Skip to main content
×
Home

40Ar–39Ar isotope constraints on the age of deformation in Charnwood Forest, UK

  • J. N. CARNEY (a1), P. ALEXANDRE (a2), M. S. PRINGLE (a3), T. C. PHARAOH (a1), R. J. MERRIMAN (a1) and S. J. KEMP (a1)...
Abstract
Abstract

40Ar–39Ar dating by a combination of spot analysis and step-heating has been carried out on mica fabrics from slaty cleavage and a shear zone in the Neoproterozoic to Cambrian rocks of Charnwood Forest, Leicestershire. The results indicate that crust adjacent to the eastern margin of the Midlands Microcraton was affected by localized epizonal metamorphism and penetrative deformation between 425 and 416 Ma (Silurian to earliest Devonian), somewhat earlier than the Acadian Phase of the Caledonian orogeny recorded elsewhere in southern Britain. The Charnwood cleavage geometry suggests that the deformation arose within a dextral transpressional regime along the eastern margin of the Midlands Microcraton. This tectonism may have overlapped with pre-Acadian sinistral transtensional movements documented for the Welsh Basin and Lake District areas, to the west and north of the Midlands Microcraton.

Copyright
Corresponding author
Author for correspondence: j.carney@bgs.ac.uk
References
Hide All
Alexandre P., Chalot-Prat F., Saintot A., Wijbrans J., Stephenson R., Wilson M., Kitchka A. & Stovba S. 2004. 40Ar/39Ar dating of magmatic activities in the Donbas Foldbelt and the Scythial Platforn (Eastern European Craton). Tectonics 23 (5), TC5002, 15 pp.
Bland B. H. & Goldring R. 1995. Teichichnus rectus Seilacher from the Charnian of Leicestershire. Neues Jahrbuch für Geologie und Paläontologie Abhandlungen 195, 523.
Bridge D. McC., Carney J. N., Lawley R. S. & Rushton A. W. A. 1998. The geology of the country around Coventry and Nuneaton. Memoir of the British Geological Survey Sheet 169 (England and Wales), 185 pp.
British Geological Survey. 1996. Tectonic map of Britain, Ireland and adjacent areas, 1:500 000 (compilers Pharaoh T. C., Morris J. H., Long C. B. & Ryan P. D.). Keyworth, Nottingham: British Geological Survey.
Carney J. N. 1999. Revisiting the Charnian Supergroup: new advances in understanding old rocks. Geology Today 15 (6), 221–9.
Carney J. N. 2005. Old Cliffe Hill and Whitwick quarries, Charnwood Forest. Mercian Geologist 16, 138–41.
Compston W., Wright A. E. & Toghill P. 2002. Dating the Late Precambrian volcanicity of England and Wales. Journal of the Geological Society, London 159, 323–39.
Dalrymple G. B., Alexander E. C. Jr, Lanphere M. A. & Kraker G. P. 1981. Irradiation of samples for 40Ar/39Ar dating using the Geological Survey TRIGA reactor. U.S. Geological Survey Professional Paper, Report P1176, 55 pp.
Debacker T. N., Dewaele S., Sintubin M., Verniers J., Muchez P. & Boven A. 2005. Timing and duration of the progressive deformation of the Brabant Massif, Belgium. Geologica Belgica 8, 2034.
Dewaele S., Boven A. & Muchez P. H. 2002. 40Ar/39Ar dating of mesothermal, orogenic mineralization in a low-angle reverse shear zone in the Lower Palaeozoic of the Anglo-Brabant fold belt, Belgium. Transactions of the Institution of Mining and Metallurgy 111, B21520.
Dewey J. F. & Strachan R. A. 2003. Changing Silurian–Devonian relative plate motion in the Caledonides: sinistral transpression to sinistral transtension. Journal of the Geological Society, London 160, 219–29.
Dodson M. H. & Robinson D. 2006. A mid-Ordovician Rb–Sr isochron age from the Ingleton Group, North Yorkshire: metamorphism or diagenesis? Proceedings of the Yorkshire Geological Society 56 (2), 81–5.
Dong H., Hall C. M., Halliday A. N., Peacor D. R., Merriman R. J. & Roberts B. 1997. 40Ar/39Ar dating of Late Caledonian (Acadian) metamorphism and cooling of K-bentonites and slates from the Welsh Basin, U.K. Earth and Planetary Science Letters 150, 337–51.
Gradstein F. M., Ogg J. G., Smith A. G. et al. 2005. A Geologic Time Scale, 2004. Cambridge University Press, 589 pp.
