| Summary: | Abstract The Earth’s lower mantle is composed of bridgmanite, ferropericlase, and CaSiO3-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 MgSiO3–CaSiO3 system were investigated at 24 GPa using a multi-anvil apparatus. The eutectic composition is (Mg,Ca)SiO3 with 81–86 mol% MgSiO3. The solidus temperature is 2600–2620 K. The solubility of CaSiO3 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 MgSiO3 component into CaSiO3-rich perovskite, with a maximum of 14–16 mol% at the solidus. The asymmetric regular solutions between bridgmanite and CaSiO3-rich perovskite and between MgSiO3 and CaSiO3 liquid components well reproduce the melting phase relations constrained experimentally.
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