Attenuation spectra of olivine/basalt partial melts: Transformation of Newtonian creep response

Abstract

The flexural creep responses of a Co‐Mg olivine‐plus‐basalt aggregate at temperatures near 1100°C have been transformed to give attenuation spectra (QE−1 vs. ω) as functions of temperature. The experimental creep response of this mantle‐analog material is well‐modeled as a Burgers solid, displaying a steady‐state creep that is preceded by a transient deceleration. Calculated attenuation spectra are based on the Burgers solid viscosities and elastic constants obtained from the creep experiments. The attenuation becomes total and zero in the low‐ and high‐frequency limits, respectively, as is appropriate for polycrystalline olivine having a diffusional creep rheology. At intermediate frequencies (10−4Hz to 10−2Hz), QE−1 experiences a local maximum. Both the magnitude (QE−1≈15) and central frequency of this loss maximum increase with temperature. The attenuation peak is an anelastic loss compatible with the transient creep response; it is inferred to represent a melt flow mechanism that adjusts the size of melt‐bearing triple‐grain junctions in response to changes in the stress state.