4H=1Si substitution in grossular and forsterite: Information from 1H NMR and first-principles calculation

Abstract

The 4H=1Si substitution is well known for hydrogrossular, and has also been suggested for other mantle minerals, such as olivine. The inference was mostly based on infrared spectra, but the interpretation is not unambiguous. Here we apply NMR spectroscopy, in combination with first-principles calculation to shed better light on this issue. We compare the proton distributions in hydrogrossular and forsterite, demonstrating that they have similar, but not identical configurations.