Reconstructing magmatic histories with 3D diffusion modeling of complex crystals

Area of Science:

• Geochemistry
• Volcanology
• Petrology

Background:

• Traditional 1D diffusion models in magmatic stopwatches overlook complex 3D crystal structures.
• This simplification can lead to inaccurate constraints on critical magmatic processes like storage, ascent, and volatile transfer.
• Accurate temporal constraints are vital for understanding eruption dynamics and volcanic hazards.

Purpose of the Study:

• To develop and apply an integrated approach using 3D finite element diffusion models and X-ray microtomography.
• To reconstruct the magmatic history of the 1820 Keanakāko'i eruption of Kīlauea.
• To provide more accurate temporal constraints on magmatic processes.

Main Methods:

• Combined X-ray microtomography of olivine crystals with 3D finite element diffusion models.
• Analyzed Fe-Mg diffusion in olivine to determine storage and mixing timescales.
• Used melt inclusions to infer decompression rates and syn-eruptive cooling rates via diffusive water loss and Mg diffusion.

Main Results:

• Decadal storage of olivine crystals preceding pre-eruptive mixing events lasting days to weeks.
• Decompression rates estimated between 1 x 10^-4 and 6.3 x 10^-3 MPa/s.
• Maximum syn-eruptive cooling rates determined to be 7.5–15 °C/s.

Conclusions:

• The 3D modeling approach provides a more robust framework for constraining magmatic histories.
• This method enhances understanding of magma evolution, volatile degassing, and eruption dynamics.
• Offers a transferable framework for diverse tectonic settings, improving volcanic hazard assessment.