Abstract
In order to investigate the effect of Fe on the equation of state (EOS), the volume of the perovskite (Pv) phases, (Mg 1− x Fe x )SiO 3, with different Fe contents ( x = 0 , 0.09, 0.15), has been measured at high pressures up to 1 Mbar in an Ar or NaCl medium. A bulk modulus ( K 0 ) ranging between 255 and 261 GPa is obtained when the Au scales consistent with the Pt scale are used and the data are fit to the second order Birch–Murnaghan (BM) equation. When the third order BM equation is used, we obtain K 0 = 250–264 GPa and K 0 ′ = 3.7–4.5, which is consistent with previous low-pressure X-ray diffraction and Brillouin measurements. Within experimental uncertainties (0.5% in volume and 6% in bulk modulus), we do not resolve differences in the EOS between Fe-bearing (up to 15%) and Fe-free Pv to 1 Mbar (2600-km depth in the mantle). This is in contrast with the much larger effect of the Fe spin transition for the EOS of ferropericlase (Fp) reported recently. This is perhaps due to much more diverse states of Fe (e.g., oxidation, coordination, and spin states) in Pv than in Fp.
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