Melting Behavior of B1 FeO Up To 186 GPa: Existence of FeO‐Rich Melts in the Lowermost Mantle

Abstract

Abstract FeO is an important component in both mantle silicates and core iron alloys. Understanding its melting behavior and physical properties is crucial for exploring the chemistry and physics of our planet. Here we report the melting curve of FeO up to 186 GPa from laser‐heating experiments in a diamond‐anvil cell coupled with synchrotron X‐ray diffraction (XRD) techniques. In‐situ observations of both temperature plateau and changes in XRD patterns were used as primary melting criteria. The ex‐situ examination of a recovered sample shows consistent melting temperatures of FeO with in‐situ determinations. Our melting curve of FeO agrees with existing low‐pressure data within uncertainties and is much lower than earlier experimental results above 100 GPa including those extrapolated by Lindemann's law. Our results indicate that FeO‐rich materials could be present as melts coexisting with surrounding solids in the lowermost mantle, providing plausible explanations to the seismically observed ultra‐low velocity zones.