Ho N.-C., Peacor D. R. & Van Der Pluijm B. A. 1999. Preferred orientation of phyllosilicates in Gulf Coast mudstones and relation to the smectite–illite transition. Clays and Clay Minerals 47, 495504.
Kaufmann B., Trapp E., Mezger K. & Weddige K. 2005. Two new Emsian (Early Devonian) U–Pb zircon ages from volcanic rocks of the Rhenish Massif (Germany): implications for the Devonian time scale. Journal of the Geological Society, London 162, 363–71.
Kemp S. J. 1997. The nature and maturity of mudstone intervals from the Ticknall borehole, Derbyshire. British Geological Survey Technical Report WG/97/18, 18 pp.
Kemp S. J. & Merriman R. J. 1995. White mica (illite) crystallinity of Charnian rocks from the Loughborough district (1:50000 geological sheet 141). British Geological Survey Technical Report WG/95/7, 12 pp.
Kisch H. J. 1990. Calibration of the anchizone: a critical comparison of illite ‘crystallinity’ scales used for definition. Journal of Metamorphic Geology 8, 3146.
Knipe R. J. 1981. The interaction of deformation and metamorphism in slates. Tectonophysics 78, 249–72.
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.
Li G., Peacor D. R., Merriman R. J. & Roberts B. 1994. The diagenetic to low-grade metamorphic evolution of matrix white micas in the system muscovite–paragonite in a mudrock from Central Wales, U.K. Clays and Clay Minerals 42, 369–81.
McDougall I. & Roksandic Z. 1974. Total fusion 40Ar/39Ar ages using the HIFAR reactor. Journal of the Geological Society of Australia 21, 81–9.
McIlroy D., Brasier M. D. & Moseley J. M. 1998. The Proterozoic–Cambrian transition within the ‘Charnian Supergroup’ of central England and the antiquity of the Ediacaran fauna. Journal of the Geological Society, London 155, 401–12.
McKerrow W. S., Mac Niocaill C. & Dewey J. F. 2000. The Caledonian Orogeny redefined. Journal of the Geological Society, London 157, 1149–55.
Meneisy M. Y. & Miller J. A. 1963. A geochronological study of the crystalline rocks of Charnwood Forest, England. Geological Magazine 100, 507–23.
Merriman R. J. & Kemp S. J. 1997. Metamorphism of the Charnian Supergroup in the Loughborough district, 1:50000 Sheet 141. British Geological Survey Technical Report WG/97/7, 12 pp.
Merriman R. J. & Peacor D. R. 1999. Very low-grade metapelites: mineralogy, microfabrics and measuring reaction progress. In Low-Grade Metamorphism (eds Frey M. & Robinson D.), pp. 160. Blackwell Science.
Merriman R. J., Pharaoh T. C., Woodcock N. H. & Daly P. 1993. The metamorphic history of the concealed Caledonides of eastern England and their foreland. Geological Magazine 130, 613–20.
Merriman R. J., Rex D. C., Soper N. J. & Peacor D. R. 1995 b. The age of Acadian cleavage in northern England, UK: K–Ar and TEM analysis of a Silurian metabentonite. Proceedings of the Yorkshire Geological Society 50, 255–65.
Merriman R. J., Roberts B. & Peacor D. R. 1990. A transmission electron microscope study of white mica crystallite size distribution in a mudstone to slate transitional sequence, North Wales, U.K. Contributions to Mineralogy and Petrology 106, 2740.
Merriman R. J., Roberts B., Peacor D. R. & Hirons S. R. 1995 a. Strain-related differences in the crystal growth of white mica and chlorite: a TEM and XRD study of the development of metapelitic microfabrics in the Southern Uplands thrust terrane, Scotland. Journal of Metamorphic Geology 13, 559–76.
Moseley J. & Ford T. D. 1985. A stratigraphic revision of the Late Precambrian rocks of the Charnwood Forest, Leicestershire. Mercian Geologist 10, 118.
Parry W. T., Bunds M. P., Bruhn R. L., Hall C. M. & Murphy J. M. 2001. Mineralogy, 40Ar/39Ar dating and apatite fission track dating of rocks along the Castle Mountain faults, Alaska. Tectonophysics 337, 149–72.
Pharaoh T. C. 1999. Palaeozoic terranes and their lithospheric boundaries within the Trans-European Suture Zone (TESZ): a review. Tectonophysics 314, 1741.
