Abstract

Detailed remapping of the Palaeogene Ardnamurchan Centre 3 gabbros, NW Scotland, suggests that this classic sequence of ring-intrusions forms a composite layered lopolith. The area mapped by previous studies as the Great Eucrite gabbro intrusion comprises 70 % by area of Centre 3. Field observations suggest that most of the other smaller ring-intrusions of Centre 3 (interior to the Great Eucrite) constitute either distinct petrological facies of the same intrusion, or included country-rock or peridotite blocks. These observations, together with syn-magmatically deformed inward-dipping modal layering, are used here to support the interpretation that significant central sagging occurred in the intrusion at a late stage in its crystallization history.

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