Interparticle Forces Between Suspended Platinum Group Element Particles in Silicate Melts

Magma generally consists of a multi-phase suspension composed of a silicate melt, bubbles, and crystals. The presence of crystals may strongly affect the magma rheology, which in turn, is one of the main controlling parameters determining whether a volcano will erupt explosively or effusively. The parameters commonly used for the characterization of these solid-bearing silicate melts include the volume fractions, shapes, and sizes of the solid phase particles. Here, we investigate whether the chemical nature of the crystals plays a role in determining viscosity and how important interparticle forces can be. We evaluate experimental data on silicate melts containing platinum group element (PGE) inclusions. Recent studies have shown a drastic increase of the suspension viscosity (up to 4 orders of magnitude) for system containing a small fractions of crystals (~ 2 vol.%). In this work, scaling analyses and comparisons with experimental and theoretical models are performed to evaluate the importance of interparticle forces between those crystals. We conclude here that there must be interparticle forces and Brownian forces playing important roles in PGE particle aggregation, which in turn, cause an increase of the suspension viscosity. To the best of our knowledge, it is the first time that interparticle forces have been considered as an important feature in crystal aggregation in silicate melts.