Published online by Cambridge University Press: 01 May 2009
Examination of layered rocks from the Currywongaun-Doughruagh Intrusion, Connemara, Eire, has suggested a possible connexion between adcumulate crystallization and the formation of thin, yet very persistent igneous layering. It is thought that as a result of adcumulate crystallization proceeding under undisturbed conditions near the top of a pile of cumulus crystals, a zone of liquid, supersaturated in those components not required for adcumulate growth, could be generated in the magma just above the cumulate pile. Crystallization from such a supersaturated zone would result in the cumulate phases, inter-directly beneath. The rhythmic deposition is lacking, could by this mechanism build up a sequence of cumulate layers interbedded with fine-scale layers of a non-depositional origin.