High-pressure X-ray diffraction and X-ray emission studies on iron-bearing silicate perovskite under high pressures

Journal Article · Tue Jun 22 04:00:00 EDT 2010 · High Pressure Res.

DOI:https://doi.org/10.1080/08957951003756962· OSTI ID:1002449

Lin, Jung-Fu; Speciale, Sergio; Prakapenka, Vitali B; Dera, Przemek; Lavina, Babara; Watson, Heather C ^[1]

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1. NIU

Iron-bearing silicate perovskite is believed to be the most abundant mineral of the Earth's lower mantle. Recent studies have shown that Fe{sup 2+} exists predominantly in the intermediate-spin state with a total spin number of 1 in silicate perovskite in the lower part of the lower mantle. Here we have measured the spin states of iron and the pressure-volume relation in silicate perovskite [(Mg{sub 0.6},Fe{sub 0.4})SiO{sub 3}] at pressure conditions relevant to the lowermost mantle using in situ X-ray emission and X-ray diffraction in a diamond cell. Our results showed that the intermediate-spin Fe{sup 2+} is stable in the silicate perovskite up to {approx} 125 GPa but starts to transition to the low-spin state at approximately 135 GPa. Concurrent X-ray diffraction measurements showed a decrease of approximately 1% in the unit cell volume in the silicate perovskite [(Mg{sub 0.6},Fe{sub 0.4})SiO{sub 3}], which is attributed to the intermediate-spin to the low-spin transition. The transition pressure coincides with the pressure conditions of the lowermost mantle, raising the possibility of the existence of the silicate perovskite phase with the low-spin Fe{sup 2+} across the transition from the post-perovskite to the perovskite phases in the bottom of the D{double_prime} layer.

• Research Organization: Advanced Photon Source (APS), Argonne National Laboratory (ANL), Argonne, IL (US)
• Sponsoring Organization: USDOE
• OSTI ID: 1002449
• Journal Information: High Pressure Res., Journal Name: High Pressure Res. Journal Issue: (2) ; 06, 2010 Vol. 30; ISSN 0895-7959; ISSN HPRSEL
• Country of Publication: United States
• Language: ENGLISH

Related Subjects

36 MATERIALS SCIENCE
58 GEOSCIENCES
EARTH MANTLE
IRON SILICATES
MAGNESIUM SILICATES
PRESSURE RANGE GIGA PA
SPIN
X-RAY DIFFRACTION