Long-lived compositional heterogeneities in magma chambers, and implications for volcanic hazard

Area of Science:

• Geology
• Volcanology
• Geochemistry

Background:

• Volcanic eruptions often show compositional variations.
• These variations are typically interpreted as new, primitive magma batches mixing with resident magma.
• This interpretation implies short timescales between magma arrival and eruption, impacting hazard assessment.

Purpose of the Study:

• To investigate the dynamics of magma mixing in shallow magma chambers.
• To determine if long-lived, stable mixed magma configurations can form.
• To re-evaluate the interpretation of short mixing timescales in volcanic products.

Main Methods:

• Numerical simulations of magma convection and mixing.
• Modeling of multi-component magma interactions in a shallow chamber.

Main Results:

• Magma convection can lead to long-lived, dynamically stable configurations.
• These stable states allow for the coexistence of diverse magma compositions.
• The simulations demonstrate that heterogeneities can persist over extended periods.

Conclusions:

• Short mixing timescales observed in eruption products may not indicate recent magma injection.
• Heterogeneities can arise from in-eruptive mixing processes within the magma chamber.
• This challenges the assumption of rapid magma arrival preceding eruptions, with implications for volcanic forecasting.