Immediate formation of core–mantle boundary heterogeneities following a giant impact

作者：Rongxi Bi, You Zhou, Yun Liu · 发表于：Journal of Physics, Conference Series · 年份：2025 · DOI：10.1088/1742-6596/3109/1/012042 · 研究领域：Physics

Seismic observations have revealed a variety of velocity anomalies near the core–mantle boundary (CMB), including Large Low Shear Velocity Provinces (LLSVPs), Ultra-Low Velocity Zones (ULVZs), and the E′ layer. Understanding the origin of these features is essential for constraining the formation and long-term evolution of Earth’s deep interior. While the potential role of giant impacts in generating large-scale CMB heterogeneities such as LLSVPs has been previously proposed, the connection between other anomalous structures and collision processes remains underexplored. In this study, we focus on a specific class of impact events—core-merging giant impacts (CMGIs)—that occurred during Earth’s accretion. These events typically result from low-angle collisions in which the impactor’s metallic core merges directly with Earth’s core, with limited interaction with the silicate mantle. Using Smoothed Particle Hydrodynamics (SPH) and Meshless Finite Mass (MFM) methods, we show that CMGIs can generate significant thermal and compositional stratification in the outermost core. Additionally, silicate mantle material may be entrained into the core during the merging process. These immediate consequences of giant impacts can naturally generate anomalous regions at the top of the core and the basal mantle, which may, over geological timescales, partially evolve into present-day E′ and ULVZs structures at the CMB Therefore, we propose that these impact-driven processes offer a novel mecha...