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β‐diopside, a new ultrahigh‐pressure polymorph of CaMgSi2O6with six‐coordinated silicon

Plonka, Anna M. ; Dera, Przemyslaw ; Irmen, Peyton ; Rivers, Mark L. ; Ehm, Lars ; Parise, John B.

Geophysical Research Letters, 28 December 2012, Vol.39(24), pp.n/a-n/a [Tạp chí có phản biện]

ISSN: 0094-8276 ; E-ISSN: 1944-8007 ; DOI: 10.1029/2012GL054023

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  • Nhan đề:
    β‐diopside, a new ultrahigh‐pressure polymorph of CaMgSi2O6with six‐coordinated silicon
  • Tác giả: Plonka, Anna M. ; Dera, Przemyslaw ; Irmen, Peyton ; Rivers, Mark L. ; Ehm, Lars ; Parise, John B.
  • Chủ đề: Clinopyroxene ; Crystal Structure ; Diamond Anvil Cell ; Diopside ; High Pressure ; Six‐Coordinated Silicone
  • Là 1 phần của: Geophysical Research Letters, 28 December 2012, Vol.39(24), pp.n/a-n/a
  • Mô tả: Minerals containing silicon in four‐fold coordination (Si) are common in crustal rocks, while those involving six‐coordinated silicon (Si) dominate the Earth's lower mantle and determine its properties. Here we show a new type of phase transition determined by single‐crystal high pressure X‐ray diffraction experiments in a diamond anvil cell (DAC) using natural diopside (CaMgSiO), the archetypic member of clinopyroxene family, and one of the most abundant minerals of the Earth's upper mantle. Above 50 GPa at ambient temperature diopside transforms to a previously unknown post‐clinopyroxene phase,‐diopside, with half of the tetrahedralSi layers converted to octahedral Sicoordination. This phase is most probably a metastable state that is kinetically accessible at room temperature and the transformation is fully reversible on decompression. This new type of phase transition provides important clues to the exact mechanisms of breakdown of clinopyroxene in the Earth's mantle and may be expected to take place in other pyroxenes at pressures higher than previously explored. Above 50 GPa diopside transforms to a phase with half of Si sites 6‐coordinated Reversible transformation shown in situ Transformation most probably applicable to all clinopyroxenes
  • Số nhận dạng: ISSN: 0094-8276 ; E-ISSN: 1944-8007 ; DOI: 10.1029/2012GL054023

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