Helium Trapping in Mg–Silicates at Multi-Megabar Pressures

Mg-Si-O minerals form</p><p dir="ltr">the dominant condensed framework of rocky interiors across broad pressuretemperature</p><p dir="ltr">conditions and throughout planetary evolution, making Mg–silicates the</p><p dir="ltr">most relevant (and stringent) minerals in which to assess helium incorporation.</p><p dir="ltr">Meanwhile rare study focuses on the high-pressure behavior between Helium and</p><p dir="ltr">Mg-Silicates.</p><p dir="ltr">Here, we explore the ternary MgO-SiO2-He system and identify two</p><p dir="ltr">thermodynamically stable helium-bearing Mg silicates, Mg2SiO4He and Mg2SiO4He2,</p><p dir="ltr">over 250–930 GPa.

We reveal a clear microscopic mechanism: pressure-driven</p><p dir="ltr">reorganization of post-perovskite-derived Mg-Si-O frameworks create interstitial</p><p dir="ltr">cavities that confine helium without chemical bonding.</p>