How ductile are ductile shear zones?

Research Article| May 01, 2006 How ductile are ductile shear zones? Neil S. Mancktelow Neil S. Mancktelow 1Department of Earth Sciences, Eidgenössische Technische Hochschule Zürich, CH-8092 Zurich, Switzerland Search for other works by this author on: GSW Google Scholar Author and Article Information Neil S. Mancktelow 1Department of Earth Sciences, Eidgenössische Technische Hochschule Zürich, CH-8092 Zurich, Switzerland Publisher: Geological Society of America Received: 19 Sep 2005 Revision Received: 06 Dec 2005 Accepted: 16 Dec 2005 First Online: 09 Mar 2017 Online ISSN: 1943-2682 Print ISSN: 0091-7613 Geological Society of America Geology (2006) 34 (5): 345–348. https://doi.org/10.1130/G22260.1 Article history Received: 19 Sep 2005 Revision Received: 06 Dec 2005 Accepted: 16 Dec 2005 First Online: 09 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn Email Permissions Search Site Citation Neil S. Mancktelow; How ductile are ductile shear zones?. Geology 2006;; 34 (5): 345–348. doi: https://doi.org/10.1130/G22260.1 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 SocietyGeology Search Advanced Search Abstract Three premises of ductile deformation in the middle and lower crust are widely accepted: (1) rocks flow with power-law viscous rheology, (2) localization in ductile shear zones involves strain softening, and (3) fluid flows into and is channelized within ductile shear zones. Ductile (viscous) shear zones should therefore initially develop along planes of maximum shear stress, strain soften, and rotate as material planes into the field of progressive extension. However, the mean stress or pressure within a weak, elongate viscous band being stretched is higher than the surrounding matrix, and this is difficult to reconcile with premise (3). In contrast, Mohr-Coulomb brittle faults always have lower pressure within the fault zone. Flow of fluid and melt into high-temperature shear zones therefore implies that "ductile" shear zones are not perfectly viscous but have a pressure-dependent viscoplastic rheology. The continued pressure dependence may reflect significant microcracking on the grain scale even when localized deformation does not produce larger-scale discrete fractures. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.