Kinetics of melting in peridotite from volume strain measurements.

Partial melting in the Earth’s mantle involves a combination of processes such as ionic diffusion and solid–liquid transition. These processes yield an array of characteristic times for the melting kinetics. Both the magnitude and time constant of melt-induced volume strain affect seismic velocity, attenuation, and buoyancy. In situ monitoring of samples during melting are enabled by multi-anvil high-pressure devices coupled with synchrotron X-ray radiation. In this study, the volume strain induced in a sample from melting is measured as a function of time using X-ray images. We find a doubling of the effective thermal expansion for only 2% melt both from our data and from thermodynamic models of peridotite. The characteristic time of melting is determined to be less than one second. These findings have a direct impact on the effect of melting on seismic velocities. [ABSTRACT FROM AUTHOR]