The elastic properties of single-crystal fayalite as determined by dynamical measurement techniques

We present new elasticity measurements on single-crystal fayalite and combine our results with other data from resonance, pulse superposition interferometry, and Brillouin scattering to provide a set of recommended values for the adiabatic elastic moduli C_ij and their temperature variations. We use a resonance method (RPR) with specimens that were previously investigated by pulse superposition experiments. The nine C_ij of fayalite are determined from three new sets of measurements. One set of our new C_ij data is over the range 300-500 K. We believe that the relatively large discrep ncies found in some C_ij are due in large part to specimen inhomogeneities (chemical and microstructural) coupled with differences in the way various techniques sample, rather than only systematic errors associated with experimental procedures or in the preparations of the specimens. Our recommendea C_ij's (GPa) and (∂C_ij/∂T)_p (GPa/K) are:[Figure not available: see fulltext.] The resulting values for the isotropic bulk and shear moduli, K_s and μ, and their temperature derivatives are:K_s=134(4) GPa; μ=50.7(0.3) GPa; (∂K_s/∂T)_p=-0.024(0.005) GPa/K; and (∂μ/∂T)_p=-0.013(0.001) GPa/K. An important conclusion is that K_s increases as the Fe/(Fe+Mg) ratio in olivine is increased.