The minor intrusive suite associated with the Criffell-Dalbeattie granodiorite complex

Abstract

The suite of minor intrusions associated with the Criffell-Dalbeattie granodiorite complex is composed of a great number of porphyrite and porphyry dykes which are the minor intrusive equivalents of the granodioritic rocks, and a relatively small number of spessartite and kersantite lamprophyre dykes which were generally intruded before the porphyrites. The petrography of the three groups of dyke-rocks is described and a comparison made between the chemical composition of the porphyrite and spessartite rocks and their hornblendes. It is suggested that high-temperature spessartite magmas developed from primary olivine basalt magma by reaction with sialic material at the roots of the Caledonian orogenic zone, and that the later passage of emanations along some of the consolidating spessartite dyke magmas effected the development of the kersantite dykes by extensive recrystallisation which continued after the consolidation of the dykes.