VARIATIONS IN THE OH CONCENTRATION OF RUTILES FROM DIFFERENT GEOLOGICAL ENVIRONMENTS

A suite of 19 rutiles form a wide range of geological environments shows a distinct variability in the OH concentrations. The analytical H2O+ content determined by IR spectroscopy varies from 0.04 to 0.21 wt.% with the greatest amounts occurring in amphibolite facies rutiles. The main feature of the IR spectra in the region of the OH stretching fundamental is a single narrow band centered at 3280 cm-1; some of the spectra show an additional band, centered either at 3360 or at 3320 cm-1. Varying OH concentrations in rutiles are probably a function of the activity of hydrous components during crystallization and are weakly correlated to a minor content of tri- and pentavalent elements.