Siderite at lower mantle conditions and the effects of the pressure-induced spin-pairing transition

B. Lavina, P. Dera, R. T. Downs, V. Prakapenka, M. Rivers, S. Sutton, M. Nicol

Research output: Contribution to journalArticle

68 Scopus citations

Abstract

Siderite (FeCO3) forms a complete solid solution with magnesite (MgCO3), the most likely candidate for a mantle carbonate. Our experiments with natural siderite reveal spin pairing of d-orbital electrons of Fe2+ at 43 GPa, as evidenced by a sharp volume collapse of about 10%. The initially colorless crystals assume an intense green color after the transition, which progressively turns to red above 60 GPa. We present clear evidence for the instability of an intermediate spin state in siderite at ambient temperature. At the transition pressure, domains of high and low spin siderite coexist. The unit cell volume difference between magnesite and siderite is significantly decreased by the spin transition, enhancing the solubility between the two calcite-type minerals. A siderite component in magnesite at lower mantle pressure would significantly increase its density and slightly increase the carbonate bulk modulus.

Original languageEnglish (US)
Article numberL23306
JournalGeophysical Research Letters
Volume36
Issue number23
DOIs
StatePublished - Dec 1 2009

ASJC Scopus subject areas

  • Geophysics
  • Earth and Planetary Sciences(all)

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