Lower-mantle iron heterogeneity constrained by the electrical conductivity of Al-bearing bridgmanite
- Kui Han
- Sinan Özaydın
- Hongzhan Fei
- Lianjie Man
- Fei Wang
- Artem Chanyshev
- Anthony C. Withers
- Alexander Grayver
- Tomoo Katsura
2026-04-24
Iron distribution in Earth’s lower mantle profoundly influences planetary evolution by regulating mineral density and mantle dynamics but remains poorly constrained due to trade-offs between temperature and composition in seismic interpretations. Here, we resolve this challenge by measuring electrical conductivity of Al-, Fe-bearing bridgmanite, the dominant lower-mantle mineral, as a function of iron content ( X Fe ) under conditions reaching 2000 K and 27 GPa. Bridgmanite conductivity increases dramatically with X Fe following an X Fe 3.6 power law, while showing minimal temperature dependence. This pronounced sensitivity enables direct inference of global iron variation from geomagnetic-derived conductivity models. Our analysis reveals iron enrichment in large low–shear velocity provinces, supporting their thermochemical rather than purely thermal nature. We identify extensive high-iron regions beneath the western Pacific extending below 1000 km, indicating a vast basaltic reservoir of subducted oceanic crust. These findings provide independent constraints on Earth’s chemical composition and evolution.