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A U/Pb age for the Shetland Islands oceanic fragment, Scottish Caledonides: evidence from anatectic plagiogranites in ‘layer 3’ shear zones

Published online by Cambridge University Press:  01 May 2009

John G. Spray  and
Gregory R. Dunning
John G. Spray
Affiliation:
Department of Geology, University of New Brunswick, Fredericton, New Brunswick, E3B 5A3, Canada
Gregory R. Dunning
Affiliation:
Department of Earth Sciences, Memorial University of Newfoundland, St John's, Newfoundland, AIB 3X5, Canada
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Abstract

High precision U/Pb data obtained from zircons extracted from plagiogranite within the gabbro unit of the Shetland Islands oceanic fragment of northeast Scotland yield an age of 492 ± 3 Ma. Field relations indicate that the plagiogranites were generated by the partial melting of amphibolitized gabbros within high-temperature shear zones formed due to crustal deformation and fluid infiltration occurring in proximity to a spreading centre. The U/Pb data therefore constrain the crystallization age of the Shetland complex. This age is similar to U/Pb ages obtained from the Leka (497±2 Ma), Karmoy (493+7-4 Ma) and Gulfjellet (489±3 Ma) oceanic fragments of the Norwegian Caledonides, and the Pipestone Pond (4943-2 Ma) and Betts Cove (4893-2 Ma) oceanic fragments of the Canadian Appalachians.

Type
Rapid Communications
Information
Geological Magazine , Volume 128 , Issue 6 , November 1991 , pp. 667 - 671
Copyright
Copyright © Cambridge University Press 1991

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