Hydrogen incorporation in a ringwoodite analogue: Mg2GeO4 spinel

摘要

Single crystals of Mg₂GeO₄ spinel, a stable analogue to mantle ringwoodite at atmospheric pressure up to 800°C, were synthesized from Mg₂GeO₄ olivine in hydrous conditions at 1.9 GPa and ~1000°C. Infrared (IR) spectra show OH-stretching peaks at 3531 and 3502 cm–1. Quantification of IR spectra reveals hydrogen in the order of 5 to 10 ppm wt. H₂O. A complete hydrogen/deuterium exchange was achieved at 700°C leading to a diffusion coefficient of deuterium of ~3x10–14 m2/s. This value is of the same order as diffusion coefficients observed in other mantle minerals, such as garnet and diopside.