High-Temperature Processes: Is it Time for Lithium Isotopes?
Horst R. Marschall, Ming Tang
Abstract
The field of high-temperature Li isotope geochemistry has been rattled by major paradigm changes. The idea that Li isotopes could be used to trace the sources of fluids, rocks, and magmas had to be largely abandoned, because Li diffusion causes its isotopes to fractionate at metamorphic and magmatic temperatures. However, diffusive fractionation of Li isotopes can be used to determine timescales of geologic processes using arrested diffusion profiles. High diffusivity and strong kinetic isotope fractionation favors Li isotopes as a tool to constrain the durations of fast processes in the crust and mantle, where other geochronometers fall short. Time may be the parameter that high-temperature Li isotope studies will be able to shed much light on.