Oxidation state of Fe in olivine in a lherzolite xenolith from Oku district, Oki-Dogo Island, Shimane Prefecture, Japan

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Author(s)

    • EJIMA Terumi
    • Department of Geoscience, Graduate School of Science and Engineering, Shimane University
    • AKASAKA Masahide
    • Department of Geoscience, Graduate School of Science and Engineering, Shimane University

Abstract

The oxidation state and distribution of Fe in olivine in a lherzolite xenolith from the Oku district, Oki-Dogo Islands, Japan, were investigated. A lherzolite xenolith collected from a volcanic neck of alkali olivine basalt contains olivine, orthopyroxene, clinopyroxene, and a small amount of spinel. Anhedral anorthite grains less than 0.01 mm across occur as inclusions in clinopyroxene. The olivine grains are nearly homogeneous in composition, with Fo contents of 80.7-81.9 mol%. Pure olivine grains for X-ray diffraction and <sup>57</sup>Fe Mössbauer analyses were separated from the fresh core of the lherzolite xenolith under a binocular microscope. The Mössbauer spectrum of the separated olivines consists of two doublets assigned to Fe<sup>2+</sup> at the M1 and M2 sites and a doublet attributed to Fe<sup>3+</sup> at the M2 site. The populations of Fe<sup>3+</sup> in the olivine derived from the Mössbauer method and Fe<i>L</i><sub>β</sub>/Fe<i>L</i><sub>α</sub>-intensity ratios are 0.02 and 0.03 atoms per formula unite (apfu), respectively. The site occupancies of Fe in the M1 and M2 sites refined using X-ray Rietveld method are 0.151 and 0.206 apfu, respectively. The chemical formula of the olivine based on the refined Fe populations at the octahedral M1 and M2 sites and oxidation state of Fe determined using Mössbauer method is [<sup>M2</sup>(Mg<sup>2+</sup><sub>0.79</sub>Fe<sup>2+</sup><sub>0.19</sub>Fe<sup>3+</sup><sub>0.02</sub>)<sup>M1</sup>([]<sub>0.01</sub>Mg<sub>0.85</sub>Fe<sup>2+</sup><sub>0.14</sub>)]<sub>Σ2.00</sub>SiO<sub>4</sub>.

Journal

  • Journal of Mineralogical and Petrological Sciences

    Journal of Mineralogical and Petrological Sciences 106(5), 246-254, 2011-10-01

    Japan Association of Mineralogical Sciences

References:  33

Cited by:  2

Codes

  • NII Article ID (NAID)
    10029479718
  • 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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