Igneous processes generate compositional gradients at different length scales. Examples include: i) interaction of magmas from variable sources (e.g. mantle and crustal melts); ii) crystallization along walls of magma chambers generating compositional gradients from the centre of the magmatic mass to its peripheral portions; iii) differential assimilation of country rocks in different regions of a magma body; iv) anatexis of heterogeneous rock volumes producing compositional gradients due to different degrees of partial melting. All these processes inevitably trigger mixing episodes and characterize most evolutionary stages of a magmatic system. Furthermore, the embedding geometry where the mixing process may occur (e.g. magma chamber, fracture/channel networks, volcanic conduits) may strongly modulate the fluid-dynamic style and process intensity.
Although increasing natural evidence indicates a major role of magma mixing in igneous systems in all geological environments, several questions still remain open. Among them: what is the smallest length-scale at which magma mixing may generate compositional heterogeneities? What are the most important factors that may promote or inhibit mixing processes? What is the space-time span for generating compositional heterogeneities by magma mixing? How do these heterogeneities may influence the composition of crystallizing minerals and melt inclusions? What are the time scales for hybrid melt production? How can we reconcile these features with classical geochemical models in which both time and space are not taken into account?
The proposed session aims at an interdisciplinary discussion on these and other magma mixing related questions, highlighting its relevance as a petrological and volcanological tool. Contributions documenting the occurrence of magma mixing processes in both plutonic and volcanic environments are welcome, as well as those focusing on experimental, theoretical and numerical modelling.