Abstract The electrical structure of Earth’s interior resolved by geophysical surveys is key to understanding its composition, dynamics and relevant properties. Electrically anomalous zones in the upper mantle have been frequently observed, yet the origin remains debated. Interpreting the geophysically imaged electrical anomalies cannot be properly made if the constraints on mantle materials from petrological and geochemical surveys and mineral physics experiments are not combined. Studying mantle samples has revealed widespread heterogeneities in their mineral constituents, elemental compositions and thermodynamic properties, in addition to the local occurrence of melts and fluids. The heterogeneities are macroscale, ranging on the levels of meters to kilometers. Four conductive candidates are identified for the electrical anomalies by laboratory experiments under mantle conditions, including olivine owing to oxidized state (but not water), lithologies (such as pyroxenites, eclogites and phlogopite-bearing assemblages due to enriched Fe, water and/or F), partial melt and aqueous fluids. Such materials are able to cause electrical anomalies in a variety of settings that are geophysically detectable, if connected forms, rational fractions and/or suitable temperature and redox state are spatially maintained along certain direction(s). Hydrous minerals except phlogopite and non-silicate minerals such as graphite, sulfides and carbonates are usually hard to lead to mantle electrical anomalies. Mantle macroscale heterogeneities cause heterogeneous electrical structure. Geophysically imaged electrical anomalies in the upper mantle are intimately related to its petrological and geochemical evolution.
Yang et al. (Thu,) studied this question.