Abstract
A model for thermal conductivity κ, based on phonon lifetimes obtained from infrared reflectivity, replicates experimental data at ambient conditions. The pressure and absolute temperature dependences of transport properties are accurately obtained from the Grüneisen parameter γTh, bulk modulusK T, and thermal expansivity α: The lattice contribution κlat equals κ298(298/T)aexp[−(4γTh + 1/3) ∫298 Tα(θ)dθ] witha = 0.33 for silicates (or 0.9 for MgO), and ∂[ln(κlat)]/∂P = (1/3 + 4γTh)/K T. The smaller, pressure-independent radiative contribution κrad equals 0.0175 – 0.0001037T + (2.245T 2/107) – (3.407T 3/1011), in units of watts per meter-kelvin, if Fe2+ is present. The resulting lithospheric geotherm is steep. Consequently, the mantle geotherm is hot if the low-velocity zone is anhydrous, but cold if hydrated.

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