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Zircon U–Pb ages of granulites from the Central Region of the Lewisian, northwestern Scotland

Published online by Cambridge University Press:  01 May 2009

R. T. Pidgeon  and
D. R. Bowes
R. T. Pidgeon
Affiliation:
Scottish Research Reactor Centre, East Kilbride, Glasgow
D. R. Bowes
Affiliation:
Department of Geology, The University, Glasgow G12 8QQ
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Summary

The overprinting of the high grade rocks of the Scourian episode, during the Inverian and Laxfordian episodes, has so far prevented a reliable estimate being made of the age of the Scourian granulite–facies metamorphism in the Central Region of the Lewisian of northwestern Scotland. In an attempt to solve this problem the U–Pb isotopic systems of zircons from two samples of hypersthene granulite from the Kylesku group have been examined. These zircons have discordant apparent ages complicating the interpretation of the results. However, by measuring a number of size fractions from each of the two zircon suites it has been possible to demonstrate that a major isotopic event or events took place approximately 2700 m.y. ago in these granulite–facies rocks. It has also been shown that the two discordance trends found for the two zircon populations can be explained in terms of episodic disturbances of the U–Pb isotopic systems at times which correspond to the known ages of ‘Laxfordian’ and ‘Caledonian’ events.

Type
Articles
Information
Geological Magazine , Volume 109 , Issue 3 , May 1972 , pp. 247 - 258
Copyright
Copyright © Cambridge University Press 1972

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References

Barooah, B. C. 1970. Significance of calc–silicate rocks and meta-arkose in the Lewisian complex south-east of Scourie. Scott. J. Geol. 6, 221–5.CrossRefGoogle Scholar
Bowes, D. R. 1969. The Lewisian of Northwest Highlands of Scotland. In Kay, M. (Ed.): North Atlantic—geology and continental drift, a symposium. Amer. Assoc. Petrol. Geol. Mem. 12, 575–94.Google Scholar
Bowes, D. R., Barooah, B. C. & Khoury, S. G. 1971. Original nature of Archaean rocks of North-West Scotland. Spec. Publ. geol. Soc. Aust. 3, 77–92.Google Scholar
Bowes, D. R., Wright, A. E. & Park, R. G. 1964. Layered intrusive rocks in the Lewisian of the North-West Highlands of Scotland. Q. Jl geol. Soc. Lond. 120, 159–92.CrossRefGoogle Scholar
Evans, C. 1965. Geochronology of the Lewisian basement near Lochinver, Sutherland. Nature, Lond. 207, 54–6.CrossRefGoogle Scholar
Gastil, R. G., De Lisle, M. & Morgan, J. R. 1967. Some effects of progressive metamorphism on zircons. Bull. geol. Soc. Am. 78, 879–906.CrossRefGoogle Scholar
Giletti, B. J., Moorbath, S. & Lambert, R. St J. 1961. A geochronological study of the metamorphic complexes of the Scottish Highlands. Q. Jl geol. Soc. Lond. 117, 233–72.CrossRefGoogle Scholar
Khoury, S. G. 1968. The structural geometry and geological history of the Lewisian rocks between Kylesku and Geisgeil, Sutherland, Scotland. Krystalinikum 6, 41–70.Google Scholar
Moorbath, S., Welke, H. & Gale, N. H. 1969. The significance of lead isotope studies in ancient, high-grade metamorphic basement complexes, as exemplified by the Lewisian rocks of northwest Scotland. Earth Plan. Sci. Letters, 6, 245–56.CrossRefGoogle Scholar
Peach, B. N. et al. 1907. The geological structure of the North-West Highlands of Scotl and. Mem. geol. Surv. U.K.Google Scholar
Pidgeon, R. T. 1969. Zircon U–Pb ages from the Galway granite and the Dalradian, Connemara, Ireland. Scott. J. Geol. 5, 375–92.CrossRefGoogle Scholar
Pidgeon, R. T., O'Neil, J. R. & Silver, L. T. 1966. Experimental investigation of U–Th–Pb isotopic stability in zircons, 1, Ceylon zircon. Trans. Am. Geophys. Union 47, 198.Google Scholar
Silver, L. T. 1963. The use of cogenetic uranium–lead isotope systems in zircons in geochronology. International Atomic Energy Agency, Vienna, 279–87.Google Scholar
Silver, L. T. 1969. A geochronological investigation of the anorthosite complex Adirondack Mountains New York. In Isachsen, Y. W. (Ed.): Origin of anorthosite and related rocks. Mem. 18. New York Museum and science service.Google Scholar
Stewart, A. D. 1969. Torridonian rocks of Scotland reviewed. In Kay, M. (Ed.): North Atlantic—geology and continental drift, a symposium. Amer. Assoc. Petrol. Geol. Mem. 12, 595–608.Google Scholar
Tilton, G. R. 1960. Volume diffusion as a mechanism for discordant lead ages. J. Geophys. Res. 65, 2933–45.CrossRefGoogle Scholar
van Breemen, O., Aftalion, M. & Pidgeon, R. T. 1971. The age of the granitic injection complex of Harris, Outer Hebrides. Scott. J. Geol. 7, 139–52.CrossRefGoogle Scholar
Wasserburg, G. J. 1963. Diffusion processes in lead–uranium systems. J. Geophys. Res. 68, 4823–46.CrossRefGoogle Scholar
Wetherill, G. W. 1956. Discordant uranium–lead ages, I. Trans. Amer. Geophys. Union 37, 320–6.Google Scholar