The origin of felsic microgranitoid enclaves: Insights from plagioclase crystal size distributions and thermodynamic models

Crystal size distributions (CSDs) of plagioclase in samples drilled from rinds and cores of three FMEs show that the rind samples are systematically finer-grained than the samples from the cores, which indicates that the FMEs cooled inwards and contradict interpretations that the FMEs are autoliths. Thermal modeling suggests that a slightly more primitive, hotter magma would be thermally equilibrated with an evolved resident melt within weeks after mixing/mingling. Upon thermal equilibrium, the FMEs would have an increased crystal cargo, and the resulting touching framework would impart a solid-like behavior to the FME-forming magma, which would lead to a contrast in rheology, fragmentation, dragging and preservation of felsic replenishment batches as distinct enclaves.