Equation of state of spinel (MgAl2O4): constraints on self-consistent thermodynamic parameters and implications for elastic geobarometry of peridotites and chromitites

Thermodynamic Properties of MgAl2O4 Spinel at High Temperatures and High Pressures

“…At room temperature conditions, the unit-cell volume from the current study is in good agreement with the data provided by Levy et al [12] within 0.3%. Meanwhile, excellent consistencies are found when compared with the values published by Nestola et al [13] and Hagiwara et al [16],…”

“…A temperature conditions, the unit-cell volume from the current study is in good agr with the data provided by Levy et al [12] within 0.3%. Meanwhile, excellent consi are found when compared with the values published by Nestola et al [13] and Ha et al [16], with the largest differences being less than 0.2% and 0.1%, respective thermore, the great agreement also holds at high temperature conditions within 0.1 pared to the experimental results of Duan et al [15]. [15]; hexagons: X-ray tion results of Levy et al [12]; squares and filled squares: X-ray diffraction results of orde disordered phases, respectively, of Nestola et al [13]; line and filled circles: theoretical resu lated from the published EoS of MgAl2O4 spinel by Hagiwara et al [16].…”

“…Figure 3 shows our calculated unit-cell volume of MgAl 2 O 4 spinel as a function of pressure at various temperatures, along with the results obtained through X-ray diffraction measurements [12,13,15] and theoretical calculations [16] for comparisons. At room temperature conditions, the unit-cell volume from the current study is in good agreement with the data provided by Levy et al [12] within 0.3%.…”

“…Petrology and geochemistry evidence suggests that the plagioclase-spinel and spinelgarnet phase transitions are considered to be two key boundaries at the top upper mantle, which are significant for investigating the processes of heterogeneity in the upper mantle rocks [4]. Therefore, the equation of state (EoS) of MgAl 2 O 4 spinel has been widely carried out using various experimental methods [5][6][7][8][9][10][11][12][13][14][15][16], which provide abundant data to derive the composition and density structure of the upper mantle. In contrast, the experimental data on the thermodynamic properties, such as thermal expansion, heat capacity, entropy, and the Grüneisen parameter, of MgAl 2 O 4 spinel at simultaneous high temperature and high pressure conditions (HT-HPs) are still scarce.…”

“…With the development of a computer simulation, the first principle calculations [33] and theoretical calculations based on the published EoS [16,34,35] definitely provide us with efficient ways to estimate the thermodynamic properties of minerals and phase transition boundaries at HT-HPs. However, the separations between the results from these theoretical works are nonnegligible, and there are still considerable controversies about the thermodynamic properties of MgAl 2 O 4 spinel at HT-HPs, especially the pressure effects on these thermodynamic properties.…”