CSEDI: Collaborative Research:The Influence of Thermal Conductivity on Stabilization and Feedback in Mantle Convection

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EAR-0207176David A. YuenThe investigators propose a three-year collaborative investigation of the pressure (P), temperature (T), and compositional-structural (X) dependence of thermal conductivity (k) to shed light on possible feedback mechanisms and plume stabilization in the mantle. The current spectroscopic model of k(T,P,X), based on classical damped harmonic oscillators, reproduces the essential features of available measurements. The spectroscopic model will be improved as follows: (1) The theory for the radiative component of k will be made exact by including the dependence of the emitted light on frequency. Impurities (hydrous species, Fe2+ and Fe3+) will be focused on because their vibrational and electronic absorptions greatly modify the black-body curve. (2) IR and visible spectra at T and P will be acquired from mantle candidate phases. (3) The model will be benchmarked against k(T) obtained using the laser flash technique: this method circumvents previously encountered experimental difficulties. Geodynamical models incorporating k(T,P,X) will be independently constrained by analogy with convection experiments on colloids that have a strongly nonlinear diffusion coefficient, through collaboration with an Italian physics group performing these laboratory studies. The issues in geodynamic numerical modeling include (1) how the mechanics of the lithospheric and slab dynamics are affected by the interplay of k with rheology, and (2) whether variable k and phase transitions can induce layered convection, delay secular cooling of the core-mantle system, or stabilize mantle flows. The geodynamic modeling will reveal which variable (T, P, X) has the greatest influence on mantle convection, and thus will guide the mineral physics experiments. The team plans to disseminate findings on the effects of nonlinear diffusion, because of its far-reaching, fundamental nature, to educational institutions in disciplines other than geosciences.