Crystal-liquid density inversions in terrestrial and lunar magmas

Equilibrium liquidus crystals will float in variety of terrestrial and lunar magmas within a wide range of mantle depths. Density inversions exist for ultrabasic mantle melts and olivine at depths between 245 and 500 km in the Earth. Olivine flotation occurs in high-Ti basalts at similar to 400 km in the lunar mantle. Basaltic and komatiitic magmas have density inversions with garnet in the upper mantle transition zone and perovskite in the lower mantle. Peridotitic magma, because of its comparatively large bulk modulus (K(T)) and pressure derivative of the bulk modulus (K'), is likely to be less dense than liquidus garnet and perovskite at all depths within the Earth. (C) 1998 Elsevier Science B.V. All rights reserved.