Viscosity of melt of soda melilite composition at high pressure

Abstract

The viscosity of melt of soda melilite (CaNaAlSi₂O₇) composition was measured using the falling sphere method with synchrotron X–ray radiography. This composition of melt was used as a model basalt, because the ratio of the non–bridging oxygen (NBO) and the tetrahedrally coordinated (T) cation is 0.67. We observed a viscosity minimum between 2 and 4 GPa. This finding shows that the partially depolymerized melt (NBO/T = 0.67) has a viscosity minimum under high pressure.