Liquid fractionation. Part IV: Scale models for liquid fractionation of calc-alkaline magmas

Liquid fractionation has been modeled experimentally using scale theory. The results confirm that under conditions of constant viscosity a low-density magma can ascend as a coherent laminar layer along the vertical walls. The results also suggest, however, that if viscosity increases with differentiation the fractionated liquid forms small centimetreized plumes not only along inclined and irregular walls and along the bottom of magma chambers, but even on vertical walls. The formation of plumes enhances the accumulation of rhyolitic magma, and may increase the efficiency of fractionation.