Primary structures of intrusive rocks

Intrusions are often quite homogeneous internally. Most of the structures shown here are at the contacts of intrusions.

Images copyright © 1998-2016, John W.F. Waldron, except where otherwise stated

Dyke and sill

Small dyke and sill of variably pegmatitic granite intrucing metasedimentary rocks. Portuguese Cove, NS.

Xenoliths

Multiple xenoliths of metasedimentary rock in margin of granite intrusion, Portuguese Cove, NS.

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Isolated xenoliths of metasedimentary rock in margin of granite intrusion, Portuguese Cove, NS.

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Margin of mafic dyke intruding granite; xenotith of granite within dyke. Georgeville NS.

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Intrusive contact of mafic sill (above) and sedimentary rocks (below). Hutton's contact, Salisbury Crags, Edinburgh, Scotland.

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Magma mingling texture: sinuous contacts indicate that both the felsic and mafic components of this intrusion were molten at the same time. Caledonia Highlands, NB.

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Flow alignment of megacrysts in granite, Portuguese Cove, NS.

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Columnar joints in mafic sill, Salisbury Crags, Edinburgh, Scotlan.d

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Sheeted dykes, Troodos ophiolite, Cyprus.