Dislocation creep may control bridgmanite deformation in the Earth’s lower mantle

Abstract Seismic anisotropy in the Earth’s lower mantle, particularly around subduction zones, is commonly attributed to deformation by dislocation creep, yet much of the lower mantle appears nearly isotropic. This contrast complicates interpretations of mantle rheology. Here we report the temperature dependence of lattice preferred orientation in bridgmanite, the most abundant lower mantle mineral, through high-pressure deformation experiments at 25 gigapascals and 1700–2100 kelvin. Both iron-free and iron-bearing bridgmanite develop lattice preferred orientations across this temperature range, with distinct slip systems occurring below and above 1800 kelvin. Low-temperature fabric produces strong seismic anisotropy, whereas high-temperature fabric yields weak, near-isotropic signatures under horizontal shearing. These results provide a unified explanation for strong seismic anisotropy near subduction zones and globally near-isotropic behavior of the lower mantle. They suggest that dislocation creep could dominate lower mantle deformation while generating diverse seismic signatures, providing important understanding for lower mantle rheology and dynamics.