Self-excited regime of sedimentation of partially molten rocks

Abstract

We consider the phenomenon of sedimentation of partially molten rocks in intrusions. During the sedimentation of the suspension, a stratified structure consisting of zones with different degree of compaction of the solid phase appears. The highest degree of compaction corresponds to a poroviscous medium. With a critical porosity at the boundary, this medium is overlaid by a thin intermediate layer. The supercritical porosity values correspond to the violation in the skeleton’s connectivity. Within the thin layer, the skeleton of the poroviscous medium generally retains its properties, although in a strongly reduced form. The grains bounded by strong hydrodynamical bonds form the structures characterized by instability. During the sedimentation, these structures periodically collapse and recover, which is perceived as periodic self-excited oscillations on the macroscopic level. The self-excited sedimentation regime leads to the formation of a periodical layered structure in the cumulates, which is detectable many millions of years after the solidification of the intrusive chamber. This process is studied in the present paper.