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<p>Grain size controls diffusion, deformation, and the textural evolution of mantle rocks. Because grain growth is driven by a reduction in grain boundary energy, the relationship between grain boundary energy and grain size provides an important constraint on microstructural evolution. To better quantify this relationship, we analyzed olivine–olivine–pyroxene (ol–ol–px) dihedral angles in peridotite xenoliths from Ichinomegata (Japan) and San Carlos (USA), as well as in experimentally sintered olivine–pyroxene aggregates. In melt-free Ichinomegata peridotites, ol–ol–opx angles (≈100°) fit single normal distributions. In contrast, melt-bearing Ichinomegata peridotites yield lower-angle ol–ol–cpx triple junction populations (≈80°), which we interpret as relict ol–ol–melt triple junctions, although the distributions of dihedral angles might also reflect the combined effects of textural evolution and system conditions. The San Carlos peridotite and experimental samples yield uniform distributions with median dihedral angles of ≈100°. Moreover, the relationships between olivine grain size, secondary-phase grain size, and secondary-phase volume fraction follow the Zener equation in both natural and experimental peridotites across four orders of magnitude in olivine grain size. These findings suggest that microstructural processes, including Zener pinning, melt–rock interaction, and dynamic recrystallization, contribute to the grain-scale evolution of peridotites across both laboratory and geological scales.</p>

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Linking interfacial energy estimates based on dihedral angles to grain size constraints in natural and experimental peridotites

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  • 发表日期：

    2026年6月26日

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  • Miki Tasaka,
  • Haruya Aida,
  • Yuto Sato

摘要

Grain size controls diffusion, deformation, and the textural evolution of mantle rocks. Because grain growth is driven by a reduction in grain boundary energy, the relationship between grain boundary energy and grain size provides an important constraint on microstructural evolution. To better quantify this relationship, we analyzed olivine–olivine–pyroxene (ol–ol–px) dihedral angles in peridotite xenoliths from Ichinomegata (Japan) and San Carlos (USA), as well as in experimentally sintered olivine–pyroxene aggregates. In melt-free Ichinomegata peridotites, ol–ol–opx angles (≈100°) fit single normal distributions. In contrast, melt-bearing Ichinomegata peridotites yield lower-angle ol–ol–cpx triple junction populations (≈80°), which we interpret as relict ol–ol–melt triple junctions, although the distributions of dihedral angles might also reflect the combined effects of textural evolution and system conditions. The San Carlos peridotite and experimental samples yield uniform distributions with median dihedral angles of ≈100°. Moreover, the relationships between olivine grain size, secondary-phase grain size, and secondary-phase volume fraction follow the Zener equation in both natural and experimental peridotites across four orders of magnitude in olivine grain size. These findings suggest that microstructural processes, including Zener pinning, melt–rock interaction, and dynamic recrystallization, contribute to the grain-scale evolution of peridotites across both laboratory and geological scales.