Abstract
Single crystals of five wadsleyite compositions, β-(Mg,Fe)2SiO4 with Fe/(Fe+Mg)=0.00, 0.08, 0.16, 0.25 and 0.40, have been synthesized at high temperature and pressure in a uniaxial, split-sphere apparatus. Crystal structures of these samples, determined by x-ray diffraction techniques, reveal that iron is significantly ordered: Fe is depleted in the M2 octahedron, while it is enriched in M1 and M3. The most iron-rich synthetic sample, which falls well outside previous estimates of wadsleyite stability, raises questions regarding published Mg2SiO4-Fe2SiO4 phase diagrams at transition zone conditions.
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Finger, L.W., Hazen, R.M., Zhang, J. et al. The effect of Fe on the crystal structure of wadsleyite β-(Mg1 − x Fe x )2SiO4, 0.00≤x≤0.40. Phys Chem Minerals 19, 361–368 (1993). https://doi.org/10.1007/BF00202973
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DOI: https://doi.org/10.1007/BF00202973