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

Published online by Cambridge University Press:  20 May 2008

J. N. CARNEY ,
P. ALEXANDRE ,
M. S. PRINGLE ,
T. C. PHARAOH ,
R. J. MERRIMAN  and
S. J. KEMP
J. N. CARNEY*
Affiliation:
British Geological Survey, Kingsley Dunham Centre, Keyworth, Nottingham NG12 5GG, UK
P. ALEXANDRE
Affiliation:
Scottish Universities Environmental Research Centre, Rankine Avenue, East Kilbride, Scotland G75 OQF, UK
M. S. PRINGLE
Affiliation:
Massachusetts Institute of Technology, Dept. Earth, Atmospheric and Planetary Sciences, Cambridge, MA 02139-4307, USA
T. C. PHARAOH
Affiliation:
British Geological Survey, Kingsley Dunham Centre, Keyworth, Nottingham NG12 5GG, UK
R. J. MERRIMAN
Affiliation:
British Geological Survey, Kingsley Dunham Centre, Keyworth, Nottingham NG12 5GG, UK
S. J. KEMP
Affiliation:
British Geological Survey, Kingsley Dunham Centre, Keyworth, Nottingham NG12 5GG, UK
*
†Author for correspondence: [email protected]
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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.

Keywords

argonAcadianCaledoniandeformation
Type
Original Article
Information
Geological Magazine , Volume 145 , Issue 5 , September 2008 , pp. 702 - 713
Copyright
Copyright © Cambridge University Press 2008

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