Thermal diffusivity of olivine single crystals and a dunite at high temperature: Evidence for heat transfer by radiation in the upper mantle

摘要: The thermal diffusivity of San Carlos olivine single crystals is measured at elevated temperatures to differentiate lattice and radiative contributions the diffusivity. Thermal was determined with a transient apparatus which allows direct observation processes in samples. method separation non-conductive purely diffusive mechanisms, i.e., intrinsic heat transport by phonons radiation. transfer photons are separated their different temperature dependencies. D approximated Dphonon = 1/(A + BT) Dphoton CT 3 , respectively. A strong increase observed increasing sample lengths were varied from 4.5 13.1 mm. In small samples, only an apparent measured. For larger contribution tends value infinite sample. these radiation contributes up 60% total 850 ◦ C. Based on numerical modelling semi-transparent media, present measurements extrapolated order model large volumes like mantle. Furthermore, behaviour finegrained dunite compared evaluate influence grain boundaries properties polycrystalline aggregates. All experiments point significant aggregates high temperature. Thus, should strongly enhance conductive upper © 2005 Elsevier B.V. rights reserved.