Nucleation of ductile shear zones on dilatant fractures

Research Article| January 01, 1986 Nucleation of ductile shear zones on dilatant fractures Paul Segall; Paul Segall 1U.S. Geological Survey, 345 Middlefield Road, MS 977, Menlo Park, California 94025 Search for other works by this author on: GSW Google Scholar Carol Simpson Carol Simpson 2Department of Geological Sciences, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061 Search for other works by this author on: GSW Google Scholar Author and Article Information Paul Segall 1U.S. Geological Survey, 345 Middlefield Road, MS 977, Menlo Park, California 94025 Carol Simpson 2Department of Geological Sciences, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061 Publisher: Geological Society of America First Online: 01 Jun 2017 Online ISSN: 1943-2682 Print ISSN: 0091-7613 Geological Society of America Geology (1986) 14 (1): 56–59. https://doi.org/10.1130/0091-7613(1986)14<56:NODSZO>2.0.CO;2 Article history First Online: 01 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn Email Permissions Search Site Citation Paul Segall, Carol Simpson; Nucleation of ductile shear zones on dilatant fractures. Geology 1986;; 14 (1): 56–59. doi: https://doi.org/10.1130/0091-7613(1986)14<56:NODSZO>2.0.CO;2 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 Small shear zones in granitic rocks of the Sierra Nevada, California, and near Roses (Rosas), northeast Spain, display features which indicate that dilatant fracturing preceded the localization of ductile shear deformation. Many zones have sharp, nearly planar boundaries between their highly deformed interiors and the undeformed wall rock. The Roses shear zones narrow continuously to hairline fractures at their ends. Mineralized microcracks oriented parallel to the shear zones cluster near the zone boundaries and are interpreted as relicts of the earlier fracturing episode. Dynamic recrystallization of minerals filling these microcracks demonstrates that fracturing predated the ductile deformation. Gradients in ductile strain suggest that deformation spread laterally into the wall rocks after nucleation of the shear zones. We suggest that cracks enhance the wall rock ductility by increasing local fluid fluxes, thereby promoting chemical alteration and/or hydrolytic weakening. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.