Silicon-substituted magnetite and accompanying iron oxides and hydroxides from the Kumano mine, Yamaguchi Prefecture, Japan : Reexamination of the so-called maghemite (γ-Fe_2O_3)

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Author(s)

    • OHKAWA Makio
    • Department of Earth and Planetary Systems Science, Graduate School of Science, Hiroshima University
    • MIYAHARA Masaaki
    • Department of Earth and Planetary Systems Science, Graduate School of Science, Hiroshima University
    • OHTA Eri
    • Department of Earth and Planetary Systems Science, Graduate School of Science, Hiroshima University
    • HOSHINO Kenichi
    • Department of Earth and Planetary Systems Science, Graduate School of Science, Hiroshima University

Abstract

Iron oxides and hydroxides found in the so-called maghemite-bearing iron oxide ores from the Kumano mine, Yamaguchi Prefecture, Japan have been investigated using polarizing microscopy, reflecting microscopy, powder X-ray diffractometry (XRD), and electron probe microanalysis (EPMA) to reevaluate the previous study carried out by Shibuya (1958).<br>     </i>The results show that the iron oxide described as maghemite by Shibuya is actually magnetite, showing a compositional zoning of Si with trace amounts of Al and Ca, and that only hematite and goethite are found as alteration products. The compositional zoning of the magnetite may indicate that the silicon-bearing magnetite was formed during reducing conditions.<br>     The <i>a</i> lattice parameter of <i>a</i> = 8.376(1) Å for the silicon-bearing magnetite is shorter than that of normal magnetite. This contraction in the crystal lattice is probably caused by a coupled substitution: Si<sup>4+</sup> for Fe<sup>3+</sup> on the tetrahedral sites and a divalent cation (mainly Fe<sup>2+</sup>) for Fe<sup>3+</sup> on the octahedral sites, with a simple substitution of Al<sup>3+</sup> for Fe<sup>3+</sup> on the tetrahedral sites.

Journal

  • Journal of Mineralogical and Petrological Sciences  

    Journal of Mineralogical and Petrological Sciences 102(3), 182-193, 2007-06-01 

    Japan Association of Mineralogical Sciences

References:  12

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Cited by:  1

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Codes

  • NII Article ID (NAID)
    10018921766
  • NII NACSIS-CAT ID (NCID)
    AA11460926
  • Text Lang
    ENG
  • Article Type
    Journal Article
  • ISSN
    13456296
  • Data Source
    CJP  CJPref  J-STAGE 
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