Hostname: page-component-77c89778f8-gvh9x Total loading time: 0 Render date: 2024-07-17T15:08:28.662Z Has data issue: false hasContentIssue false
  • English
  • Français

Composite Ordovician lamprophyre (spessartite) intrusions around the Midlands Microcraton in central Britain

Published online by Cambridge University Press:  01 May 2009

R. S. Thorpe ,
J. W. Gaskarth  and
P. J. Henney
R. S. Thorpe
Affiliation:
Department of Earth Sciences, The Open University, Milton Keynes MK7 6AA, U.K.
J. W. Gaskarth
Affiliation:
School of Earth Sciences, Birmingham University, P.O. Box 363, Birmingham B15 2TT, U.K.
P. J. Henney
Affiliation:
Mineral & Geochemical Surveys, British Geological Survey, Keyworth, Nottingham NG12 5GG, U.K.
Get access Rights & Permissions [Opens in a new window]

Abstract

Lamprophyre sills and dykes of Ordovician age were emplaced within Cambrian–Lower Ordovician sedimentary rocks around the northern margins of the Midlands Microcraton. The intrusions show internal mineralogical and chemical variations indicating emplacement as multiple intrusions of co-magmatic pulses. The chemical characteristics of the lamprophyre magmas indicate formation by small-degree volatile-rich partial melting of lithospheric mantle enriched and modified by Lower Palaeozoic subduction (Th/Ta 5.3–11.6, La/Ta 29–82.3), together with a contribution from within-plate mantle source (Zr/Yc. 6) and/or mineralogically heterogeneous lithosphere, followed by varying degrees of fractional crystallization during uprise.

Type
Articles
Information
Geological Magazine , Volume 130 , Issue 5 , September 1993 , pp. 657 - 663
Copyright
Copyright © Cambridge University Press 1993

