Abstract
Constraining the timescales of pre-eruptive magmatic processes in active volcanic systems is paramount to understand magma chamber dynamics and the triggers for volcanic eruptions. Temporal information of magmatic processes is locked within the chemical zoning profiles of crystals but can be accessed by means of elemental diffusion chronometry. Mineral compositional zoning testifies to the occurrence of substantial temperature differences within magma chambers, which often bias the estimated timescales in the case of multi-stage zoned minerals. Here we propose a new Non-Isothermal Diffusion Incremental Step model to take into account the non-isothermal nature of pre-eruptive processes, deconstructing the main core-rim diffusion profiles of multi-zoned crystals into different isothermal steps. The Non-Isothermal Diffusion Incremental Step model represents a significant improvement in the reconstruction of crystal lifetime histories. Unravelling stepwise timescales at contrasting temperatures provides a novel approach to constraining pre-eruptive magmatic processes and greatly increases our understanding of magma chamber dynamics.
Highlights
Constraining the timescales of pre-eruptive magmatic processes in active volcanic systems is paramount to understand magma chamber dynamics and the triggers for volcanic eruptions
It has long been known that the timescale of magma formation, storage and ascent beneath active volcanoes is the key to constrain pre-eruptive magmatic processes and magma chamber dynamics, which provide the basis for volcanic hazard assessment
Magma eruption freezes the smoothing of the stepped compositional zoning profile, allowing temporal information to be unlocked by means of diffusion chronometry
Summary
Constraining the timescales of pre-eruptive magmatic processes in active volcanic systems is paramount to understand magma chamber dynamics and the triggers for volcanic eruptions. When more than one compositional boundary is present (that is, multi-stage evolution), it is important to take into account that elemental diffusion rates of the internal and external compositional boundary layers can be significantly different, depending on temperature contrast and elemental activation energy for a given crystal This is critical to diffusion chronometry studies aiming to establish meaningful crystal residence times and set constraints on magma chamber dynamics. Our new NonIsothermal Diffusion Incremental Step (NIDIS) model considers different diffusion coefficients for each crystal compositional boundary to match its specific equilibrium temperature This permits reconstruction of the lifetime history of complex compositionally zoned crystals, and contributes to a better understanding of magmatic storage and pre-eruptive processes in the plumbing systems of active volcanoes
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