Liquid collection in sidewall crystallization of magma: A comment on “liquid fractionation. Part I”, by A.R. McBirney, B.H. Baker and R.H. Nilson

The term liquid fractionation is inappropriate for a process driven by crystallization; liquid collection is proposed instead. The amount of evolved residual liquid produced by sidewall crystallization is not greater than that produced by any perfect fractional crystallization process and the fractionation products must be balanced somewhere by less evolved crystal deposits. There is no free lunch in petrology. Sidewall heating limits the local duration of liquid collection and the complementary crystal products should be sought in conduits. Flux ratios rather than diffusivities control the differences between thermal and chemical boundary layers.