Diffusion in Solid Silicates: A Tool to Track Timescales of Processes Comes of Age

Understanding how processes occurring on a wide range of temporal and spatial scales combine to produce a stable dynamic Earth is a major goal of the Earth scientist. Determining durations of processes is a key step toward attaining that goal. Records of incomplete diffusive equilibration preserved in minerals are uniquely suited for the purpose of unraveling timescales of a variety of processes. Compositional zoning in minerals is like the tracks of a CD that can be decoded with suitable technology. This review discusses the causes for the limited use of this tool until recently and how these hindrances are being overcome. Examples are presented to illustrate that diffusion modeling can clock processes that last from only a few days to those that last over tens of millions of years, recorded in rocks that range in age from current volcanic eruptions to condensates from the early solar nebula.