Lyell Collection
Geological Society, London, Special Publications
Lyell Centre  |   Lyell Collection  |   Subscriptions   |   Geological Society  |   Email alerts  |   Online bookshop  |   Help

Keywords:
Author:
Advanced search>>
This Article
Right arrow Full Text (PDF)
Right arrow References
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrow Request Permissions
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Gapais, D.
Right arrow Articles by Balé, P.
Right arrow Search for Related Content
GeoRef
Right arrow GeoRef Citation
Geological Society, London, Special Publications; 1990; v. 51; p. 169-179;
DOI: 10.1144/GSL.SP.1990.051.01.11
© 1990 Geological Society of London

Armorican Massif

Shear zone pattern and granite emplacement within a Cadomian sinistral wrench zone at St Cast, N. Brittany

D. Gapais & P. Balé

Laboratoire de Tectonique, CAESS (CNRS), Campus de Beaulieu, Université de Rennes I, 35042 RENNES Cedex, France

The St Cast shear zone, situated in Northern Brittany, is a crustal-scale sinistral wrench zone of Cadomian age. We describe the associated deformation history on the basis of a detailed analysis of structures, microstructures and quartz fabrics of rocks outcropping at the Pointe de St Cast.

The study area shows rocks of dominantly granodioritic composition which are intruded by a leucogranite (the Roche de St Cast). Strain measurements, foliation trajectories and outcrop-scale shear zones reveal a heterogeneous pattern of plane-strain type, associated with a bulk sinistral transcurrent shearing within both intrusion and country rocks. rocks.

Local shear zone patterns are however different within the two units. Country-rocks show decimetre scale shear zones anastomosed around low strain domains. In contrast, the intrusion shows a more homogeneous structure with a single set of parallel pervasive millimetre scale shear bands (sinistral C-S structures). These differences are interpreted in terms of different local kinematics and bulk thermal history as expected between a magmatic intrusion and its surrounding country-rocks during syntectonic emplacement. The overall structural pattern emphasizes that the Roche de St Cast is a syntectonic granite emplaced within a major zone of Cadomian sinistral wrenching.





This article has been cited by other articles:


Home page
 Geological Society, London, Special PublicationsHome page
R. D. Nance, J. B. Murphy, R. A. Strachan, J. D. Keppie, G. Gutierrez-Alonso, J. Fernandez-Suarez, C. Quesada, U. Linnemann, R. D'lemos, and S. A. Pisarevsky
Neoproterozoic-early Palaeozoic tectonostratigraphy and palaeogeography of the peri-Gondwanan terranes: Amazonian v. West African connections
Geological Society, London, Special Publications, 2008; 297: 345 - 383.
[Abstract] [Full Text] [PDF]

Home page
 Geological Society, London, Special PublicationsHome page
M. F. Pereira and J. B. Silva
Development of local orthorhombic fabrics within a simple-shear dominated sinistral transpression zone: the Arronches sheared gneisses (Iberian Massif, Portugal)
Geological Society, London, Special Publications, 2004; 224: 215 - 227.
[Abstract] [PDF]