The role of mixing and crystallization in the differentiation of magmatic systems

Abstract Understanding magma differentiation and formation of eruptible magmas is one of the key issues in Earth sciences. Many studies have either focused on mixing or crystallization, but none have studied these two processes simultaneously. Here, we conduct an innovative experimental study investigating the simultaneous occurrence of crystallization and dynamic mixing, using basaltic and dacitic end members at sub-liquidus conditions. We reproduce the injection of mafic magma into felsic magma and their mixing while crystallization occurs. Our results indicate that crystallization of basaltic magmas occurs faster than mixing between basalt and dacite leading to the formation of crystal-rich mafic enclaves within a felsic magma and the development of basaltic andesitic to andesitic melts. Then, convection promotes stretching and folding that favor chemical and physical magma mixing, disaggregation of enclaves and formation of clusters of crystals in disequilibrium with the surrounding melt. Magma mixing is the predominant process after the initial crystallization event. Our results provide insights into pre-eruptive dynamics, which is crucial for improving volcanic hazard assessment.