Pharaoh T. C., Merriman R. J., Webb P. C. & Beckinsale R. D. 1987. The concealed Caledonides of eastern England: preliminary results of a multidisciplinary study. Proceedings of the Yorkshire Geological Society 46, 355–69.
Pharaoh T. C. & Carney J. N. 2000. Introduction to the Precambrian rocks of England and Wales. In Precambrian Rocks of England and Wales (eds Carney J. N., Horák J. M., Pharaoh T. C. et al. ), pp. 317. Geological Conservation Review Series no. 20. Peterborough: Joint Nature Conservation Review Committee.
Renne P. R., Swisher C. C., Deino A. L., Karner D. B., Owens T. L. & Depaolo D. J. 1998. Intercalibration of standards, absolute ages and uncertanties in 40Ar/39Ar dating. Chemical Geology 145, 117–52.
Robinson P., Tucker R. D., Bradley D., Berry H. N. & Osberg P. H. 1998. Palaeozoic orogens in New England, USA. GFF 20, 119–48.
Sherlock S. C., Kelley S. P., Zalasiewicz J., Schofield D., Evans J., Merriman R. J. & Kemp S. J. 2003. Precise dating of low-temperature deformation: Strain-fringe analysis by 40Ar–39Ar laser microprobe. Geology 31, 219–22.
Sintubin M., Brodkom F. & Laduron D. 1998. Cleavage-fold relationships in the Lower Cambrian Tubize Group, southeast Anglo-Brabant Fold Belt (Lembeek, Belgium). Geological Magazine 135, 217–26.
Smith N. J. P. 1987. The deep geology of central England: the prospectivity of the Palaeozoic rocks. In Petroleum Geology of North West Europe (eds Brooks J. & Glennie K.), pp. 217–24. London: Graham & Trotman.
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.
Soper N. J. & Woodcock N. H. 2003. The lost Old Red Sandstone of England and Wales: a record of post-Iapetan flexure of Early Devonian transtension? Geological Magazine 140, 627–47.
Turner J. S. 1949. The deeper structure of central and northern England. Proceedings of the Yorkshire Geological Society 27, 280–97.
Van de Pluijm B. A., Ho N.-C., Peacor D. R. & Merriman R. J. 1998. Contradictions of slate formation resolved. Nature 392, 348.
Van Grootel G., Verniers J., Geerkens B., Laduron D., Verhaeren M., Hertogen J. & De Voss W. 1997. Timing of magmatism, foreland basin development, metamorphism and inversion in the Anglo-Brabant fold belt. Geological Magazine 134, 607–16.
Villa I. M. 1998. Isotopic closure. Terra Nova 10, 42–7.
Warr L. N. & Rice A. H. N. 1994. Interlaboratory standardization and calibration of clay mineral crystallinity and crystallite size data. Journal of Metamorphic Geology 12, 141–52.
Winchester J. A., Pharaoh T. C. & Verniers J. 2002. Palaeozoic amalgamation of Central Europe: an introduction and synthesis of new results from recent geological and geophysical investigations. In Palaeozoic amalgamation of Central Europe (eds Winchester J. A., Pharaoh T. C. & Verniers J.), pp. 118. Geological Society of London, Special Publication no. 201.
Woodcock N. H. 1990. Transpressive Acadian deformation across the Central Wales Lineament. Journal of Structural Geology 12, 329–37.
Woodcock N. H. & Pharaoh T. C. 1993. Silurian facies beneath East Anglia. Geological Magazine 130, 681–90.
Woodcock N. H., Soper N. J. & Strachan R. A. 2007. A Rheic cause for Acadian deformation in Europe. Journal of the Geological Society, London 164, 1023–36.
Recommend this journal

Email your librarian or administrator to recommend adding this journal to your organisation's collection.

Geological Magazine
  • ISSN: 0016-7568
  • EISSN: 1469-5081
  • URL: /core/journals/geological-magazine
Please enter your name
Please enter a valid email address
Who would you like to send this to? *
×

Keywords:

Metrics

Full text views

Total number of HTML views: 3
Total number of PDF views: 6 *
Loading metrics...

Abstract views

Total abstract views: 72 *
Loading metrics...

* Views captured on Cambridge Core between September 2016 - 22nd November 2017. This data will be updated every 24 hours.