Cataclastic deformation mechanism for the development of core-mantle structures in amphibole

Abstract

Research Article| May 01, 1992 Cataclastic deformation mechanism for the development of core-mantle structures in amphibole Matthew W. Nyman; Matthew W. Nyman 1Department of Geological Sciences, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061 Search for other works by this author on: GSW Google Scholar Richard D. Law; Richard D. Law 1Department of Geological Sciences, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061 Search for other works by this author on: GSW Google Scholar Eugene A. Smelik Eugene A. Smelik 1Department 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 Matthew W. Nyman 1Department of Geological Sciences, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061 Richard D. Law 1Department of Geological Sciences, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061 Eugene A. Smelik 1Department of Geological Sciences, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061 Publisher: Geological Society of America First Online: 02 Jun 2017 Online ISSN: 1943-2682 Print ISSN: 0091-7613 Geological Society of America Geology (1992) 20 (5): 455–458. https://doi.org/10.1130/0091-7613(1992)020<0455:CDMFTD>2.3.CO;2 Article history First Online: 02 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Matthew W. Nyman, Richard D. Law, Eugene A. Smelik; Cataclastic deformation mechanism for the development of core-mantle structures in amphibole. Geology 1992;; 20 (5): 455–458. doi: https://doi.org/10.1130/0091-7613(1992)020<0455:CDMFTD>2.3.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 Core-mantle structures in mineral grains have typically been interpreted as having formed during crystal plastic deformation. Optical, scanning electron, and transmission electron microscope investigations of what appear to be core- mantle structures in amphibole from the Cheyenne belt, southeastern Wyoming, indicate that subgrainlike structures (herein "subgrains") formed as a result of cataclastic rather than crystal plastic deformation. Optical and scanning electron microscope evidence to support a cataclastic origin include (1) the angular shape of subgrains with boundaries commonly parallel to (110) cleavage; (2) the wide variety of subgrain sizes; (3) the compositional zonation of the amphibole subgrains with actinolitic hornblende interiors overgrown by magnesio- hornblende; and (4) the observation that some of the undulatory extinction in porphyroclast cores is due to slip along cleavage planes. Whether dislocations observed in the amphibole grains were formed prior to cataclastic deformation (work hardening) or formed in response to crack propagation is unknown. The implication of these observations is that core-mantle structures in other minerals may, at least in some cases, have also formed during cataclastic deformation rather than during recovery and/or recrystallization. Therefore, optical identification of core-mantle structures is not a priori evidence for a crystal plastic deformation mechanism. This content is PDF only. Please click on the PDF icon to access. 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.