The Earth’s lower mantle is composed of bridgmanite, ferropericlase, and CaSiO 3 -rich perovskite. The melting phase relations between each component are key to understanding the melting of the Earth’s lower mantle and the crystallization of the deep magma ocean. In this study, melting phase relations in the MgSiO 3 –CaSiO 3 system were investigated at 24 GPa using a multi-anvil apparatus. The eutectic composition is (Mg,Ca)SiO 3 with 81–86 mol% MgSiO 3 . The solidus temperature is 2600–2620 K. The solubility of CaSiO 3 component into bridgmanite increases with temperature, reaching a maximum of 3–6 mol% at the solidus, and then decreases with temperature. The same trend was observed for the solubility of MgSiO 3 component into CaSiO 3 -rich perovskite, with a maximum of 14–16 mol% at the solidus. The asymmetric regular solutions between bridgmanite and CaSiO 3 -rich perovskite and between MgSiO 3 and CaSiO 3 liquid components well reproduce the melting phase relations constrained experimentally.
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