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

Allen, J. R. L. 1968. The Cambrian and Ordovician systems. In The Geology of the East Midlands (eds Sylvester-Bradley, P. C. and Ford, T. D.), pp. 20–40. Leicester University Press.Google Scholar
Eastwood, T., Gibson, W., Cantrill, T. C. & Whitehead, T. H. 1923. The geology of the country around Coventry. Memoirs of the Geological Survey, Explanation of Sheet 169.Google Scholar
Leat, P. T. & Thorpe, R. S. 1986 a. Geochemistry of an Ordovician basalt–trachybasalt–subalkaline/peralkaline rhyolite association from the Lyn peninsula, N. Wales, U.K. Geological Journal 21, 29–41.CrossRefGoogle Scholar
Leat, P. T. & Thorpe, R. S. 1986 b. Ordovician volcanism in the Welsh Borderland. Geological Magazine 123, 629–40.CrossRefGoogle Scholar
Leat, P. T. & Thorpe, R. S. 1989. Snowdon basalts and the cessation of Caledonian subduction by the Longvillian. Journal of the Geological Society, London 146, 965–70.CrossRefGoogle Scholar
Leat, P. T., Jackson, S. E., Thorpe, R. S. & Stillman, C. J. 1986. Geochemistry of bimodal basalt–subalkaline/peralkaline rhyolite provinces within the southern British Caledonides. Journal of the Geological Society, London 143, 259–73.CrossRefGoogle Scholar
Le Bas, M. J. 1968. Caledonian igneous rocks. In The Geology of the East Midlands (eds Sylvester-Bradley, P C. and Ford, T. D.), pp. 41–59. Leicester University Press.Google Scholar
Le Bas, M. J., Le Maitre, R. W., Streckeisen, A. & Zanettin, B. 1986. A chemical classification of volcanic rocks based on the total alkali–silica diagram. Journal of Petrology 11, 745–50.CrossRefGoogle Scholar
Lee, M. K., Pharaoh, T. C. & Soper, N. J. 1990. Structural trends in central Britain from images of gravity and aeromagnetic fields. Journal of the Geological Society, London 147, 241–58.CrossRefGoogle Scholar
Macdonald, R., Thorpe, R. S., Gaskarth, W. & Grindrod, A. R. 1985. Multi-component origin of Caledonian lamprophyres of northern England. Mineralogical Magazine 49, 485–94.CrossRefGoogle Scholar
McKenzie, D. & Bickle, M. J. 1988. The volume and composition of melt generated by extension of the lithosphere. Journal of Petrology 29, 625–79.CrossRefGoogle Scholar
Pearce, J. A. 1982. Trace element characteristics of lavas from destructive plate boundaries. In Orogenic Andesites (ed. Thorpe, R. S.), pp. 525–48. Chichester: J. Wiley & Sons.Google Scholar
Pearce, J. A. 1983. Role of the sub-continental lithosphere in magma genesis at active continental margins. In Continental basalts and mantle xenoliths (eds Hawkesworth, C. J. and Norry, M. J.), pp. 230–49. Nantwich: Shiva Publishing.Google Scholar
Pearce, J. A. & Norry, M. J. 1979. Petrogenetic implications of Ti, Zr, Y and Nb variations in volcanic rocks. Contributions to Mineralogy and Petrology 69, 33–7.CrossRefGoogle Scholar
Pharaoh, T. C., Merriman, J. R., Webb, P. C. & Beckinsale, R. D. 1987. The concealed Caledonides of eastern England preliminary results of a multi-disciplinary study. Proceedings of the Yorkshire Geological Society 46, 355–69.CrossRefGoogle Scholar
Pickering, K. T., Bassett, M. G. & Siveter, D. J. 1988. Late Ordovician–early Silurian destruction of the Iapetus Ocean: Newfoundland, British Isles and Scandinavia – a discussion. Transactions of the Royal Society of Edinburgh: Earth Sciences 79, 361–82.CrossRefGoogle Scholar
Pocock, R. W., Whithead, T. H., Wedd, C. B. & Robertson, T. 1938. The geology of the country around Shrewsbury (including the Hanwood Coalfield). Memoirs of the Geological Survey, Explanation of Sheet 152.Google Scholar
Potts, P. J., Thorpe, O. W. & Watson, J. S. 1981. Determination of the rare-earth element abundances in 29 international rock standards by instrumental neutron activation analysis: a critical appraisal of calibration errors. Chemical Geology 34, 331–52.CrossRefGoogle Scholar
Rock, N. M. S. 1984. Nature and origin of calc-alkaline lamprophyres: minettes, vogesites, kersantites and spessartites. Transactions of the Royal Society of Edinburgh: Earth Sciences 74, 193–227.CrossRefGoogle Scholar
Soper, N. J. & Hutton, D. H. W. 1984. Late Caledonian sinistral displacements in Britain. Implications for a three-plate collisional model. Tectonics 3, 175–92.CrossRefGoogle Scholar
Soper, N. J., Webb, B. C. & Woodcock, N. H. 1987. Late Caledonian (Acadian) transpression in north-west England: timing, geometry and geotectonic significance. Proceedings of the Yorkshire Geological Society 46, 175–92.CrossRefGoogle Scholar
Wood, D. A. 1980. The application of a Th–Hf–Ta diagram to problems of tectonomagmatic classification and to establish the nature of crustal contamination of basaltic lavas of the British Tertiary volcanic province. Earth and Planetary Science Letters 50, 11–30.CrossRefGoogle Scholar
Wood, D. A., Joron, J-L. & Treuil, M. 1979. A reappraisal of the use of trace elements to classify and discriminate between magma series erupted in different tectonic settings. Earth and Planetary Science Letters 45, 326–36.CrossRefGoogle Scholar
Woodcock, N. H., Awan, M. A., Johnson, T. E., Mackie, A. H. & Smith, R. D. A. 1988. Acadian tectonics of Wales during Avalonia/Laurentia convergence. Tectonics 7, 483–95.CrossRefGoogle Scholar