The effect of hydrogen on oxygen diffusion in quartz: Evidence for fast proton transients?

The importance of water in modifying the physico-chemical and mechanical properties of minerals has long been recognized. Water dramatically weakens quartz and enhances oxygen diffusion in silicates at high pressures and temperatures, with important geological consequences, but the underlying mechanisms are poorly understood. Recent attention has focused on the role of H and O in these mechanisms. Here we report the results of a study of the diffusion of oxygen in quartz at high pressure and temperature in the presence of water and of dry H gas, and compare the results with those of experiments in the presence of dry O gas. We conclude that oxygen diffusion is inhibited in the presence of dry H but enhanced in the presence of HO, and deduce that fast H transients rather than H movement may be responsible for oxygen diffusion enhancement in framework silicates. Because of their high mobility, such transients may well be experimentally unquenchable within the silicate framework.