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Lower Palaeozoic and Precambrian igneous rocks from eastern England, and their bearing on late Ordovician closure of the Tornquist Sea: constraints from U-Pb and Nd isotopes

  • S. R. Noble (a1), R. D. Tucker (a2) and T. C. Pharaoh (a3)
Abstract
Abstract

The U-Pb isotope ages and Nd isotope characteristics of asuite of igneous rocks from the basement of eastern England show that Ordovician calc-alkaline igneous rocks are tectonically interleaved with late Precambrian volcanic rocks distinct from Precambrian rocks exposed in southern Britain. New U-Pb ages for the North Creake tuff (zircon, 449±13 Ma), Moorby Microgranite (zircon, 457 ± 20 Ma), and the Nuneaton lamprophyre (zircon and baddeleyite, 442 ± 3 Ma) confirm the presence ofan Ordovician magmatic arc. Tectonically interleaved Precambrian volcanic rocks within this arc are verified by new U-Pb zircon ages for tuffs at Glinton (612 ± 21 Ma) and Orton (616 ± 6 Ma). Initial εNd values for these basement rocks range from +4 to - 6, consistent with generation of both c. 615 Ma and c. 450 Ma groups of rocksin continental arc settings. The U-Pb and Sm-Nd isotope data support arguments for an Ordovician fold/thrust belt extending from England to Belgium, and that the Ordovician calc-alkaline rocks formed in response to subductionof Tornquist Sea oceanic crust beneath Avalonia.

