Temperature-dependent thermal diffusivity of the Earth’s crust and implications for magmatism

The Earth's crust: wrap-up warm The rate of heat transfer by conduction is the dominant factor that determines the thermal evolution of planetary crust and lithosphere. Most thermal models of the Earth's crust assume constant values for thermal diffusivity, owing to large experimental uncertainties in measuring this property of rocks at high temperature. Whittington et al. have used recent advances in laser-flash analysis on three different crustal rocks types to show that thermal diffusivity strongly decreases with increasing temperature. They find thermal diffusivity to be about half that commonly assumed at mid-crustal temperatures and therefore conclude that the hot middle and lower crust is a much more effective thermal insulator than previously thought. They also present models of lithospheric thermal evolution during continental collision, and demonstrate that the temperature dependence of rock properties leads to a positive feedback between strain heating in shear zones and more efficient thermal insulation, removing the requirement for unusually high radiogenic heat production to achieve crustal melting temperatures.