Crystal chemistry of Sr–rich piemontite from manganese ore deposit of the Tone mine, Nishisonogi Peninsula, Nagasaki, southwest Japan

• NAGASHIMA Mariko

  Division of Earth Science, Graduate School of Science and Technology for Innovation, Yamaguchi University

• SANO Yuko

  Department of Geosphere Science, Faculty of Science, Yamaguchi University

• KOCHI Takako

  Department of Geosphere Science, Faculty of Science, Yamaguchi University

• AKASAKA Masahide

  Department of Geoscience, Interdisciplinary Graduate School of Science and Engineering, Shimane University

• SANO–FURUKAWA Asami

  J–PARC Center, Japan Atomic Energy Agency

抄録

The crystal chemistry of Sr–rich piemontite from a layered manganese ore deposit of the Tone mine, Nishisonogi Peninsula, Japan, was studied using methods of electron microprobe analysis, single crystal X–ray structural refinement, ⁵⁷Fe Mössbauer spectroscopy, and X–ray and Time–of–Flight neutron Rietveld analyses to elucidate the intracrystalline distributions of Sr, Mn, and Fe and the general and individual features on the structural changes with Sr contents in piemontite and epidotes. Piemontite in the most piemontite–dominant layer of an ore is [Ca_1.73(15)Sr_0.22(13)]_Σ1.95[Al_1.99(9)Mn³⁺_0.68(8)Fe³⁺_0.37(8)Mg_0.01(0)]_Σ3.05<br>Si_2.99(1)O₁₂(OH) (Z = 2) in the average chemical formula. A single crystal X–ray structural refinement (R₁ = 2.51% for 2417 unique reflections) resulted in the unit–cell parameters of a = 8.8942(1), b = 5.6540(1), c = 10.1928(2) Å, and β = 115.100(1)°; and the occupancies of Ca_0.711(3)Sr_0.289, Al_0.898(4)(Mn + Fe)_0.102, and (Mn + Fe)_0.949(4)Al_0.051 at the ^XA2, ^VIM 1, and ^VIM 3 sites, respectively. All Fe in a powdered piemontite sample was Fe³⁺ as indicated by the two Mössbauer doublets (isomer shift = 0.351 and 0.367 mm/s and quadrupole splitting = 2.189 and 1.93 mm/s, respectively) assigned to Fe³⁺ at the M 3 site. The neutron Rietveld refinement of the powder sample (R_wp = 2.11%; R_e = 0.88%) resulted in the occupancies of ^{M 1}[Al_0.902(5)Mn_0.098] and ^{M 3}[Mn_0.534(5)Fe_0.267Al_0.20], where ^{M 3}Al was fixed to 0.20Al obtained by X–ray Rietveld refinement (R_wp = 2.95%; R_e = 2.13%). By applying the oxidation state of Fe and the distributions of Al, Fe, and Mn in the M 1 and M 3 sites in the powder sample, the site occupancies in the piemontite single crystal are constructed as ^A2[Ca_0.711(3)Sr_0.289], ^{M 1}[Al_0.898(4)Mn³⁺_0.102] and ^{M 3}[Mn³⁺_0.633Fe³⁺_0.316Al_0.051]. The A2–O7, –O2’, and –O10 distances, 2.303(2), 2.562(1), and 2.592(2) Å, respectively, are longer than those of Ca–piemontites. The mean <M 3–O> and <M 1–O> distances, 2.050 and 1.923 Å, respectively, are close to the published data of Ca–piemontites and Sr–rich and –bearing piemontites with Mn³⁺ + Fe³⁺ contents in the M 3 and M 1 sites similar to those of the Tone piemontite.

収録刊行物

• Journal of Mineralogical and Petrological Sciences

  Journal of Mineralogical and Petrological Sciences 115 (5), 391-406, 2020

  一般社団法人　日本鉱物科学会

キーワード

• Strontian Piemontite
• Tone mine
• X–ray diffraction
• TOF neutron diffraction
• Mössbauer analysis
• Crystal structure

詳細情報

• CRID: 1391130851442842112
• NII論文ID: 130007935423
• DOI: 10.2465/jmps.191122
• ISSN: 13493825
• ISSN: 13456296
• Web Site: https://www.jstage.jst.go.jp/article/jmps/115/5/115_191122/_pdf
• 本文言語コード: en
• データソース種別:
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