The shapes of dikes: Evidence for the influence of cooling and inelastic deformation

Abstract

Research Article| July 01, 2012 The shapes of dikes: Evidence for the influence of cooling and inelastic deformation Katherine A. Daniels; Katherine A. Daniels † 1School of Earth Sciences, University of Bristol, Wills Memorial Building, Queen's Road, Bristol BS8 1RJ, UK †E-mail: k.a.daniels@bristol.ac.uk Search for other works by this author on: GSW Google Scholar Janine L. Kavanagh; Janine L. Kavanagh 2School of Geosciences, Monash University, Clayton Campus, Wellington Road, Clayton, Victoria 3800, Australia Search for other works by this author on: GSW Google Scholar Thierry Menand; Thierry Menand 3Clermont Université, Laboratoire Magmas et Volcans, Université Blaise Pascal, BP 10448, F-63000 Clermont-Ferrand, France4Centre National de la Recherche Scientifique, UMR 6524, Laboratoire Magmas et Volcans, F-63038 Clermont-Ferrand, France5Institut de Recherche pour le Développement, R 163, Laboratoire Magmas et Volcans, F-63038 Clermont-Ferrand, France Search for other works by this author on: GSW Google Scholar J. Sparks R. Stephen J. Sparks R. Stephen 1School of Earth Sciences, University of Bristol, Wills Memorial Building, Queen's Road, Bristol BS8 1RJ, UK Search for other works by this author on: GSW Google Scholar Author and Article Information Katherine A. Daniels † 1School of Earth Sciences, University of Bristol, Wills Memorial Building, Queen's Road, Bristol BS8 1RJ, UK Janine L. Kavanagh 2School of Geosciences, Monash University, Clayton Campus, Wellington Road, Clayton, Victoria 3800, Australia Thierry Menand 3Clermont Université, Laboratoire Magmas et Volcans, Université Blaise Pascal, BP 10448, F-63000 Clermont-Ferrand, France4Centre National de la Recherche Scientifique, UMR 6524, Laboratoire Magmas et Volcans, F-63038 Clermont-Ferrand, France5Institut de Recherche pour le Développement, R 163, Laboratoire Magmas et Volcans, F-63038 Clermont-Ferrand, France J. Sparks R. Stephen 1School of Earth Sciences, University of Bristol, Wills Memorial Building, Queen's Road, Bristol BS8 1RJ, UK †E-mail: k.a.daniels@bristol.ac.uk Publisher: Geological Society of America Received: 24 Apr 2011 Revision Received: 25 Aug 2011 Accepted: 05 Oct 2011 First Online: 08 Mar 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 © 2012 Geological Society of America GSA Bulletin (2012) 124 (7-8): 1102–1112. https://doi.org/10.1130/B30537.1 Article history Received: 24 Apr 2011 Revision Received: 25 Aug 2011 Accepted: 05 Oct 2011 First Online: 08 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Katherine A. Daniels, Janine L. Kavanagh, Thierry Menand, J. Sparks R. Stephen; The shapes of dikes: Evidence for the influence of cooling and inelastic deformation. GSA Bulletin 2012;; 124 (7-8): 1102–1112. doi: https://doi.org/10.1130/B30537.1 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract We provide detailed observations on the shape of dikes from well-exposed field locations in the Isle of Rum, Scotland, and Helam Mine, South Africa. The basaltic Rum dikes crop out on a smaller scale than the Helam kimberlite dikes and have a smaller length to thickness ratio (∼100:1 Isle of Rum, ∼1000:1 Helam Mine). We compare the dike thickness field measurements with the geometry predicted by elastic theory, finding best-fit models to estimate magma overpressure and regional stress gradients at the time of dike emplacement. Most of the dike shapes fit poorly with elastic theory, being too thick at the dike ends and too narrow in the middle. Even for dikes where the model fit is acceptable, the calculated overpressures and stress gradients are very large and much larger than independent estimates based on rock strength, particularly for the small-scale basaltic dikes on Rum, where calculated overpressures average 687 MPa, and calculated stress gradients average 622 MPa m−1. The Swartruggens dikes have calculated overpressures of between 4 and 40 MPa and calculated stress gradients in the range of 15–87 kPa m−1. Dike shape can be explained by a combination of host-rock inelastic deformation prior to and coeval with magma emplacement, and by magma chilling at the dike's tapering edges, which prevented its closure as magma pressure declined during emplacement; this sequence provides the most complete explanation for the mismatches between the data and the model. The permanent wedging of the dike edges due to chilling has implications for crustal magma transport and strain response in the crust due to dike emplacement. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.