Magma mingling and immiscibility
Corona texture – concentric texture developed around a mineral (xenocryst or antecryst) or a rock fragment (enclave, xenolith) that is not in equilibrium with the surrounding magma. The concentric texture can correspond to mineral overgrowth and/or to recrystallisation of the outer part of the xenolith/cryst, with or without chemical exchanges with the surrounding magma. Magmatic context - for corona in metamorphic context, see Recrystallisation page.
Magma mingling – distinct magmas with irregular lobate contacts. Limited reaction (or mixing) can occur at the contact between the intrusive phases, but complete chemical mixing is far from being achieved. This generally results from a replenishment event inside a magma intrusion that has not yet solidified. Mingling is generally detected only when the intrusive phases have contrasted chemistry (which comes with viscosity, etc., contrasts that render mixing difficult).
Immiscibility – An initially single magmatic phase that separates into two magmas with distinct chemistry. This has been proposed for carbonatite magmas, which are generally spatially associated with alkaline intrusive phases. This mechanism is also invoke for Fe-S-rich melt in mafic or ultramafic magmas, with the separation of a Fe-S-rich melt from the rest of the magma induced by the introduction of a large amount of S in the magma system (leading to S-saturation without vapor loss). Immiscibility has also been proposed for Fe-Ti-V-dominated magmatic unit in the upper part of layered intrusions, and in other context of extreme mineral segregation, but this is more debated.