Temperature dependence and mechanism of hydrogen incorporation in olivine at 12.5–14.0 GPa
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چکیده
[1] The concentration and incorporation mechanisms of hydrogen into (Mg, Fe)2SiO4 olivine have been studied under water saturated conditions at 12.5–14.0 GPa and 1100–2000 C. The hydrogen content of olivine (Fo90–Fo95) coexisting with enstatite and hydrous melt increases from about 4600 ppmw at 1100 C to a maximum of 6250 ppmw at 1200 C. Above 1400 C, the hydrogen content of olivine decreases non-linearly, reaching 160– 240 ppmw in the 1800–2000 C range where there is a high melt fraction and no enstatite. Polarized infrared spectra of the recovered olivines exhibit OH absorption bands in both the 3450–3650 cm 1 range (group I) and 3160–3450 cm 1 range (group II). Results indicate that hydration of olivine is associated with both Mg and Si site vacancies. Microprobe analyses of the samples show a clear deficit of Si in olivine. The water storage capacity of olivine is probably no more than 1.5–2.0 times less than wadsleyite at 1400 C and transition zone pressures. Citation: Litasov, K. D., E. Ohtani, H. Kagi, S. D. Jacobsen, and S. Ghosh (2007), Temperature dependence and mechanism of hydrogen incorporation in olivine at 12.5–14.0 GPa, Geophys. Res. Lett., 34, L16314, doi:10.1029/ 2007GL030737.
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