Chapter 4 - Melting in the Earth's Deep Interior

Abstract

In this chapter, I focus on melting in the deep Earth from the transition zone to the core–mantle boundary (CMB), with a brief overview of recent works dedicated to such melting properties. Two regions in the deep Earth are likely to be the locus of partial melting of the mantle: the transition zone and the CMB. In the transition zone region, melts can be produced on the top of the transition zone or at the top of the lower mantle. In the lower mantle, estimates of the initial CMB temperature exceed the melting temperature of the mantle, indicating extensive lower mantle melting in the early Earth, compatible with the formation of a deep magma ocean. It is likely some relics of this early magma ocean have been kept at the CMB. Most measurements or calculations of iron partitioning between bridgmanite and the silicate indicate that these partial melts are likely to be gravitationally stable at the CMB. Further studies are required to evaluate the influence of light incompatible species such as H2O and CO2 on melting at the CMB, as are precise mechanisms for transportation and delivery of volatiles to the very deep mantle.