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Elemental diffusion chronostratigraphy: time-integrated insights into the dynamics of plumbing systems
  • Chiara Maria Petrone,
  • Martin Mangler
Chiara Maria Petrone
The Natural History Museum

Corresponding Author:c.petrone@nhm.ac.uk

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Martin Mangler
The Natural History Museum
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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 temperatures at which diffusion occurred. This is particular difficult for multiple zoned minerals where the different compositional boundaries indicate multiple physicochemical changes of melt environments during the lifetime of a crystal. Here, we argue that 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. We further argue that 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 pyroxenes from Stromboli and Popocatepetl volcanoes are used as examples to reconstruct the time-dependent elemental diffusion chronostratigraphy of single crystals and discuss magma dynamics implications. 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 modelled timescales, which need to be correctly evaluated and mitigated. Elemental diffusion chronostratigraphy is an extremely powerful tool to obtain time-related temporal information on the dynamics and histories of volcanic plumbing systems, which can lead to an in-depth knowledge of the magmatic system far beyond late-stage pre-eruptive processes. Combined with monitoring data and other petrological, geological and geophysical constraints at active volcanoes, they can greatly enhance our capability to inform volcanic hazard assessments.
31 May 2021Published in Geophysical Monograph Series on pages 177-193. 10.1002/9781119564485.ch8