The Kilmelford intrusives were emplaced in Dalradian metasediments and eruptives during the late stages of the Caledonian orogeny. The suite of rocks includes biotite–hornblende diorite and, to a minor extent, biotite–pyroxene and biotite–hornblende–pyroxene diorites, together with hornblende–biotite–quartz diorite, granodiorite, porphyrites of dioritic and dacitic composition and volcanic breccia. The major element geochemistry shows that the Kilmelford rock suite is alkali-calcic having petrogenetic affinities with the igneous rocks of the New Guinea 'continental arc'. The high contents of K, Sr, Ba, Rb, Zr and Ce, together with a high K2O/Na2O ratio, give these rocks their shoshonitic signature, which is of interest as an unusual example of the occurrence of shoshonites in the Scottish Caledonides. The rocks have very steep REE patterns (CeN/YbN = 10−28) and do not show a Eu anomaly. The shoshonitic signature of the Kilmelford rocks is interpreted as due to the late orogenic nature of the magmatism which took place when subduction had abated following the collision of the two continents.

This content is PDF only. Please click on the PDF icon to access.

First Page Preview

First page PDF preview
You do not currently have access to this article.