Abstract

New uranium–lead isotope data from monazites yield an emplacement age of 470 ± 1 Ma for the 'S'-type Aberdeen granite. Emplacement of this intrusion was late-tectonic with respect to the Grampian (early Caledonian) orogeny, and followed closely on the upper amphibolite facies meta-morphic climax in the Dalradian country rocks. The field relations of the associated vein complexes suggest that this isotopic age also dates the local D3 deformation of the Dalradian supergroup. Previously published isotope data indicate that the granite originated largely by melting of metasediments with a minimum crustal residence time of c. 1.2 to 1.8 Ga. Rocks with comparable isotopic characteristics form the migmatitic country-rock envelope to the granite, and we advocate extensive contemporaneous melting of such rocks at shallow depths below the level of emplacement (then 17–20 km).

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