possibly caused by an influence of paleotopography.
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