Petrology of the lowermost mantle

Abstract

Seismic observations of the thermal boundary layer above the core-mantle boundary (CMB), including Ultra-Low Velocity Zones and D" discontinuities with velocity jumps of either sign, suggest that the bottom of the mantle may be compositionally distinct and, in places, partially molten[1]. Our new shock-wave data constrain the melting curve and liquid equation of state (EOS) of the key lower mantle component MgSiO_3 perovskite and suggest neutral or negative buoyancy of this melt at CMB pressure.

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