Thermodynamic properties of anhydrous and hydrous wadsleyite, β−Mg₂SiO₄

Hydration-reduced lattice thermal conductivity of olivine in Earth’s upper mantle

“…Note that, because the variation in the thermal conductivity during 8 GPa to 11 GPa is within our measurement uncertainty of about 15%, there isn't a thermal conductivity anomaly within such a pressure range. Compared with the effect of proton weakening on the sound velocities and thermodynamic properties (e.g., heat capacity) of olivine and its high-pressure polymorphs [typically of the order of only a few percent (5,11,12)], the proton-induced lattice thermal conductivity reduction at high pressures, by a factor as large as 2, is dramatic and much more significant than previously expected. Such a large pressure-induced suppression of hydrous Fo90 lattice thermal conductivity is likely due to higherdensity ionic defects when compressed to higher pressures.…”

“…It has been suggested that olivine, a primary mineral in the upper mantle, and its high-pressure polymorphs (wadsleyite and ringwoodite) could store a large amount of water (hydrogen ions) in their crystalline defects and act as a major water reservoir within Earth (2-4). Incorporation of water in these mantle minerals has been shown to influence their physical properties (5)(6)(7)(8)(9)(10)(11)(12) and the dynamics of the mantle and subducting slabs (13). In particular, water enrichment could influence the minerals' thermal transport properties, which, in turn, alters the temperature gradient in the mantle and subducting slabs.…”

Phase diagrams, thermodynamic properties and sound velocities derived from a multiple Einstein method using vibrational densities of states: an application to MgO–SiO2

“…Generally, the VDoS of each substance is of such quality that low-temperature heat capacity is accurately represented. That in turn puts better constraints on high-temperature heat capacity, such as demonstrated for wadsleyite and ringwoodite for which the most recent high-temperature heat capacity data of Jahn et al (2013) and Kojitani et al (2012) are preferred over older DSC data. By constraining dispersion in Grüneisen parameters of forsterite with spectroscopic data, our analysis prefers the V-T data of Kajiyoshi (1986), consistent with thermal expansivity predicted by Li et al (2007).…”

Lower mantle hydrogen partitioning between periclase and perovskite: A quantum chemical modelling

“…Although extensive investigations (e.g. Mosenfelder et al, 2013;Jahn et al, 2013;Ghosh et al, 2013) have been devoted to hydrogen incorporation, there is much uncertainty about the microscopic mechanisms underlying such reactions. In literature, several models are available to account for the uptake of hydrogen in high-pressure mineral phases: cation-vacancy occurrence and H-compensation (hydro-garnet-like substitution); double replacement, such as 2Mg/1Si M Al(Fe 3+ ) + H; reduction of iron to Fe-metallic (Keppler and Bolfan-Casanova, 2006;Litasov, 2010).…”