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Incorporation of Fe3+ in phase-X, A2–xM2Si2O7Hx, a potential high-pressure K-rich hydrous silicate in the mantleстатья
Информация о цитировании статьи получена из
Web of Science,
Scopus
Статья опубликована в журнале из списка Web of Science и/или Scopus
Дата последнего поиска статьи во внешних источниках: 18 июля 2013 г.
- Авторы: Bindi L., Bobrov A., Litvin Yu A.
- Журнал: Mineralogical Magazine
- Том: 71
- Номер: 3
- Год издания: 2007
- Издательство: Mineralogical Society
- Местоположение издательства: United Kingdom
- Первая страница: 265
- Последняя страница: 272
- DOI: 10.1180/minmag.2007.071.3.265
- Аннотация: Phase-X, a potential sink for K in the mantle, is a synthetic hydrous K-rich silicate formed by the breakdown of K-amphibole at high pressure. It has the general formula A2xM2Si2O7Hx where A = K, Na, Ca, & (vacancy), and M = Mg, Al, or Cr. No other isomorphic substitutions, either for the A or the M site, were reported for such a synthetic compound. Here we report the crystal structure and chemical composition of a crystal of phase-X containinglarg e amounts of trivalent Fe. This crystal was synthesized in the model system garnet lherzoliteK2CO3 at lower pressure (P = 7 GPa) and higher temperature (T = 14501650ºC) with respect to the stability range reported in the literature (i.e. P = 917 GPa and T = 11501400ºC). Quantitative analysis led to the followingformula: (K1.307Na0.015Ca0.007)S = 1.329(Mg1.504Fe3+ 0.373Al0.053Ti4+ 0.004Mn2+ 0.001)S = 1.935Si2O7.00H0.360. The lattice parameters (hexagonal setting) are: a = 5.005(1), c = 13.148(2) A ˚ , V = 285.23(9) A ˚ 3, and Z = 2. The structure was refined in space group P63cm to R = 5.06% using199 independent reflections and consists of MO6 octahedra layers stacked alongthe c axis and linked together by Si2O7 groups. The Si2O7 groups form pillars in the layer that contains A atoms in the cavities between the pillars. The Raman spectrum in the OH-stretchingreg ion indicates the existence of two different OH environments. However, the position of H could not be determined. The substitution of Fe3+ for Mgshortens octahedral bond distances. In addition, the entry of Fe3+ in M induces geometrical changes to the adjacent A site. The crystal-chemical characteristics are compared with published data on synthetic Fe-free phase-X.
- Добавил в систему: Бобров Андрей Викторович