Effect of Fe on the nature of OH-defects in olivine

Ingrin, Jannick and Blanchard, Marc and Balan, Etienne and Kovács, István János (2015) Effect of Fe on the nature of OH-defects in olivine. In: Goldschmidt 2015, 16–21 Aug 2015., Prague.

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Abstract

OH-defects involved in the storage of hydrogen in mantle olivine remain poorly identified. This greatly impairs our ability to quantify the water content of the Earth’s upper mantle. Significant progresses have been achieved in the identification of OH-defects through the study of the Mg endmember forsterite [1-3]. However, it is not the case for olivine for which, the assignment of several key OH FTIR bands remains unclear. We report here the results of a detailed infrared study of these OH bands in natural olivines, between - 194°C and 50°C, and results from a numerical simulation of OH spectra in Fe-doped forsterite. We focused on OH bands in three frequency domains: around 3200 cm-1, between 3300- 3400 cm-1 and at 3600 cm-1. We highlight the respective role of Fe3+ and Fe2+ on the frequency and occurrence of these bands and discuss the implications for the storage of water in olivines of the lithospheric mantle.

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