Accounting for Thermal Resorption of Bubbles in Magma in Experiments and Volcanic Eruptions

Abstract

The growth of bubbles drives volcanic eruptions and plays a major role in determining eruption style. Therefore, understanding bubble growth processes is essential for forward modelling of volcanic eruptions and for interpretation of vesicular eruptive products. Decompression experiments at high temperature and pressure have been widely used to investigate bubble growth processes. However, most studies neglect bubble resorption, which occurs during the quench process as water solubility increases with decreasing temperature. Resorption may alter final textures, so accounting for this process is important for interpretation of experimental products.
This study quantifies the extent to which bubble resorption during cooling/quenching modifies the gas volume fraction () of the products of a series of decompression experiments. A numerical model is applied that captures bubble growth and resorption over arbitrary pressure-temperature-time (P-T-t) pathways to a published experimental dataset. The analysis proceeds in three stages: 1) Reconstruct the experimental P-T-t pathways and determine how evolves with time, in order to reconstruct pre-quench values. 2) Vary values of experimental parameters, such as bubble number density () and cooling rate to show when quench modification is most important. 3) Carry out a parametric sweep and advise on the best experimental conditions to use to avoid over-printing of experimental samples via resorption.
Resorption occurs in all experimental samples that are analysed. In one sample, the final is over a 50% decrease of the original bubble growth, consistent with values determined by a previous study. The analysis indicates that thermal resorption must be accounted for in the interpretation of experimental results and that greater resorption occurs when is high and cooling rate is low. In some instances, this leads to bubbles resorbing completely from a peak value as high as 0.10. The numerical model can be used as a tool to design experiments and minimise the effect of resorption, and it is anticipated that this will support more meaningful interpretation of vesicle textures and size distributions.