This project involves characterization of the rate and mechanism of diffusion of hydrogen in OH-bearing feldspars at magmatic temperatures (800-1000°C) through modeling of experimental diffusion data. The diffusion rate of hydrogen at magmatic temperatures determines the amount of OH preserved in a feldspar phenocryst during a typical eruptive event, and the extent to which zoning of OH in feldspar phenocrysts with complex magmatic histories should be preserved. Models of integrated loss and diffusion profiles across heated slabs of feldspar will determine if diffusion is dependent on the concentration of some hydrous species.