Pb isotopic composition of feldspars from Scottish Caledonian Granites, and the nature of the underlying crust
- 7 June 1979
- journal article
- Published by Geological Society of London in Scottish Journal of Geology
- Vol. 15 (2) , 139-151
- https://doi.org/10.1144/sjg15020139
Abstract
Synopsis: Common Pb isotopic ratios for 11 feldspar separates from Caledonian granite intrusions (400 Ma old) show a linear alignment on a 207 Pb/ 204 Pb vs 206 Pb/ 204 Pb diagram, the best-fit regression line suggesting a lower intercept age of 2700 Ma, using conventional growth-curve models. This accords well with previously published Pb ages for the Lewisian basement in north-west Scotland ( Chapman and Moorbath, 1977 ), and strongly suggests a Lewisian Pb component in the Caledonian granites. Furthermore, the feldspars from the Southern Uplands granites are significantly more radiogenic than those from the Highlands and Midland Valley; this relationship is consistent with the presence of an older crustal layer beneath the more northerly regions which does not extend southwards into the Southern Uplands.Keywords
This publication has 28 references indexed in Scilit:
- Initial Pb of the Amîtsoq gneiss, West Greenland, and implications for the age of the EarthGeochimica et Cosmochimica Acta, 1977
- Lead isotope measurements from the oldest recognised Lewisian gneisses of north-west ScotlandNature, 1977
- LISPB–III. Upper crustal structure of northern BritainJournal of the Geological Society, 1977
- Grenville age for rocks in the Moine of north-western ScotlandNature, 1976
- Separation of trace amounts of uranium and thorium and their determination by mass spectrometric isotope dilutionAnalytical Chemistry, 1974
- Precision Measurement of Half-Lives and Specific Activities ofandPhysical Review C, 1971
- A model for the Lower Palaeozoic evolution of the southern margin of the early Caledonides of Scotland and IrelandScottish Journal of Geology, 1971
- Mass spectrometry of nanogram-size samples of leadAnalytical Chemistry, 1969
- ISOTOPIC AGES OF LATE CALEDONIAN GRANITIC INTRUSIONS IN THE BRITISH ISLESProceedings of the Yorkshire Geological and Polytechnic Society, 1968
- V.—The Tectonic Evolution of the Midland Valley of ScotlandTransactions of the Geological Society of Glasgow, 1958