Effects of secondary phases on crystallographic preferred orientations in mylonites

Abstract

Research Article| August 08, 2017 Effects of secondary phases on crystallographic preferred orientations in mylonites Andrew J. Cross; Andrew J. Cross 1Department of Earth and Planetary Sciences, Washington University in St. Louis, St. Louis, Missouri 63130, USA Search for other works by this author on: GSW Google Scholar Greg Hirth; Greg Hirth 2Department of Geological Sciences, Brown University, Providence, Rhode Island 02912, USA Search for other works by this author on: GSW Google Scholar David J. Prior David J. Prior 3Department of Geology, University of Otago, Dunedin 9056, New Zealand Search for other works by this author on: GSW Google Scholar Author and Article Information Andrew J. Cross 1Department of Earth and Planetary Sciences, Washington University in St. Louis, St. Louis, Missouri 63130, USA Greg Hirth 2Department of Geological Sciences, Brown University, Providence, Rhode Island 02912, USA David J. Prior 3Department of Geology, University of Otago, Dunedin 9056, New Zealand Publisher: Geological Society of America Received: 04 Jan 2017 Revision Received: 13 Jul 2017 Accepted: 14 Jul 2017 First Online: 08 Aug 2017 Online Issn: 1943-2682 Print Issn: 0091-7613 © 2017 Geological Society of America Geology (2017) 45 (10): 955–958. https://doi.org/10.1130/G38936.1 Article history Received: 04 Jan 2017 Revision Received: 13 Jul 2017 Accepted: 14 Jul 2017 First Online: 08 Aug 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Andrew J. Cross, Greg Hirth, David J. Prior; Effects of secondary phases on crystallographic preferred orientations in mylonites. Geology 2017;; 45 (10): 955–958. doi: https://doi.org/10.1130/G38936.1 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 Crystallographic preferred orientations (CPOs) are widely used to infer deformation conditions in the ductile crust and mantle. However, the effects of secondary phases on CPO evolution are not fully understood, despite the compositional diversity of Earth's lithosphere. Here we examine the role of plagioclase on the evolution of quartz CPOs through general shear experiments at 900 °C and 1.1 GPa. Pistons featuring an "asperity" on the shear plane were used, providing a novel way of visualizing CPO evolution under increasing shear strains and with material flow path variations. With the addition of albite, grain boundary pinning inhibits a transition from basal to prism slip, which is observed in single-phase quartz aggregates deformed under the same conditions. Simultaneously, crystallographic axes are modified by rotations around the kinematic vorticity axis, resulting in pronounced weakening of [c]-axis CPOs in the two-phase experiments, where quartz [c]-axes are oriented perpendicular to the vorticity axis. After only modest amounts of deformation (shear strain, γ < 5), CPOs in the single- and two-phase materials become markedly different. These findings highlight complications in using CPOs to infer deformation conditions in well-mixed polymineralic mylonites typical of most lithospheric shear zones. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.