R2: Crystal structure, crystal chemistry, physical properties of minerals, crystal growth and applied mineralogy

[R2P-01] Hydrogen incorporation mechanism in the lower-mantle bridgmanite

Narangoo Purevjav¹, Naotaka Tomioka², Shigeru Yamashita⁷, Keiji Shinoda³, Sachio Kobayashi², Kenji Shimizu², Motoo Ito², Suyu Fu⁴, Jesse Gu⁴, Christina Hoffmann⁵, Jung-Fu Lin⁴, *Takuo Okuchi⁶ (1. Univ. Bayreuth, 2. JAMSTEC, 3. Osaka Metropolitan Univ., 4. Univ. Texas, 5. ORNL, 6. Kyoto Univ., 7. Okayama Univ.)

Keywords:bridgmanite, lower mantle, hydrogen substitution, neutron diffraction

We investigated the crystallographic site of hydrogen and its incorporation mechanism in bridgmanite by single-crystal neutron diffraction for the first time. Our results show that the primary hydrogen site has an OH bond direction nearly parallel to the crystallographic b^_axis of the bridgmanite lattice, where hydrogen is located between two oxygen anions to form a straight geometry of covalent and hydrogen bonds. Our modelled results show that hydrogen is incorporated via substitution of Al³⁺ + H⁺ simultaneously exchanging for Si⁴⁺, which does not require any cation vacancy.