The structure of the Rogart igneous complex, Sutherland, Scotland

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Abstract
The Rogart igneous complex, Sutherland, is of Newer Granite age and consists of a zoned tonalite-granodiorite-granite body (the central granodiorite complex) emplaced in Moine metasediments which to the east and north are involved in a peripheral zone of migmatization (the migmatite complex). Although the migmatite complex is genetically related to the central complex, it is not a static contact-effect. Evidence is presented which suggests the following sequence of events. An ascending body of granodiorite magma was preceded by a 'front' of migmatization. When it reached a higher crustal level, migmatization ceased and continued forceful intrusion of the magma deformed the migmatites into a plastic envelope around the expanding magma body, which consolidated as tonalite and granodiorite. Lateral distension exceeded upward movement and a partly funnel-shaped structure resulted. The granite cross-cuts structures in the tonalite and granodiorite and was emplaced later under more brittle conditions. An analysis of the deformation of 'regional' linear structures around the complex confirms the forcefully intrusive nature of the igneous mass. The geometry of the deformation of the migmatites during the emplacement of the central complex is related to the stress field obtaining at this period as deduced from planar and linear structures in the tonalite.