U-Pb geochronology and Sm-Nd isotopic composition of Proterozoic gneisses, Channel Islands, UK
A precise date of 2061 ± 2 m.y., determined by single zircon U-Pb techniques, confirms the Palaeoproterozoic age of the Icart gneiss of Guernsey. Positive initial εNd values for this and other gneisses on Guernsey (Lihou Island, Pea Stacks, Soldier's Bay) indicate that pre-Cadomian basement was...
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Published in | Journal of the Geological Society Vol. 155; no. 4; pp. 609 - 618 |
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Main Authors | , |
Format | Journal Article |
Language | English |
Published |
London
Geological Society of London
01.07.1998
The Geological Society of London Geological Society Geological Society Publishing House |
Subjects | |
Online Access | Get full text |
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Summary: | A precise date of 2061 ± 2 m.y., determined by single zircon U-Pb techniques, confirms the Palaeoproterozoic age of the Icart gneiss of Guernsey. Positive initial εNd values for this and other gneisses on Guernsey (Lihou Island, Pea Stacks, Soldier's Bay) indicate that pre-Cadomian basement was an important site of new crustal production at ∼ 2100 m.y. These data, combined with the age of the Icart gneiss, provide a more robust link between Cadomian basement and the ∼ 2100 Birimian terrains of West Africa than could be made solely on general age similarities. High-precision U-Pb dating has shown that the protolith to an orthogneiss at Port du Moulin, Sark, is 616+4-2 m.y. rather than being Palaeoproterozoic. These new dates, combined with published 40Ar/39Ar data, show that deformation, magmatism and amphibolite-facies metamorphism took place at ∼ 605-615 m.y. in this region. |
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ISSN: | 0016-7649 2041-479X |
DOI: | 10.1144/gsjgs.155.4.0609 |