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Short Communication |
1 1School of GeoSciences, Grant Institute, University of Edinburgh, West Mains Road, Edinburgh EH9 3JW, UK
2 2School of Earth and Environmental Science, University of Portsmouth, Burnaby Building, Burnaby Road, Portsmouth PO1 3QL, UK (e-mail: rob.strachan@port.ac.uk)
Geochronological data indicate that the Caledonian thrust sheets of NW Scotland were assembled in <18 Ma, yet regional Barrovian metamorphism to amphibolite facies and local melting occurred syn-thrusting. From theoretical studies, it is clear that there is insufficient time to generate the high metamorphic temperatures during the thrusting event. We suggest that a plausible explanation for the heat source is that it resulted from a 2025 Ma period of crustal heating in a back-arc setting between the Grampian and Scandian orogenic events. Most of the orogenic heat therefore came from the pre-existing back-arc rather than the orogenic process itself.