Hydrogen and deuterium diffusion in non-stoichiometric spinel

作者：Bromiley Geoffrey D^*; Brooke Jennifer; Kohn Simon C

来源：High Pressure Research, 2017, 37(3): 360-376.

DOI：10.1080/08957959.2017.1353091

• Spinel
• hydrogen
• deuterium
• diffusion
• mantle

High pressure/temperature annealing experiments are used to determine diffusivities of H+ and D+ in non-stoichiometric spinel, a low-pressure analogue for nominally anhydrous minerals in Earth's mantle. Data are fitted to the following Arrhenius law: Diffusivity (m(2)/s) = 4 +/- 1 x 10(-12) exp(-54 +/- 2 kJ mol(-1)/RT). At low temperatures, H+ and D+ diffusion in non-stoichiometric spinel is charge balanced by flux of O vacancies, with infrared data consistent with protonation of both octahedral and tetrahedral O-O edges in non-stoichiometric spinel, and additional fine structure due to Mg-Al mixing and/or coupling of structurally incorporated H+ with cation vacancies. Absence of changes in the fine structure of O-H absorption bands indicates that H+ can become locally coupled and uncoupled to other defects during bulk diffusion. As such, proton conductivity in spinel group minerals, arising from faster flux of uncoupled H+, can only be calculated from H+ mobility data if the extent of defect coupling is constrained.

• 出版日期2017