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Allsop J. M. 1987. Patterns of late Caledonian intrusive activity in eastern and northern England from geophysics, radiometric dating and basement geology. Proceedings of the Yorkshire Geological Society 46, 335–53.
André L. 1991. The concealed crystalline basement in Belgium and the “Brabantia” microplate concept: constraints from the Caledonian magmatic and sedimentary rocks. Annales de la Société Géologique de Belgique 114, 117–40.
André L., Hertogen J. & Deutsch S. 1986. Ordovician-Silurian magmatic provinces in Belgium and the Caledonian orogeny in middle Europe. Geology 14, 879–82.
Carney J., Glover B. J. & Pharaoh T. C. 1992. Pre-conference fieldexcursion guide: Midlands. British Geological Survey Technical Report WA/92/72. 28 pp.
Cocks L. R. M. & Fortey R. A. 1982. Faunal evidence for oceanic separations in the Palaeozoic of Britain. Journal of the Geological Society, London 139, 465–78.
Corfu F. & Ayres L. D. 1984. U-Pb ages and genetic significance of heterogeneous zircon populations in rocks from the Favourable Lake area, northwestern Ontario. Contributions to Mineralogy and Petrology 88, 86101.
Davies G., Gledhill A. & Hawkesworth C. 1985. Upper crustal recycling in southern Britain: evidence from Nd and Sr isotopes. Earth and Planetary Science Letters 75, 112.
Davis D. W. 1982. Optimum linear regression and error estimation applied to U-Pb data. Canadian Journal of Earth Science 19, 2141–9.
DePaolo D. J. & Wasserburg G. J. 1976. Nd isotopic variations and petrogenetic models. Geophysical Research Letters 3, 249–52.
Evans J. A. 1989. Resetting of the Rb-Sr whole-rock isotope system of an Ordovician microgranite during Devonian low-grade metamorphism. Geological Magazine 126, 675–9.
Evans J. A. 1991. Resetting of Rb-Sr whole-rock ages during Acadian low-grade metamorphism in North Wales. Journal of the Geological Society, London 148, 703–10.
Evans J. A. 1992. Geochemical and isotope composition of pebbles from the Caban Conglomerate Formation and their bearing on the source of Welsh Palaeozoic sedimentary rocks. Geological Magazine 129, 581–7.
Geyh M. A. & Schleicher H. 1990. Absolute age determination. Berlin: Springer-Verlag.
Harland W. B., Armstrong R. L., Cox A. V., Craig L. E., Smith A. G. & Smith D. G. 1989. A Geologic Time Scale 1989. Cambridge University Press.
Jacobsen S. B. & Wasserburg G. J. 1980. Sm-Nd evolution of chondrites. Earth and Planetary Science Letters 50, 139–55.
Krogh T. E. 1973. A low contamination method for the hydrothermal decomposition of zircon and extraction of U and Pb for isotopic age determinations. Geochimica et Cosmochimica Acta 37, 485–94.
Krogh T. E. 1982. Improved accuracy of U-Pb zircon ages by the creation ofmore concordant systems using an air-abrasion technique. Geochimica et Cosmochimica Acta 46, 637–49.
Krogh T. E. & Davis G. L. 1975. The production and preparation of 205Pb for use as a tracer for isotope dilution analysis. Carnegie Institution of Washington, Yearbook 74, 416–17.
Le Bas M. J. 1972. Caledonian igneous rocks beneath central and eastern England. Proceedings of the Yorkshire Geological Society 39, 7186.
Le Bas M. J. 1982. Geological evidence from Leicestershire on the crust ofsouthern Britain. Transactions of the Leicester Literary and Philosophical Society 76, 5467.
Lee M. K., Pharaoh T. C. & Soper N. J. 1990. Structural trends in central Britain from images of gravity and aeromagnetic fields. Journal ofthe Geological Society, London 147, 241–58.
Ludwig K. R. 1980. Calculation of uncertainties of U-Pb isotope data. Earth and Planetary Science Letters 46, 212–20.
Ludwig K. R. 1989. PBDAT: a computer program for processing Pb-U-Th isotope data, version 1.20. United States Geological Survey, Open-file report 88542.
Ludwig K. R. 1990. Isoplot: a plotting and regression program for radiogenic-isotope data, version 2.03. United States Geological Survey, Open-file report 88557.
Merriman R. J., Pharaoh T. C., Woodcock J. H. & Daly P. 1993. The metamorphic history of the concealed Caledonides of Eastern England and their foreland. Geological Magazine 130, 613–20.
O'Brien S. J., O'Driscoll C. R., Tucker R. D. & Dunning G. R. 1992. Four-fold subdivision of the Late Precambrian magmatic record ofthe Avalon Zone type area (East Newfoundland): Nature and Significance. Geological Association of Canada/Mineralogical Association of Canada Joint Annual Meeting 17, A85.
Old R. A., Hamblin R. J. O., Ambrose K. & Warrington G. 1991. Geology of the country around Redditch. Memoir for 1:50000 geological sheet 183. British Geological Survey.
Oliver G. J. H., Corfu F. & Kroch T. E. 1993. U-Pb ages from SW Poland: evidence for a Caledonian suture zone between Baltica and Gondwana. Journal of the Geological Society, London 150, 355–69.
Pharaoh T. C., Brewer T. S. & Webb P. C. 1993. Subduction-related magmatism of late Ordovician age in eastern England. Geological Magazine 130, 647–56.
Pharaoh T. C., Merriman R. J., Evans J. A., Brewer T. S., Webb P. C. & Smith N. J. P. 1991. Early Palaeozoic arc-related volcanism in the concealed Caledonides of southern Britain. Annales de la Société Géologique de Belgique T114, 6391.
Pharaoh T. C., Merriman R. J., Webb P. C. & Beckin-sale R. D. 1987. The concealed Caledonides of eastern England: preliminary results of a multidisciplinary study. Proceedings of the Yorkshire Geological Society 46, 355–69.
Pidgeon R. T. & Aftalion M. 1978. Cogenetic and inherited zircon U-Pbsystems in granites: Palaeozoic granites of Scotland and England. In Crustal Evolution in Northwestern Britain and Adjacent Regions (eds Bowes D. R. and Leake B. E.), pp. 183220. Geological Journal Special Issue No. 10. Liverpool: Seal House Press.
Smith N. J. P. (Compiler) 1985. Pre-Permian geology of the United Kingdom (South). British Geological Survey.
Soper N. J., Webb B. C. & Woodcock N. J. 1987. Late Caledonian (Acadian) transpression in North West England: timings, geometry and geotectonicsignificance. Proceedings of the Yorkshire Geological Society 46, 175–92.
Stacey J. S. & Kramers J. D. 1975. Approximation of terrestrial lead isotope evolution by a two-stage model. Earth and Planetary Science Letters 26, 207–21.
Steiger R. H. & Jäger E. 1977. Subcommission on geochronology: convention on the use of decay constants in geo- and cosmochronology. Earth and Planetary Science Letters 36, 359–62.
Thorogood E. J. 1990. Provenance of the pre-Devonian sediments of England and Wales: Sm-Nd isotopic evidence. Journal of the Geological Society, London 147, 591–4.
Thorpe R. S., Gaskarth J. W. & Henney P. J. 1993. Composite Ordovician lamprophyre (spessartite) intrusions emplaced during Caledonian convergence around the Midlands Microcraton in central Britain. Geological Magazine 130, 657–63.
Trench A., Torsvik T. H. & McKerrow W. S. 1992. The palaeogeographicevolution of Southern Britain during early Palaeozoic times: a reconciliation of palaeomagnetic and biogeographic evidence. Tectono-physics 201, 7582.
Tucker R. D. & Pharaoh T. C 1991. U-Pb zircon ages for Late Precambrian igneous rocks in southern Britain. Journal of the Geological Society, London 148, 435–43.
Wasserburg G. L., Jacobsen S. B., DePaolo D. J., McCulloch M. T. & Wen T. 1981. Precise determination of Sm/Nd ratios, Sm and Nd isotopic abundances in standard solutions. Geochimica et Cosmochimica Acta 45, 2311–22.
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Geological Magazine
  • ISSN: 0016-7568
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