Elemental diffusion chronostratigraphy: time-integrated insights into the dynamics of plumbing systems

Time-related information of pre-eruptive magmatic processes is locked in the chemical profile of compositionally zoned minerals and can be retrieved by means of elemental diffusion chronometry. However, only the timescale of the outermost rim is commonly resolved, limiting our knowledge of timescales to those directly preceding the eruption. A major obstacle is the need to accurately constrain the temperatures at which diffusion occurred. Elemental diffusion chronostratigraphy can be fully resolved for crystals that have spent their lifetime in hot storage. Under this condition, crystals will be kept at the temperature of the eruptible magma(s), and diffusion timescales approximate the storage of the crystal in question in different melt environments. Hot storage conditions are typical of open-conduit systems in steady state and are driven by the regular supply of fresh hot magmas determining the constant presence of eruptible magma. Fe-Mg interdiffusion in pyroxene crystals from Stromboli and Popocatépetl are used to reconstruct elemental diffusion chronostratigraphies of single crystals and to discuss their implications for magma dynamics. Uncertainties introduced by temperature estimates and other input data, including experimentally derived values for the activation energy E and the pre-exponential factor D₀, have large effects on the accuracy of modeled timescales, which need to be evaluated and mitigated. Elemental diffusion chronostratigraphy is an extremely powerful tool for obtaining time-related temporal information on the dynamics and histories of volcanic plumbing systems, providing in-depth knowledge of the magmatic system far beyond late-stage pre-eruptive processes.