In situ high-temperature visible microspectroscopy for volcanic materials

Area of Science:

• Geochemistry
• Materials Science
• Spectroscopy

Background:

• Volcanic materials undergo color changes due to high-temperature processes.
• Understanding these changes requires kinetic measurements at relevant temperatures.
• Existing methods may not capture dynamic spectral shifts in situ.

Purpose of the Study:

• To develop and validate a novel in situ high-temperature visible microspectroscopy technique.
• To investigate the kinetics of color change in olivine at 600-800°C.
• To determine the activation energy for diffusion processes in olivine.

Main Methods:

• Utilized in situ high-temperature visible microspectroscopy.
• Heated olivine thin sections on an alumina plate from 600-800°C.
• Monitored visible absorption spectra every 60 seconds for 5 hours.

Main Results:

• Observed a gradual increase in absorbance (400-600 nm) over time.
• Noted a significant increase in 430 nm absorbance (Fe3+ ligand field transition) at higher temperatures.
• Calculated apparent diffusion coefficients and an activation energy of 208 ± 17 kJ/mol for diffusion in olivine.

Conclusions:

• The developed technique successfully measures kinetic spectral changes in materials at high temperatures.
• The determined activation energy is consistent with metal vacancy diffusion in olivine.
• This method offers a new approach for studying high-temperature material transformations, particularly in volcanology.