Solidification contraction: another approach to cumulus processes and the origin of igneous layering.

Abstract

The transformation from liquid to solid state involves a relative decrease in volume of 6-10% for most silicate melts. This contraction leads to melt percolation when occurring in a rigid, partially solidifed crystal pile. As solidification contraction leads to flow of solute enriched liquid in a direction opporite to the main growth, solute-rich liquids accumulate along the margins of the magma chamber, and give rise to a marginal, inverse compositional zonation. If the refractory growth sector at the front of the crystal pile seals off the underlying volume, a discontinuous fluid dynamic situation will develop, which prevents refractory crystal growth until precipitation of another crystal pile has reached sufficient height. This process can produce repeated layers of adcumulus to orthocumulus sequences with regular spacing, provided the crystal accretion and growth rate remain constant. -from Author