Thermal parameters of the Earth's lower mantle

Laboratory and seismological measurements of bulk and shear moduli (K-s and mu(s)) have been combined to derive the specific temperature and frequency dependencies of pressure, K-s and mu(s) as a function of depth in the lower mantle of the Earth. The results depend on the mineralogical model and temperature profiles chosen, as well as on the bulk Fe content in the lower mantle. If the Fe/Mg + Fe content in the lower mantle does not exceed 0.15, two important conclusions remain after a large variety of models have been investigated. (1) High-frequency (MHz or GHz) laboratory measurements of mu(s) of mantle phases should be corrected by 3-20% before comparison with seismological data can be done. Dispersion laws such as those provided by the PREM model underestimate this correction. (2) The lower mantle material, described as a Debye solid, cannot be silicon rich (e.g., pure perovskite) and the values of K-0' are constrained between 3.5 and 3.7. (C) 1998 Elsevier Science B.V. All rights reserved.