Nanoscale X-ray fluorescence analysis of crystals and volcanic glass

Magma viscosity has a significant control on the explosivity of a volcanic eruption. An increase in viscosity during magma ascent can promote magma fragmentation and a highly explosive eruption. Nanoscale crystals, or 'nanolites' can increase magma viscosity, through their aggregation and impact on residual melt chemistry. However, the conditions and timescales of nanolite crystallisation are less constrained. Here, we propose to use 2D XRF to visualise and quantify nanoscale compositional variations in crystals and glass in volcanic products. As crystals form under specific physico-chemical conditions, analysis of compositional variations will provide insight into the conditions prevailing during crystal growth. Quantitative maps of compositional heterogeneities within matrix glass will be used to estimate crystallisation timescales. These results will provide important constraints for numerical models of magma ascent, essential for hazard assessments of explosive volcanic eruptions.