Crystal chemistry of neptunite from the Khan Bogdo alkaline massif (Mongolia)

A. A. Zolotarev, N. V. Vladykin, S. V. Krivovichev, T. L. Panikorovskii

Результат исследований: Научные публикации в периодических изданияхстатья

Аннотация

Crystal chemical characteristics have been studied for neptunite from alkaline granites of the Khan Bogdo massif (Southern Mongolia). The mineral occurs to be the practically clear Fe-variety of its species. Refinement of its crystal structure was carried out in two space groups: centric C2/c and acentric Cc. It is indicated that correct space group is the acentric Cc due to ordering of octahedral cations Ti and Fe. The structure was refined to R 1 = 0.025 (wR 2 = 0.057) for 4889 reflections with |Fo| ≥ 4σF. Unit cell parameters: a = 16.4542(7), b = 12.5115(4), c = 9.9980(4) Å, β = 115.542(5)°, V = 1857.10(15) Å 3 , Z = 4. Ti octahedra show strong distortions: one bond Ti-O 1.75 Å, another bond 2.20 Å, and four Ti-O bonds around 2.0 Å. Fe octahedra have a more regular shape with an average bond length Fe-O 2.13-2.14 Å. Empirical formula calculated on the basis of chemical analysis is (K 0.86 Cs 0.02 Zn 0.02 Ca 0.01 ) S0.91 Na 1.90 Li 0.82 (Fe 1.54 2+ Fe 0.22 3+ Mn 0.16 Mn 0.04 ) S1.96 Ti 2.1 (Si 7.76 Al 0.25 )O 24 . Structural formula is K 0.97 Na 1.90 (Li 0.94 Na 0.06 ) S1.00 (Fe 1.80 Mn 0.15 Mg 0.05 ) S2.00 Ti 2 Si 8 O 22 (O,OH) 2 . Idealized formula is KNa 2 LiFe 2 Ti 2 Si 8 O 24

Язык оригиналаанглийский
Страницы (с-по)112-127
Число страниц16
ЖурналZapiski Rossiiskogo Mineralogicheskogo Obshchestva
Том145
Номер выпуска2
СостояниеОпубликовано - 1 янв 2016

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Предметные области Scopus

  • Геохимия и петрология
  • Геология
  • Экономическая геология
  • Химия материалов

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