Distribution of orthocumulate textures in the Jimberlana intrusion ( Australia).

Abstract

The P and U contents and the texture of cumulates have been used to document variations in residual porosity in the Jimberlana Intrusion. The results show that rocks with low residual porosity (adcumulate textures) occur where heat loss through the floor of the chamber was low or where the viscosity of the melt from which they crystallized was low. Low residual porosity also correlates with the appearance of plagioclase as a cumulus phase and with zones of well-developed rhythmic layering. It is suggested that the initial porosity of cumulates is controlled by the balance nucleation and crystal growth at the crystal-liquid interface. The residual porosity of cumulates has an important influence on the efficiency of fractional crystallization. -from Author Show more