R4: Mineral sciences of the Earth surface

4:00 PM - 4:15 PM JST(7:00 AM - 7:15 AM UTC)

[R4-08] Variation of lattice constants with Na substitution in biogenic aragonites

*Taiga Okumura¹, Masahiro Yoshimura¹, Toshihiro Kogure¹ (1. Univ. Tokyo Sci.)

Keywords:

biogenic aragonite,sodium,lattice constant,axial ratio,biomineralization

The lattice constants of 14 biogenic and five abiogenic aragonites were measured in this study. The aragonites with larger axial ratios (a/b and c/b) showed a higher concentration of Na. The axial ratios of a marine molluscan shell decreased by heating at 250°C, and Na was diffused out of the aragonite crystals and locally concentrated after heating. These results infer that variation of the lattice constants in biogenic aragonites is caused by the substitution of Na⁺ for Ca²⁺.