Early igneous activity within the Caledonides, Northern Highlands of Scotland

Johnstone, G S and Mykura, W. 1989. British regional geology: Northern Highlands of Scotland. Fourth edition. Keyworth, Nottingham: British Geological Survey.

Early igneous activity within the Caledonides

Major intrusions, granite gneiss and migmatites within the Caledonides of the Northern Highlands. P915476.

Formerly all igneous and migmatitic rocks within the Caledonides (P915476) were considered to belong to a magmatic cycle related to the Caledonian Orogeny, and could be classed as Pre-, Syn- or Post-tectonic. It now appears that many of the ‘Pre-tectonic’ basic rocks are unrelated to the Caledonian cycle and that the migmatites, although having a Caledonian component, originated in a pre-Caledonian event. The igneous activity within the Caledonides will therefore be discussed under the following headings.

Early basic rocks - These comprise amphibolites and associated rocks which, though Affected by Caledonian metamorphism, comprise members which may be pre-Morarian in age.

Migmatites - These include rocks formed both in the pre-Caledonian and Caledonian events

Early Caledonian igneous rocks - These include intrusions of post-Morarian age involved in one or more periods of progressive regional metamorphism.

Early granites

Syenites

Basic and intermediate rocks

Two major syntheses of Scottish igneous activity provide more detail than can be given in this Handbook. These are Igneous Rocks of the British Isles (Sutherland, editor, 1982) and the synopsis by Brown (in The Geology of Scotland, Craig, editor, 1983).