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<p>Earth’s early mantle probably existed as a deep, vigorously convecting magma ocean, and its solidification is considered central to the long-term chemical and dynamical evolution of the planet. Yet a notable uncertainty is the grain size of bridgmanite—the dominant lower-mantle phase—whose nucleation behaviour at extreme pressure has remained experimentally inaccessible. Here we show, using a combination of cutting-edge techniques, including large-scale molecular dynamics simulations consisting of up to 1 million atoms driven by machine learning potentials (MLPs), seeding and enhanced sampling, that crystal–melt interfacial energies of MgSiO<sub>3</sub> bridgmanite increase substantially with pressure, surpassing those of silicate–liquid systems at ambient pressure by a factor of up to ten (refs. <sup><CitationRef AdditionalCitationIDS="CR2" CitationID="CR1">1</CitationRef>–<CitationRef CitationID="CR3">3</CitationRef></sup>). In a deep basal magma ocean (BMO), this amplified interfacial energy, combined with the potential sluggish cooling, may permit the formation of unusually large bridgmanite crystals, up to centimetre-to-metre-scale sizes. Such potentially large crystals could drive efficient fractional crystallization and cause substantial chemical differentiation and mantle compaction. If operative, this mechanism would provide a new physical pathway linking lower-mantle material properties to early Earth stratification and it motivates future geodynamic models that explicitly incorporate supercooling, compositional convection and elemental partitioning. Our findings thus offer a plausible hypothesis connecting microscopic nucleation processes with macroscopic planetary structure, refining present views of how the Earth’s interior acquired its initial compositional architecture.</p>

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The potential for bridgmanite megacrysts to drive magma ocean segregation

  • 期刊论文

  • 发表日期：

    2026年1月21日

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  • Jie Deng,
  • Junwei Hu,
  • Yidi Shi,
  • Jina Lee,
  • Haiyang Niu,
  • Lars Stixrude

摘要

Earth’s early mantle probably existed as a deep, vigorously convecting magma ocean, and its solidification is considered central to the long-term chemical and dynamical evolution of the planet. Yet a notable uncertainty is the grain size of bridgmanite—the dominant lower-mantle phase—whose nucleation behaviour at extreme pressure has remained experimentally inaccessible. Here we show, using a combination of cutting-edge techniques, including large-scale molecular dynamics simulations consisting of up to 1 million atoms driven by machine learning potentials (MLPs), seeding and enhanced sampling, that crystal–melt interfacial energies of MgSiO3 bridgmanite increase substantially with pressure, surpassing those of silicate–liquid systems at ambient pressure by a factor of up to ten (refs. 1–3). In a deep basal magma ocean (BMO), this amplified interfacial energy, combined with the potential sluggish cooling, may permit the formation of unusually large bridgmanite crystals, up to centimetre-to-metre-scale sizes. Such potentially large crystals could drive efficient fractional crystallization and cause substantial chemical differentiation and mantle compaction. If operative, this mechanism would provide a new physical pathway linking lower-mantle material properties to early Earth stratification and it motivates future geodynamic models that explicitly incorporate supercooling, compositional convection and elemental partitioning. Our findings thus offer a plausible hypothesis connecting microscopic nucleation processes with macroscopic planetary structure, refining present views of how the Earth’s interior acquired its initial compositional architecture.