SIMS ionization of hydrogen in silicates: a case study of kornerupine

H/Si ionization in kornerupine, an (Mg, Al)-rich silicate mineral, has been investigated. There are significant variations (about 30% rel.) in the relative-to-Si ion yield for H [IY(H/Si)] as a function of chemical composition of the matrix kornerupine: similar to 38-45 wt% Al2O3, similar to 29-32 wt% SiO2, similar to 15-20 wt% MgO, similar to0-11 wt% FeOtot, similar to2-4 wt% B2O3 and minor variations for the remaining components. There are strong correlations between IY(H/Si) and (Fe+Mn)(at) [where (at) represents the cation abundance in the sample (by atoms)] (r(2) = 0.80); for Mg and Al(at), r(2) = 0.73 and 0.90, respectively. The absolute ion yield for H [IY(H)] is strongly correlated with (Fe+Mn)- and Si(at) (r(2) = 0.92 and 0.94, respectively). It is possible to make adequate corrections to IY( H/Si) as a function of sample composition to obtain accurate H2O (wt%) concentrations, reducing (if not overcoming) the need for specific standards (in most cases unavailable) that match the chemical composition of the sample. A model is proposed for H ionization in this matrix. The present outcome is qualitatively similar to the results obtained for other silicates (schorl, foitite, dravite, axinite, amphibole) and represents a valid basis for modelling SIMS ionization of H in silicates.