Journal of Mineralogical and Petrological Sciences
Online ISSN : 1349-3825
Print ISSN : 1345-6296
ISSN-L : 1345-6296
Volume 98 , Issue 5
October
Showing 1-3 articles out of 3 articles from the selected issue
ORIGINAL ARTICLES
  • Kazuki KOMATSU, Takahiro KURIBAYASHI, Yasuhiro KUDOH
    Type: Others
    Subject area: Others
    2003 Volume 98 Issue 5 Pages 167-180
    Published: 2003
    Released: April 22, 2004
    JOURNALS FREE ACCESS
    The effect of temperature and pressure was analyzed on the crystal structure of natural topaz from Gilgit division, Pakistan. The unit cell parameters at 298K, 423K, 573K, 723K, 873K, 1023K and 1173K, and X-ray diffraction intensity data at 298K, 573K, 873K and 1173K were collected using an imaging plate X-ray diffractometer equipped with rotating anode generator. Thermal expansion coefficients along the unit cell edges and of the volume are αa=6.4(7)×10-6K-1, αb=5.5(6) ×10-6K-1, αc=8.1(6) ×10-6K-1 and αV =2.0(1) ×10-5K-1. The results of structure refinement taking into account the anisotropic displacement parameters at these temperatures yielded R values of 2.48, 2.60, 2.56 and 2.70%. The increase of mean Al-O distance with temperature was greater than those of Al-F and Si-O. The Al-F-Al bond angle decreased with the increase of displacement parameter of fluorine-atom. The unit cell parameters under pressures up to 6.8 GPa and X-ray diffraction intensity data under 0.0001(ambient pressure), 3.7, 5.1 and 6.2 GPa were collected by a four-circle X-ray diffractometer. The bulk modulus determined by the Birch-Murnaghan equation-of-state is K0T=154(2)GPa (assuming K’=4). The axial compressibilities of this sample are βa=2.02(8)×10-3 GPa-1, βb=1.42(5)×10-3 GPa-1 and βc=2.25(4)×10-3 GPa-1. The results of structure refinement at each pressure with anisotropic displacement parameters at ambient pressure and with isotropic displacement parameter at high pressures yielded R values of 2.66, 5.61, 5.43 and 5.91%, respectively. The mean Al-O bond distance was significantly decreased by compression. The inverse relationships of variation against temperature and pressure are observed for both the unit cell parameters and bond distances.
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  • Yukiyasu TSUTSUMI, Kazumi YOKOYAMA, Kentaro TERADA, Yuji SANO
    Type: Others
    Subject area: Others
    2003 Volume 98 Issue 5 Pages 181-193
    Published: 2003
    Released: April 22, 2004
    JOURNALS FREE ACCESS
    Radiometric ages of detrital zircons in psammitic schists from the Nagasaki, Kurume, Konoha and Kiyama areas, northern Kyushu, were obtained from 238U/206Pb ratio and isotopic compositions of Pb using a Sensitive High Resolution Ion Microprobe (SHRIMP II). Zircons from the Nagasaki, Kurume and Konoha areas show bimodal age distribution with peaks at ca. 1900 Ma and 250 Ma. It is suggested from this study that the older zircons were derived from Proterozoic landmass and the Korean Peninsula. Zircons from the Kiyama metamorphic rock show a different pattern with ages concentrated at 380-590 Ma. Such zircons are rare in rock samples from the Nagasaki, Kurume and Konoha areas, indicating that Kiyama rocks had a different origin than those from the other three areas.
    The youngest zircons from the Kiyama, Nagasaki, Kurume and Konoha areas show ages of 382±28 Ma, 238±13 Ma, 249±13 Ma, and 175±4 Ma, respectively. These data mark the upper age limit of their deposition. Since a continuous igneous activity occurred during the period from 300 to 170 Ma in Far East Asia, and the metamorphic age has been close to the zircon age of each area, these youngest ages for the Nagasaki, Kurume and Konoha areas are considered nearly contemporary to the depositional ages. An evaluation of the nature of metamorphism and available ages suggest the possibility that the Nagasaki metamorphic rocks as well as the schist from the Kurume area belong to the Suo zone of the Sangun belt, whereas the metamorphic rocks in the Konoha area may belong to the Ryoke belt or Suo zone of the Sangun belt.
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