Thermoelastic properties of MgSiO₃ perovskite determined by in situ X ray observations up to 30 GPa and 2000 K

Abstract

In situ X ray experiments on MgSiO 3 perovskite at pressures of 21 -29 GPa and temperatures of 300-2000 K were carried out using an MA8-type high-pressure apparatus, employing sintered diamond anvils, combined with synchrotron radiation. The thermal expansion at 25 GPa up to 2000 K was determined from interpolation of the P-V-T data obtained in the present study. The 95% confidence level was estimated by taking all possible errors into account, including statistical error and systematic error caused by uncertainty of pressure scales, etc. The thermal expansivity at 25 GPa is expressed as 0[T,25 '-a25 + b25T -c25T 2 with the bestfit parameters ofa25=2.11x10-SK -• b25= 1 80x10-OK-2, andc25 1.93 K. The equation of state of MgSiO 3 perovskite has been determined using our new data combined with the lower-pressure data of Wang et al. [ 1994] and Utsumi et al. [ 1995]. The optimal set of parameters of the third-order Birch-murnaghan equation of state, which is expressed as P-(3/2)Kr,0[(VT,0/V) 7/3-(VT.0/V)S/3]{ 1 -(3/4)(4-KT,O')[(VT,o/V) 2/3-1]}, where KT, o -K3oo, o + (•KT,o/•T)p(T -300), Kr,o' -K3oo,o', VT,(, = T • __ Voexp .[3{•)ø•T,odT, and CZr, o % + boT -Co T-2, is K3oo, o = 261 GPa, K3(•),o '= 4, a o 1.982x10 -5 K -•, b o = 0.818x10-8 }(2, Co = 0.474 K, and (3Kr,o/3T)p = -0.0280 GPa/K. The reliability of the result is discussed in detail.

Phase relations in the system MgO‐FeO‐SiO2 to 50 GPa and 2000°C: An application of experimental techniques using multianvil apparatus with sintered diamond anvils

“…[12] The lattice volume of MgSiO 3 Pv has been measured by a number of authors, and the reported values of the lattice volume range from 162.0 to 162.75 Å 3 [Liu, 1974;Ito and Matsui, 1978;Yagi et al, 1978;Mao et al, 1991;Wang et al, 1994;Funamori et al, 1996;Fiquet et al, 1998]. In this study, the lattice parameters of MgSiO 3 Pv were determined precisely using 33 diffraction peaks and the lattice volume was found to be 162.373 (16) Table 3.…”

Shock‐induced melting of MgSiO3 perovskite and implications for melts in Earth's lowermost mantle

“…[2] The perovskite (pv) structure of (Mg, Fe)SiO 3 is considered to be the most abundant phase in the lower mantle, which makes its high-pressure, high-temperature behavior a matter of some interest. Of particular importance, given seismic ultra-low velocity zones (ULVZs) [Williams and Garnero, 1996] above the core-mantle boundary, are constraints on the phase relations and density contrasts among mantle solids, mantle melts, and the core that may explain the presence and stability of partial melting at the very base of the mantle [Montague and Kellogg, 2000;Namiki, 2003;Zhong and Hager, 2003].[3] The thermal EOS of MgSiO 3 pv has been constrained by numerous static experiments and computational studies [Wang et al, 1994;Utsumi et al, 1995;Funamori et al, 1996;Saxena et al, 1999;Fiquet et al, 2000;Karki et al, 2001;Marton et al, 2001;Brodholt et al, 2002]. Previous dynamic pressure-density-internal energy (P-r-E) data for MgSiO 3 composition are compiled in Marsh [1980] and Simakov and Trunin [1973].…”

Microscopic properties to macroscopic behaviour: The influence of iron electronic state

“…The isothermal bulk modulus of MgSiO 3 and (Mg,Fe)SiO 3 perovskites have been established to generally fall within the range 250 260 GPa by numerous laboratories (e.g., Funamori et al, 1996;Fiquet et al, 1998;Fiquet et al, 2000;Sinogeikin et al, 2004); however measurements on perovskite compositions incorporating Al (hence stabilising some of the iron, if present, as Fe 3+ ) show dramatically different results, but with a large variation in observed behaviour. Some high pressure measurements show a 5 10% decrease in bulk modulus (Zhang and Weidner, 1999;Kubo et al, 2000;Daniel et al, 2001;Yagi et al, 2004), some show an increase in bulk modulus Ono et al, 2004) and some show no change (Yagi et al, 2004;Jackson et al, 2004).…”