Effects of the Fe3+ spin transition on the equation of state of bridgmanite. Issue 11 (4th June 2015)

• Record Type: Journal Article
• Authors: Mao, Zhu; Lin, Jung‐Fu; Yang, Jing; Inoue, Toru; Prakapenka, Vitali B.
• Is Part Of: Geophysical research letters. Volume 42:Issue 11(2015:Jun.)
• Page Start: 4335
• Page End: 4342
• Publication Date: 2015-06-04
• Subjects: bridgmanite -- spin transition -- equation of state -- lower mantle -- density -- bulk sound velocity; Geophysics -- Periodicals; Planets -- Periodicals; Lunar geology -- Periodicals; 550
• DOI: 10.1002/2015GL064400
• Languages: English
• ISSNs: 0094-8276

Abstract

Abstract: We have investigated the equation of state of Fe‐bearing bridgmanite, (Mg0.9 Fe0.1 )SiO3, using synchrotron X‐ray diffraction in diamond anvil cells up to 125 GPa and 300 K. Combined with previous synchrotron Mössbauer spectroscopy results, we have found that the occurrence of the low‐spin Fe 3+ in the octahedral sites (B site) of bridgmanite has produced a 0.5(±0.1)% reduction in the unit cell volume at 18–25 GPa and has increased the isothermal bulk modulus to 284(±4) GPa, consistent with recent theoretical calculations. Together with literature results, we note that the addition of Fe can cause an increase in the density, bulk modulus, and bulk sound velocity in both Al‐free and Al‐bearing bridgmanite at lower mantle pressures. The presence of Fe 3+ in the B site of bridgmanite can further enhance this increase. The observed spin transition of B site Fe 3+ in bridgmanite is thus important for understanding the density and velocity structures of the lower mantle. Key Points: The spin transition of Fe 3+ is observed in Pv10 at 18–25 GPa using XRD The spin transition causes a sudden decrease in the volume and increase in K The effect of Fe and Al on the density and K of bridgmanite is discussed